A.   CRUISE NARRATIVE: P19A

A.1. HIGHLIGHTS
WHP Cruise Summary Information

WOCE section designation                  P19A
Expedition designation (EXPOCODE)         74JC002_1
Chief Scientist(s) and their affiliation  Nicholas J.P. Owens/UN*
Dates                                     1992.11.01 - 1992.12.08
Ship                                      JAMES CLARK ROSS
Ports of call                             Stanley to Faraday
Number of stations                        65
                                                    62°56.93' S
Geographic boundaries of the stations     85°47.90' W         60°38.40' W
                                                    70°20.00' S
Floats and drifters deployed              none
Moorings deployed or recovered            none
Contributing Authors                      Gwyn Griffiths, Bill Miller, 
                                          Anne Morrison, Colin Day, 
                                          Tony Poole, Phil Taylor, 
                                          Raymond Pollard, John Allen, 
                                          Polly Machin, Jane Read, 
                                          David Turner, Ian Bellan, 
                                          Alison Weeks, Gerald Moore, 
                                          Jane Robertson, Sean Debney, 
                                          Susan Knox, Bob Head, 
                                          Phil Nightingale, 
                                          Wendy Broadgate, Colin Attwood, 
                                          Alistair Murray, Doug Bone, 
                                          Graham Savidge, Howard Waldron, 
                                          Mike Behrenfeld, Mike Hilles, 
                                          Rod Pearce, E. Morozov, 
                                          J.C. Jennings

* Department of Marine Sciences and Coastal Management 
  The Ridley Building -- The University of Newcastle 
  Newcastle upon Tyne, NE1 7RU  UK
  Tel:   +44-0191-222-8885  
  Fax:   +44-0191-222-7891  
  Email: n.owens@newcastle.ac.uk


A.2 INTRODUCTION

This cruise formed part of the Sterna 92 expedition, carried out in conjunction 
with RRS James Clark Ross. It is noteworthy that this, the final expedition of 
the BOFS programme, saw new and productive collaboration with other groups of 
oceanographers. The collaboration with the British Antarctic Survey was most 
marked on the James Clark Ross, although we were pleased to welcome two BAS 
scientists to BOFS aboard the Discovery. The major new collaboration aboard the 
Discovery was with physical oceanographers from the WOCE community, whose 
enthusiastic participation helped to make this the most thoroughly 
interdisciplinary cruise of the BOFS programme. Equally welcome and 
enthusiastic was the contribution of visiting American and South African 
scientists to the primary production studies. The full scientific party in 
listed in Appendix A.


A.3 CRUISE OBJECTIVES

The overall objective of the Sterna 92 expedition, as set out in the cruise 
proposal, was "To evaluate the magnitude and variability of biogeochemical 
fluxes (particularly carbon and nitrogen), during early summer in the South 
East Pacific Sector of the Southern Ocean, with emphasis on rates and processes 
in the marginal ice zone".

Four specific objectives were identified:

1. To determine ocean-atmosphere exchanges of radiatively active gases, and the 
   factors influencing such fluxes, over a wide latitudinal range.

2. To investigate the interactions between the biological, chemical and 
   physical 
   processes that control carbon fluxes in the euphotic zone.

3. To assess the impact of sea-ice on biogeochemical fluxes, in order to 
   estimate the importance of climatic feedback effects.

4. To determine the export of biogenic material from the upper ocean and its 
   subsequent fate.

The Discovery programme, with a strong emphasis on underway survey 
measurements, concentrated on the first two of these components, while the 
James Clark Ross concentrated on components 3 and 4 with a programme emphasiing 
station work.


A.4 CRUISE ITINERARY

5/11/92   Discovery arrives in Stanley
10/11/92  Discovery departs Stanley for Berkeley Sound
11/11/92  Bunkering complete: Discovery departs Berkeley Sound
17/12/92  Discovery arrives in Punta Arenas


A.5 SCIENTIFIC ACHIEVEMENTS

The cruise track is shown in Figure 1.1. The first objective listed above was 
addressed by two transects, one across the Drake Passage and one along 
longitude 88°W. Measurements of a wide range of gases in surface water (oxygen, 
carbon dioxide, sulphur gases, halocarbons and hydrocarbons) were complemented 
by biological, physical, and meteorological measurements. The line of the Drake 
Passage transect was chosen to coincide with a WOCE repeat section, thus 
allowing the physical oceanographers to address WOCE objectives simultaneously 
with the BOFS studies. Similarly, the 88°W transect coincides with a WOCE 
Hydrographic Programme line to be worked during 1993, with the hope that the 
BOFS data will complement that of WOCE. Both transects crossed the Subantarctic 
and Polar Fronts and will, when the data are worked up, provide valuable 
information on gas concentrations and fluxes in those areas. The 88°W transect 
is particularly valuable since it is an area where no previous pCO2 
measurements are available.

The second objective was addressed by two intensive grid surveys, together with 
a CTD section, centred around longitude 85°W (see Figure 1). The surveys were 
designed to map an intense phytoplankton bloom which extended southwards for 
approximately 70 miles from a sharp northern boundary close to 67°S. The first 
survey covered the northern edge of the bloom, and the second the southern 
edge. The two surveys overlap, thus providing information on the temporal 
evolution of the bloom. A wide range of physical, chemical, and biological 
measurements were carried out during the survey, as can be seen from the 
detailed scientific reports in section C.

Many features of this bloom remain unexplained at the present time. We had 
envisaged in the proposal that blooms close to the ice edge would be formed in 
shallow mixed layers of lower salinity water, i.e. stabilised by fresher water 
from melting ice: this expectation was based on (scanty) published data from 
the Ross and Weddell Seas, there being no previous work from the Bellingshausen 
Sea to guide us. The bloom we found, in waters which had been largely covered 
by brash ice only a few weeks before, was actually in water more saline than 
the surface water immediately to the north (which contained very little chloro-
phyll;. Our colleagues on the James Clark Ross reported that even at the ice 
edge, which was to the south of our working area, there was no sign of a mixed 
layer stabilised by meltwater. Nutrients were plentiful both within and outside 
the bloom. It is clear that this bloom is unlike those encountered in the North 
Atlantic in previous BOFS cruises.

In scientific terms, the cruise can be judged successful. We have successfully 
mapped a large phytoplankton bloom off the ice edge. In addition, station work 
by the James Clark Ross within our survey area has complemented our underway 
survey measurements with a wide range of in situ rate and particle flux 
measurements.


A.6  LOGISTICS AND EQUIPMENT

A number of problems in this area added to the difficulties of the cruise, and 
limited the amount of scientific work which could be carried out, although the 
major cruise objectives were achieved as reported above. The major problem 
areas are summarised here; a full report has been submitted separately to RVS.

FIRST, the ship. This was the first scientific cruise on the Discovery 
following a major rebuild which added 11m to the ship's length. Prior to the 
cruise, a significant time had been spent on winch trials, but very little time 
had been available for scientific trials. This resulted in some delays and slow 
progress, particularly in the first few days of the cruise, since many systems 
were being used or deployed for the first time.

SECOND, the ship's chef became seriously ill in the early part of the cruise, 
and had to be evacuated to land by the James Clark Ross. This was a major loss 
of science time to Sterna 92 as a whole.

THIRD, the loss of the SeaSoar halfway through the second survey was a major 
blow to the scientific programme. We were fortunate to be able to borrow a UOR 
from the James Clark Ross to enable us to collect at least some data on mixed 
layer structure during the final part of that survey.



B.  CRUISE NARRATIVE

B.1 MOBILISATION

Following cancellation of our original flights (2/11/92) by the RAF, the 
scientific party flew to Stanley in two groups: an advance party of 6 
scientists and 2 RVS technicians (arrived in Stanley 30/10/92), and a main 
party (arrived in Stanley on 7/11/92 after a 30 hour delay in their RAF 
flight). Discovery arrived in Stanley on 5/11/92, 48 hours later than planned, 
having been delayed 60 hours in Capetown awaiting the arrival of spares by 
airfreight. Departure from Stanley on the planned date of 8/11/92 was 
impossible because (i) the late arrival of Discovery and of the main scientific 
party meant that preparation of scientific equipment for sailing was far from 
complete, and (ii) it was necessary to await further airfreighted ship's 
spares, which arrived on the evening of 10/11/92. Discovery then left Stanley 
for Berkeley Sound for bunkering: this was completed on the morning of 
11/11/92. The scientific log begins on departure from Berkeley Sound.

With the benefit of hindsight, it is apparent that Stanley is an inconvenient 
port for RVS ships. Port calls at Stanley leave scientists and RVS staff 
reliant on the RAF, whose Tristars provide the sole air link between the UK and 
the Falklands. Seats on the RAF flights are available only when not required by 
the military, and are not confirmed until a few weeks before departure: we were 
given 4 weeks notice that our request for seats on 2/11/92 could not be met. It 
also appears that delays to the flights are not uncommon: our main party were 
delayed 30 hours at Brize Norton, while the scientific party returning from the 
James Clark Ross BOFS cruise were delayed 24 hours at Ascension Island. It is 
recommended that future Southern Ocean cruises should use ports served by 
commercial airlines wherever possible.


B.2 SCIENTIFIC LOG

Note: all times are in GMT and all dates as day number: see Appendix I for day 
      number to date conversions.

DRAKE PASSAGE TRANSECT
Discovery got under way at 316/1400 following completion of bunkering. Since 
there had been no scientific trials prior to this cruise, the first requirement 
was to test all equipment to be deployed overside. We steamed east in order to 
reach 300m depth for a shallow CTD cast. On reaching this depth (1615), further 
work was required before the CTD was deployed, so we steamed south to remain at 
this water depth, heaving to at 2230 for a shallow CTD cast. This was completed 
successfully, together with firing of Niskin bottles. This was Discovery 
station 12198, the first scientific station for over two years. On the same 
station, a 30L GoFlo cast was also successfully completed, using a kevlar line 
on the starboard gantry. The BAS acoustic fish was given a brief test, 
revealing some problems in the deck unit. Deck lab watches, including regular 
water sampling, started at 317/0200. Instruments on line at that stage were 
pCO2, oxygen, and the autoanalyser. The RVS surface system had also begun 
logging. ADCP calibration was carried out between 317/0030 and 317/0353. The 
James Clark Ross had turned south at that time, having reached 65°S 84°W.

SeaSoar was launched at 317/1355, and was soon undulating well to 380m. It was 
decided to proceed with the Drake Passage SeaSoar and ADCP transect for UK 
WOCE. The SeaSoar cable was shortened to 90m for passage over Burdwood Bank 
(317/1826 to 320/0502). The Turner Designs fluorometer was by this time on-line 
in the deck lab. Lightfish was deployed at 318/1458 using the starboard stern 
crane instead of the Schatt Davit, which towed the fish too close to the ship. 
Even on the crane, the lightfish appeared to tow close to the SeaSoar, which 
was itself to starboard of the centre line. The potentiometric pH system was 
on-line at this stage, and tests of the various batches of TCO2 chemicals 
continued. Major problems were encountered with the oxygen titrator. The size-
fractionated productivity groups began a 3-4 day experimental sequence. 

At 319/0940 the SeaSoar cable was shortened to 200m due to fog, increasing 
again to 600m at 319/1400 in clearer weather. At 319/1652 SeaSoar cable was 
again shortened (to 300m) and speed reduced to 6 knots in poor visibility. The 
first icebergs were sighted on the radar south of the Polar Front in very cold 
surface water(-1°C). The remainder of the SeaSoar transect was completed with 
300m cable out at 6 knots: SeaSoar undulating to 200m but not reaching the 
surface. SeaSoar was recovered at 320/0745. Even in calm water the SeaSoar 
swung to within 18" of the ship's stern on leaving the water, showing the need 
for improved control of the fish on recovery. Discovery then continued on 
passage to Potter Cove (King George Island) for calibration of the acoustic 
fish. At 320/1100 the fog cleared, giving a stunning view of Elephant Island as 
the ship steamed into the Bransfield Strait. At 320/1330, the wire jumped off 
the PES winch sheave during recovery of the acoustic fish. Fast reactions by 
Colin Day, and skilful work by RVS and ship's staff ensured a safe recovery. 
Deck lab watches stood down at 320/1900 following completion of the transect 
into the Bransfield Strait.

POTTER COVE
Discovery anchored in Potter Cove at 321/1233. Another stunning view! The 
initial anchorage dragged, with re-anchoring complete by 1420. The acoustic 
fish calibration began at 1436, and was complete at 2040. Radio contact was 
made with the Argentine research base Jubany, which is situated on the shore of 
Potter Cove: Jane Robertson communicating very effectively in Spanish. At 1700, 
when the weather had abated a little, a small party (David Turner, Jane 
Robertson and Anne Morrison) went ashore to the base, bearing traditional gifts 
(whisky and wall shield) which were well received. We were given a friendly 
reception, although there were few English speakers on the base. Plans to 
entertain some of the base staff to dinner on Discovery, and for more 
scientists to visit the base, were curtailed by worsening weather. Getting the 
ship's boat off a lee shore for return to the Discovery could be described as 
challenging, but was safely accomplished thanks to the efforts of Andy Adams, 
Phil Gauld and Ian Slater. All were back on board at 2050.

BELLINGSHAUSEN SEA TRANSECT
With the Drake Passage transect and acoustic calibration completed, Discovery 
headed for the 85°W longitude along which the James Clark Ross had made their 
transect into the ice. We headed initially for 65°S 85°W, following which the 
intention was to carry out an exploratory transect southwards. SeaSoar was not 
be towed on this westward transect - the physicists had discovered that the CTD 
level A had been incorrectly programmed, and had to reprocess the raw data 
files from the Drake Passage transect. Changes to the code could not be made on 
board (development software not licensed for this ship), so revised code was 
awaited from Barry in time for the next Seasoar deployment. On day 321 one of 
the thermosalinograph temperature sensors failed, leaving us with no high 
quality sea surface temperature measurement (although in the event the ADCP 
sensor gave good data, see section C.4).

Productivity stations (300m CTD followed by GoFlo casts on kevlar) were carried 
out at 1100 on days 322 and 323, complete within 2 hours each time. The 
acoustic fish was recovered at 323/1300 following completion of a shelf break 
transect to allow the ship to proceed quickly to 85°W (the acoustic fish cannot 
be towed safely above 10 knots). Most of the rest of day 323 was spent doing 3 
knots in thick fog! The fog cleared at 2000.

A third daily productivity station at 324/1100 resulted in the loss of a 30L 
GoFlo bottle when the kevlar line broke, for reasons which were not clear. The 
weather then steadily worsened, and by 1540 the lightfish was recovered and the 
ship battened down in 40-50 knot winds. At 1718 the roller door to the water 
bottle annex was stove in by a wave, which proceeded to flood the deck lab to a 
depth of several inches, causing wet feet but no other damage. The ship then 
hove to for repairs, which were complete at 325/0030. During day 324 the Master 
became increasingly concerned about the health of Chef Glyn Davies, and spoke 
at length to the doctor on board the James Clark Ross. As a result, it was 
agreed that the two ships should rendezvous as soon as possible to allow the 
doctor to examine Glyn. On-line measurements and sampling continued in the deck 
lab during passage to the rendezvous.

The two ships met at 325/1600: the James Clark Ross doctor came over to 
Discovery, examined Glyn Davies, and advised that he required urgent evacuation 
to shore on medical grounds. The use of Discovery for this evacuation was 
offered, but the doctor was clear that medical considerations, which were 
paramount in this situation, favoured the use of the James Clark Ross. This was 
a major blow to the scientific programme on the James Clark Ross, which had 
already suffered one medical evacuation during their cruise. Glyn was duly 
transferred and evacuated to Stanley, receiving a blood transfusion on the 
ship. He was later reported to be recovering well in the Falklands. During the 
rendezvous, Nick Owens visited Discovery to discuss plans for the two cruises, 
and intercalibration CTD casts were carried out. The ship remained hove to for 
the evening. On day 326, following a productivity station at 1100, the ship 
remained on station until 1500 to allow completion of welding work to make good 
storm damage. At the same time, the oxygen and alkalinity photometers were 
moved to the cooler climes of the water bottle annex and the hangar 
respectively to try to overcome the problems of intense degassing of samples 
during titration. At 326/1500 the weather was too poor to launch SeaSoar as 
hoped, so we carried out instead a section of 1000m CTD stations every 20 miles 
from 82°W to 85°W along 65°S. The surface water was much warmer at 85°W, 
probably on the edge of the polar front. The westerly section was completed at 
328/0030, with weather still too poor for launching SeaSoar, so a southerly CTD 
section at 20 mile spacings was begun along 85°W. On the southerly course there 
was a heavy swell on the starboard quarter, but there seemed to be no danger of 
being pooped at 10 knots, much to the relief of the productivity groups with 
their incubators on the aft deck.

FIRST SURVEY
The CTD station at 65°40'S, together with productivity casts, was completed by 
328/1324, and with an improvement in the weather SeaSoar was launched and a 
southerly transect begun. We crossed the Antarctic Circle at 2134. By 329/0200 
we had reached 67°09'S, and headed northwest away from the ice during the hours 
of darkness to avoid the need to recover SeaSoar: the ice edge at this time was 
believed to be between 67°30'S and 68°S. A southerly course was resumed at 
329/0800 in improved light and weather: a further northwesterly diversion was 
caused by a blizzard between 1100 and 1150. When the southerly course was 
resumed we were at longitude 86°20'W. South of 67° we encountered high 
chlorophyll (seen briefly also at the southern end of the earlier transect on 
85°W). The James Clark Ross had earlier encountered high chlorophyll at this 
latitude when the area was covered with brash ice. It was decided to survey 
this chlorophyll patch with north-south legs at 8 mile (20' longitude) 
spacings, with northern and southern limits of 66°30'S and 68°S. In order to 
minimise speed reductions due to poor visibility, the survey was arranged so 
that the northern end was carried out at night and the southern end during the 
day. The current tow along 86°20'W was declared to be the first leg of the 
survey. The intention was to work to 84°W, and to ask the James Clark Ross to 
work from 68°S into the ice on their return.

The first 6 legs of the survey worked according to plan, although leg Z 
(85°20'W) was terminated early in order to keep the correct day/night timing. 
Some deviations were required to avoid icebergs, and occasional slowing was 
required in fog. On day 331, Nick Owens confirmed that the James Clark Ross 
would work southwards down 85°W on their arrival (expected day 332). The 
timetable for their ice station work had been reduced from 4 days to 2 days per 
station in view of the time lost. On day 332, it was impossible to keep to the 
southerly course planned for leg C (84°20'W) owing to 50 knot winds and heavy 
seas; the track drifted steadily to the east. At 332/1943 the survey was 
abandoned, and the ship headed northwest into the weather. A further problem 
concerned the pendulum arm attached to the stern gantry: it could be seen that 
the securing bolts had worked loose, rendering the arm liable to come away 
entirely if the remaining supports (hydraulic ram and weld) gave way. Since the 
arm was above the SeaSoar recovery position, SeaSoar could not be recovered 
either.

On day 333 the weather had moderated: at 0940 the lightfish was recovered and 
the SeaSoar cable shortened. The weather was calm enough to allow access to the 
top of the stern gantry, and temporary repairs to the pendulum arm were 
completed by 1727, following which SeaSoar was recovered using a drogue to keep 
the fish away from the stern: this worked very successfully.

INTENSIVE CTD SECTION
The next scientific activity was a CTD section crossing the northern edge of 
the chlorophyll patch: the water to the north is less saline, flowing easterly, 
and has very low chlorophyll concentrations. The survey had revealed a large 
bloom, but nothing like the meltwater-stabilised mixed layer envisaged in the 
proposal! The plan was to carry out casts every 5 miles from 66°45'S to 67°30'S 
along 85°W, with 4000m casts at the ends, 1000m elsewhere. The stations at 
67°05'S and 67°15'S incorporated productivity casts in low and high chlorophyll 
water respectively. The first deep cast was very slow (333/2227 to 334/0543) 
due to spooling problems on recovery, although this problem was successfully 
overcome by Colin Day and Tony Poole, and deep casts ran very smoothly 
thereafter. When the first deep cast was eventually completed, the multisampler 
was found to have fired all the bottles at the same depth. A replacement 
multisampler was installed ready for the next cast at 334/1625. The remainder 
of the section proceeded without incident, and bottle samples eventually 
obtained for all stations. The section was completed at 335/2125. Despite the 
large number of samples, the deck lab crew managed to cope with full sets of 
oxygen and nutrient samples from this section.

SECOND SURVEY
The initial plan for the second survey was a repeat of the first, but moving 
30' further south to map the southern edge of the chlorophyll bloom, and to 
study the evolution of the bloom itself. Contacts with the James Clark Ross 
revealed that the chlorophyll decreased to a low level at about 68°15'S, and 
remained low all the way to the ice edge at 69°S: this indicated that there was 
no value in the Discovery working all the way to the ice edge. The SeaSoar was 
launched at 335/2230, and the ship steamed towards the survey start point at 
67°S 84°W (the survey worked east to west this time, again synchronising the 
north/south cycle with night/day in the same way). However, SeaSoar was 
recovered at 336/0300 before the start of the survey itself, due to incipient 
bad weather. Recovery, in poor conditions, using the drogue once again, plus 
lateral lines, kept the fish well under control. When the weather had abated, 
the SeaSoar was launched once again at the start point (67°S 84°W) at 337/0200 
and the survey restarted.

On the first leg, there was a sharp change in chemistry at about 68°25'S, with 
pCO2 increasing rapidly to equilibrium with the atmosphere, and nutrients also 
increasing sharply. The leg was continued to 68°35'S to sample these new 
conditions fully: however, when the SeaSoar data were processed it was clear 
that this had not been far enough south to define the physical boundary, so 
with effect from leg B (84°40'W) the survey was run from 67°30'W to 69°S in 
order to map the southern boundary fully. The northern boundary of the 
chlorophyll bloom was abandoned in order to keep the survey legs the correct 
length for a repeating day/night cycle. All went well until SeaSoar was lost at 
338/1037 just after completing leg A. Separate reports have been submitted on 
this event.

In order to obtain mixed layer information for the western half of this second 
survey, we requested loan of the UOR, plus driver Ian Bellan, from the James 
Clark Ross. To our pleasure they readily agreed. The James Clark Ross was then 
on station at 68°15'S  85°W, so we steamed along leg Z (85°20'W) to collect 
surface data before rendezvous at 339/2045. The transfers were completed 
successfully, and a new UOR cable was wound onto the SeaSoar winch.

In order to re-establish the day/night cycle correctly, we steamed to 67°40'S 
85°20'W, and launched the UOR at 340/0518. Ian Bellan had advised that tows of 
no more than 8-9 hours should be attempted due to limited battery life in these 
cold waters. The UOR was recovered at 1327, and launched again at 1700 for leg 
Y (85°40'S). However, shortly after commencing this leg, examination of the 
first leg data revealed a problem with the temperature sensor. The UOR was 
recovered and the sensor replaced, launching again at 2300. This leg was 
completed successfully, but a fault was found with the UOR conductivity sensor 
on recovery. Further attention by Ian Bellan solved this problem, and two 
further tows were carried out along legs X and YZ (86°W and 85°30'W), these 
being chosen to cover the western half of the survey as effectively as 
possible. All survey work was completed by 342/0527. Discovery hove to close to 
the James Clark Ross at 342/1230, but no transfer was possible due to poor 
weather. A productivity station was carried out while hove to. The Master of 
the James Clark Ross preferred to wait until day 343 for transfer, and 
transfers were finally completed by 343/1250, although the weather was by then 
poorer than on the afternoon of day 342. 

88°W TRANSECT
This transect had originally been envisaged as a combined SeaSoar/surface 
chemistry/CTD transect. With the loss of the SeaSoar, it was decided to carry 
out CTD stations at 2.5' (150 mile) intervals, with XBT casts every 20 miles, 
and full surface chemistry and biology sampling, with the addition of 
particulate sampling (section C.28). A limited number of productivity stations 
were also worked. The transect was started at 69°S (344/0024) in order to 
assess the extent of the chlorophyll bloom at this longitude. The final station 
at 51°30'S was completed at 349/1315.



C.  SCIENTIFIC ACTIVITIES

Note: all times are in GMT and all dates as day number: see Appendix I for day 
      number to date conversions.


C.1 NAVIGATION 
    (Gwyn Griffiths)

Discovery is presently fitted with five satellite navigation receivers; four 
operate with the Global Positioning System (GPS), of which one is the radio-
code clock, and the fifth operates on the Transit system. Of the GPS receivers, 
the bridge tend to prefer the Racal/Decca receiver for navigation, with the 
older Trimble receiver as a back-up. Scientific navigation information comes 
from the Trimble. The other GPS receiver is a 24 channel Ashtech instrument, 
used primarily for attitude measurements - see below on measuring the ship's 
heading.

DEAD RECKONING
Unlike the Trimble receiver on Charles Darwin, the one on Discovery is not 
supplemented by a rubidium clock that allows fixes when only two satellites are 
visible. The periods of two satellites amounted to about 45 minutes a day in 
the working area. Therefore, the lack of an external clock compromised the 
navigation for a significant period, for both deck officers and scientists. The 
traditional method of coping with an absence of navigation fixes is to use dead 
reckoning, using ship's heading and speed. However, the electromagnetic speed 
log had been unusable since Cape Town. Phil Taylor and Bill Miller traced the 
problem to the sensor unit itself, and searched in vain for a spare unit on 
board. There was no spare - this is unacceptable for such an essential 
navigation tool. There were occasions on which it was necessary to keep the 
bridge informed by telephone from the main lab every 2 minutes of the ship's 
speed through the water from the ADCP.

GPS AVAILABILITY
The availability of GPS coverage, irrespective of quality, during the cruise 
was generally acceptable, indeed had the rubidium clock been available, it 
would have approached 100%. Typically, there were 30 gaps a day of over 1 
minute, with about 6 greater than 10 minutes. However, many fixes were of poor 
precision due to satellite geometry, the cumulative time of poor fixes (pdop>5) 
amounting to about three hours a day. The 'mission planning' software supplied 
with the Ashtech GPS receiver allows graphical and tabular displays of GPS 
availability and it was invaluable in planning the time of the adcp 
calibration, when good GPS coverage is essential. As the almanac data are 
obtained from the satellites each pass, the information is up-to-date and 
accurate.

GPS ACCURACY
The quoted accuracy of GPS with Selective Availability (SA) in operation is 
that a position is within 100m of the true position for 95% of the time (SA is 
the deliberate degradation of the GPS signal for commercial users). The error 
can be estimated from a stationary ship, and this was done whilst tied up to 
the pontoon at Port Stanley. Over an 18 hour period, the standard deviation of 
the longitude was 25.8m, and that of the latitude was 32.5m from the Trimble 
receiver. The comparable figures for the Ashtech receiver were 27.4m and 37.9m. 
This accuracy is acceptable for normal navigation requirements, but when 
deriving ship's speed over the ground for the calculation of absolute 
velocities from the ADCP the degradation introduced by SA is very noticeable.

NAVIGATION PROCEDURE
The raw one second GPS position data from the Trimble were read from the level 
C into PStar. Fixes with a pdop of greater then 5 were rejected, and then 
averaged to provide positions one minute apart. Gaps in the position data were 
filled by linear interpolation between good fixes as no DR was possible. The 
speed of the ship over the ground, and the distance run were then calculated 
from the one minute data. The ship velocity over the ground needed for 
obtaining absolute currents from the adcp were obtained by taking the one 
minute velocities, median filtering and then averaging to 15 minutes, to match 
the adcp averaging interval. Archive copies in PStar format of the raw GPS and 
Transit navigation data were made at the end of the cruise.

MEASURING THE SHIP'S HEADING - GYRO AND 3D GPS
The ship's heading is traditionally measured using a gyrocompass, the new 
Discovery is fitted with two SG Brown Mk1000 instruments, known as No.1 and 
No.2. Heading input to the shipboard computer system was from No.1 gyro 
throughout the cruise. The No.1 gyro was also used as the navigating gyro from 
leaving Port Stanley until 334/1600, when a power failure caused both gyros to 
shut down. As No.2 settled quicker, it was switched to act as the navigation 
gyro.

This cruise saw the first operational use on an NERC research vessel of a new 
system to determine heading based on differential GPS measurements. By 
measuring the relative positions of an array of four antennas to a precision of 
1-2mm over baselines of 6-10m, it can provide heading measurements to an 
accuracy of 0.05°. The technique is free from drift and heading dependent 
errors that can reach 2-3° with marine gyrocompasses. The primary reason for 
installing the system is to provide accurate heading for underway ADCP current 
measurements. However, the GPS heading data are not continuously available, as 
each of four antennas needs to be locked on to four satellites to acquire 
attitude information. With the present incomplete GPS constellation, this 
requirement is only met for part of the day, such that only some 40% of 15 
minute intervals through a day had attitude data from GPS. The system also 
suffers from short-term drop-outs, even in the presence of good satellite 
coverage, and no data are available for tens of seconds whilst the system re-
acquires lock. This may well be due to two of the antennas being located next 
to the lifeboats, and it is suggested that they be raised whilst maintaining 
their rigidity.

The new heading data were used to correct the gyro headings, the gyro then 
acting as an interpolation method between 3D GPS data. A series of four C shell 
scripts running PStar programs (including two new ones) were written to handle 
the attitude data and to apply the corrections to the adcp velocity data. An 
example of where the GPS system showed a significant drift in the gyrocompass 
was along the Drake Passage section. A drift of 2° occurred over the three days 
of the passage.  The effect of correcting the adcp for the heading error was to 
reduce the mean east component of current from 11cm.s-1 to 7.1cm.s-1, the 
difference, 3.9cm.s-1, being due to a spurious component to the left of the 
ship's track caused by gyro error.


C.2  ACOUSTIC DOPPLER CURRENT PROFILER 
     (Gwyn Griffiths, Bill Miller)

INSTRUMENTATION
The RD Instruments 150kHz ADCP was in operation throughout the cruise. Neither 
the instrument or the IBM data acquisition system (DAS) gave any hardware 
problems. The firmware version was 17.10, released on 5 March 1992, and the DAS 
software was version 2.48.  The system PC should not be run in 'turbo' mode as 
this will cause gpib comms errors. VMtest was run whilst at Port Stanley, with 
satisfactory results. The firmware revision incorporates a new 'fish rejection' 
algorithm and minor improvements to bottom tracking.

Air was bled from the transducer space several times during the cruise, 
probably the air was getting trapped during the frequent periods of heavy seas. 
It is recommended that a more automated method of bleeding the system should be 
devised.

Whilst alongside the pontoon at Port Stanley, the ADCP heading was checked 
against gyro compass No.1, and was found to agree to 0.1°. The ADCP temperature 
sensor was also checked against the hull temperature readout on the bridge - 
the ADCP showing 0.9° low. The configuration was 64 by 8m cells, the ensemble 
average period was two minutes, and the auto scaling mode was selected for 
sound velocity correction using the ADCP sea surface temperature.

CALIBRATION
The zig zag course technique was used to calibrate the ADCP whilst steaming at 
8 knots on the continental shelf on passage from the Falklands to the first 
station, each leg of the zig zag was 20 minutes. The scaling factor (A) and the 
misalignment angle (phi) were calculated following the procedure developed on 
previous cruises. However, after the Drake Passage section, it became clear 
that the calibration was incorrect. There was a bias towards the left of the 
ship's track, and currents approaching and leaving a station were inconsistent 
with those on station. The source of the problem, and the solution, took a few 
days to puzzle out. The culprit was found to be the method of calculating the 
ship's velocity from successive 1 minute GPS fixes averaged over the steady 
part of the zig-zags. This method had proved itself using GPS without 
degradation due to Selective Availability (SA). Evidently, with SA in full 
effect, the method did not work, as it introduced a bias into the ship speed 
estimate because of the 'bad' fixes that were thrown out before forming the one 
minute averages. The effect of this editing was to bias the ship velocity. For 
example, setting an acceptance window of ±500cm.s-1 for ship speed rejects 
spikes above 500cm.s-1 but does not reject a spike to -499cm.s-1 from a true 
value of +400cm.s-1. The solution was to calculate the mean ship speed during 
the zig zag from the positions at the start and end of the steady section only. 
This revised procedure gave an amplitude scaling factor (A) of 0.997 with a 
standard deviation of 0.016  The alignment angle error (phi) was -1.55° with a 
standard deviation of 0.65°.

DATA PROCESSING
The majority of the data processing for the ADCP was done using PStar command 
scripts as developed on Vivaldi and previous cruises. The ADCP data were 
processed every 24 hours as one set. After all calibration, editing and merging 
with navigation, it was split into two series: 'on station' covering periods of 
minimal ship speed whilst on CTD and productivity stations, and 'underway' 
covering SeaSoar runs and all associated course changes and manoeuvres. 
Obtainable ranges varied from in excess of 450m down to 100m, primarily related 
to the amount of scattering organisms present in the water column and the 
ship's speed. The greatest ranges were achieved in the plankton bloom and when 
the wind and sea were low - the lowest ranges were on courses steaming into 
moderate to high winds (>25 knots) and at ship speeds in excess of 10 knots. At 
such times there were periods of total data loss, where the %good did not 
exceed 25% at any depth, and there were periods where there was an indication 
of a spurious current along the ship's track. However, the installation is a 
great improvement on the original Discovery installation with the transducer in 
the asdic pod, and subjectively, the performance in poor weather was better 
than, or certainly  no worse than on the Charles Darwin.

RESULTS
Colour contoured velocities were plotted for each section of the SeaSoar 
surveys. They showed clear correlation between the ADCP cross track currents 
and the density structure. In general, the currents showed little shear, the 
features extending to beyond the depth range of the instrument. Maps of the 
currents at 101m along the survey tracks were also produced. Whilst on station 
the ADCP velocity measurements showed much lower scatter than whilst underway.
 
The ADCP backscatter strength forms a broad-brush estimate of zooplankton 
abundance. The two minute ensemble averages for all beams clearly showed 
diurnal migration, and enhanced scattering near fronts and eddies. The contrast 
in scattering across the polar front in the Drake Passage was particularly 
remarkable. Single ping data were also collected from the individual beams. At 
times, these data showed the presence of krill swarms, with spatial dimensions 
such that only some of the beams were affected, and that the 2 minute average 
(covering typically 500m) hardly showed a signature. The backscatter intensity 
of such swarms was at times over 50dB above the background level, and the new 
RD fish rejection algorithm was turned off to avoid data rejection.


C.3  METEOROLOGY 
     (Polly Machin, Gwyn Griffiths, Bill Miller)

INSTRUMENTATION
The meteorological monitoring system used on Discovery is a modified version of 
the metlogger installed on James Clark Ross in 1991 and comprises the following 
instruments:

  (i) an R.M.Young Instruments 05103 wind monitor (sn 11277), including wind 
      vane and anemometer - this is situated on the foremast
 (ii) two Vector Instruments psychrometers, located port and starboard on the 
      foremast (sn 1072 and 1073 respectively), measuring wet and dry bulb air 
      temperatures
(iii) two Didcot cosine collector PAR sensors (spectral range 400-700nm)  
      located port and starboard on the foremast (sn 27150 and 27151 
      respectively)
 (iv) two Kipp and Zonen total irradiance sensors located port and starboard 
      (sn 92015 and 92016 respectively)
  (v) a longwave pyrgeometer, fitted by Keith Birch prior to Discovery's 
      departure from UK waters, also on the foremast;
 (vi) a hull-mounted RS Components platinum resistance thermometer, recording 
      sea surface temperatures
(vii) a Vaisala DPA21 aneroid barometer (sn 465569), located in the main lab

(ii) and (v) are IOSDL instruments replacing components of the standard RVS 
system. The metlogger system was designed as a general purpose meteorological 
data package for use on cruises not requiring meteorological research standard 
instrumentation and therefore complements the IOSDL designed Multimet system 
which is geared towards a higher standard of performance. The Discovery 
metlogger system was developed as part of a joint project between BAS and the 
Instrument and Sensors Group at RVS and uses modular sensor packages and signal 
conditioning. For all sensors apart from the barometer, the conversion to 
digital data takes place at the module (by Rhopoint) and data are transmitted 
to the logger by an RS485 link (data from the barometer are transmitted by an 
RS232C link). Pre-cruise maintenance and inspection of the foremast sensors was 
carried out in Port Stanley,  but no maintenance was done at sea.

DATA PROCESSING
As this cruise was the first time the metlogger system had been used on 
Discovery, considerable thought was given on how best to process the data from 
the various instruments. Unlike most shipboard instruments that have a 
dedicated Level A interface, the metlogger PC emulates a standard Level A 
interface and transmits the data directly to the Level B in Ship Message 
Protocol (SMP). The data are transferred to the Level C and then reformatted 
from Level C to PStar format to allow processing under Unix, using a series of 
pexec scripts based on the set of scripts used for the IOSDL Multimet system. 
However, given the new instrument configuration on this cruise and a number of 
errors and inconsistencies in the Multimet scripts, a considerable degree of 
rewriting was necessary. Additionally, since the emlog was unavailable for the 
cruise, the speed of the ship over ground was calculated from GPS position 
fixes, averaged over one minute. Note that all wind velocities in this report 
are given in meteorological convention, i.e. where the wind is coming from - 
this differs from the standard oceanographic convention for currents etc which 
are defined as where they are going to.

The Unix shell script metexec0 was used to retrieve 24 hour sections of data 
from the Level C and convert them into PStar format. Metexec1 was used to 
calibrate all instruments apart from the aneroid barometer and wind monitor, 
and histograms of the calibrated output were produced for all sensors as a 
range check, to allow editing of obvious spikes. Ship's navigation data were 
merged with the met file by metexec2. Metexec3 would normally be used to merge 
the emlog file and was therefore not used for this cruise. Ship's heading 
(gyro) was merged by metexec4 and a combination of the ship's velocity 
components and heading was used in metexec5 for the conversion from relative to 
absolute wind velocities. Metexec6, an appending script was used to generate a 
full time series from the individual 24 hour files and 10 minute averaged data 
files (vector averaging for the absolute wind velocities) were created by 
metexec7, both for general use by interested scientists and to allow the 
production of time series and vector summary plots.

CALIBRATION
With the exception of the aneroid barometer and wind monitor, which were 
calibrated by the manufacturers prior to installation and were therefore logged 
through to the Level B as calibrated output, all instruments were calibrated 
during PStar processing of the met. data. The calibration algorithms applied 
were derived either from manufacturers calibration certificates or from 
calibrations undertaken by RVS and IOSDL prior to the cruise. Details are given 
in Table 3.1.

Table 3.1  Calibration coefficients for the met. sensors

Measurement      Calibration         Source         Comments
-------------------------------------------------------------------------
wind speed       y = 0.1x            manufacturer   dm.s-1 to ms-1
wind dir         none                manufacturer   calibrated on 
                                                       installation
port wet         a = -23.71101       IOSDL          equation takes the form: 
  bulb temp        b = 6.84806E-3                      y=a+x(b+x(c+dx))
                 c = 5.626587E-6
                 d = 1.077627E-9  
port dry         a = -23.84735       IOSDL          as above
  bulb temp      b = 5.788879E-3
                 c = 5.648462E-6
                 d = 9.076649E-10  
starboard wet    a = -21.63646       IOSDL          as above
  bulb temp      b = 2.580562E-3
                 c = 7.893778E-6
                 d = 6.608683E-10  
starboard dry    a = -20.18834       IOSDL          as above
  bulb temp      b = 9.73387E-4
                 c = 7.835114E-6
                 d = 5.250384E-10  
sea surface      a = 2.9755E-4       RVS (range     equation takes the form:
  temp           b = 0.99189          +5 to +25°C)     y=ax2+bx+c
                 c = 0.26705 
port PAR         y = x/(5*12.86E-6)  manufacturer   5 is the signal 
                                                       amplification factor
starboard PAR    y = x/(5*12.87E-6)  manufacturer   as above
port total       y = x/(2*48.49E-3)  manufacturer   2 is the signal 
                                                       amplification factor
starboard total  y = x/(2*43.63E-3)  manufacturer   as above
  irradiance 
longwave         y = 0.23364486x     IOSDL          includes a *5 signal 
  radiation                                            amplification factor
barometric       none                manufacturer   calibrated prior to 
  pressure                                             installation



PERFORMANCE
Generally, the instruments performed very well, particularly for a first 
cruise. The PC display was very useful and frequently consulted, particularly 
when crossing fronts, during storms and generally by those who resented being 
cut off from reality by dogged portholes! There were, inevitably, a couple of 
problems which have been detailed below, but these are minor details in a 
system which has generally proven reliable and readily usable.

The port dry bulb sensor was very noisy throughout the majority of the cruise, 
particularly at near-zero and sub-zero temperatures; the reason for this is not 
clear. However; the remaining signal is strongly correlated with the port wet 
bulb temperature and is almost certainly worth keeping - the noise can easily 
be flagged out at BODC using an interactive graphical editor. 

The longwave radiometer channel gave intermittent communication errors, which 
most likely arise from the Rhopoint module. Both PAR sensors recorded negative 
irradiances during dark periods. At present it is not clear whether this is a 
calibration offset, in which case the entire PAR profiles will be consistently 
underestimated by approximately 5Wm-2 or whether it is a nonlinearity near 
zero, as suggested by comparison at low-zero light levels with the output from 
the PML PAR sensor  However, this comparison is of limited use due to the 
different configurations of the two types of sensor. (The Didcot instruments 
are cosine collectors; the PML sensor is hemispherical - i.e. 2pi). 
Recalibration of the sensors would be the only unequivocal way to resolve this 
problem.

The conversion from relative to absolute wind velocities is dependent upon a 
continuous record of heading from the ship's gyro. The current PStar processing 
script merges the ship's navigation file to the met file by linear 
interpolation: this is not suitable for a parameter such as ship's heading 
which "wraps around" at 360°. The problem was circumvented on this cruise by 
going back to the original 1 second gyro file, but this is, at best, a 
temporary solution.

Redrawing of the LabTech display on the PC causes an unacceptable loss of data 
acquisition. This is exacerbated by users' impatience with the slow screen 
redraw, sometimes resulting in several redraw commands being issued. Separation 
of the screen handling and data acquisition functions of the system would be a 
welcome bonus - the display is an excellent one, but need not compromise data 
acquisition.

RESULTS
Winds were predominantly northeasterlies and northwesterlies, and were fairly 
stable in terms of direction (although a reversal did occur during leg C of the 
second SeaSoar survey). The second survey was generally blessed with lighter 
winds than the first, whereas the westward transect was more prone to strong 
winds (and greater swell) than the Drake Passage run, with the final part of 
the westward transect / start of the first SeaSoar survey being particularly 
hard hit by winds consistently in the range 10-20 ms-1. The 88°W transect was 
notable for the consistently westerly winds, mostly in the range 8-15 ms-1.

The solar radiation data, although noisy, are encouraging - where there is a 
drop in longwave radiation signalling breaks in cloud cover, total irradiance 
increases relative to PAR (clouds are less "transparent" to PAR). From the 
longwave radiation plots it is apparent that cloud cover is intermittent, but 
generally quite high - there are very few cloud-free periods greater than 12 
hours.

The wind speed and barometric pressure data show that the operational area was 
swept by rapidly changing weather systems, where wind speed was not closely 
related to pressure. Even when the pressure dropped to almost 950mb, the wind 
speed did not exceed 20ms-1, while the period of 15-20ms-1 winds persisted for 
less than 12 hours. There were very few occasions when the wind speed dropped 
below 5ms-1 and these also tended to be of short duration (6 - 12 hours).

FUTURE WORK
Several of the data channels as they stand are fairly noisy and need to be 
rigorously screened on a datacycle-by-datacycle basis; this can probably be 
best achieved at BODC by making use of the available interactive graphical 
editing facilities. The port dry bulb temperature in particular needs careful 
attention. The calibration uncertainties  of the port and starboard PAR would 
ideally be resolved by a recalibration of the instruments. Failing that, 
detailed comparisons of all the available, fully screened PAR and total 
irradiance channels will be necessary to determine and correct the calibration 
offsets. Given a relatively cloud-free day, it should be possible to predict 
the ratio of PAR to total irradiance, given the solar constant and knowledge of 
the appropriate geometries of the hemispherical and cosine collector 
instruments.


C.4  SURFACE TEMPERATURE AND SALINITY 
     (Anne Morrison, Bill Miller)

INSTRUMENTATION
The thermosalinograph (TSG) system consists of a Falmouth Scientific (FSI) 
Ocean Temperature Module (OTM) mounted in the hull, at the non-toxic water 
supply intake, and an Ocean Conductivity Module (OCM) mounted, along with a 
second TM, within a polythene tube, through which the non-toxic supply passes. 
The OTM contains an FSI reference grade PRT. The hull-mounted OTM (sn 1339) is 
located in the forward hold at a depth of approximately 4-4.5m below the water 
surface, 2.2m to the starboard of the centreline: the datastream from this 
module is known as the "remote temperature". The OCM (sn 1331) and second OTM 
(sn 1340) are located on the starboard side of the hangar; they are mounted in 
a polythene tube through which the non-toxic water supply is pumped: this OTM 
measures the "housing temperature". A header tank is located approximately 2.5m 
above (by the winch control room) to supply enough water pressure for adequate 
rate of flow, free of bubbles; the volume flow rate through the tube is 
approximately 20L.min-1, well within the manufacturer's recommendations. The 
flow through the tube is upwards, passing the OTM before the OCM. The 
measurements of temperature and conductivity from all the modules are logged 
through a PC, emulating a level A interface, and on to the level B at 15s 
intervals. The sampling frequency is adjustable, through the computer. The 
temperature resolution of the FSI OTM is 0.0001°C with manufacturer's quoted 
accuracy being 0.003°C in the range -2 to 32°C. Its specifications state that 
is should be stable to 0.0005°C per month. 

During the first few days of the cruise it was apparent that the remote 
temperature module had noise spikes in the data (0.01 to 0.015°C)). On day 321 
whilst investigating this problem by swopping with the housing temperature 
module, the latter module stopped functioning properly. For the rest of the 
cruise the original remote temperature module was used in the housing in order 
to get salinity data, relying on the met. and ADCP sensors for sea surface 
temperature. The problems with the FSI temp modules have been reported 
separately to RVS and to the manufacturers, who are in the process of providing 
modifications.

SEA SURFACE TEMPERATURE
Near-surface temperature measurements were obtained from four different 
sensors: (i) SeaSoar; (ii) met. package sensor; (iii) ADCP sensor; (iv) 
thermosalinograph (FSI) sensor. 

SEASOAR TEMPERATURE SENSOR
This is believed to be the most accurately calibrated and most stable of the 
temperature sensors; its resolution is 0.0005°C and is accurate to 0.001°C. In 
the following sections, the results from the other sensors are compared with 
those from SeaSoar to assess their stability and accuracy. The SeaSoar was 
deployed in the Drake Passage and in the two ice edge surveys. Data from all of 
these surveys are used in this assessment of the quality and calibration of 
temperature measurements from each instrument.

MET. PACKAGE SENSOR
This is a hull-mounted sea temperature module consisting of an RS components 
platinum resistance thermometer (PRT) mounted on the port side (around 4m from 
the centreline) of the hull in the forward hold at approximately 3m below the 
sea surface. 30s averages of 1s data are transferred to the level B system. 
After extraction to the level C computer, the sensor output is corrected 
according to Table 3.1; it should be noted that the calibration was valid only 
down to 5°C, while the temperatures in our survey regions were within the range 
-2 to 8°C.

SeaSoar temperatures at 3m depth were extracted and combined with the 
meteorological measurement of sea temperature. The correlation between the two 
temperatures is quite good at low temperatures, but poorer at the higher 
temperatures in our range of measurements. The met-measured sea temperature is 
steadily higher than the SeaSoar temperatures by about 0.15°C, with standard 
deviation of 0.175°C, which can be applied as a shift to correct the met. 
measurement. The Rhopoint module for this sensor limits its resolution to 
0.1°C, which makes it of very limited value for sea surface temperature 
measurements;  0.05°C or better would be more useful. However, it is worth 
noting that this instrument gives stable results.

ADCP TEMPERATURE SENSOR
This is a PRT mounted in the transducer unit at the forward end of the winch 
room, about 1.2m to port of the ship's centreline, at approximately 5m below 
the sea surface. Temperature is sampled every ping, approximately once per 
second, then averaged over each 2 minute ensemble and logged through a PC which 
emulates a level A interface unit. The 2 minute measurement is then transferred 
to the level B system. No laboratory calculated calibration coefficients are 
available for this device. The temperature resolution of the PRT is 0.012°C, 
and the manufacturer's specification accuracy is 0.2°C within the range -5 to 
45°C.

SeaSoar data between 4.5 and 5.5m below the sea surface were extracted from the 
survey datasets, and merged with the ADCP temperature. Over the Burdwood Bank 
region, massive spikes occur, as great as 0.7°C in magnitude; these are 
believed to occur because there is much structure in the near-surface 
temperature, and if the SeaSoar depth and ADCP measurement depth are different 
by even a small amount, a large temperature difference will be recorded. During 
the first of the two ice edge surveys, a shift in differences from day 330 to 
day 332 cannot be explained. Excluding the large differences at the higher 
temperatures, a temperature dependent relationship is evident between the 
SeaSoar/ADCP temperature difference and ADCP temperature. A linear regression 
gives

                       delta-T = (-0.014 * TADCP) + 0.011

After applying the correction delta-T T to ADCP temperature, the ADCP 
temperature to SeaSoar temperature difference has a standard deviation of 
0.031°C.

THERMOSALINOGRAPH
During the transect of the Drake Passage, both temperature sensors were 
available on the TSG. Comparisons of its temperature measurements with those of 
SeaSoar were made with extracts from SeaSoar data at depths between 3.5 and 
4.5m, because the TSG is taking the temperature of water at around 4m. In 
regions where the SeaSoar was towed at shallow depths (less than 200m of 
cable), for example, over Burdwood Bank, the agreement is poor because there 
was a great deal of structure in the near-surface temperature, which means that 
even a small error in matching SeaSoar depth to thermosalinograph intake depth, 
leads to large differences in temperature. In the region from 55 to 58°S, the 
agreement between the remote temperature and SeaSoar temperature is excellent. 
Within this region, the offset has a mean value of -0.008°C and standard 
deviation of 0.008°C, which can be applied as a correction to the remote 
temperature. At 58°S the SeaSoar was again towed at shallow depth (fog and the 
risk of icebergs slowed the ship down) causing large differences between the 
remote and SeaSoar temperatures. On returning to deeper towing (59°S). the same 
offset as before is seen in remote temperature, but the data is much spikier, 
having a standard deviation of 0.035°C, which was why the remote module was 
removed for investigation. During the two ice edge surveys, only housing 
temperature was available. This does not show a steady difference from SeaSoar 
temperatures, not surprisingly, because heating of the non-toxic supply on its 
way to the hangar unit may vary. Variations in the mean of the difference 
between the housing temperature and SeaSoar temperature are of the order of 
0.1°C.

SALINITY
The output from the conductivity and housing temperature sensors of the TSG 
were processed using PStar program sal83 to give salinity measurements, taking 
the pressure to be 0db at all times. Water bottle samples were taken from the 
non-toxic system at hourly intervals throughout the duration of the cruise, and 
their salinities determined using a salinometer (section C.11). These were 
combined and compared with the TSG salinity data. This showed that the TSG 
salinities differed from the bottle salinities by a varying amount up to 0.1psu 
It was decided that the best way to calibrate the TSG was to first of all 
ignore any bottle salinities which differed greatly from the TSG (probably due 
to errors in recording the time of drawing the sample). Then, the bottle 
samples being sparser in time than the TSG data, the differences were 
interpolated in time to assign a correction factor to each TSG value. This 
correction was then added to the TSG data. The mean difference was -0.091psu, 
with standard deviation of 0.019. Therefore, corrected salinities should be 
correct to within about 0.02psu.


C.5  STARBOARD WINCH 
     (Colin Day, Tony Poole)

A total of 39 CTD operations were required during this cruise. The depths of 
deployment ranged between 150m and 5200m. Considering that this was the first 
fully operational scientific cruise since the Discovery conversion, the 
operation of both the winch and starboard gantry systems proved to be reliable 
and effective. Several problems were encountered on the first deep cast 
(station 12212), as was only to be expected on the first operational use of the 
new Discovery winch to full depth. A slack turn on the cable drum at the start 
of the haul caused cable lay problems which were not spotted until 2500m of 
wire had been hauled in. Several hours were lost while the cable was paid out 
and the drum relaid. This teething problem was resolved thereafter by careful 
setting of the back-tension on the inboard accumulator, and all subsequent CTD 
operations were successfully completed. The winch/gantry system demonstrated 
the potential to significantly reduce the deployment and recovery time, the 
limiting factors in this case being the operational speed of the CTD package 
through the water. The operation of the starboard gantry provided the 
additional benefit of allowing CTD operations to proceed safely and unhindered 
in sea conditions which would have made deployment hazardous on other NERC 
ships.


C.6  CTD OPERATIONS 
     (Bill Miller, Phil Taylor, Raymond Pollard)

INSTRUMENTATION
The main sensor package included an EG&G Neil Brown MK IIIb CTD (sn 01-1195) 
fitted with a new oxygen sensor (sn 2-6-20). Also fitted were a Chelsea 
Instruments Aquatracka MK II fluorometer (sn SA226), a Sea Tech 25D 
transmissometer (sn 79D), and two PAR sensors measuring upwelling light (sn 8) 
and downwelling light (sn 10). In addition a General Oceanics 1015 rosette 
sampler (sn RVS-02) was used for bottle sampling; this comprised 12 x 10L 
Niskin bottles fitted with stainless springs. Finally 2 x SIS 4002 (sn 220 and 
238) deep sea reversing thermometers were fitted to one of the bottles.

Some initial problems were encountered with connectors: the sea cable tail and 
its Y-cable mating connector gave intermittent operation as did the rosette 
bulkhead connector and its mating connector. The sea cable connection was 
bypassed (spliced) and the rosette bulkhead connector replaced. The 
transmissometer mating connector had to be 'adjusted' after one noisy cast.

During the first deep cast (station 12212) the rosette failed (a manufacturing 
fault on the pylon top plate assembly), this was replaced by the spare rosette 
unit (sn RVS-04) which, apart from not confirming, worked fine. Bottle depths 
were confirmed from salinity measurements. The original unit functioned 
properly in the lab after the damaged top plate had been replaced with a new 
assembly and the unit refilled with oil. 

CTD CASTS
CTD casts (see Appendix B for details) can be divided into three kinds:
(i) shallow (150-300m) casts to determine near-surface productivity and light 
levels for productivity casts using 30L GoFlos that immediately followed
(ii) intermediate depth casts to 1000m to determine the upper ocean water 
masses, often used also for light and productivity information
(iii) full depth casts to determine water masses and geostrophic transport 
through the whole water column

After an initial trial cast (station 12198) shortly after sailing from Port 
Stanley, the next five casts (12200-04) were shallow productivity casts usually 
in the morning. One of these (12203) was occupied during a rendezvous with the 
James Clark Ross, who made a CTD cast simultaneously. Duplicate salinity 
samples were drawn and exchanged between ships for calibration and 
intercalibration (see section C.7 for results). Five casts to 1000m (12205-09) 
were then made along 65°S at 20 mile intervals.

On reaching the working longitude of 85°W, the weather was too poor to launch 
SeaSoar, so the CTD section was continued down 85°W for two more casts (12210-
11) at 20 mile intervals. The SeaSoar was then deployed for a 4-day survey, 
following which 12 more CTD stations (12212-23) were occupied along 85°W. These 
casts were designed to span the west to east front which had been repeatedly 
crossed during the SeaSoar survey. The casts were to 1000m at 5 mile intervals, 
to resolve deeper structure than the 400m SeaSoar could observe. The northern- 
and southern-most casts (12212 and 12223) were to full-depth to allow the 
geostrophic transport to be calculated. As noted above, the multisampler failed 
on the first deep station (12212): on analysis of the bottle samples it was 
realised that all had been tripped at the same depth. Indeed, the multisampler 
could not be cocked at the start of 12213, so the cast was done without bottle 
samples to obtain light levels so that productivity work could proceed, and the 
station was reworked with multisampler later as 12214. Similarly, the top 1000m 
of the first deep cast (12212) were reworked as station 12218 once the 
multisampler had been replaced. At the beginning of 12213 it was also found 
that the conductivity cell had frozen, and the cast was restarted once it had 
defrosted.

After 12223, the SeaSoar was deployed for the second ice-edge survey, which 
terminated prematurely with the loss of the SeaSoar. Stations 12224-6 were 
occupied for productivity during the subsequent UOR survey. Finally, stations 
12227-37 were worked along 88°W from 69°S to 51°30'S. Deep stations were 
occupied every 2.5° of latitude, occasionally preceded by a shallow cast for 
productivity work.


C.7  CTD DATA PROCESSING AND CALIBRATION 
     (Raymond Pollard, John Allen, Anne Morrison, Jane Read)

PROCESSING
CTD data were logged in the usual way through the RVS Level A/B/C computer 
system, then transferred into the IOSDL PStar system on another workstation. 
Each cast was split into down and up casts, the former being fully processed, 
the latter used only to obtain calibration values. In processing the SeaSoar 
data (section C.9), it was realised that the Level A software, which had been 
rewritten, no longer obeyed the correct algorithm for matching the time 
constant of the temperature sensor to that of the conductivity sensor in order 
to calculate salinity without bias and with minimal spiking. This problem was 
present in the CTD Level A also, but to a lesser extent because of its slower 
profiling rate, particularly during the first 6 casts, all of which were 
shallow. Revised Level A software was received and tested in time for use in 
all the 1000m casts, starting with station 12205. Final calibrations were 
derived and applied as described below.

CALIBRATION
Initial calibration was done by PStar program 'ctdcal'. Further calibrations 
were applied later, as described below.

PRESSURE
The calibration used was:

                        P = -7.1 + 0.1 * 0.9987653 * Praw

The constant offset supplied by RVS was -5.13287, but this was changed to -7.1 
after noting the value of pressure when the CTD entered the water.

TEMPERATURE
The calibration supplied by RVS was used throughout:

                   T = 0.0044057 + Traw * 0.0005 * 0.9999902

The reversing thermometers (section C.6) were used to record temperature on 27 
casts. After correction, T220 read higher than T238 by between 0 and 2mK, 
giving a difference of (0.85 + 0.82mK) (mean + standard deviation). Thus the 
thermometers agreed to better than 0.001°C in the mean. The comparable CTD 
temperature was between 0 and 8mK higher than the mean of the two thermometers, 
giving a correction to the CTD temperatures (if the SIS thermometers are 
absolutely correct) of (-4.48 + 1.74mK). However, experience has shown that the 
SIS reversing thermometer calibrations are no more reliable than the CTD 
calibration, so the CTD temperatures have not been adjusted. We conclude that 
the CTD calibration was stable throughout the cruise, and that temperatures are 
absolutely correct to within 0.004 - 0.005°C, and are possibly high by that 
amount.

SALINITY
CTD salinity was first calculated using the default conductivity ratio 

                    conductivity = 0.001 * raw conductivity.

To match the differing time constant of the temperature and conductivity cells, 
the temperature response was speeded up by 0.5s. During the first part of the 
cruise salinity samples were drawn from all 12 Niskin bottles, fired at various 
depths. The samples were analysed by three analysts (section C.11). Once it was 
established that the conductivity cell was stable, the number of samples drawn 
was reduced, first to 6 and later to 4 samples per cast. The exceptions were 
the two full depth casts (12212 and 12223) made on either side of a front in 
the Bellingshausen Sea. The first of these had problems and the bottles were 
all tripped together at an unknown depth. Samples from the second cast gave 
greater confidence to the calibration. The difference between discrete bottle 
samples and CTD values was found to vary with salinity so a linear correction 
was calculated. Where the difference between bottle and CTD values was less 
than 0.025 and greater than 0.045 the values were ignored. The calibration 
coefficients calculated were:

                         Strue = SCTD * 0.99347 + 0.257

with a standard deviation of + 0.002

OXYGEN
Oxygen is calculated for the Beckmann oxygen sensor attached to the CTD by

            [O2]/mL.L-1 = rho* Coxy * exp ( - alpha* T + beta * P )
where
                T = a * TCTD + b * Toxy     (with     a + b = 1)

and Coxy and Toxy are the oxygen sensor current and temperature readings 
respectively and P is the CTD pressure. The CTD oxygen sensor was calibrated 
from 126 discrete bottle samples drawn from various depths over 13 different 
casts up to 12223. The data were combined to produce the coefficients 

                 rho=1.276292, alpha=-0.02666 and beta=0.0001494

with a standard deviation of 0.12 mL.L-1 . The residuals from this least 
squares regression varied from cast to cast, averaging from -0.14 to +0.15, and 
over depth, with the greatest residuals in the thermocline. Oxygen temperature 
was weighted to CTD temperature in the ratio b:a=0.25:0.75 for the 
calculations.

Considerable problems were experienced with the oxygen titration unit (section 
C.21), so the bottle values may require further reworking and culling to 
improve the calibration. However, it was noted that the surface values of 
percent oxygen saturation for stations 12209-23 using the above calibrations 
were well correlated with the patchy blooms that were present, ranging from 
104% in the strong bloom to 98% where the bloom was virtually absent. This 
suggests that the oxygens are correct within about 2%.

CHLOROPHYLL
This calibration is reported separately (section C.24)

TRANSMISSOMETER
The A/D converter in the transmissometer scales 4096 counts to 0 to 10V. The 
instrument converts 100% transmittance to 5V. The basic conversion equation is 
thus
                         %T = 0.002442 * 20.0 * count.

Ageing of the light source may change this calibration, so the highest deck 
reading after thorough cleaning of the glass (4.763) was used to correct 
transmittance by comparison with the manufacturer's value (4.744) to give

                     corrected %T = (4.744 / 4.763) * raw %T

Potential transmittance (potran) is then calculated by correcting for the index 
of refraction and compressibility of seawater using in situ values of pressure, 
temperature and salinity. The RVS transmissometer has a 0.25m path length. 
Thus, the beam attenuance per metre, independent of instrument, is given by the 
attenuance divided by path length:

               beam attenuance (m-1) = - ln (potran/100)  / 0.25

LIGHT. 
The CTD was fitted with upward and downward looking PAR irradiance sensors, 
with calibrations supplied as follows:

               dwirr (downward) = 6.6470 - 0.001 * 12.353 * count
                uwirr (upward) = 6.5746 - 0.001 * 12.427 * count.

CTD INTERCALIBRATION BETWEEN DISCOVERY AND JAMES CLARK ROSS
During the first rendezvous between the Discovery and the James Clark Ross an 
intercalibration of CTD and discrete samples was undertaken. This was Discovery 
station 12203 (Appendix B) and James Clark Ross station 27. Two sets of samples 
were drawn on board each ship and duplicates exchanged almost immediately. The 
results are shown in Tables 3.2 and 3.3. The duplicate samples from each cast 
are within 0.004 of each other with a mean difference of better than 0.002 
(0.0017) and standard deviation of ±0.0008. The results from the Discovery 
analysis are all consistently higher than those from the James Clark Ross, 
which should be born in mind if making comparisons between the data from each 
cruise. Comparison between the samples from the different casts reflects the 
variability in the upper ocean structure, and the only real comparison that can 
be made is within the surface layer. This was well mixed down to 50m and it can 
be seen that the samples from the two casts were generally within 0.001psu. CTD 
data in the tables is uncalibrated and so cannot usefully be compared.

Table 3.2 Salinity intercalibration on Discovery samples (Station 12203)

       CTD READINGS   | ANALYSIS (DISCO) | ANALYSIS (JCR)
Wire   Temp  Salinity | Bottle  Salinity | Bottle  Salinity |Difference
out/m  (°C)   /psu    |  no      /psu    |  no      /psu    | /psu
----------------------|------------------|------------------|----------
 250   1.492  34.415  |  B31     34.446  |  S1      34.445  | 0.001
 200   0.860  34.280  |  B32     34.314  |  S3      34.313  | 0.001
 150   0.710  34.177  |  B35     34.187  |  S5      34.186  | 0.001
 100  -1.382  33.941  |  B37     33.976  |  S6      33.976  | 0.000
  80  -1.372  33.782  |  B39     33.819  |  S8      33.818  | 0.001
  60  -1.173  33.765  |  B41     33.801  |  S10     33.800  | 0.001
  40  -1.099  33.763  |  B43     33.800  |  S15     33.799  | 0.001
  30  -1.084  33.763  |  B45     33.799  |  S13     33.798  | 0.001
  20  -1.064  33.761  |  B47     33.800  |  S17     33.799  | 0.001
  10  -1.045  33.761  |  B49     33.800  |  S18     33.798  | 0.002
   2  -1.038  33.761  |  B51     33.799  |  S19     33.797  | 0.002
                      |  B52     33.799  |  S22     33.797  | 0.002
   2  -1.038  33.761  |  B53     33.799  |  S23     33.797  | 0.002


Table 3.3 Salinity intercalibration on James Clark Ross samples (Station 27)

       CTD READINGS   | ANALYSIS (DISCO) | ANALYSIS (JCR)
Wire   Temp  Salinity | Bottle  Salinity | Bottle  Salinity |Difference
out/m  (°C)   /psu    |  no      /psu    |  no      /psu    | /psu
----------------------|------------------|------------------|----------
 250   1.391  34.345  |  14      34.430  |  3       34.432  | 0.002
 200   0.903  34.240  |  15      34.328  |  4       34.324  | 0.004
 150   0.294  34.095  |  16      34.171  |  5       34.173  | 0.002
 100  -1.360  33.873  |  17      33.966  |  6       33.967  | 0.001
  80  -1.384  33.729  |  18      33.818  |  7       33.820  | 0.002
  60  -1.102  33.710  |  19      33.798  |  8       33.801  | 0.003
  40  -1.108  33.711  |  20      33.798  |  9       33.800  | 0.002
  30  -1.052  33.710  |  21      33.798  |  10      33.800  | 0.002
  20  -1.052  33.710  |  22      33.798  |  11      33.800  | 0.002
  10  -1.042  33.709  |  23      33.798  |  12      33.799  | 0.002
   2  -1.032  33.708  |  24      33.797  |  13      33.799  | 0.002


C.8  SEASOAR OPERATIONS
     (Bill Miller, Phil Taylor, Raymond Pollard)

INSTRUMENTATION
The RVS SeaSoar (manufactured by Chelsea Instruments) was fitted with a Chelsea 
Instruments Aquatracka MK II fluorometer (sn SA 240) together with an EG&G Neil 
Brown MK IIIb CTD (sn 01-1181) fitted in a lightweight pressure case. The CTD 
was also fitted with oxygen and light sensors. The oxygen sensor (sn 1-8-27) 
was a new unit fitted prior to deployment. An independent pressure sensor, used 
for control purposes only was also included.

The performance of SeaSoar was good maintaining a yoyo from surface to 400m 
plus at ship speeds between 7.5 and 9 knots, sometimes in heavy swells. In 
periods of bad weather the ship's speed reduced to 5-6 knots and SeaSoar would 
not reach the surface. Data quality was good with only the occasional fouling 
of the conductivity cell.

At 339/1034 the towing cable parted some 20m from the SeaSoar, with the ensuing 
loss of all instrumentation. No warning of impending failure was given, good 
data being collected until 2s before. The details of the loss have been 
reported separately.

SEASOAR SURVEYS
The SeaSoar tows undertaken are summarised in Appendix C. One day after sailing 
from Port Stanley, Falkland Islands, the SeaSoar was deployed on day 317 for a 
trial run in the passage south of the Falklands and north of Burdwood Bank. 
However, as it functioned perfectly, the first survey line, across Drake 
Passage, was run without a break. The cable length outboard was shortened from 
600m to 200m during the transit across Burdwood Bank from 317/1830 to 318/0440, 
and was again shortened to increase the ship's manoeuvrability in poor 
visibility and in the vicinity of ice from 319/0940 to 319/1040 and from 
319/1630 to 320/0707.

The second deployment began as an exploratory run from 65°40'S at 85°W south 
towards the ice edge. It was soon decided to convert the run without a break 
into the first ice edge survey. After a dogleg to move the southward track 
westward to 86°20'W, a survey of 8 legs at 8 mile spacing (20' longitude) from 
66°30'S to 68°S was planned. The central leg down 85°W is labelled A. The first 
six legs (W, X, Y, Z, A and B) were completed without major incident, although 
there were detours to avoid icebergs and it was occasionally necessary to drop 
the speed below the optimum 8 knots in poor visibility.

Weather conditions were poor throughout the first ice edge survey, and on the 
7th leg (C), running south along 84°20'W it was impossible to keep to the 
track. It was also found that a boom attached to the stern gantry had sheared 
several bolts and was in danger of falling onto the SeaSoar cable. Because the 
SeaSoar could not safely be recovered until the boom was secured, and the boom 
could not be secured until the weather abated, the ship steamed slowly into the 
wind on a northwestward track from 332/2000 and later east of north until 
repairs could begin at 333/1100. Although the survey was officially abandoned 
at the end of leg C, the last run across the middle of the survey area has been 
processed as 'stormleg'.

The first attempt at a second survey (335/2230 to 336/0300) was aborted because 
of forecast severe weather, and the ship remained hove to for 24 hours until 
337/0200, when SeaSoar was again successfully deployed. Thus the second survey  
began nearly 4 days after the first had ended. The intention was to run north-
south at the same longitudes as in the first ice edge survey, but from 67°S to 
68°30'S, later extended to 69°S. Also, the lines were worked upstream from east 
to west, as the first ice edge survey had repeatedly crossed a strong front 
with an eastward flowing frontal jet. The first four legs (D, B, C and A, using 
the same labels as for the first survey) were completed without incident. 
Shortly after the end of leg A along 85°W, the SeaSoar was lost.

C.9  SEASOAR DATA PROCESSING AND CALIBRATION 
     (Raymond Pollard, John Allen, Polly Machin, Anne Morrison, Jane Read)

PROCESSING
SeaSoar data were logged in the usual way through the RVS Level ABC computer 
system, then transferred into the IOSDL PStar system on another workstation. 
Data were split into 4-hourly sections, for the convenience of watchkeepers, 
who processed, applied initial calibrations, plotted and edited the data. The 
major task, as always, was to examine the data for offsets caused by biological 
fouling, usually requiring an offset in salinity to recover to a good 
calibration relative to data before and after the fouling event. While this 
procedure is time-consuming, the great merit of the Neil Brown conductivity 
cell is that, once the fouling clears, it recovers its calibration reliably, 
and calibration drift is rare.

Towards the end of the Drake Passage survey, it was realised that the Level A 
software, which had been rewritten, no longer obeyed the correct algorithm for 
matching the time constant of the temperature sensor to that of the 
conductivity sensor in order to calculate salinity without bias and with 
minimal spiking. The value allowed for pressure spiking had also been set too 
small, resulting in good data being discarded whenever the climb or dive rate 
exceeded 2ms-1, which commonly occurs shortly after each turn. The software 
could only be corrected by RVS at Barry. While this was being done, the entire 
Drake Passage survey was replayed from the backups of raw 8Hz data maintained 
by the RVS electronics division. A PStar program to reduce the data from 8Hz to 
approximately one sample per second using the correct algorithm was revived, 
and very clean data with the 16 light channels correctly demultiplexed were 
retrieved. The time base was retrieved by setting the start time, which was 
logged on the backup tape, and calculating the time between samples so that the 
resultant plots matched those originally processed through the Level A. This 
revealed that the CTD sampling rate was 8 samples in 1.02413s. Revised Level A 
software was received and tested in time for use in the ice edge surveys. It 
was not perfect, particularly in regard to demultiplexing of the light 
channels, but the time constants of temperature and conductivity could be 
correctly matched, so the normal Level A route was used for the remainder of 
the cruise. The 4-hourly sections were appended and contoured either every 12 
hours (Drake Passage) or for each leg (ice edge surveys). Final calibrations 
were derived and applied as described below.

CALIBRATION
Initial calibration was done by PStar program 'ctdcal', and further 
calibrations were applied later, as described below.

TEMPERATURE
The calibration supplied by RVS was used throughout:

                     T = 0.00274 + Traw * 0.0005 * 0.9996194

Experience has shown that the temperature calibration is precise and very 
stable, and cannot be easily checked, as it is more accurate than any other 
sensor onboard ship. Any shift would probably manifest itself as a severe 
offset in salinity, which was not observed. No bias could be detected when our 
T/S plots were compared with those of other investigators who had recently 
worked in similar areas (R Peterson, Burdwood Bank, September 1992, personal 
communi-cation; J Swift, Bellingshausen Sea along 67°S, February 1992, personal 
communication). We therefore take the SeaSoar temperatures to be absolutely 
correct to within perhaps 0.003°C, with relative drift during the survey no 
more than that.

SALINITY
The SeaSoar salinity was first given an approximate calibration by use of a 
conductivity ratio that gave reasonable answers for the area being surveyed. 
Bias between down and up profiles caused by the different time constants of the 
temperature and conductivity cells was minimised by choosing a time constant by 
which the temperature was speeded up (for the calculation of salinity only) to 
minimise the hysteresis between down and up T/S profiles. The value chosen was 
0.35s, on the large side for the Neil Brown platinum resistance thermometer.

Relative calibration was maintained by comparing T/S profiles four at a time 
with a master T/S plot which was gradually developed for each survey area. 
Fouling of up to 0.2 or larger in salinity could occur, with frequent offsets 
of order 0.010 to 0.050. These were not always easy to spot, but the contour 
plots proved to be sensitive indicators of offsets (maintained for a profile or 
more) of as little as 0.010. Despite the care that was taken, there were 
occasions, in particular when the T/S relation changed rapidly across the front 
that lay across the ice edge survey area, when determination of the timing and 
magnitude of an offset proved almost impossible to correct with 100% 
confidence. Thus there may be occasions when the salinity is in error by as 
much as 0.030, but we expect the calibration to be within 0.010 more than 99% 
of the time.

Absolute calibration was subsequently achieved by comparison with hourly 
samples drawn from the sea-water supply to the thermosalinograph. The taking of 
the samples was timed to coincide with the SeaSoar surface turn, however, later 
comparisons between the time the bottle sample was drawn and the corrected 
SeaSoar time showed that the two rarely coincided. However, the seasonal mixed 
layer was sufficiently horizontally homogeneous that interpolating between 
SeaSoar profiles gave a good comparison with the bottle samples, except across 
fronts where the surface gradients were higher. These latter data were ignored 
in assessing the salinity correction.

The SeaSoar conductivity cell proved very stable for most of the cruise and 
straight offsets were applied for the first two deployments to bring the 
surface data within +0.010 of the salinity samples. Across the Drake Passage 
salinity was corrected by +0.015 and for the first ice edge survey the 
correction increased to +0.024. On the second ice edge survey the conductivity 
cell displayed a previously unobserved, aberrant behaviour, oscillating wildly 
over a 0.04 salinity range. The cause of this is unknown but it was most likely 
some kind of fouling, possibly by krill, as it recovered eventually. The 
oscillation in salinity made it very difficult to identify offsets due to 
fouling, or to ascertain the relative calibration. Comparison with discrete 
salinity samples showed that the deployment began with a +0.024 offset, but 
after the conductivity cell started oscillating this was masked by a larger and 
more variable offset which appeared to jump randomly between two values about 
0.030 apart. Together with the 0.024 offset, we estimate the correction to be 
0.044+0.015. About half way through the deployment the conductivity cell 
appeared to recover and relative calibration of the potential 
temperature/salinity plots left a correction of only +0.010 to be made.

OXYGEN
Oxygen is calculated for the Beckmann oxygen sensor attached to the CTD by

            [O2]/mL.L-1 = rho* Coxy * exp ( - alpha * T + beta * P )
where
                T = a * TCTD + b * Toxy       (with  a + b = 1)

where Coxy and Toxy are the oxygen current and temperature values, and P is the 
CTD pressure. For deep CTDs, normal practice has been to choose 'a', the ratio 
between the CTD temperature (which has a short time constant) and the internal 
Beckmann unit temperature (Toxy) to reduce hysteresis between down and up 
casts. The constants rho alpha and beta are then chosen by a least squares fit 
to all available oxygen data from one or many CTD casts. This procedure did not 
significantly reduce the hysteresis when tried on the sensor in the SeaSoar, 
because (a) there was very little temperature variation with depth south of the 
Polar Front and (b) the SeaSoar cycles through the oxygen gradient much more 
rapidly than a CTD.

A new procedure was therefore adopted on this cruise. The oxygen current was 
speeded up by the formula

Coxy (t0) =  rawCoxy (t0) + tau[rawCoxy (t1) - rawCoxy (t-1)]/(t1 - t-1)

where t-1, t0 and t1 were successive 1-second values, and the oxygen 
temperature was ignored (b = 0). Several values of tau were tried until 
hysteresis was minimised. It was found that the value of tau depended on the 
depth of profiling, and two values which improved the fit were chosen as 15s 
for the Drake Passage section, and 10s for the ice edge surveys. The least 
squares fit to determine the remaining constants also could not be applied 
because (a) oxygen samples obviously cannot be drawn at the SeaSoar position, 
(b) the least squares fit equations tend to be ill-conditioned. This is so 
because both pressure and temperature tend to vary monotonically with depth, so 
the fit is sensitive to errors in bottle values caused by sampling problems or 
samples not carefully matched to the SeaSoar values in space and time.

Oxygen samples available consisted of (a) those drawn from CTD casts along 85°W 
between the first and second ice edge surveys and (b) two-hourly surface 
samples during SeaSoar runs. The latter were used to choose rho with a typical 
value of alpha (-0.036), but exhibited rather wide scatter with some obviously 
bad sample values possibly caused by difficulties in sampling off the non-toxic 
supply. However, it had been noted that the percent saturation of the 
calibrated CTD oxygens correlated well with patches of high and low 
productivity, ranging from 1.04 (104%) in the major bloom, through 1.00 in 
smaller blooms to 0.98 where the bloom was absent. By choosing rho = 1.472, 
alpha = - 0.036, these percent saturations were closely matched by the SeaSoar 
oxygens in and out of the bloom areas. The pressure coefficient __does not 
affect the fit at zero pressure.

To approximate the vertical profiles of oxygen, we made use of the samples 
drawn on CTD casts at 300m. T/S profiles from the CTD casts along 85°W were 
compared with SeaSoar T/S profiles from the 4-km gridded file (averaged over 
down and up casts) for the 85°W run during the first ice edge survey. As this 
survey crossed and recrossed the front, where the T/S relation changed rapidly, 
profiles could be matched within a few km of similar features. Applying rho and 
alpha given above, with a nominal value of beta = 0.00014, it was found that 
the SeaSoar values were too low. By adjusting the value of beta to 0.0003965, 
the 300m values were brought in line with the sample values to within 0.02 + 
0.10 mL.L-1, where 0.10 is the standard deviation over 10 samples. This is 
equivalent to a near-linear stretching of the oxygen values with pressure, 
because

                         exp (beta * P) = 1 + beta * P
for beta * P << 1.

In the thermocline, accurate calibration is impossible because of the oxygen 
sensor hysteresis. In summary, we expect that our calibrated oxygen values will 
be correct within about 2%, and are more likely to be low than high (if the 98% 
surface saturation values should be increased to 100%, say).

CHLOROPHYLL (See section C.24)

LIGHT (See section C.12)


C.10  UNDULATING OCEANOGRAPHIC RECORDER 
      (David Turner, Ian Bellan)

After the loss of the SeaSoar, the second ice edge survey was completed using 
the UOR loaned by the James Clark Ross. Five runs were completed, four of them 
of about 8 hours duration, which was the maximum battery life at this water 
temperature; the UOR tows are summarised in Appendix D. The second tow, along 
leg Y, was terminated after less than an hour, since examination of the data 
from the first tow revealed a problem with the temperature sensor. The UOR was 
recovered, the sensor replaced, and the tow restarted. On completion, a fault 
was found with the UOR conductivity sensor, although this did not affect the 
other sensors on this tow. Further attention by Ian Bellan solved this problem, 
and two further tows were carried out along legs X and YZ (86°W and 85°30'W), 
these being chosen to cover the western half of the survey as effectively as 
possible. After transfer to PStar, the UOR data was processed in a similar way 
to that from SeaSoar.


C.11  DISCRETE SALINITY MEASUREMENTS 
      (Anne Morrison, Jane Read, John Allen)

The RVS Autosal salinometer (Model 8400A, sn 52395) was used routinely 
throughout the cruise to measure the salinity of samples drawn hourly from the 
thermosalinograph and from most CTD casts. The salinometer was operated at 24°C 
in a controlled environment of 22°C, and proved to be fairly stable. However, 
on day 345 it was extremely unstable, apparently a result of power surges in 
the 'clean' electricity supply, which cut out completely at 0840. Subsequently 
an uninterruptable power supply unit was used to ensure steady power to the 
Autosal, and very stable results were obtained. We suspect that some air was 
being drawn into the cell, leading to slow filling and the odd bubble, but 
because the coils were completely covered, the results were not adversely 
affected. Standard sea water ampoules (batch P120) were used to standardise at 
the beginning and end of each session, which generally consisted of 24 samples: 
this standardising was less frequent than is usually recommended, because we 
had a limited supply of standard sea water. We used the "Salinity Master" Excel 
spreadsheet to generate salinities from hand-recorded conductivity ratios.

We also experimented with the SIS Softsal (Version 1) data management package. 
This system acquires the conductivity ratio data directly from the salinometer 
to a personal computer, where they are converted to salinities by an 
undocumented method. The user can select the allowed standard deviation and 
standardise using standard sea water and substandards. The results are stored 
to datafiles with headers containing information on the status of the Autosal. 
In automatic mode the system requires that three consecutive measurements are 
within the selected standard deviation, with each single measurement being the 
average of ten consecutive readings which must be within another selected 
standard deviation. We found that this can sometimes mean that many flushings 
are required if the standard deviation allowed is small, and the occasional 
rogue value is occurring. This can be overcome by operating in manual mode, 
where the user selects which measurements to accept. The package also includes 
a post-processing facility which uses the control data (standard sea water, 
substandards) to remove zero order drift from the results. We found a few bugs 
in operating the package, but nothing insurmountable. The salinities achieved 
from Softsal were compared with the results from "Salinity Master" for the same 
dataset, and found to be very close, within 0.0005psu.


C.12  OPTICS 
      (Alison Weeks, Gerald Moore)

SEASOAR
Optical sensors were installed on Seasoar to provide data for the 
interpretation of images from SeaWiFS (Sea viewing Wide Field of view Sensor), 
due to be launched in mid to late 1993; the spectral reflectance from surface 
Seasoar data will be used for early development of Southern Ocean bio-optical 
algorithms. In addition, the relationship between the optical properties of the 
ocean and the mixed layer depth (from spectral diffuse attenuation 
coefficients, Kd, Ku, derived from Seasoar data) will be investigated. 

The data from the upwelling and downwelling irradiance sensors on Seasoar have 
been processed for the first time on this cruise. The sensors measured 
upwelling and downwelling radiance at seven wavelengths centred on the SeaWiFS 
bands (410, 443, 490, 520, 550, 635 and 665nm); additionally downwelling PAR 
and upwelling chlorophyll natural fluorescence (683nm) were recorded. The data 
from the seven SeaWiFs bands were used to derive reflectance, Kd & Ku, and the 
data from PAR to derive Kd. The data was processed separately from the other 
Seasoar sensors because it was necessary to pair adjacent up and down casts to 
eliminate the attitude change between up and down casts.

The data obtained from Seasoar were processed to obtain optical profiles from 
the upper 180m of the water column, the exact extent of the profile depending 
on light levels and water constituents. The Drake passage transect produced 287 
profiles, and the first and second surveys produced 441 and 255 respectively. 
Of the sensors, good data were obtained from all but the 665nm sensors and the 
683nm upwelling sensor; these sensors proved insufficiently sensitive. A number 
of problems were encountered in processing the data: first, that the sign bit 
was not passed to the Level-A, causing light levels at the surface to be 
apparently lower than those at depth; and second, the optical data were 
multiplexed whereas the CTD data were not. The CTD data comes from Seasoar in 1 
second averages, but the light data comes in discrete samples within that 
second. Furthermore, the upwelling and downwelling lights are sampled out of 
phase. The maximum rate of climb or descent from Seasoar can be up to 4ms-1. 
The result of this is that reflectance is changed by ±10% in waters with high 
Kd when Seasoar  has a high vertical velocity, and that Kd/Ku is changed when 
SeaSoar decelerates or accelerates. With some software effort these problems 
were resolved, and the entire SeaSoar data set was processed to produce 
reflectance, Kd and Ku.

Preliminary analysis has begun on the first SeaSoar survey. Near surface 
reflectance has been related to chlorophyll fluorescence, which had a simple 
linear quench function applied (section C.24), removing some of the variance 
due to quenching, but not all. The relationship between reflectance and 
chlorophyll fluorescence (Table 3.4) shows the best agreement at 443nm, or the 
peak chlorophyll a in vivo absorbance, indicating a species assemblage with low 
accessory pigment levels for the levels of chlorophyll encountered.

Table 3.4 Chlorophyll-reflectance relationships from SeaSoar dataa

                       Wavelength/nm   r2    alpha   beta
                           410        0.48   1.31   -28.64
                           443        0.66   1.42   -19.16
                           490        0.53   1.31   -31.83
                           520        0.40   1.51   -34.41
                           550        0.01     -       -
                           632        0.04     -       -
                           665          -      -       -

a  parameters quoted for the regression ln[chl] = alpha + beta * R

A comparison of surface Kd from the SeaSoar with chlorophyll from the 
calibrated underway fluorometer (Turner Designs) from the first survey shows 
that the parameters are highly correlated. The average optical depth north of 
the front is 14m, whereas to the south it is only 6m.  

Chlorophyll and reflectance data were compared using the NASA CZCS (Coastal 
Zone Color Scanner) algorithm i.e. chl = A.(Ri/Rj)B, where the wavelengths i,j 
are usually 443nm and 550nm for oceanic waters. The initial fit for the data 
with A = 2.63 and B = -0.88 (r2 = 0.42) was promising; however the exponent B 
was higher than that expected value of -1.27. A comparison against solar 
altitude showed little improvement. When the data was restricted to those 
occasions where there was vector illumination (i.e. clear skies), as determined 
from long wave radiation, and the solar altitude was greater than 70° the 
resulting  exponent was -1.18 (A = 3.11, r2 = 0.79) within error limits of the 
standard result. The scale factor is much higher than the expected 0.51, 
indicating a possible underestimate of chlorophyll, and differences in 
phytoplankton biology. The use of the standard NASA retrieval algorithm would 
result in an  underestimate of chlorophyll in remote sensed images.

Work is in progress relating the above water light field to the data, by 
comparing data from the hemispherical and cosine par detectors. Fully 
calibrated chlorophyll which will be needed to complete the algorithms is in 
preparation (section C.24). The results to date indicate that the SeaSoar light 
sensors have provided a valuable data set to aid interpretation of Antarctic 
remote sensing. 

LIGHTFISH
Lightfish was deployed to provide sub-surface irradiance measurements at 6 
wavelengths for the development of multi-spectral reflectance algorithms for 
phytoplankton biomass for SeaWiFS. It was also used to compare the horizontal 
scales of variation of ocean colour, phytoplankton biomass and physical 
structure. By conducting a spatial survey in an area of 200km2 where the 
phytoplankton biomass is heterogeneous, it will be possible to calculate the 
loss of accuracy of SeaWiFS by the averaging effect of the pixel dimensions 
(1.1km local coverage or 4km global coverage).

The data from the upwelling and downwelling irradiance sensors have been logged  
for the first time via a Level A, along with the other underway parameters. The 
parameters derived from these sensors are reflectance at 6 wavelengths (410, 
443, 490, 520, 550, and 670 nm). Lightfish was deployed for 21 days during the 
cruise (Appendix E). 

The NASA CZCS algorithm for phytoplankton retrieval was applied to uncalibrated 
fluorescence (Turner) data during the cruise, and showed encouraging results, 
with typical r2 values from .5 to.75. Surface plots of reflectance ratios 
log10(R443/R550), and clearly correlate with the areas of high and low 
chlorophyll (high chl = low log10(R443/R550)). We anticipate some exciting work 
comparing the reflectance ratio values from Lightfish with other underway 
parameters sampled on the cruise, such as pCO2, TCO2, and HPLC pigment 
measurements.

A number of problems were encountered with deployment and data acquisition of 
Lightfish. Firstly, as the portable winch which was situated on the starboard 
side of the aft deck had no slip rings (despite timely requests to RVS) it was 
necessary to disconnect Lightfish on every deployment, and every time the depth 
was adjusted. When Lightfish was disconnected, the Level A had to be reset, 
sometimes repeatedly. A slip ring winch would have resulted in an uninterrupted 
data flow between deployments. A second problem was that the ships wiring in 
the four junction boxes used needed checking and tightening. Other problems 
with Lightfish concerned the design of the casing around the optical filters, 
and with the sensitivity of the sensors: these will be addressed at 
Southampton.

It would be useful to be able to check the linearity and calibration of both 
the SeaSoar and the Lightfish sensors on board, by using a calibrated light 
source and a series of ND filters that could be mounted in a Gershun tube.  
Diffuse Attenuation (Kd) from CTD casts.

Kd(PAR) was calculated on CTD profiles to enable optical depths of 100, 50, 
25,10,1 and 0.1% to be determined for obtaining water for primary production 
experiments. The resulting values are shown in Table 3.5 (for full details of 
CTD stations see Appendix B).


Table 3.5 Diffuse attenuation values from CTD casts

                  Stationa  Kd       r(Kd)   Ku        r (Ku)
                  -------------------------------------------
                  12198p  -0.08857  -0.636   b         b
                  12200p  -0.07393  -0.975  -0.08039  -0.885
                  12201p  -0.04908  -0.995  -0.05612  -0.987
                  12202p  -0.04646  -0.992  -0.04835  -0.977
                  12203p  -0.12164  -0.995  -0.13197  -0.993
                  12204p  -0.07612  -0.993  -0.08583  -0.994
                  12205   -0.06934  -0.984  -0.06648  -0.845
                  12206   -0.09345  -0.424   b         b
                  12207p  -0.06709  -0.990  -0.07531  -0.982
                  12208   -0.07451  -0.980  -0.09006  -0.983
                  12209   -0.04122  -0.994  -0.04175  -0.971
                  12210   -0.08549  -0.751   b         b
                  12211p  -0.09685  -0.993  -0.10855  -0.995
                  12213p  -0.05118  -0.983  -0.05422  -0.917
                  12214   -0.04607  -0.975  -0.05802  -0.961
                  12215   -0.04016  -0.993  -0.05438  -0.991
                  12216   -0.03985  -0.991  -0.06344  -0.828
                  12217   -0.05448  -0.993  -0.06336  -0.955
                  12218   -0.06541  -0.951  -0.06022  -0.612
                  12219   -0.06105  -0.923  -0.07438  -0.978
                  12220p  -0.11298  -0.968  -0.09884  -0.997
                  12221   -0.15623  -0.988  -0.19077  -0.978
                  12222   -0.15401  -0.966  -0.16003  -0.984
                  12224p  -0.15625  -0.99   -0.17855  -0.990
                  12225p  -0.12049  -0.995  -0.16295  -0.897
                  12226p  -0.1192   -0.998  -0.12471  -0.997
                  12227p  -0.04602  -0.998  -0.05386  -0.997
                  12230p  -0.04779  -0.999  -0.05045  -0.999
                  12234p  -0.06275  -0.999  -0.07290  -0.994

             a  productivity stations are indicated by the suffix p
             b  insufficient upwelling light for determination of Ku


C.13  EXPENDABLE BATHYTHERMOGRAPHS
      (John Allen, Bill Miller)

The Bathy Systems Inc. XBT program version 1.1 was used on a S.E.S.U. 
(Hydrographic Department) supplied deck unit to record XBT launches.  The XBT 
probes were launched from a Sippican Corporation hand launcher belonging to 
RVS.  The preferred launch position was the stern quarter more in the lee of 
the wind. The connection point located in the Bosun's store was used since it 
provided the best shelter whilst preparing the launcher.  The XBT program on 
the deck unit converted the voltage drop across the probe into resistance and 
thence to temperature using the manufacturers algorithms.  In addition the XBT 
program identified critical turning points on the temperature v depth trace and 
transmitted the information in batches to the GOES satellite (part of the GTS 
network).  The XBT data was transferred to the RVS level A by a 'walknet' 3.5" 
disk as no hard wiring existed between the XBT deck unit and the RVS firmware.  
The transferred data took the form of a string of ASCII temperature values 
recorded at 10Hz. This system is both cumbersome and time consuming, and it is 
suggested that a level A be programmed to receive ASCII coded hex data direct 
from the XBT controller in real time.

The probe depth (D) was calculated from a 2nd order time of flight (t) 
polynomial supplied by the manufacturers of the probes, Sippican Corporation.

                For T7 (760m) probes    D = 6.472t - 0.00216t2
                For T5 (1800m) probes   D = 6.828t - 0.00182t2

Several authors have suggested that these polynomials are poor and have put 
forward alternatives.  Seven XBT's on the northward transect along 88°W were 
coincident with CTD stations, and further work will include the assessment of 
alternative fall rate equations.  However, initial comparison of CTD and XBT 
temperature traces did not suggest any problem existed with the manufacturer's 
equation.

During the bulk of the cruise five T7 and three of the deeper T5 XBT probes 
were launched at various points of interest.  These were:

xp198012 
in 415m of water off the Falkland Islands shelf, partly as an equipment test 
and partly to obtain a temperature profile during the ADCP calibration tracks.

xp198016, 017, 019 
deep XBT T5 drops during the SeaSoar transect across Drake Passage to examine 
the deeper temperature structure. Copper wire found around the SeaSoar cable 
discouraged further XBT launching during SeaSoar tows.

xp198020, 021, 022, 023 
XBTs dropped alternately with CTD casts on the east-west transect along 65° S.

The other 59 XBT probes, all T7s, were launched on the transect up 88° W at the 
end of the cruise. Details of all successful XBT launches are given in Appendix 
H. Gaps in the sequential numbering indicate probe failures for one or more of 
the following reasons:


  (i) INSULATION LEAKAGE 
      During periods of poor weather, when launching from the rear of the 
      afterdeck was felt to be unsafe, the probes were launched from just 
      outside the Bosun's workshop.  Under such circumstances the ship was 
      generally turned into the wind when launching, however the shape of the 
      superstructure was such that a considerable quantity of the copper wire 
      was blown over the afterdeck as it spooled from the launcher resulting in 
      short circuiting of the copper wire.

 (ii) PREMATURE AND DELAYED LAUNCHING OF THE PROBE 
      This generally resulted from poor use of radios when communicating 
      between the main lab and the afterdeck.

(iii) THERMAL SHOCK 
      The first box of T7 XBTs were brought out of the hold and stored at too 
      high a temperature before being launched into sub-zero water 
      temperatures. Two probes are believed to have failed for this reason.

A fourth, and more serious problem encountered with the XBT probes was that of 
wire stretch.  The thin, two core, copper can become stretched during the 
descent of a probe due to snagging at either the spool in the launching 
canister or that in the probe itself.  This has the effect of increasing the 
resistance measured at the deck unit and hence recording erroneously high 
temperatures.  Once the wire has stretched it can of course never recover and 
if detected on a temperature trace, any record below that point of detection 
should be disregarded.  Occasionally wire stretch was obvious, however, more 
often the wire stretch would be very gradual and a temperature would look good: 
in such cases detailed comparison with known T/S curves for the area was 
required in order to identify erroneous temperature profiles.


C.14  MACSAT SATELLITE RECEIVER 
      (John Allen)

This cruise saw the first use of this latest version of Newcastle Computer 
Services satellite image grabbing software and hardware on an RVS ship.  As 
with the previous version, it can only be used on board ship with an omni-
directional aerial which can receive infrared (IR) and visible spectrum images 
from polar orbiting satellites.  The major change with the new version 
concerned hardware as virtually all the receiver switching was software driven 
via a Dartcom micro-controlled interface box and an Apple Macintosh standard 
SCSI connection.  The requirement for a special interface board to be inserted 
into the Macintosh has disappeared and an LC or more powerful Macintosh could 
be used as a platform for the software.  In addition, the new software 
contained several useful new image processing tools; of particular merit were 
the image resampling and the auto contrast options.  The most welcome change 
was the auto-save option, not for the reason that its name suggests, but that 
with this option switched on both the IR and the visible images were recorded 
simultaneously.  A major disappointment, however, was the new geographical 
overlay tool, which, despite great care being taken to input our position 
correctly, failed to be of much assistance at these high latitudes.  The 
suggested overlay was simply not believable and our doubts were generally 
confirmed when on odd occasions land was identified on an image.

Unfortunately cloud cover, as expected at these latitudes, prevented any useful 
thermal images of fronts being made during the cruise.  However, ice extent 
could be identified at times and the tracks of particular storms were followed.  
Only the long near overhead passes were worth receiving as others were not 
geographically relevant and gave poor reception.

Little attempt was made to pick up other than NOAA satellites as it was not 
clear how old our prediction data was for other polar orbiting platforms.  
NOAA's 10, 11 and 12 were successfully received during the cruise.  Table 3.6 
lists all images that have been archived on 3.5" disk.  The image format still 
takes up considerable space and compression routines do not help very much.  A 
shortage of disks forced the making of only one copy of each image and only 
images that could be located geographically and showed significant cloud free 
areas were archived.

Table 3.6 Archived MacSat images

                    Date      Time    IR  Visible  Disk no.
                    ---------------------------------------
                    11/11/92  23:26z  yes  yes     198001
                    14/11/92  20:33z  yes  yes     198002
                    15/11/92  11:31z  yes  yes     198003
                    17/11/92  04:28z  yes  yes     198004
                    17/11/92  06:08z  yes  yes     198006
                    18/11/92  03:52z  yes  yes     198005
                    18/11/92  05:56z  yes  yes     198007
                    19/11/92  10:05z  yes  yes     198008
                    23/11/92  06:36z  yes  no      198009
                    26/11/92  12:38z  yes  no      198009
                     1/12/92  12:00z  yes  no      198010
                     1/12/92  12:34z  yes  no      198010
                     2/12/92  01:37z  yes  yes     198011
                     2/12/92  08:13z  yes  yes     198012
                     2/12/92  03:58z  yes  no      198013
                     3/12/92  16:58z  yes  yes     198014
                     5/12/92  09:27z  yes  yes     198015
                     5/12/92  12:04z  yes  yes     198016
                     6/12/92  22:53z  yes  yes     198017
                     7/12/92  23:15z  yes  yes     198018
                     8/12/92  11:42z  yes  yes     198019
                     8/12/92  13:25z  yes  yes     198020
                     9/12/92  11:20z  yes  yes     198021
                     9/12/92  20:34z  yes  yes     198022
                    10/12/92  10:57z  yes  yes     198023
                    10/12/92  11:40z  yes  yes     198024
                    10/12/92  12:39z  yes  yes     198025
                    11/12/92  10:37z  yes  yes     198026
                    11/12/92  12:17z  yes  yes     198027
                    12/12/92  07:52z  yes  yes     198028
                    12/12/92  11:54z  yes  yes     198029


C.15  NON-TOXIC SUPPLY 
      (David Turner)

The non-toxic intake is drawn from approximately 4m below the waterline, using 
a pump with a nominal throughput of 200L.min-1. This supply is fed to a header 
tank on the hangar top through 2" stainless steel piping, and thence to the 
non-toxic taps in the laboratories. Since a debubbled non-toxic supply was 
required for this cruise, the normal non-toxic taps were not used: instead the 
non-toxic supply on the hangar top was fed directly into a black plastic header 
tank (nominal volume 50L) with a headspace connected to the atmosphere. The 
(debubbled) outlet from this tank was then piped directly to the laboratories: 
hangar (3 taps); water bottle annex (3 taps); deck laboratory (3 taps). We are 
grateful to Tony Poole for installing the necessary pipework in time for the 
cruise. The RVS surface system in the hangar (thermosalinograph, transmis-
someter, fluorometer) was fed by two further debubbling header tanks connected 
in parallel. The arrangement of the supply to the various on-line instruments 
is shown in.

During most of the cruise, a regular sampling schedule from the debubbled 
supply was maintained. The sampling periods are detailed in Appendix G, where 
it can be seen that sampling was suspended on days 320-321 (Potter Cove), days 
326-327 (first James Clark Ross rendezvous), and days 342-343 (final James 
Clark Ross rendezvous). Samples were taken for chlorophyll (section C.23), 
phytoplankton species (section C.23), oxygen (section C.21), alkalinity 
(section C.19), and ammonium (section C.22). Salinity samples (section C.11) 
were drawn from close to the thermosalinograph. From flow rate measurements, 
the water was estimated to take 2 minutes on average to travel from the hull 
inlet point to the deck lab sampling position: this delay was taken into 
account in synchronising water sampling with SeaSoar surfacing. Salinity 
samples (section C.11) were drawn from close to the thermosalinograph.


C.16  pCO2 
      (Jane Robertson)

pCO2 was measured using a gas chromatograph and showerhead equilibrator. Air 
for the GC system was supplied using a compressor in the lab and hydrogen 
through the piped gas supply into the deck lab. The hydrogen line was pressure 
tested before leaving Stanley and was found to be leak free, but subsequently 
several leaks were found on the valve and tap fittings in the gas bottle store. 
It is not apparent whether this was the result of vibration from the ship or 
the change in temperature experienced as the ship went south. The leaks did not 
set off the gas alarm in the gas bottle store, which could have been due to the 
considerable draught in the store as both doors were commonly kept open and/or 
due to a fault in the alarm itself. Subsequent to this event both doors were 
kept closed and a faulty electrical connection on the alarm repaired. It is 
recommended that checks are made periodically on both the gas supply lines and 
the respective alarms.

The equilibrator was placed in the water bottle annex as this kept it close to 
both the de-aerated non-toxic supply and the GC in the deck lab. The water 
bottle annex was kept cold, with auxiliary  heating switched off enabling us to 
keep the temperature in the equilibrator as close as possible to the in situ 
temperature. The pCO2 system required a few modifications as originally it was 
designed to operate on one continuous run of lab bench. After some soldering by 
the PSO the equipment was joined up around a corner. The programme for the 
system was written on board with an original cycle time of 17 mins which was 
reduced to 13 mins following the first survey. During each cycle two 
measurements of the pCO2 in the water were made bracketed by standard and 
marine air measurements. Marine air was approx. 355 ppm ± 2 ppm as measured 
throughout the cruise with no discernible change with latitude, which is as 
expected in the Southern Ocean. The equilibrator caused some problems by 
filling up with water, which was not draining away fast enough to cope with the 
flow. This was partially solved by re-machining parts of it, although it still 
required occasional attention. There was an average increase in temperature of 
1.5° in the equilibrator from in situ temperature, which is four times that 
experienced on previous (temperate water) BOFS cruises. After about one week of 
constant use the two motors on the system sheared and had to be replaced with 
spares. The spares worked successfully with no further problems. The system was 
working almost continuously on surveys and the final transect, giving a pCO2 
value approximately every 6 minutes.

Preliminary calibration with a single standard value was done on board to 
provide data for the first survey to be contoured. The contour map shows 
considerable structure similar to chlorophyll and pH distributions, and related 
to the front that was part of the survey area. This data is only preliminary 
and further calibration using a running standard and temperature corrections 
will be necessary before the data is ready to go onto the Bidston database. 
These corrections and changes should be made in the next few months and the 
data will be sent to Bidston by the end of April along with data from a further 
cruise in the Southern Ocean in Feb/March 1993 (Discovery 200).


C.17  TOTAL CO2 
      (Sean Debney, Jane Robertson)

Total CO2 is a measurement of dissolved inorganic carbon (DIC) and represents 
carbonate, bicarbonate and un-ionised species of CO2. A thermodynamic rela-
tionship exists between TCO2, pCO2, pH and alkalinity and it was an aim of this 
cruise to determine all four parameters sequentially at sea for the first time.

The analytical system consists of two main components, the extractor unit and 
coulometric detector.  A sea water sample is filled from the non toxic supply 
and is fed under gravity to a calibrated pipette. This is discharged into a 
stripping chamber where orthophosphoric acid quantitatively converts the DIC to 
CO2.  The CO2 is purged by a nitrogen carrier gas flow into the reaction cell 
where it is coulometrically titrated to an end point.

It was originally intended to measure TCO2 in continuous underway mode to 
parallel pCO2 and pH but several major problems made this impossible. The 
coulometer chemicals and the WOCE TCO2 standards of known carbon content were 
stored in the deck lab chill store during transit from the UK. At some time 
during this period the temperature fell from the nominal 10°C to below 0°C as 
was evident from the shattered remains of the standard storage bottles. The  
standards were stored in 500mL Pyrex bottles and well insulated with 
polystyrene suggesting that the temperature remained below 0°C for a 
significant period.  Apart from the financial loss, which was in excess of 
£500, the loss of standards meant that the quantity and quality of the science 
originally proposed for this cruise was completely disrupted. The coulometer 
chemicals would also have been subjected to freezing temperatures and it is not 
certain what effect this had on the solutions. The chemical suppliers were 
contacted once freezing was suspected, and they explained that the chemistry of 
the solutions may be sensitive to such a temperature change. These factors 
forced a change to discrete sampling from the non toxic supply, and the 
analysis of up to 5 repli-cates of each sample to give a measure of confidence 
in analytical precision of the technique. There were additional periods of 
system downtime due to various hardware problems in the extractor unit. These 
included the failure of  two valves, contaminated sample lines, defective 
glassware and degassing of the water in the sample bottle, the latter being 
solved by the employment of an insulation jacket.

A continual problem throughout the duration of the cruise was the intermittent 
electrical spikes and surges from the 'clean' supply . This was also 
experienced by other operators in the deck lab, main lab and winch control. It 
is difficult to determine the absolute effect of this variability in supply on 
the perfor-mance of the coulometer, though there were definite periods when 
large surges adversely affected several other pieces of instrumentation 
simultaneously. The synergistic effect of substandard chemical performance and 
variability in power supply undoubtedly reduced the sensitivity and stability 
of the coulometer. This was manifested in poor intra sample reproducibility, 
high unstable blank values and premature demise of the reaction cell. 

In discrete mode the system allowed, at best, a sample throughput of twenty 
samples a day, which seriously reduced the spatial resolution of surface 
mapping compared with that achievable in underway mode. Despite this, the 
initial inter-calibration of raw TCO2, pCO2 and pH data from survey one shows 
no major offset, giving some confidence in the accuracy of all three 
measurements made on this cruise. The forced employment of a discrete sampling 
regime, although vital for quality control under the imposed conditions, did 
not provide a large number of data points for accurate contouring. The plot 
included, however does indicate the delineation of TCO2 across the front which 
compares favourably with contouring plots of pCO2 and pH. (TCO2 data points 
used in contouring are marked on the plot). All TCO2 analyses have been entered 
on the 'underway' spreadsheet, however the data have to be recalculated to take 
into account calibration of the pipette volume and corrected thermosalinograph 
data. These data will therefore not be ready for inclusion on the BOFS database 
at BODC until the summer  of 1993.


3.18  pH
      (Richard Bellerby)

As a master variable, pH exerts an important control on geochemical and 
biological processes in aquatic systems. Seawater pH reflects the status of the 
carbonate system which provides the major short term CO2 buffer. The carbonate 
system can be quantified by measuring any two of the parameters pH, pCO2, TCO2 
and alkalinity. It was the aim of this work to accurately measure pH and in so 
doing validate a novel spectrophotometric method for the on-line, real-time 
measurement of seawater pH. Seawater pH, on the total hydrogen scale, was 
measured using a continuous, on-line multi-wavelength spectrophotometric method 
which utilises the acid-base absorption properties of the sulfonaphthalein 
indicator phenol red. Simultaneously, an on-line potentiometric system was 
available to compare methods on the same seawater. 

pH was measured at temperatures some 20-25°C above in situ, and require 
correction for in situ salinity. Preliminary calculations have been performed 
at selected times in the first survey: coincident pCO2 and TCO2 measurements 
were used to calculate pH, and the result compared with the measured 
spectrophoto-metric pH. The results should be treated with some caution, since 
all three parameters require further salinity and/or temperature corrections. 
The mean residual for all analyses was 0.01pH units with a standard deviation 
of 0.007pH (n=48). This reduces to 0.007+0.005pH when only those values with 
absorption standard deviation less than 0.001 are used (n=24). Continual 
analysis of discrete samples have shown a precision of about 0.005 pH units 
throughout the cruise. Contour plots of raw pH data for surveys 1 and 2 show 
distinct areas of high and low pH which correlate well with features on the 
survey plots of pCO2 and temperature.

Data from the traditional potentiometric method experienced large jumps in 
electrode potential observed on other cruises. This has previously been 
attributed to electrical noise from the ship's motion through the water, 
passing through the on-line system, and the ship's electrical supply. 
Maintaining a constant temperature between the pH buffers and the seawater also 
proved difficult. Spectrophotometric measurements in areas with high 
chlorophyll levels were affected by the particulate load of the seawater. High 
standard deviations were observed in these regions possibly due to settling of 
detritus whilst the sample is held in the flowcell for analysis. Increasingly 
throughout the northward transect, small bubbles were seen to become entrapped 
in the flowcell where previously they had passed through. This was thought to 
be due to organics coating the inner walls. The system was flushed with Decon 
to no avail, and then with nitric acid, which worked only in the short term. It 
is suggested that the on-line seawater should be filtered prior to analysis to 
reduce the particulate load of the supply and that regular flushing with 
hydrogen peroxide may alleviate the problem of bubble trapping.


C.19  ALKALINITY 
      (Susan Knox)

Alkalinity was measured by photometric titration of seawater with hydrochloric 
acid in a procedure developed at Plymouth Marine Laboratory. The indicator was 
bromophenol blue, chosen because its pK value lies beyond the  bicarbonate 
equivalence point, the area of the titration curve of interest. The absorbance 
was measured at 582±2nm in a 100mL sample bottle: the hardware is based on a 
standard oxygen endpoint detector, modified for measurement at the appropriate 
wavelength.

The alkalinity procedure was fully automated until the Metrohm burette 
irretrievably broke down. The only other  burette on board was attached to the 
oxygen titration system and so had to be shared between the two analyses. 
Unfortunately the replacement burette had different external control connec-
tions, with the result that alkalinity titrations had to be run by a semi-
manual procedure. As with the oxygen titration method, a rapid and precise 
photometric measurement was necessary, this time at each addition of acid, in 
order to obtain a good titration curve. Initially all the problems that beset 
the oxygen analysis (section C.21) applied to the alkalinity titration, 
especially degassing which was exacerbated by the release of carbon dioxide as 
the sample became more acidic. By  moving the equipment to a cold area (the 
hangar) the degassing was effectively subdued, as was the analyst in these 
spartan conditions. Thereafter it became apparent that the movement of the 
ship, either itself or in its effect on the water in the water jacket was 
causing the light signal to vary significantly so that no reliable alkalinity 
data was forth-coming. Several series of samples were analysed when the ship 
was hove to and at quiet intervals but the amount of successful data was very 
scanty.

The alkalinity procedure itself has been shown to work but more modification is 
necessary before it can be used at sea.


C.20  ON-LINE OXYGEN 
      (Susan Knox)

On-line oxygen was measured using an Endeco type 1125 pulsed dissolved oxygen 
system loaned by Southampton University Department of Oceanography. The oxygen 
sensor comprises a Clarke type polarographic cell containing a silver anode and 
a gold cathode surrounded by  electrolyte and covered by a Teflon membrane. Two 
such sensors were mounted in a perspex container through which the bubble free 
non-toxic supply flowed at a rate of 2 litres per minute. The sampling rate was 
micro-processor controlled and was set to  once every 5 minutes. Four sensors 
were provided and each had been pre-calibrated in low temperature seawater at 
Southampton University. To provide extra calibration points, samples were taken 
from the sensor container outlet every 2 hours and analysed by Winkler titra-
tion. A more detailed analysis of the calibration data is necessary before 
absolute oxygen values can be extracted from the Endeco output.

At the start of the cruise the pair of sensors did not track one another, with 
one sensor steadily drifting downwards and the other appearing to respond as 
expected. A replacement electrode with fresh electrolyte and a new membrane 
also showed the same downward drift . At first this was thought to be due to 
the low temperature of the seawater, about 1°C, but the same drift was also 
seen in distilled water held at ambient laboratory temperature. A closer 
inspection of the sensors revealed the gold cathode to be heavily tarnished. A 
light application of crocus paper removed the film and thereafter the 
electrodes performed satisfactorily. As a result of the delay in getting the 
sensors to work continuous oxygen data is available from one electrode for the 
second box survey and from two sensors for the 88°W transect north.


C.21  OXYGEN TITRATIONS 
      (Susan Knox)

Discrete oxygen samples were taken from the non-toxic supply at 2 hourly 
intervals throughout the cruise, and from Niskin bottles on selected CTD casts. 
These samples were analysed by Winkler titration with a photometric endpoint 
detection using equipment loaned from Queens University, Belfast.

At first the system was unworkable because of air leaks in the Metrohm burette. 
These were traced to the washers which proved to be incompatible with the tube 
terminations. Once the washers were removed the system became airtight and 
usable. The next area of concern was the endpoint detection. It was often very 
difficult and at times impossible to get an endpoint due to the degassing of 
the sample as it warmed up from its sampling temperature of 1°C or less to the 
laboratory temperature of 23°C. Minute gas bubbles coated the sides of the 
sample bottle and floated free in the solution causing interference with the 
light path. Neither allowing the sample to warm to ambient temperature before 
analysis, nor filling the water jacket with ice cold water helped in any way. 
The eventual solution was to move the equipment to a cold environment (the 
water bottle annex) with an ambient temperature near that of the sample. This 
solved the gas bubble problem, and in doing this the water jacketed measuring 
cell was sited fore and aft rather than athwartships as it had been in the 
laboratory. This reduced the slopping of the water across the light path 
whenever Discovery rolled, which the new ship has a marked tendency to do, and 
reduced the noise on the photometer output.

The oxygen titration data available at the end of the cruise require further 
correction for (i) the standardised thiosulphate concentration, and (ii) the 
correct calibrated bottle volumes, which were not available from Belfast during 
the cruise. The Antarctic surface waters were generally saturated with respect 
to dissolved oxygen and the CTD casts in this area showed the presence of a 
very well marked  oxygen depletion layer below about 200m.  Along the 88°W 
transect going north the oxygen minimum layer occurred at 1500m. 


C.22  NUTRIENTS 
      (Bob Head)

A Chemlab based autoanalyser system (ex North Sea Community project and Charles 
Darwin cruises 46/90 and 47/90 of the BOFS programme) was used to measure con-
centrations of nitrite, nitrate, phosphate, silicate and ammonium. The methods 
used were the standard wet chemical methods developed at PML. The colorimeter 
outputs were logged to a Siemens chart recorder and a level A interface. The 
autoanalyser system was used in an online mode with the seawater input being 
taken from the Turner designs fluorometer outflow (section C.23): the fluoro-
meter output was logged to the same chart recorder to enable visual comparison 
and fluorescence and nutrient changes). Change-over to discrete sampling mode 
was effected by a three way valve in the autoanalyser sample input line to 
enable the input of both calibration standards and discrete samples from CTD 
casts or productivity experiments (sections 3.31 and 3.32). Nutrient 
calibration was effected by daily running of standards dissolved in low 
nutrient seawater (collected at Berkeley Sound, Falkland Islands) until a 
constant plateau was attained. Milli-Q water was used as a reagent blank. 

Discrete sample analysis required human autosamplers, running each sample for 4 
minutes interspersed with a 1 minute wash in low nutrient seawater.  
Calibration was effected by running standards in the same way. Ammonium samples 
were run manually using 10mL seawater samples in test tubes, addition of 
reagents and colour development in the dark for 3 hours. The sample was then 
introduced into the flowcell (minus the debubbler) with a 20mL syringe. Optical 
densities were recorded as chart units. The main bulk of samples was composed 
of the CTD section across the working area on 85°W and samples from 
productivity experi-ments (sections 3.31 and 3.32). Workup of the discrete data 
should be completed in approximately 6 months. Work up of the on-line 
measurements will be undertaken by BODC.

In the working area typical maximum nutrient values were 35_m nitrate, >50_m 
silicate and 2_m phosphate. Ammonium values were low with maximum values being 
of the order of 0.6-0.7_m. In the high bloom areas during the two surveys 
nutrient reduction could be observed corresponding to changes in chlorophyll 
fluorescence. Some small surface ammonium increases could be detected in areas 
of intense krill swarms. The high values of nitrate and silicate were an 
analytical problem which needed to be resolved as the system was set up 
initially for nutrient levels encountered in the North Atlantic. Nitrate and 
silicate concentrations were physically reduced by incorporating a Milli-Q 
diluent line in a ratio of 1:4. Due to the set up of the analyser with 50mm 
flowcells it was observed that for both these analytes that there was a non-
linear relationship between concentration and output. Concentrations of nitrate 
and silicate will therefore have to be calculated using a nonlinear curve fit. 
The main reason for non linearity at high concentrations was assumed to be the 
provision of a 50mm flowcell, use of a 15mm cell would have improved the 
precision of calibration values. During the cruise the ammonium channel gave 
trouble due to precipitation of reagents in the analytical line. The reason for 
this was unclear, but it was certainly due in part to the low water 
temperature.  There was also contamination of the reagents in the deck lab 
which manifested itself as a steady upward drift. Due to all these factors, 
ammonium was measured manually as described above, with samples taken hourly 
from the non-toxic supply.

The Chemlab system has now been around for a number of years and is really 
overdue for refurbishment and updating. As the autoanalyser is a multi-user 
piece of equipment, there is a need for a manual together with parts lists and 
suppliers to be written and supplied with the equipment as not all users are 
expert in automated analysis. Hopefully in the near future some funding can be 
made available to update a number of the components to enable continued use and 
better reproducibility.



C.23  ON-LINE FLUORESCENCE, CHLOROPHYLL, AND PHYTOPLANKTON SAMPLING 
      (Bob Head, Bill Miller)

On-line chlorophyll fluorescence was measured with a Turner Designs model 10-
005 rack mounted fluorometer (kindly loaned by M J Fasham of the Rennell 
Centre) fitted with a 10-020 high volume flowcell with a debubbled seawater 
input at a flowrate of 3 litres per minute. The fluorometer output was recorded 
on a Siemens chart recorder and also logged to a level A interface. In 
addition, a fluorometer (sn 229) and transmissometer (sn 99D) were incorporated 
in the RVS 'surface' system in the hangar (see sections 3.4, 3.15) These were 
logged by the same system as the thermosalinograph (section C.4), and ran 
virtually continuously through the cruise, outputting their data in SMP format 
to the level B system. There appeared to be no problems communicating directly 
with level B. During mobilisation a communication error with the 
transmissometer and fluorometer Rhopoint modules was indicated. This was found 
to be a software  error and was soon rectified. At present, the FSI and 
Rhopoint modules communicate through separate ports on the PC. Future 
modifications to the FSI modules should allow the system to be configured using 
a single port as was originally planned.

More than 800 discrete samples were taken for chlorophyll 'a' and phaeophytin 
determinations. Samples were taken both from the fluorometer output at hourly 
or 2 hourly intervals, and from CTD and GoFlo casts. At the same time 100mL 
preserved samples for phytoplankton species identification were taken into both 
Lugols iodine and borax-buffered formaldehyde. Analysis of these samples will 
be used not only to identify the distribution of the different  species of 
phytoplankton in the cruise area, but also to estimate levels of phytoplankton 
carbon.

Analysis of chlorophyll 'a' and phaeopigments was carried out by filtering 
100mL aliquots of seawater onto 25mm GFF micropore filters and extraction by 
10mL 90% acetone for a minimum of 15 hours. Prior to analysis a further 
addition of 10mL acetone was made. Analysis was carried out on a Turner Designs 
10AU fluorometer (QUB Belfast) fitted with a 25mm cuvette system: the 
chlorophyll fluorescence was measured before and after the addition of 10% 
hydrochloric acid. Fluorometer calibration was carried out with pure 
chlorophyll 'a' standard (Sigma C5753 from spinach). Calibration checks  were 
made at regular intervals during the cruise. The results are reported as mg.m-3 
chlorophyll 'a' and phaeopigments. The underway discrete chlorophyll 'a' 
analyses have been used to calibrate the Turner Designs on-line fluorometer, 
the Chelsea Instruments Aquatracka fluoro-meter mounted in the tank in the 
hanger area, and the SeaSoar fluorometer. Similarly, the chlorophyll 'a' data 
from CTD bottle casts have been used to calibrate the CTD sensors (see section 
C.24 for details of these calibrations).

All chlorophyll analyses were completed during the cruise. The time scale for 
work up of the Lugols and formaldehyde preserved samples is uncertain but it is 
hoped that a proportion of the samples may be completed before the end of 1993. 
In the survey area, chlorophyll 'a' values were low both to the north and south 
of the bloom (<1mg.m-3) whilst in the main bloom values greater than 7mg.m-3 
were observed. Phaeopigment values were generally low, both in the bloom and 
non-bloom areas. 


C.24  CHLOROPHYLL CALIBRATIONS 
      (Gerald Moore, Alison Weeks)

CTD
The fluorescence from the CTD sensor was quenched at the surface. Data for an 
initial calibration was selected where PAR was below 2Wm-2. On this basis two 
distinct calibrations were determined, for stations 12198 and 12200 combined, 
and for stations 12201 and beyond:

ln[chl] = -8.0345 + 6.313V - 1.2020V2     (stations 12198, 12200; r2=0.95)
ln[chl] = -7.5940 + 4.603V - 0.5721V2      (stations 12201 et seq; r2=0.88)

where V (volts) = fluorescence raw counts * 0.002441

The difference in calibration is due to a change in species assemblage. Both 
calibrations were found to be non-linear at low chlorophylls or depths greater 
than 50m. The calibrations are given below. There were insufficient data to 
determine a reliable quench correction factor. When the individual calibration 
curves are combined the overall variance explained was 95%, which gives an 
upper bound on the variability of the chlorophyll analysis. 

ON-LINE
The initial intention was to use the suite of programs developed during the 
Vivaldi cruise by John Hemmings (Rennell Centre). However, there were problems 
in using these programs due to instrument errors, the light regime, and the 
species assemblages encountered during the cruise. John Hemmings' methodology 
was used whenever possible, as discussed below.

The initial problem was caused by the Turner Designs fluorometer. The first 
stage was to establish an instrument offset, which proved to be difficult due 
to range switching of the fluorometer. The new level A software automatically 
adjusts the recorded data for the instrument range setting. This assumes that 
the gain for each range is calibrated exactly, and that no offsets occur 
between ranges. Without processing a set of standards it was not possible to 
determine if the gains were correctly calibrated, however a simple manual range 
check showed that there was a change in offset between ranges. The range is not 
recorded by the level A, so the range change was determined by examination of a 
probability plot of the output from the fluorometer. This showed a range change 
at 6.5 and 12.7V rather than the expected 5 and 15.8V. For a preliminary 
calibration, the ranges identified were adjusted by inter-calibration with the 
Chelsea Instruments fluorometer, a second underway sensor. A full check will 
involve a test of the instrument base and manual extraction of the range 
changes from the chart recorder output.

With the Turner and Chelsea datastreams adjusted it was possible to determine 
an offset and an initial calibration. From this the chlorophyll  yield was 
determined at the light minimum (PAR less than 5Wm-2 as logged by the met. 
system, section C.3).  This "night" yield was adjusted for changes in region, 
by using cluster analysis. Three regions were determined: the Drake Passage 
transect; Potter Cove to the survey grid; and the survey grid. These areas 
provided a base to adjust the "dark" chlorophyll for quenching. When John 
Hemmings' model was used it was not possible to get a reliable fit between 
fluorescence yield and PAR. Six other theoretical and empirical models were 
tested on the data. None of these proved able to remove the effect of light in 
a reliable manner. The cause of this problem is twofold: first the particular 
characteristics of the area; and second the statistical bias produced by the 
operational need to survey the high chlorophyll area in the daytime (see 
section B). There are two possible methods to correct the data: first is to use 
an empirical fit of the daily yield to a smooth function and correct the 
chlorophyll on a sample to sample basis; the second is to develop a better 
model of the quenching, to account for latitude and variation in 
photoadaptation. For preliminary data analysis, the calibrations developed for 
the Chelsea and Turner fluorometers for night time are detailed below.

Turner:     (output is V volts)
Designs     Instrument offset 5.9240; calibration after offset correction is:
                [chl] = 0.009853V + 0.004236V2 (r2=0.86)
            Region adjustments (scale factor)  6.0849 (Drake Passage)
                                               4.2519 (from Potter Cove)
                                               0.9622 (survey area)

Aquatracka  (output X is exp(volts))
            Instrument offset 2.8368; calibration after offset correction is: 
                [chl] = 0.02772X + 0.001753X2  (r2=0.91)
            Region adjustments (scale factor)  3.4571 (Drake Passage)
                                               1.4859 (from Potter Cove)
                                               0.9416 (survey area)
SEASOAR
The Chelsea Instruments fluorometer on the Seasoar showed a good relationship 
with the underway samples when data were selected for PAR less than 2Wm-2. Two 
linear calibrations were obtained, one for the Drake Passage transect and one 
for the survey area. One of the main problems with the calibration was the poor 
time recording for the samples, which resulted in about 5% of the values being 
unusable because it was ambiguous as to which undulation they corresponded to. 
The SeaSoar chlorophyll was subject to the same problems in determining a 
quench function as discussed above. The calibrations are given below.

       Drake Passage transect:  ln[chl] = -2.5067 + 1.1071V  (r2 = 0.81)
              Survey area: ln[chl] = -4.8823 + 1.8957V (r2 =0. 92)

where V (volts) = fluorescence raw counts * 0.002441

DISCUSSION
The major problem was caused by the range changes in the Turner Designs 
fluorometer. This could have been solved if the ranges were available on the 
level A datastream, for incorporation into a calibration model, and this is 
strongly advised. Another option is to keep the instrument on a single range; 
this would give a resolution of 0.2% for the selected range, which is 
sufficient on a 0-10 mg.m-3 nominal range given the accuracy of the instrument. 
Although the nature of the present survey caused special problems, it is 
doubtful that full calibration of chlorophyll fluorescence data can be achieved 
in near real time except on cruises which return to a previously studied area.


C.25  BIOGENIC SULPHUR COMPOUNDS 
      (PHIL Nightingale, Wendy Broadgate)

The main aim of this work was to determine the surface water concentration 
field for dimethyl sulphide (DMS) in order to estimate sea to air fluxes. Of 
particular interest was the opportunity to investigate the influence of the 
large seasonal algal blooms in the Antarctic ocean on the global flux of marine 
biogenic sulphur. A secondary aim was to determine the inter-relationships 
between DMS, its precursor dimethyl sulphoniopropionate (DMSP) in both the 
particulate and dissolved phases and chlorophyll, temperature, salinity, 
phytoplankton species and other parameters such as primary productivity.

METHODOLOGY
Samples were predominantly collected from the ship's non-toxic seawater supply, 
sampling being coordinated with discrete measurements of oxygen, alkalinity, 
chlorophyll and preserved phytoplankton.  In addition, comparative samples of 
surface seawater were collected from CTD casts.  All samples were processed 
within 10 minutes of collection (except for deep water casts where samples were 
stored underwater at in situ temperatures for a maximum of 6 hours).  Volumes 
of seawater used for DMS analyses were typically between 100 and 200mL 
reflecting the low levels observed in the study area.  All samples were 
filtered using AP25 depth filters, the filter then being used for DMSP 
particulate analysis.  These were stored in the dark in a NaOH solution (~ 
0.3M) for a minimum of six hours.  Dissolved levels of DMSP were determined by 
addition of 35mL of seawater to 1mL of 10M NaOH and samples stored as for DMSP 
particulate. DMS was extracted from samples and pre-concentrated using purge 
and cryo-trap techniques and subsequently analysed in situ by dual channel 
flame photometric gas chromatographic techniques.

RESULTS    
Over 150 samples were successfully analysed for DMS and DMSP in both the 
particulate and dissolved phases. These were collected with a 4 hourly 
frequency on the transects south from the Falklands and west from Elephant 
Island to the Bellingshausen Sea. Extremely low levels of these compounds were 
encountered, concentrations were typically between 5 and 25ngSl-1 and 150 to 
1000ngSl-1 for DMS and DMSP (particulate) respectively. Levels of DMSP 
(dissolved) were regularly below the detection limit, estimated to be 300ngSl-
1.  The sampling frequency was doubled during the first bloom survey and 
considerably elevated levels of DMS and DMSP were observed in this region.  
Preliminary data analysis suggests  the maximum DMS concentration to be 
300ngSl-1, over an order of magnitude lower than levels typically encountered 
in algal blooms in the North Sea and North Atlantic.

Unfortunately, equipment problems encountered close to the end of the first 
survey lead to the cessation of both DMS and DMSP determinations, permanently 
in the latter case.  The fault appears to be electronic and the GC will require 
specialised attention back in the UK. Total loss of detector sensitivity 
coincided with other equipment failures and the problem may well be related to 
surges and/or spikes in the ship's electrical supply.  Damage to one channel of 
the FPD GC initially appeared to be of a temporary nature only and DMS analyses 
were resumed after a loss of nearly four days. However, detector sensitivity 
was unusually unstable and data collected during the second bloom survey will 
require careful screening in the UK to assess it's validity.  This second 
channel ceased to work permanently during the 88°W transect, and DMS 
determinations were reluctantly abandoned.


C.26  LOW MOLECULAR WEIGHT HALOCARBONS 
      (Phil Nightingale)

A combination of electron capture detection and megabore capillary analytical 
techniques enables the concentrations of a wide range of halogenated compounds 
in seawater to be determined.  The sources of these compounds can be 
predominantly natural (eg methyl iodide), purely anthropogenic (eg carbon 
tetrachloride) or may be a combination of both (eg bromoform).  One of the main 
aims of this cruise was to obtain data on the spatial variation in levels of 
halocarbons in areas where no data have been reported.  Data obtained will be 
used to obtain estimates for sea to air fluxes.  In addition, this cruise 
offered a unique opportunity to investigate the marine source of biogenic 
halocarbons in particular, methyl iodide, chloroiodomethane, dibromomethane, 
bromoform, dibromochloromethane, dichlorobromomethane and chloroform.  
Previously the only field data to provide firm evidence for natural production 
of these compounds has come from coastal areas (such as the North Sea ) where 
macroalgae known to release halocarbons are present.  Data from a bloom area 
where both anthropogenic and macroalgal sources are absent will be invaluable 
in determining the role of phytoplankton in the global cycling of bromine and 
iodine.  Deep water casts are also useful in this respect as the presence of 
these compounds in waters where carbon tetrachloride and freon-11 are absent 
indicates that they must have substantial natural sources.

METHODOLOGY
Underway samples were collected from the non-toxic supply and coincided with 
sampling for DMS, chlorophyll, oxygen and other parameters also measured 
discretely.  Samples were collected from CTD rosette casts, using steel-sprung 
Niskins, varying in depth from 2 to 4500m.  Initial comparison of surface 
waters collected from the non-toxic supply and from the CTD indicate that 
although the former is heavily contaminated with F11 it is suitable for 
determination of most low molecular weight halocarbons.  Samples were analysed 
within 10 minutes  with the exception of deep water casts where samples were 
stored under water at ambient seawater temperatures for up to a maximum of ten 
hours.  Halocarbons were extracted from seawater by purging with nitrogen doped 
with hydrogen (1%) that had been precleaned by passage over a palladium 
catalyst.  Samples were preconcentrated  by trapping above liquid nitrogen and 
separation achieved using a DB 624 megabore column.  Detection was by electron 
capture and chromatograms were collected and archived using a specialised data 
software package.

RESULTS
No results are available for the transects south from the Falklands to Elephant 
Island and west from there to the Bellingshausen Sea.  The extraction system 
was badly contaminated and a new line consisting of entirely new valves, tubing 
and fittings had to be constructed.  In addition, peak separation by the DB624 
column originally used was found to be unacceptably poor and a new column 
plumbed in.  Problems were also encountered with one of the PCB's in the GC and 
with spiking affecting the data capture unit.    However, all of the aims of 
the cruise were achieved.  Samples were collected at frequencies of 1hr and 2hr 
during both bloom surveys, from deep CTD casts and on the 88°W transect.  
During the latter period, samples were taken to coincide with Si, TCO2, POC, 
C/N ratio determinations in an effort to gain more insight into possible 
production of methyl iodide by diatoms and other species of phytoplankton.  
Transects into and out of the bloom area should also give unique information on 
production of halocarbons by phytoplankton.  Samples of marine air have also 
been collected for analysis using a GCMS that should enable some of the unknown 
peaks routinely seen on chromatograms to be identified.  Data will, however, 
require considerable and careful analysis before any conclusions can be 
reached.


C.27  HYDROCARBONS 
      (Wendy Broadgate)

Due to their high reactivity, particularly with the OH radical, light non-
methane hydrocarbons play an important role in tropospheric chemistry, 
especially in the global budget of carbon monoxide and  ozone.  Anthropogenic 
emissions (fossil fuel burning, natural oil and gas excavation, and biomass 
burning) are the major source of these compounds. However, little data has been 
published on the marine production of non-methane hydrocarbons, although it's 
importance has been recognised. Measurements in both air and surface seawater 
in unpolluted regions, especially during periods of high biological activity, 
are necessary to determine the fluxes of hydrocarbons between the sea and air 
and therefore the global marine source. Samples were analyzed for the following 
non-methane hydrocarbons using gas chromatography and flame ionisation 
detection (GC-FID): ethane, ethene, propane, propene, acetylene, n- and i-
butane, butene, pentane, pentene, hexane, hexene, heptane, heptene, benzene, 2-
methyl butane, 2,2-dimethyl propane, 2-methyl pentane, 3-methyl pentane and 
2,2-dimethyl butane.

METHODS
Samples of air and seawater were preconcentrated and analyzed in situ by GC-FID  
employing a 50m 0.53mm i.d. Al2O3 capillary column. Air samples (2L) were 
cryoconcentrated on a 1/8" o.d stainless steel trap packed with 60 mesh glass 
beads. Seawater samples (1.4L) were purged with nitrogen gas (CP grade) at 60 
mL/min for 30 minutes to remove the volatile gases which were carried in the 
gas stream through several water traps and condensers and  concentrated in the 
same way as the air samples. Calibration of the system was carried out by the 
injection of gaseous standards into a nitrogen gas stream and concentration as 
above. The sample bottles were flushed six times to 60 p.s.i. with nitrogen gas 
between each analysis and a blank was run. After each seawater analysis the 
sample was drained from the purge tube under nitrogen gas and a blank was 
obtained by purging the empty vessel. Because the temperature programme of the 
GC took one hour the rate of analysis was reduced to approx. one sample every 3 
hours. As the analysis required constant attention it was not run 24 hours a 
day.

None of this work could have  been carried out without a reliable supply of 
liquid nitrogen. In general this is a problem at sea because loss rates from 
storage dewars are such that 100% loss is observed within 30 days. However, the 
use of an "Iwatani" liquid nitrogen plant on this cruise has proved to be very 
successful. It consists of a nitrogen gas generator, a cooling unit and a 
compressor. The 40L dewar which the unit uses was maintained at a level greater 
than 30L  despite the removal of around 10L per day for use in experiments.

SAMPLING AND STORAGE
Air samples were obtained by pumping air into stainless steel electropolished 
canisters  using a battery operated metal bellows pump. Due to potential 
problems with navigation and communication it was not permitted to run a 
stainless steel tube from the mast on the monkey  island to the lab. Two tubes 
(one nylon and one teflon, 1/4" o.d.) were installed along this route and 
tested for contamination by comparison with samples taken on the monkey island 
using a 3m stainless steel tube (1/4" o.d.) but both were found to be 
unsatisfactory. All air samples were therefore taken through a 3m stainless 
steel tube either on the monkey island or through a window on the bridge  with 
the tube protruding over a metre from the bridge to windward (14m above sea 
level). To eliminate the possibility of  contamination from the ship's funnel 
no samples were taken when the wind direction was astern. Samples obtained in 
this way were analyzed within 2 hours of collection.

High pressure air samples were taken at five sites. These samples are stable 
for several years and can be taken back to the laboratory for reanalysis by gas 
chromatography-mass spectrometry. Bottles were flushed with the sample as 
above, then partially immersed in liquid nitrogen for 5 minutes. This liquefies 
air and a pressure of 200 p.s.i. can be obtained once the bottle warms to room 
temperature.

Water samples (1.6L) were taken from the non-toxic supply. The bottles were 
stored in the dark under flowing seawater for up to 4 hours but generally 
analyzed immediately. Samples at depth were taken from CTD and GoFlo 
deployments. Underway samples were routinely collected over the whole cruise 
track, although analytical problems resulted in few successful measurements 
early in the cruise. Seven CTD casts were analyzed each at two depths 
(combinations of 2m, 25m, 40m, 150m and 4000m). Surface CTD samples were 
compared with non-toxic seawater samples at the same site.

PROBLEMS ENCOUNTERED
Initial problems with the air sampling lines were time consuming. Once these 
had been overcome, severe problems with the seawater blanks were observed. 
Eventually it was found that the prep. line was contaminated, and it was 
rebuilt with new valves and tubing. Further contamination resulted from two O-
rings which were replaced with teflon fittings. There were also ongoing 
problems with the sensitivity of the detector. These were thought to be due to 
changing flow rates of the air and hydrogen gas supply lines which were shared 
with two other GC's. However it may also be due to changing voltages and spikes 
produced by the "clean" electricity supply which was found to be "dirty". 
Confusing behaviour from the data acquisition system attached to the computer 
was also due to spikes in the electricity supply.  The removal of a high 
current-drawing air compressor from the circuit corrected this malfunction.

RESULTS
Despite the problems encountered during the first half of the cruise, a varied 
raw data set has been acquired from regions of diverse biological productivity. 
However, the data requires processing before the results are available.


C.28  PARTICULATE SAMPLING 
      (Jane Robertson)

Along the 88°W transect, samples were taken and filtered on an hourly basis for 
approximately 20 hours per day. The samples were frozen and will be taken back 
to the UK at the end of Discovery 200 (March 1993). They will be analysed by 
Dr. H. Kennedy (UCNW) for particulate and dissolved 13C, and for particulate C, 
N, and Si.The resulting data will be analysed in conjunction with concomitant 
measurements of pCO2 , TCO2 and pH. The analyses will probably be complete by 
the end of 1993.


C.29  13C SAMPLING 
      (Colin Attwood)

Stable carbon isotope ratios are useful indicators of fluxes of carbon around 
the globe and through trophic webs.  The primary variation of the ratio of 
inorganic 13C:12C occurs latitudinally on a macro-scale in the atmosphere and 
in the ocean, and between water masses of different origin.  Both air and sea-
water samples were taken for later mass-spectral analysis in Cape Town to 
measure the carbon isotope ratios in the Bellingshausen Sea and Antarctic 
Peninsula regions.

AIR SAMPLING
A polycarbonate hose of 8mm internal diameter was secured to an upright 
structure on the ship's monkey island, 16m above the water line and well 
forward of the ship's exhaust outlets.  The hose was run down to the water 
bottle annex and connected to the sampling apparatus.  This consisted of a 
water trap and a glass sampling bottle (500mL) with a silicon sealed plastic 
screw-cap through which an inlet and an outlet 6mm tube were inserted.  Air was 
sucked from the supply hose through the water trap and through the sample 
bottle with a suction pump. After twenty minutes of suction, the pump and water 
trap were disconnected and the air sample was sealed in the bottle. Initially a 
tubular drying chamber was attached at the terminal end of the supply hose on 
the monkey island. This chamber was later inserted adjacent to the water trap 
inside the deck laboratory as sub-zero temperatures had blocked the chamber 
with ice. In total, forty air samples were taken, seventeen of which were 
spaced one degree of latitude apart along the northward transect of 88°W.

SEAWATER SAMPLING
While underway, seawater samples were taken from the ship's non-toxic sea-water 
supply. When the CTD was deployed, water was taken from selected depths. The 
sampling procedure was the same in both cases. 350mL plastic sampling bottles 
with a press on cap were used to store the samples.  The bottles were filled to 
overflowing from a Teflon tube. 0.15mL of 50% saturated HgCl2 solution was 
pipetted into the sample to poison metabolic activity.  The bottles were 
slightly squeezed when sealed, which allowed for the expansion of sea-water as 
it warmed without the necessity of leaving an air space. Thirty-three underway 
samples were collected covering a range of latitudes between 53 and 69°S.  141 
samples were taken from Niskin bottles deployed with the CTD.  From shallow 
casts samples were taken from the following depths: 2, 40, 100, 200, 300, and 
500m; from the deeper casts samples were taken from 2, 500, 1500, 2500, 3500m 
and the bottom.

SAMPLE PROCESSING
The samples will be processed at the University of Cape Town upon the ship's 
arrival (February 1993).  From air and water samples, CO2 gas will be extracted 
and then injected into a mass-spectrometer for 13C analysis.  Details of 
procedures to be carried out in Cape Town will be made available together with 
the results.   


C.30  KRILL ACOUSTICS 
      (Alistair Murray and Doug Bone)

OBJECTIVES
The study aims to provide an acoustic data set at two frequencies (38 and 
120kHz) in the marginal ice edge zone (MIZ) in the Bellingshausen Sea, an area 
not previously surveyed by BAS.  We hope this will lead to an increased 
understanding of the physical and biological factors controlling the 
distribution and aggregation of krill.

EQUIPMENT AND DEPLOYMENT
The equipment used was a Simrad EK400 scientific sounder operating in multiplex 
mode at 38 and 120kHz.  The data were logged to a PC using a custom data 
acquisition card and software - the Biosonics Echo Signal Processor (ESP).  The 
PC and sounder were set up in the main lab.  Some problems were experienced 
with the EK400 and PC in the early stages of the cruise.  It proved impossible 
to achieve multiplex operation although everything appeared satisfactory when 
logging either frequency on its own.  After a visit from the BAS technician 
from James Clark Ross the problem was resolved by reverting to the earlier 
version of the Biosonics software running under Windows 3.00.

The towfish was installed whilst the ship was alongside at Port Stanley. A test 
deployment of the fish was made not long after departing Berkeley sound.  
Unfortunately, whilst lowering the fish to the water, it swung as the ship 
rolled and the tail fins struck the side of the ship distorting them 
sufficiently to cause problems later in the cruise when attempting to tow at 
more than about 9 knots. This problem was cured temporarily by fitting thin 
wire stays to realign the fins, unfortunately these soon broke and thicker 
replacements had sufficient drag to cause the fish to veer under the ship.  
This problem prevented us using the system on the final transect up 88°W where 
it was necessary to maintain 10 knots steaming speed.

CALIBRATION
This was carried out on day 321 with the ship anchored in Potter Cove, King 
George Island in a depth of about 30m.  The calibration rig was assembled on 
the starboard deck and craned over the side with the standard target (a 38.1mm 
tungsten carbide sphere) suspended about 5m below it. The calibration of the 
38kHz sounder was straightforward and the results appear satisfactory. However, 
the 120kHz calibration was very difficult and the results are suspect.

OPERATION
Details of all acoustic tows are given in Appendix F. On the transect from the 
Falklands to Elephant Island, several acoustic runs were made at both 38 and 
120kHz.  After the calibration at Potter Cove, the passage down the Bransfield 
Straight was run at 38kHz. The fish was recovered during the passage to the 
marginal ice edge zone study area as the ship's speed was at times too fast for 
the towfish.  The towfish was deployed during the first and second grid surveys 
and much useful data collected.

RESULTS
Some targets were detected on the runs just to the south of the Antarctic polar 
front.  A few scattered marks were seen on the 38kHz run from Potter Cove down 
the Bransfield Strait. On arrival at the MIZ study area, no significant targets 
were detected for some two days, until the ship steamed south of about 67°30'S. 
Most echo traces were characteristic of krill swarms in appearance. No large 
layers or concentrations were found, and only a few large swarms.  Most swarms 
were small and many were fairly shallow (in the top 80m or so of the water 
column). There was a total absence of the diffuse layer type targets that are 
common around South Georgia (for instance) and which usually turn out to be 
copepods or small species of euphausid. When observed on the scope display  
most swarms gave a very similar response on both 38 and 120kHz.  Some swarms 
were clearly associated with chlorophyll patches and some were being preyed on 
by Minke whales. The area where krill swarms were found was south of a front 
found during the first grid survey. Thus there was a clear association of krill 
with watermass. Some swarms at the southern end of the second survey were in an 
area of low chlorophyll and high nutrients where the CO2 was in equilibrium 
with the atmosphere - suggesting that there had not been any bloom in this 
area.  When the physics and biology of the survey area are further analyzed and 
interpreted it may be possible to make some inferences about the processes 
controlling the distribution of krill swarms.


C.31  SIZE-FRACTIONATED PRIMARY PRODUCTION 
      (Graham Savidge)

This work was designed to address two linked objectives based on separate but 
complementary experimental approaches. The foremost aim of the programme was to 
employ the 14C uptake technique to establish the spatial variability of size-
fractionated (SF) primary production within the survey zone and to relate this 
to the prevailing conditions. The secondary objective was to obtain estimates 
of the growth potential of SF phytoplankton populations maintained under a 
range of ambient irradiances using batch cultures of natural populations 
obtained from the survey area.

With the cruise programme being based on survey mode, it was not possible to 
obtain estimates of primary production from in situ incubations. The consider-
able variability expected in the ambient environmental conditions for the area 
suggested that the optimal approach to determining primary production should be 
based on estimates derived from alpha and Pmax values obtained from P:I curves 
generated under defined artificial irradiance conditions. During the cruise, 
the P:I characteristics of 40 samples were determined with 11 samples being 
assayed during the transect to the main survey area, 21 assayed during the 
study in the main survey area and the remaining 8 samples being collected from 
the final northwards transect. Comparisons between productivity determined from 
in situ observations and derived values of alpha and Pmax have been made during 
the concurrent James Clark Ross cruise.

Samples were collected once or twice per day either from the surface using a 
bucket or from selected depths using clean GoFlo bottles mounted on Kevlar line 
and incubated for 4h at 24 constant irradiances in a light gradient incubator. 
The samples were cooled by running seawater from the non-toxic supply, with 
temperatures generally being held within 0.5°C of ambient. Following 
incubation, samples were filtered under controlled vacuum through a cascade of 
defined pore size filters allowing separation of the phytoplankton population 
into fractions >18_m (microphytoplankton), 2-18_m (nanophytoplankton) and 0.2-
2_m (picophyto-plankton). 14C uptake by the SF populations was assayed using 
standard liquid scintillation techniques with the counts being corrected for 
dark uptake based on samples to which 100_L of saturated DCMU had been added. 
No problems were encountered with the 14C uptake technique. alpha and Pmax 
values were estimated from the uptake data using a curve fitting routine based 
on a standard P:I curve. For each 14C uptake determination, complementary 
samples were also taken for the determination of SF chlorophyll concentrations 
in the initial sample and also for taxonomic assay. Primary processing of the 
14C and associated data has been virtually completed.

Seven growth experiments were carried out during the cruise with the initial 
three sample populations being taken during the transit passage to the main 
survey area and the remaining four samples being taken from a range of sites in 
the survey area itself. The experiments were set up using surface samples which 
were incubated for 4 days in 1l polycarbonate bottles under 100, 70, 53, 34, 14 
and 3% ambient irradiance in an incubator mounted on the aft deck and cooled 
from the non-toxic seawater supply. Sub-samples were taken at approximately 24h 
intervals for the determination of SF chlorophyll concentrations, using size 
divisions as previously, and also for the assay of nutrient concentrations in 
the culture bottles. These data were available from all experiments at the end 
of the cruise.

Preliminary assessment of the SF chlorophyll data has confirmed the generally 
low chlorophyll concentrations throughout much of the cruise area indicated 
from other approaches employed with the exception of the well-defined band of 
high chlorophyll located well offshore of the ice edge in the main survey zone. 
In the extensive low chlorophyll areas, the nano- and picophytoplankton 
constituted the greater proportion of the total phytoplankton population but 
with the microphytoplankton fraction responsible for the major increases in the 
zone of higher chlorophyll. Large diatom cells were clearly visible in several 
samples from this area.

The 14C productivity data indicated particularly low values of alpha and Pmax 
expressed on a per unit chlorophyll to be predominant throughout the cruise 
area with values for alpha generally ranging from 0.001-0.002µgC[_Em-2s-1]-
1[µgchl]-1h-1 and Pmax values ranging from <0.5 to 1 µgC[µgchl]-1h-1. Higher 
values of both parameters were typically associated with the two smaller size 
fractions. On a per unit volume basis, values of Pmax tended to reflect the 
local chlorophyll concentration. Within the detailed survey area variations in 
the values of alpha and Pmax on a per unit chlorophyll basis were, however, 
observed and these data will be analysed in relation to the local phytoplankton 
population characteristics and hydrographic structure.

A significant and unexpected observation from the cruise was the relative 
constancy of the mixed layer depth (MLD), as indicated by the distribution of 
chlorophyll fluorescence, at approximately 70m across much of the cruise area, 
including the detailed survey zone. The transcending of this common depth 
across hydrographic structures characterised by contrasting phytoplankton 
biomass levels suggests that the MLD may not be significant in controlling the 
growth of phytoplankton in this region. A very marked feature of the region was 
the extremely short time scale variability in the meteorological conditions and 
a major objective in data work-up will be to model the phytoplankton response 
to this variability using observed alpha and Pmax values together with 
represen-tative data on ambient irradiance input, MLDs, PAR vertical 
attenuation coefficients and vertical distributions of chlorophyll as obtained 
during the cruise. The basic format for an appropriate model is in place. The 
model will also provide predictions of integrated column productivity.

Phytoplankton population increases were recorded in all growth experiments with 
greatest increases generally being observed for the microphytoplankton 
fraction. In cultures with relatively large inocula nutrient limitation was 
recorded after 2-3 days. A clear pattern to emerge was for maximum growth to be 
associated with the two lowest irradiances employed and for growth to commence 
after a 24h lag period. Data on the growth;irradiance characteristics will be 
referred to ambient irradiance levels recorded over the period of the 
experiment and analysed in conjunction with both the depth distribution of 
total irradiance and the MLD.

This report would be incomplete without an especial thanks to Mike Behrenfeld 
and Mike Hilles for their help in sample collection, to Bob Head for carrying 
out the nutrient analyses and to Alastair Murray for his willingness to assist 
with the chlorophyll analyses.


C.32  SIZE-FRACTIONATED NEW AND REGENERATED PRODUCTION 
      (Howard Waldron, Colin Attwood)

The primary objective of this study was to investigate the nitrogen dynamics of 
the phytoplankton community in an open ocean area of the Bellingshausen Sea, 
close to the retreating ice-edge during the austral Spring, and along a S-N 
transect from the main study area to around 50°S. Additional work of a similar 
nature was also undertaken opportunistically across the Drake Passage and in 
the north eastern sector of the Bellingshausen Sea whilst en route from the 
Falkland Islands. The sampling programme consisted mainly of two types of 
experiment:

1. SIZE-FRACTIONATION. 
This work was carried out while underway using bucket samples of surface water. 
Grazers were excluded by pre-screening (<200µm) and two 5L sub-samples (for NO3 
and urea uptake) and one 6L (for NH4 uptake and regeneration) were supplemented 
with the appropriate concentration of 15N salt solution. 1L of the NH4 sub-
sample was drawn off and treated for later particulate N and isotope dilution 
analyses at time zero (R0). The three 5L bottles were then incubated at ambient 
sea surface temperature for 24h on deck at the 100% light level. The samples 
were size-fractionated, post-incubation (<200µm, 2L; <20µm, 2L; <2µm, 1L) and 
the experiment terminated by filtration onto pre-ashed 47mm GFF filters. 900mL 
of the NH4 filtrate was retained as previously for isotope dilution 
measurements at time Rt.


2. PRODUCTIVITY STATIONS. 
A light profile was obtained from the CTD deployment and bulk GoFlo water 
samples were subsequently obtained from the 100, 50, 25, 10, 1 and usually 0.1% 
light levels. For each of these depths two 2L subsamples of water were 
supplemented with the appropriate concentration of Na15NO3 and CO(15NH2)2 
respectively. For NH4-N uptake, a 3L sample was spiked with 15NH4Cl. 2L of this 
were drawn off and incubated with the NO3 and urea samples for 24h on deck at 
the appropriate light level (cooled/warmed by surface water supply). Note that 
all samples were pre-screened. As in the case of size-fractionated work, 1L of 
the NH4 subsample was used at time R0 and time Rt for a combination of 
particulate N and isotope dilution analyses. Experiments were terminated by 
filtration.

In addition to the above, a time-series experiment was conducted over 3 days 
during the early part of the cruise and one of the productivity stations 
consisted of an inter- calibration exercise with the James Clark Ross. In 
summary, 14 productivity stations were completed (including one inter-
calibration) and 8 underway experiments (one of which was a time-series). The 
identification of a density (haline-dominated) and fluorescence front during 
the SeaSoar survey made for a particularly rewarding choice of station 
positions.

Results from this work will not be available until some time after Discovery 
returns to Cape Town in early February 1993. It is anticipated, however, that 
when post-cruise analyses have been completed, figures will be published of new 
and regenerated production (and ammonium regeneration) over the depth range of 
the euphotic zone and between different size classes of the phytoplankton 
community. This has important implications for the biological viability of the 
early spring bloom and the extent to which these waters act as a sink for 
carbon.


C.33  UV-B RADIATION AND PRIMARY PRODUCTION 
      (Mike Behrenfeld, Mike Hilles)

Man-made chemicals released at the earth's surface are resulting in global 
decreases in stratospheric ozone concentrations. The direct effect of 
stratospheric ozone depletion is an increase in surface intensities of 
ultraviolet-B radiation (UVBR: 290-320nm).  The short wavelengths of UVBR are 
biologically damaging and, therefore, increases in UVBR represent a significant 
threat to both terrestrial and marine organisms. Currently, the largest 
decreases in stratospheric ozone have occurred over Antarctica each austral 
spring since 1978.  This cruise provided a unique opportunity to measure UVBR 
effects on marine organisms in this region of large stratospheric ozone 
depletions.

Measurements were made on the photoinhibitory potential of UVBR on Antarctic 
marine phytoplankton productivity, as measured by radiolabelled carbon uptake 
(NaH14CO3). UVBR effects on phytoplankton photosynthesis were determined for 
both ambient and artificially enhanced UVBR doses. Enhanced UVBR doses were 
both quantitatively and spectrally realistic.  Phytoplankton samples were 
collected from 100%, 10%, and 1% light levels during cruise stations using 
GoFlo bottles and incubated at surface intensities.  Three sample depths were 
used to allow determination of UVBR photoadaptation as a function of light 
history.  In addition to productivity experiments, measurements were also made 
of ambient solar radiation.  These measurements included broadband 
photosynthetically active radiation (PAR) doses, narrow band UVBR doses (at 
290, 300, 310, 320nm), and per-nm spectral measurements for 280-330nm.  Light 
data were collected as mean intensity over 1-2 minute intervals.

Carbon fixation rate, as measured during the UVBR studies, ranged from 0.02 to 
3.05 mgCm-3hr-1 in phytoplankton samples exposed to surface intensities of PAR 
and shielded from all UVBR. Carbon fixation in the ambient UVBR treatment 
samples were generally not significantly different than those in the UVBR 
excluded treatment.  The lack of an ambient UVBR effect was not surprising, 
however, since weather conditions during almost the entire cruise were such 
that solar UVBR intensities were negligible.  Carbon fixation rates in the 
enhanced UVBR treatment were significantly depressed compared to the UVBR 
excluded treatment.  Decreases in carbon uptake from UVBR enhancement ranged 
from <10% to 50%, with an average decrease of U15%.  All productivity values 
stated above are preliminary and will require additional analysis before being 
publishable.

Solar broadband PAR measurements were collected for each day from 316 to 347 
(excluding 320), have been condensed onto Lotus spreadsheets, and copies 
rendered for the BOFS database. Spectral and narrow band measurements of UVBR 
were also completed each day during the cruise (excluding days 334 and 335), 
but will require substantial time for analysis since these data have to be 
carefully checked for wavelength offset and calibrated for intensity.  At best, 
this data may be available for the BOFS database at BODC by June/July, 1993. 


C.34  INSTRUMENTATION NOTES 
      (Bill Miller, Phil Taylor)

WAVE RECORDER
The system was run only during deep CTD cast when the ship was hove to. No 
problems were observed; the data will be analysed at the Rennell Centre to 
assess system performance.

MILLIPORE WATER PURIFICATION SYSTEM
The system provided good quality water throughout the cruise; many thanks to 
Tony Poole for connecting it the ship supply prior to arrival at Port Stanley.

TEST EQUIPMENT
It is strongly recommended that a few thousand pounds be invested in new 
equipment for use by RVS personnel on the ship. There is not a decent 
oscilloscope on board, the equipment looks like that which came off the old 
Discovery over two years ago. 

CLEAN AC SUPPLY
This has already been reported to RVS and actions proposed. The salinometer had 
periods of instability until it was supplied through an UPS (borrowed from 
BAS). The clean supply is going to cause problems until an adequate dirty 
distribution is put in so as to keep the clean supply clean. This is 
particularly so in the deck lab.

30L GOFLO BOTTLES
All bottles were serviced on board before deployment and worked well. One 
bottle was lost when the kevlar line parted as the bottle was being hauled to 
the surface. It is suspected that a slack turn may have fouled a roller on the 
rex roth winch and jammed; as a precaution the roller was removed.

EM LOG
No EM log data was provided during the cruise owing to a faulty sensor and a 
lack of spares on board. It was confirmed soon after leaving Port Stanley that 
the fore/aft sensor on the EM log was u/s, one of the electrodes showing a 
32omega resistance path to ground. The log was subsequently removed and a 
blanking plug inserted in its place.

SIMRAD EA 500 ECHO SOUNDER
The EA 500 echo sounder had to be run on the hull transducer for the duration 
of the cruise because the PES winch was being used for the deployment of the 
BAS acoustic fish (section C.30). Performance was adversely affected (no bottom 
trace!) when the ship was pitching even in moderate weather, however no such 
deterioration in performance was present when the ship was rolling. Although 
much improved, the same characteristics were displayed when the ship was on 
station.


C.35  COMPUTING 
      (Rod Pearce, Raymond Pollard)

ABC SYSTEM
Discovery was equipped with an RVS ABC data logging and processing system. 
Scientific, navigational and operation data were logged in 'real-time' by 13 
level A units and a further 3 level A emulating PC's.  Details of the 
instruments and equipment logged by level A are given below:

NAVIGATIONAL 
Trimble GPS receiver, Ashtech GPS receiver, Transit satellite receiver, 
Chernikeef log, gyrocompass.

UNDERWAY SAMPLING 
RVS surface sampling system, nutrient analyzer, Turner Designs fluorometer, 
pCO2 analyzer, pH analyzer.

DEPLOYED PACKAGES 
CTD, SeaSoar, Lightfish.

OTHER INSTRUMENTS 
RVS metlogger, PML PAR light meter, wave recorder, echo sounder, RVS winch 
monitoring system.

The CTD and SeaSoar instrument packages were logged using an VME architecture, 
OS-9 based Mk 2 level A.  After completing the first SeaSoar transect it was 
identified by Raymond Pollard that the Mk 2 level A software derived the deltaT 
variable incorrectly. Gerald Moore also identified that the level A was 
misinterpreting some of the sign information in the raw data frames.  It was 
not possible to rectify these faults on board as no code development facilities 
for the Mk 2 level A's had been provided.  Details of the problems and the 
associated solutions had to be sent to RVS Barry for compilation, copies of the 
corrected Level A executables were then returned five days later via the ship-
shore communications link. The raw data from the first SeaSoar transect was 
retrieved from the PC archive files and converted into level C format for 
reprocessing by the PStar team.

Both the Trimble and the Ashtech GPS receivers were logged by Syntel/OS-9 based 
Mk 2 level A units.  There were problems associated with the logging of data 
from both receivers; the Trimble level A frequently failed to log all the data 
contained in the fix messages output by the receiver; the Ashtech level A 
regularly stopped logging data and had to be restarted manually. Both of these 
problems have been reported to RVS Barry for further investigation.

The level B unit received over 1.2 Gigabytes of serial data and system messages 
from the various level A sources during the cruise.  The messages were logged 
to tape and forwarded via an ethernet link to the level C system.

The level C system was based around a single SUN IPC workstation with 400 
Mbytes of hard disk capacity for holding raw and processed data files.  In 
addition to the data received from the level B the level C system also logged 
data directly from the PC controlling the ADCP (section C.2). Data from other 
off-line sources (including the towed UOR package, the acoustic fish, the XBT 
system and some surface sample analyzers) were also incorporated into level C 
system as individual data files.

Level C data processing was limited to navigation, depth and the contouring of 
some surface sample files.  As the ship's log was inoperative, the processed 
navigation data was derived purely from averaged GPS fixes.  The SeaSoar/CTD 
processing and the surface sample calibration work was carried out by the PStar 
team.  A further three SUN workstations were provided for use by the PStar 
team.  All four workstations were connected to the ship LAN (Local Area 
Network) allowing PStar users direct access to the raw data files held on the 
level C workstation.

PSTAR
Three SUN workstations were used for PStar processing throughout the cruise, 
with several Macs used as extra terminals. All saw heavy use. Most of the 
system and data were held on a 1.4Gbyte drive attached to Discovery2, but three 
0.3Gbyte drives attached to Discovery3 and 4 were also filled. One of the disks 
associated with PStar workstations developed a fault early in the cruise, it is 
unclear whether this fault was in any way linked with the electrical supply 
problems experienced by other scientific equipment during the cruise. The large 
space allocation proved most valuable in allowing data to be reworked and 
scientifically analysed during the cruise. Archiving utilised 150mbyte 
cartridges, and an optical drive was a new innovation. Files were backed up on 
both media before being deleted from the system. Heavy use was made of an HP 
Laserjet colour printer and the Nicolet drum plotter. While there were a few 
system or computer crashes, most often through lack of swop space, the system 
proved reliable, allowing all data from the CTD, SeaSoar, ADCP and navigational 
instruments to be processed to near-final state during the cruise.



                          APPENDIX A.  Scientific Party

David Turner      (Principal Scientist)  Plymouth Marine Laboratory
John Allen        James Rennell Centre
Colin Attwood     University of Capetown
Mike Behrenfeld   Oregon State University
Richard Bellerby  Plymouth Marine Laboratory/University of Plymouth
Doug Bone         British Antarctic Survey
Wendy Broadgate   University of East Anglia
Sean Debney       University College of North Wales/Europa Scientific
Gwyn Griffiths    James Rennell Centre
Bob Head          Plymouth Marine Laboratory
Mike Hilles       Western Washington University
Susan Knox        Plymouth Marine Laboratory
Polly Machin      British Oceanographic Data Centre
Gerald Moore      Southampton University/Plymouth Marine Laboratory
Anne Morrison     NERC Remote Sensing Applications Development Unit
Alistair Murray   British Antarctic Survey
Phil Nightingale  University of East Anglia/Plymouth Marine Laboratory
Raymond Pollard   James Rennell Centre
Jane Read         Institute of Oceanographic Sciences Deacon Laboratory
Jane Robertson    Plymouth Marine Laboratory/University College of North Wales
Graham Savidge    Queen's University, Belfast
Howard Waldron    University of Capetown
Alison Weeks      Southampton University
Bill Miller       (Senior Technical Officer)NERC Research Vessel Services
Colin Day         NERC Research Vessel Services
Rod Pearce        NERC Research Vessel Services
Tony Poole        NERC Research Vessel Services
Phil Taylor       NERC Research Vessel Services



                          APPENDIX B.  Stations Worked

                                               Cast     Water   Gear
      Day  Time  Station  Lat. S    Long. W   depth/m  depth/m
      -------------------------------------------------------------------
      316  2255  12198#1  52°29.2'  57°38.7'   349       361    CTD
      317  0009  12198#2  52°30.7'  57°37.7'                    30L GoFlo
      320  0805  12199#1  60°49.5'  54°45.6'    70              30L GoFlo
      320  0824  12199#2  60°49.5'  54°45.5'    30              30L GoFlo
      320  0830  12199#3  60°49.5'  54°45.5'     5              30L GoFlo
      322  1138  12200#1  62°49.9'  60°34.8'   248       293    CTD
      322  1215  12200#2  62°50.1'  60°34.9'   124              30L GoFlo
      322  1224  12200#3  62°50.2'  60°35.0'    62              30L GoFlo
      322  1230  12200#4  62°50.2'  60°35.0'    37              30L GoFlo
      322  1236  12200#5  62°50.2'  60°35.0'    23              30L GoFlo
      322  1242  12200#6  62°50.2'  60°35.0'     2              30L GoFlo
      323  1126  12201#1  63°27.5'  66°17.5'   299      3246    CTD
      323  1210  12201#2  63°26.7'  66°17.5'   182              30L GoFlo
      323  1226  12201#3  63°26.8'  66°17.5'    97              30L GoFlo
      323  1235  12201#4  63°26.6'  66°17.5'    54              30L GoFlo
      323  1244  12201#5  63°26.4'  66°17.4'    28              30L GoFlo
      324  1130  12202#1  64°05.8'  73°28.9'   298      3748    CTD
      324  1207  12202#2  64°06.1'  73°30.0'    60              30L GoFlo
      324  1215  12202#3  64°06.3'  73°30.3'   100              30L GoFlo
      324  1225  12202#4  64°06.5'  73°30.6'    80              30L GoFlo
      324  1233  12202#5  64°06.6'  73°30.9'    40              30L GoFlo
      324  1336  12202#6  64°06.6'  73°31.9'    12              30L GoFlo
      325  1835  12203#1  65°01.1'  79°22.6'   246      4109    CTD
      325  1930  12203#2  65°00.6'  79°20.3'    27              30L GoFlo
      325  1940  12203#3  65°00.6'  79°20.3'     2              30L GoFlo
      326  1120  12204#1  64°54.4'  79°28.5'   297      4175    CTD
      326  1204  12204#2  64°55.6'  79°25.7'     2              30L Go Flo
      326  1211  12204#3  64°55.6'  79°25.7'   100              30L Go Flo
      326  1221  12204#4  64°55.7'  79°25.7'    76              30L Go Flo
      326  1228  12204#5  64°55.9'  79°25.7'    46              30L Go Flo
      326  1235  12204#6  64°56.0'  79°25.6'    23              30L Go Flo
      326  2342  12205    65°00.7'  81°39.3'   993      4299    CTD
      327  0601  12206    64°59.7'  82°30.8'   994      4478    CTD
      327  1100  12207#1  65°00.4'  83°22.1'  1000      4540    CTD
      327  1254  12207#2  65°00.7'  83°22.7'     2              30L GoFlo
      327  1302  12207#3  65°00.7'  83°22.8'    99              30L GoFlo
      327  1312  12207#4  65°00.8'  83°22.8'    66              30L GoFlo
      327  1320  12207#5  65°00.9'  83°22.8'    33              30L GoFlo
      327  1324  12207#6  65°00.9'  83°22.9'    20              30L GoFlo
      327  1327  12207#7  65°01.0'  83°22.9'    10              30L GoFlo
      327  1736  12208    65°00.2'  84°09.8'   996      4547    CTD
      327  2358  12209    64°59.2'  85°00.3'   993      4591    CTD
      328  0421  12210    65°20.0'  84'59.9'   995      4537    CTD
      328  1220  12211#1  65°40.4'  84°59.9'   993      4533    CTD
      328  1309  12211#2  65°40.6'  84°59.6'    60              30L GoFlo
      328  1317  12211#3  65°40.7'  85°00.1'    30              30L GoFlo
      328  1323  12211#4  65°40.7'  85°00.0'     2              30L GoFlo
      334  0012  12212    66°44.7'  85°00.5'  4349      4389    CTD
      334  0953  12213#1  67°04.3'  84'55.8'   999      4310    CTD
      334  1210  12213#2  67°05.9'  84°51.1'     5              30L GoFlo
      334  1220  12213#3  67°06.0'  84°50.9'    38              30L GoFlo
      334  1226  12213#4  67°06.0'  84°50.9'    19              30L GoFlo
      334  1237  12213#5  67°05.9'  84°50.4'     6              30L GoFlo
      334  1707  12214    67°05.3'  84°57.2'  1000      4310    CTD
      334  1946  12215    66°59.4'  84'59.7'  1001      4329    CTD
      334  2145  12216    66°54.9'  84°59.0'   999      4346    CTD
      334  2334  12217    66°49.9'  84°59.6'   998      4356    CTD
      335  0143  12218    66°45.0'  84°59.9'   998      4386    CTD
      335  0714  12219    67°09.8'  84°59.1'   998      4291    CTD
      335  1123  12220#1  67°16.1'  85°00.8'   998      4281    CTD
      335  1229  12220#2  67°15.6'  84°59.6'    60              30L GoFlo
      335  1238  12220#3  67°15.5'  84°59.3'    40              30L GoFlo
      335  1244  12220#4  67°15.5'  84°59.1'    20              30L GoFlo
      335  1249  12220#5  67°15.5'  84°59.1'    12              30L GoFlo
      335  1254  12220#6  67°15.4'  84°59.0'     2              30L GoFlo
      335  1431  12221    67°20.2'  84°59.4'   999      4295    CTD
      335  1642  12222    67°25.4'  84°59.6'  1001      4243    CTD
      335  1957  12223    67°29.8'  84°59.2'  4185      4207    CTD
      339  1322  12224#1  67°25.6'  85°18.3'   301      4220    CTD
      339  1351  12224#2  67°25.7'  85°18.6'    43              30L GoFlo
      339  1357  12224#3  67°25.7'  85°18.7'    28              30L GoFlo
      339  1403  12224#4  67°25.8'  85°18.8'    14              30L GoFlo
      339  1408  12224#5  67°25.8'  85°18.8'     9              30L GoFlo
      339  1412  12224#6  67°25.8'  85°18.8'     4              30L GoFlo
      341  0748  12225#1  67°27.6'  86°00.1'   301      4159    CTD
      341  0808  12225#2  67°27.5'  85°59.9'    46              30L GoFlo
      341  0820  12225#3  67°27.5'  85°59.9'    30              30L GoFlo
      341  0830  12225#4  67°27.5'  85°59.9'    15              30L GoFlo
      341  0840  12225#5  67°27.5'  85°59.9'     9              30L GoFlo
      341  0845  12225#6  67°27.5'  85°59.9'     5              30L GoFlo
      342  1310  12226#1  67°36.0'  85°03.7'   300      4146    CTD
      342  1336  12226#2  67°35.9'  85°03.9'    57              30L GoFlo
      342  1343  12226#3  67°35.8'  85°04.0'    38              30L GoFlo
      342  1352  12226#4  67°35.8'  85°04.1'    19              30L GoFlo
      342  1356  12226#5  67°35.7'  85°04.2'    12              30L GoFlo
      342  1401  12226#6  67°35.7'  85°04.2'     6              30L GoFlo
      344  0039  12227    69°00.0'  88°00.3'   154      3440    CTD
      344  0235  12228    69°00.5'  88°02.1'  3423      3445    CTD
      344  2129  12229    66°30.6'  88°00.1'  4459      4470    CTD
      345  1411  12230    63°59.9'  87°59.4'   295      4761    CTD
      345  1745  12231    63°58.6'  87°59.8'  4710      4763    CTD
      346  1110  12232    61°29.9'  87°59.8'  4781      4868    CTD
      347  0550  12233    59°00.4'  88°00.2'  5012      5023    CTD
      347  2143  12234    56°30.7'  87°59.4'   204      5476    CTD
      347  2359  12235    56°31.8'  87°58.0'  5071      5482    CTD
      348  1827  12236    53°59.9'  88°01.0'  5025      5060    CTD
      349  1137  12237    51°29.4'  87°59.2'  4700      4759    CTD
  


                           APPENDIX C.  Seasoar Tows

1. Drake Passage transect (66 hours)
                                            DAY  TIME  LAT. S    LONG. W
       Launch                               317  1330  53°08.0'  59°11.0'
       Recovery                             320  0745  60°44.5'  54°46.6'


2. First survey (125 hours)
                                            DAY  TIME  LAT. S    LONG. W
       Launch, northern end of leg A        328  1355  65°40.7'  85°01.2'
       Alter course to NW in heavy weather  329  0200  67°09.2'  84°59.4'
       Begin leg W                          329  0820  66°43.1'  86°20.4'
       Alter course to NW again             329  1059  67°03.6'  86°14.1'
       Resume leg W                         329  1148  66°59.9'  86°23.8'
       Turn to leg X                        329  1924  67°58.7'  86°26.0'
       Begin leg X                          329  2024  67°59.7'  86°04.8'
       Turn to leg Y                        330  0730  66°32.5'  86°05.3'
       Begin leg Y                          330  0843  66°31.7'  85°42.6'
       Turn to leg Z                        330  2018  67°56.4'  85°41.7'
       Begin leg Z                          330  2142  67°59.0'  85°19.0'
       Turn to leg A                        331  0930  66°41.9'  85°29.4'
       Begin leg A                          331  1130  66°50.3'  84°59.6'
       Turn to leg B                        331  2020  67°59.5'  84°59.0'
       Begin leg B                          331  2122  67°58.9'  84°40.0'
       Turn to leg C                        332  0845  66°36.4'  84°46.0'
       Leg C, forced off course by weather  332  1045  66°39.2'  84°18.7'
       'Stormleg'                           332  2007  67°47.1'  83°39.4'
       Recovery                             333  1906  66°23.7'  85°51.2'


3. Passage tow (5 hours)
                                            DAY  TIME  LAT. S    LONG. W
       Launch                               335  2232  67°29.4'  84°58.2'
       Recovery                             336  0356  67°04.4'  84°05.5'
       
       4. Second survey (56 hours)
       
                                            DAY  TIME  LAT. S    LONG. W
       Launch, northern end of leg D        337  0245  66°59.7'  83°58.5'
       Turn to leg C                        337  1651  68°35.2'  84°00.2'
       Begin leg C                          337  1751  68°35.9'  84°17.2'
       Turn to leg B                        338  0620  67°00.0'  84°20.0'
       Begin leg B                          338  0730  67°01.4'  84°38.4'
       Turn to leg A                        338  2132  68°59.6'  84°41.0'
       Begin leg A                          338  2245  68°58.2'  85°00.1'
       Turn to leg Z                        339  1010  67°29.3'  84°59.6'
       SeaSoar lost                         339  1037  67°29.0'  85°07.9'
       
       
       
                              APPENDIX D.  UOR Tows

                                            DAY  TIME  LAT. S    LONG. W
       Launch, leg Z                        340  0518  67°37.2'  85°20.4'
       Recover, leg Z                       340  1327  68°22.6'  85°19.7'
       Launch, leg Y                        340  1700  69°00.4'  85°32.9'
       Recover to fix temp. sensor          340  1754  69°00.5'  85°52.7'
       Relaunch, leg Y                      340  2312  68°37.3'  85°39.6'
       Recover, leg Y                       341  0700  67°28.7'  85°59.2'
       Launch, leg X                        341  0906  67°27.9'  86°00.0'
       Recover, leg X                       341  1733  68°48.8'  86°00.3'
       Launch, leg YZ                       341  2012  68°59.0'  85°59.9'
       Recover, leg YZ                      342  0503  67°52.2'  85°35.5'
       



                                  APPENDIX E.  Lightfish Tows
       
       File                   START                            END
              DAY  TIME  LAT.S     LONG.W    DAY  TIME  LAT.S     LONG.W
       -------------------------------------------------------------------
       lf318  318  1233  55°51.5'  57°52.6'  319  0000  57°18.8'  57°01.3'
       lf319  319  0000  57°18.8'  57°01.3'  320  0000  59°54.0'  55°22.0'
       lf320  320  0000  59°54.0'  55°22.0'  320  1300  61°13.0'  54°41.8'
       lf322  322  1503  62°55.1'  61°10.0'  323  0000  63°15.4'  63°54.0'
       lf323  323  0000  63°15.4'  63°54.0'  323  2331  63°42.7'  69°06.3'
       lf324  324  1105  64°05.6'  73°28.2'  324  1457  64°09.2'  73°56.1'
       lf328  328  1711  65°58.2'  85°00.9'  329  0000  66°52.7'  85°02.8'
       lf329  329  0000  66°52.7'  85°02.8'  330  0000  67°30.8'  86°03.4'
       lf330  330  0000  67°30.8'  86°03.4'  331  0000  67°44.4'  85°19.0'
       lf331  331  0000  67°44.4'  85°19.0'  332  0000  67°39.6'  84°37.8'
       lf332  332  0000  67°39.6'  84°37.8'  333  0000  67°37.1'  84°28.4'
       lf333  333  0000  67°37.1'  84°28.4'  333  0926  66°33.1'  84°54.0'
       lf335  335  2159  67°25.5'  84°56.5'  336  0000  67°20.9'  84°47.3'
       lf336  336  0000  67°20.9'  84°47.3'  336  0300  67°05.1'  84°10.8'
       lf337  337  0257  67°00.9'  84°00.0'  338  0000  67°48.7'  84°21.3'
       lf338  338  0000  67°48.7'  84°21.3'  339  0000  68°47.5'  85°00.1'
       lf339  339  0000  68°47.5'  85°00.1'  339  2142  68°19.2'  84°56.4'
       lf340  340  0000  68°17.3'  85°08.7'  340  2351  68°30.9'  85°39.3'
       lf341  341  0000  68°30.9'  85°39.2'  341  1258  68°03.1'  86°00.3'
       lf343  343  1859  68°21.4'  86°28.5'  344  0000  68°59.4'  87°57.4'
       lf344  344  0000  68°59.4'  87°57.4'  344  1530  67°11.2'  88°05.7'



                        APPENDIX F.  Acoustic Fish Tows

                           START                           END
       RUN DAY  TIME  LAT.S     LONG.W    DAY  TIME  LAT.S     LONG.W
       ----------------------------------------------------------------
        1  319  1143  58°34.2'  56°10.0'  319  1300  58°42.4'  56°05.6'
        2  319  1301  58°42.4'  56°05.6'  319  1400  58°48.0'  56°03.8'
        3  319  1400  58°48.0'  56°03.8'  320  0700  60°41.6'  54°48.3'
        4  320  1110  60°54.0'  54°35.0'  320  1253  61°13.0'  54°41.8'
        5  322  0200  62°22.5'  58°42.3'  322  1055  62°50.1'  60°34.5'
        6  322  1340  62°51.3'  60°49.2'  323  1040  63°27.8'  66°15.6'
        7  327  0734  64°54.7'  82°55,0'  327  1100  65°00.0'  83°20.6'
        8  327  1100  65°00.0'  83°20.6'  327  1202  65°00.4'  83°22.1'
        9  327  1400  65°00.9'  83°28.2'  328  0100  65°00.3'  85°00.6'
       10  328  0130  65°00.3'  85°00.6'  328  0324  65°20.2'  84°59.8'
       11  328  0909  65°17.7'  85°10.8'  328  1125  65°40.2'  84°59.5'
       12  328  1400  65°40.7'  85°01.2'  330  0608  66°42.2'  86°03.5'
       13  330  0844  66°31.7'  85°42.6'  331  0930  66°41.9'  85°29.4'
       14  331  1130  66°50.3'  84°59.6'  332  0845  66°34.0'  84°46.0'
       15  332  1043  66°39.2'  84°18.7'  333  0922  66°35.1'  84°52.6'
       16  333  1920  66°24.9'  85°48.0'  333  2215  66°44.7'  85°01.0'
       17  334  0645  66°44.1'  84°58.7'  334  0852  67°05.1'  84°57.8'
       18  334  1757  67°05.3'  84°55.4'  334  1857  66°59.7'  85°00.1'
       19  334  2026  66°59.5'  84°59.4'  334  2057  66°55.0'  84°59.8'
       20  334  2228  66°54.9'  84°58.4'  334  2304  66°49.9'  84°59.8'
       21  335  0224  66°44.8'  85°00.3'  335  0618  67°10.0'  85°00.1'
       22  335  1318  67°15.3'  84°58.5'  335  1821  67°30.2'  84°59.8'
       23  335  2320  67°24.0'  84°53.4'  336  0245  67°05.1'  84°10.8'
       24  336  2315  66°38.0'  83°34.9'  337  0130  66°57.4'  83°57.0'
       25  337  0300  67°00.9'  84°00.0'  337  1700  68°35.8'  84°01.7'
       26  337  1700  68°35.8'  84°01.7'  338  0620  67°00.0'  84°20.0'
       27  338  0632  66°59.2'  84°22.6'  338  2230  68°59.5'  84°58.0'
       28  338  2230  68°59.5'  84°58.0'  339  1010  67°29.3'  84°59.6'
       29  339  1430  67°25.9'  85°19.0'  339  2051  68°19.2'  84°57.1'
       30  339  2345  68°18.2'  85°02.5'  340  0500  67°37.8'  85°20.5'
       31  340  1400  68°42.2'  85°20.2'  340  1820  68°59.0'  85°52.1'
       32  340  2315  68°37.3'  85°39.6'  341  0615  67°29.5'  85°41.4'
       33  341  0916  67°27.9'  86°00.0'  341  2000  69°00.4'  85°30.0'
       34  341  2015  68°59.0'  85°29.9'  342  0500  67°52.3'  85°31.6'
       35  343  1525  67°57.0'  85°29.2'  343  2354  68°59.4'  87°57.4'
       36  344  0406  68°59.4'  88°04.9'  344  1212  67°39.9'  87°59.8'
       37  344  1445  67°19.0'  88°00.9'  344  1620  62°02.0'  88°03.1'
       38  344  2335  66°29.8'  88°02.1'  345  0245  65°59.8'  88°00.7'



                    APPENDIX G.  Non-Toxic Samplling Periods

                          START                           END
          DAY  TIME  LAT.S     LONG.W    DAY  TIME  LAT.S     LONG.W
          ------------------------------------------------------------
          317  0200  52°41.8'  57°39.4'  320  1900  61°40.3'  55°46.8'
          322  0400  62°26.0'  59°01.7'  325  1400  64°44.1'  78°56.9'
          328  0000  64°59.2'  85°00.3'  342  0300  68°04.7'  85°31.3'
          344  0000  68°59.4'  87°57.4'  349  0900  51°35.0'  87°58.5'



                            APPENDIX H.  XBT Casts

                                                      DEPTH  PROBE
             XBT NO.   DAY  TIME  LAT.S     LONG. W    (M)   TYPE
             -----------------------------------------------------
             xp198012  317  0007  52°30.7   57°37.7'   415    T7
             xp198016  318  1512  56°13.2'  57°43.9'  3761    T5
             xp198017  319  0203  57°34.0'  56°53.2'  3620    T5
             xp198019  320  0815  60°44.5'  54°45.5'  3167    T5
             xp198020  327  0011  65°00.8'  81°40.1'  4333    T7
             xp198021  327  0252  64°59.9'  82°07.1'  4313    T7
             xp198022  327  0910  65°00.0'  82°56.8'  3866    T7
             xp198023  327  1520  65°00.0'  83°45.7'  3887    T7
             xp198026  344  0053  69°00.2'  88°00.6'  3482    T7
             xp198028  344  0354  69°00.1'  88°03.4'  3488    T7
             xp198029  344  0607  68°40.0'  88°05.0'  3880    T7
             xp198030  344  0759  68°19.8'  88°03.6'  4450    T7
             xp198031  344  1002  67°58.9'  88°00.8'  4024    T7
             xp198032  344  1212  67°39.9'  87°59.8'  4060    T7
             xp198033  344  1418  67°20.1'  87°59.5'  4390    T7
             xp198034  344  1654  66°59.6'  88°04.0'  4446    T7
             xp198035  344  1848  66°40.0'  88°00.0'  4324    T7
             xp198036  344  1959  66°30.1'  87°59.7'  4500    T7
             xp198037  345  0040  66°20.0'  88°00.6'  4534    T7
             xp198038  345  0240  66°00.0'  88°00.4'  4061    T7
             xp198039  345  0436  65°39.9'  87°59.8'  4616    T7
             xp198040  345  0618  65°20.0'  88°00.0'  4643    T7
             xp198041  345  0759  64°59.8'  88°00.3'  4676    T7
             xp198043  345  1039  64°39.4'  88°04.3'  4700    T7
             xp198044  345  1238  64°20.0'  88°01.4'  4813    T7
             xp198045  345  1533  63°59.8'  87°59.3'  4779    T7
             xp198046  345  2138  63°38.5'  88°00.9'  4800    T7
             xp198047  345  2315  63°19.7'  88°01.0'  4810    T7
             xp198048  346  0055  63°00.0'  88°00.1'  4820    T7
             xp198049  346  0248  62°39.7'  88°01.4'  4829    T7
             xp198050  346  0434  62°19.9'  88°00.5'  4842    T7
             xp198051  346  0620  62°00.0'  87°59.9'  4850    T7
             xp198053  346  0818  61°39.0'  88°00.6'  4600    T7
             xp198054  346  1247  61°30.0'  87°59.7'  4880    T7
             xp198055  346  1440  61°19.3'  88°01.6'  4880    T7
             xp198056  346  1642  61°00.0'  88°00.6'  3920    T7
             xp198057  346  1845  60°39.1'  88°00.1'  4371    T7
             xp198058  346  2038  60°19.8'  88°00.0'  4446    T7
             xp198059  346  2232  59°59.8'  87°58.2'  4900    T7
             xp198060  347  0029  59°39.5'  87°59.4'  5056    T7
             xp198061  347  0215  59°19.9'  87°59.1'  4607    T7
             xp198062  347  0717  59°00.5'  88°00.4'  5041    T7
             xp198063  347  0922  58°29.2'  87°59.1'  5232    T7
             xp198064  347  1101  58°20.3'  88°00.0'  5107    T7
             xp198066  347  1300  57°59.3'  88°00.4'  5175    T7
             xp198068  347  1458  57°37.8'  88°00.6'  5240    T7
             xp198069  347  1636  57°19.9'  88°00.0'  4984    T7
             xp198070  347  1824  56°59.8'  87°59.3'  4081    T7
             xp198071  347  2013  56°39.9'  88°00.8'  4000    T7
             xp198072  348  0156  56°32.6'  87°56.9'  5440    T7
             xp198074  348  0335  56°19.9'  88°00.2'  5000    T7
             xp198075  348  0528  56°00.0'  88°00.0'  4743    T7
             xp198076  348  0720  55°40.1'  88°02.4'  4000    T7
             xp198077  348  0911  55°20.0'  87°59.9'  4613    T7
             xp198078  348  1104  54°59.5'  87°59.3'  4000    T7
             xp198079  348  1305  54°40.0'  88°00.4'  4000    T7
             xp198080  348  1459  54°19.7'  87°59.9'  4601    T7
             xp198081  348  2002  54°00.1'  88°01.4'  5150    T7
             xp198082  348  2156  53°39.8'  88°01.5'  5016    T7
             xp198083  348  2335  53°20.1'  88°01.7'  4996    T7
             xp198084  349  0118  53°00.0'  88°00.2'  4944    T7
             xp198085  349  0302  52°40.0'  88°00.5'  4850    T7
             xp198086  349  0449  52°19.3'  88°00.8'  4680    T7
             xp198087  349  0638  51°59.9'  88°00.5'  5000    T7
             xp198088  349  0830  51°40.0'  87°59.0'  4697    T7
             xp198089  349  0945  51°29.6'  87°59.9'  4500    T7
             


                  APPENDIX I.  Day Number/Date Interconversion

                  DATE      DAY  DATE      DAY  DATE      DAY
                  -------------------------------------------
                  11/11/92  316  22/11/92  327  03/12/92  338
                  12/11/92  317  23/11/92  328  04/12/92  339
                  13/11/92  318  24/11/92  329  05/12/92  340
                  14/11/92  319  25/11/92  330  06/12/92  341
                  15/11/92  320  26/11/92  331  07/12/92  341
                  16/11/92  321  27/11/92  332  08/12/92  342
                  17/11/92  322  28/11/92  333  09/12/92  343
                  18/11/92  323  29/11/92  334  10/12/92  344
                  19/11/92  324  30/11/92  335  11/12/92  345
                  20/11/92  325  01/12/92  336  12/12/92  346
                  21/11/92  326  02/12/92  337  13/12/92  347
                  14/12/92  348



F.  WHPO SUMMARY

Several data files are associated with this report. They are the p19a.sum, 
p19a.hyd, p19a.csl and *.wct files. The p19a.sum file contains a summary of the 
location, time, type of parameters sampled, and other pertient information 
regarding each hydrographic station. The p19a.hyd file contains the bottle 
data. The *.wct files are the ctd data for each station. The *.wct files are 
zipped into one file called p19a.wct.zip. The p19a.csl file is a listing of ctd 
and calculated values at standard levels.

The following is a description of how the standard levels and calculated values 
were derived for the p19a.csl file:

Salinity, Temperature and Pressure: These three values were smoothed from the 
individual CTD files over the N uniformly increasing pressure levels using the 
following binomial filter-

             t(j) = 0.25ti(j-1) + 0.5ti(j) + 0.25ti(j+1) j=2....N-1

When a pressure level is represented in the *.csl file that is not contained 
within the ctd values, the value was linearly interpolated to the desired level 
after applying the binomial filtering.

Sigma-theta(SIG-TH:KG/M3), Sigma-2 (SIG-2: KG/M3), and Sigma-4(SIG-4: KG/M3): 
These values are calculated using the practical salinity scale (PSS-78) and the 
international equation of state for seawater (EOS-80) as described in the 
Unesco publication 44 at reference pressures of the surface for SIG-TH; 2000 
dbars for Sigma-2; and 4000 dbars for Sigma-4.

Gradient Potential Temperature (GRD-PT: C/DB 10-3) is calculated as the least 
squares slope between two levels, where the standard level is the center of the 
interval. The interval being the smallest of the two differences between the 
standard level and the two closest values. The slope is first determined using 
CTD temperature and then the adiabatic lapse rate is subtracted to obtain the 
gradient potential temperature. Equations and Fortran routines are described in 
Unesco publication, Processing of Oceanographic Station Data, 1991.

Gradient Salinity (GRD-S: 1/DB 10-3) is calculated as the least squares slope 
between two levels, where the standard level is the center of the standard 
level and the two closes values. Equations and Fortran routines are described 
in Unesco publication, Processing of Oceanographic Station Data, 1991.

Potential Vorticity (POT-V: 1/ms 10-11) is calculated as the vertical component 
ignoring contributions due to relative vorticity, i.e. pv=fN2/g, where f is the 
coriolius parameter, N is the bouyancy frequency (data expressed as 
radius/sec), and g is the local acceleration of gravity.

Bouyancy Frequency (B-V: cph) is calculated using the adiabatic leveling 
method, Fofonoff (1985) and Millard, Owens and Fofonoff (1990). Equations and 
Fortran routines are described in Unesco publication 44.

Potential Energy (PE: J/M2: 10-5) and Dynamic Height (DYN-HT: M) are calculated 
by integrating from 0 to the level of interest. Equations and Fortran routines 
are described in Unesco publication, Processing of Oceanographic Station Data, 
1991.

Neutral Density (GAMMA-N: KG/M3) is calculated with the program GAMMA-N 
(Jackett and McDougall) version 1.3 Nov. 94. 



G.  DATA QUALITY EVALUATION

G.1 DQE OF CTD DATA FOR THE 2ND CRUISE OF THE R/V "JAMES CLARK ROSS" (P19A)
    IN THE SOUTH EAST PACIFIC.
    (Eugene Morozov)

Data quality of 2-db CTD temperature, salinity and oxygen profiles and 
reference rosette samples were examined. Vertical distributions and theta-
salinity curves were compared for individual stations using the data of up and 
down CTD casts and rosette probes. Data of several neighboring stations were 
compared.

The CTD and bottle temperature and salinity measurements were usually made to 
not very deep levels. Sometimes the depth of the measurements was limited by 11 
db. Here were several points of measurements with repeated stations. The 
majority of the stations were to 500db. There are only two deep stations 664 
and 768. For each of the group of stations made approximately in one point of 
the ocean there was one or two reference stations. The CTDSAL measurements 
match well with the SALINTITY bottle samples. As a result we have 10 or 11 
points of not very deep measurements that could be formed to a section and 
there are about 10 repeated shallow stations in every point.

The oxygen data needs more work. The CTDOXY calibration is usually higher than 
norm in the upper 100db. I account it for freezing of the oxygen sensor at low 
temperatures in the upper layer. Sometimes the cold water temperatures did not 
affect the sensor and the CTDOXY data matches well with the OXYGEN. You can see 
this for station 744, but for the station 742 made 5 hour before the 
malfunction of the oxygen sensor gave discrepancies over 20 mol.kg in the upper 
100 db where temperatures are below 0 centigrade. The CTDOXY data should be 
checked again by the orinators and all bad data should be flagged.


G.2 BOTTLE DATA DQE NOTES (P19A)
    (J. C. Jennings, Jr.*)
    13-Jun-97

These stations are all located between 67 and 71°S at about 85°W longitude in 
the Bellingshausen Sea. Most are shallow and have incomplete bottle data. Only 
4 stations have samples from > 600m. In general, the precision of the nutrient 
data appears to be less than that desirable in a WOCE data set. Several 
stations had either phosphate or nitrate concentrations that seem too high when 
compared with nearby stations. One station (32664) had deep-water silicate 
concentrations that seem to high, but there aren't enough data to firmly 
establish this. The lack of bottle salinity data and very limited dissolved 
oxygen data further restrict the utility of this data set.

Notes from examining variable/variable plots using WHPEDIT and ODV. Nutrient 
data was plotted versus both pressure and theta and phosphate/nitrate plots 
were also examined. The following specific problems were identified:

      Stn #  Btls   Nut  Problem                                     Flag
      -------------------------------------------------------------------
      32664  All?   Sil  Deepest Sil is 140, which seems a bit high.   3
                         Highest value at other stations as ca. 135.4  
      32736  All    NO3  High versus theta. PO4 agrees with other deep 3
                         stns but NO3 is ca 5 uM higher.  
      32746  1,3,4  NO3  High NO3                                      3
      32748  1, 2   NO3  High                                          3
      32676  All    PO4  High. Stands out on both PO4/theta and        3
                         PO4/NO3 plots Sil and NO3 look ok.  


*College of Oceanic and Atmospheric Sciences
 Oregon State University
 Corvallis, OR 97331-5503    USA
 jenningj@oce.orst.edu



H.  WHPO DATA PROCESSING NOTES

Date      Contact       Data Type  Data Status Summary
-------------------------------------------------------------------------------
05/12/95  Morozov       CTD        DQE Report rcvd @ WHPO    
          
06/13/97  Jennings-Jr.  NUTs/S/O   DQE Report rcvd @ WHPO    
          
08/15/97  Uribe         DOC        Submitted  See Note:  
          2000.12.11 KJU:  File contained here is a CRUISE SUMMARY and NOT 
                     sumfile. Documentation is online.
          2000.10.11 KJU:  were found in incoming directory under whp_reports. 
                     This directory was zipped, files were separated and placed 
                     under proper cruise. All of them are sum files.
                     Received 1997 August 15th.
          
10/12/00  Huynh         DOC        Website Updated  pdf, txt versions online  
					
01/25/02  Kappa         DOC        Compiled Final PDF and Text cruise reports
