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CRUISE REPORT: SAVE4
(Updated APR 2011)



HIGHLIGHTS

                          Cruise Summary Information

          WOCE Section Designation  SAVE4
Expedition designation (ExpoCodes)  318M19881207
                  Chief Scientists  Robert M. Key/Princeton
                Co-Chief Scientist  Alberto R. Piola
                             Dates  1988 December 7 - 1989 January 15 
                              Ship  R/V Melville
                     Ports of call  Punta Arenas, Chile - 
                                    Capetown, South Africa

                                                 29° 57.9' S
             Geographic Boundaries  60° 49.2' W               15° 21.7' E
                                                 47° 4.3' S

                          Stations  29
      Floats and drifters deployed  0
    Moorings deployed or recovered  0


                      Chief Scientist Contact Information
                                 Robert M. Key
               Princeton University • Department of Geosciences
         401B Sayret Hall • Princeton University • Princeton, NJ 08544
               Phone: (609) 258-3595 • E-Mail: key@princeton.edu

                               Alberto R. Piola 
            Departamento Oceanografia Servicio de Hidrografia Naval 
  Servicio de Hidrografia Naval • Avenida Montes de Oca 2124 • Buenos Aires, 1271 
                                     ARGENTINA
              Phone: +54-1-21-3091 or -2918 • Fax: +54-1-303-2299 
                          Email: apiola@oceanar.mil.ar





              South Atlantic Ventilation Experiment (SAVE) Leg 4

                   Shipboard Chemical and Physical Data Report

                                  PRELIMINARY

                       7 December 1988 - 15 January1989

                                 R/V Melville


                            Data Report Prepared by:

                          Oceanographic Data Facility
                      Scripps Institution of Oceanography
                      University of California, San Diego

                                  June 1989






Sponsored by
National Science Foundation
Grant OCE-86 13330                                     ODF Publication No. 227


 
                  South Atlantic Ventilation Experiment Leg 4
                 Punta Arenas, Chile to Capetown, South Africa
                       7 December 1988 - 15 January 1989





INTRODUCTION

The second phase of the South Atlantic Ventilation Experiment (SAVE) began on 
December 7, 1988. Leg 4 departed from Punta Arenas, Chile about 15:00 GMT 
aboard the R/V Melville.

The sailing date was delayed by a problem with a cam lobe on the main engine. 
After lengthy discussions the only reasonable solution was to have temporary 
repairs performed by a local ship yard. This patch job did not last the 
entire leg, however, we were able to maintain l0kts or better throughout the 
cruise. This was accomplished by running the engine on "low" cam and being 
assisted almost the entire crossing by tail winds.

After leaving the Straits of Magellan we proceeded north northeast to the 
shelf break at approximately 47°S and 61°W for the first station. The first 
portion of this leg (section A) was an east to west section along 4TS from 
the shelf break (station 171) across the southern region of the Argentine 
Basin to just west of the Mid Atlantic Ridge (station 199 at 19.5°W). This 
section was originally planned to continue eastward to the ridge axis, 
however, this was modified as a result of time loss due to bad weather. The 
second section of this leg (B) went northeast from station 199 to station 215 
at 30°S and 3.75°W. The first half of this section was along the eastern 
shoulder of the ridge and passed over the Crawford Seamount. The second half 
was over the extreme southern end of the Angola Basin and relatively close to 
the ridge line which extends from the Crawford Seamount to the Walvis Ridge. 
Time loses during the first section and the fact that this section was not as 
clean, relative to basin scale interpretation, led us to decrease sample 
density along this section in order to carry out full sampling along the 
third and last section. From station 215 we proceeded due east along 30°S to 
station 235 at 15.3°E. This section (C) completed coverage of the southern 
end of the Angola Basin, crossed over the Walvis Ridge and Namibia Abyssal 
Plain, and ended with close spaced sampling up to the shelf break over the 
northern edge of the Orange River Cone. Leg 4 ended by deadheading to 
Capetown, South Africa.


SECTION 4A:  STATION 171 - 199
             47°S 60.8°W - 47°S 19.5°S

This section was designed to provide the primary zonal data for the Argentine 
Basin. The latitude was chosen to cross the Falkland Current and deepest 
portion of the Argentine Abyssal Plain. The original plan called for a total 
of 40 stations with increased sampling density near the western boundary. Of 
the 40 stations, 9 were to be large volume. When the sampling plan was made 
we intentionally allowed no time for weather and used cast estimates based on 
Knorr experience. Twenty-nine stations including 9 large volume were actually 
occupied along this section and the easternmost station was approximately 5 
west of the planned turning point. In addition to weather losses, large 
volume stations took longer than planned because the maximum speed for the 
Melville coring wench was approximately 40m/min compared to 50-60m/min on 
Knorr. Small volume station spacing was increased during the last third of 
section A and on section B to compensate. Two rather bad storms resulted in a 
400km gap between stations 192 and 193 (compared to the average of 
approximately 150km for open ocean) and a 300km gap between stations 198 and 
199. A total of 51 XBT's were used between stations. The large volume 
sampling density is shown in figure 1.

Given the general foul weather we were fortunate to collect as dense a data 
set as we did without major injury or loss of equipment. Several 101 Niskin 
bottles were either lost or destroyed, however. The most notable near 
disaster occurred when a full Gerard barrel was pulled into the large A-frame 
sheave. In the process the piggyback Niskin exploded, parts of the Gerard 
were bent, the sheave was significantly rearranged and the deck crew was 
scared half to death. Obviously, the outcome could have been much worse.

Some major features of section A are illustrated by the temperature section 
(figure 2). In the upper kilometer, between stations 171 and 175, the 
Falkland Current is clearly defined along the western boundary. Further east 
the general confused nature of the isotherms in the upper water column is 
result of crossing in and out of the Antarctic Circumpolar Current. This is 
most clearly demonstrated by the two isotherm depression areas between 
approximately 45°W and 53°W. In the lower water column the isotherms roughly 
mirror the topography. In this section the most notable bottom water features 
are:

  The coldest (θ = ~0.3) and lowest salinity (<34.66‰) waters were found on 
  the eastern side of the abyssal plain (station 192 at 37.7°W). Bottom 
  waters on the eastern side of the basin generally had higher nutrient, 
  oxygen and CFC (chlorofluorocarbon) concentrations than on the western 
  side. This finding is opposite to what was expected because Antarctic 
  Bottom Water was believed to flow northward in a deep western boundary 
  current along the base of the South American continental slope. The 
  strong signal which we observed may result from significant AABW inflow 
  east of the Islas Orcadas Rise. This is consistent with an inflow path 
  suggested by Georgi (1981).

  There is indication of a western boundary current with an AABW core along 
  the continental slope at 4000m (station 177). This core is characterized 
  by a potential temperature less than 0°, salinity less than 34.68‰ and 
  high CFC concentration.

The main water masses encountered along "A" are also illustrated by the 
oxygen and nutrient (nitrate in this case) data shown in figure 3. These data 
compare quite closely to the Western Atlantic GEOSECS data. As discussed 
above AABW is denoted by maxima in both nutrients and oxygen with the eastern 
half of the basin showing higher values than the western. The North Atlantic 
Deep Water core is centered around 2500m and marked by an oxygen maximum and 
nutrient minimum. Both NADW extrema are stronger in the western half of the 
basin than in the eastern. The extreme core values measured for these masses 
are summarized in table 1:


TABLE 1:  Section A Deep Water Mass Extrema

                       Property   NADW    AABW   units
                       --------  ------  ------  -----
                       salinity   34.84   34.64    ‰
                       oxygen    229     231     uM/kg
                       AOU       101     122     uM/kg
                       nitrate    24.6    34.8   uM/kg
                       phosphate   1.71    2.43  uM/kg
                       silicate   51.9   134.7   uM/kg


The thermocline region for this section is generally characterized by a 
nutrient maximum (e.g. 34-35 uM/kg in nitrate) directly overlying an oxygen 
minimum (~180 uM/kg) in the depth range 900-1500 m (see figure 3).


SECTION 4B:  STATION 199-215
             47°S 19.5°W - 30°S 3.75°W

This section was originally planned to begin at 47°S over the Mid Atlantic 
Ridge (~14°W) and continue to 30°S 5°W in the center of the southern 
extension of the Angola Basin. Rather than risk losing station density along 
the 30°S section (4C) we decided to move the turn point for the start of this 
section ~5° west and the end point ~1° east to make up the lost time. This 
resulted in an angled crossing of the Mid Atlantic Ridge, but allowed us to 
maintain approximately "standard" SAVE station spacing. A total of 17 
stations were occupied along this track. This included 3 full water column 
and 2 upper water column LV stations. The large volume sample density and sv 
positions are shown in figure 4. Thirty-two XBT's were taken between stations. 
Once we crossed approximately 40°S the weather began to improve. As is 
generally the case, as the sea state improved, so did the station times. The 
largest factors were increased wench speed and shallower depths. By the end 
of the leg, Jim Wells had a station planning program working which was based 
on average steaming speed, wench speed and water depth. The program estimates 
proved to be very accurate and a great help in planning.

The major features of 4B are illustrated in the temperature (figure 5), 
salinity (figure 6a) and phosphate (figure 6b) sections. The strongest 
thennocline feature is the frontal zone between stations 202 and 204 
(43.75-41.9°S) separating Subantarctic surface waters from South Atlantic 
surface waters. In many of the property sections the gradient clearly 
extended below 1km. The major water mass tongues (AAIW, NADW and AABW) are 
all easily discernable in these sections (especially phosphate, figure 6b). 
High bottom water phosphate values and. low potential temperatures at 
stations 210 & 211 (greater than 1.8 uM/kg and less than 1.6°C respectively) 
in the Angola Basin indicate a sill depth connection greater than 4km between 
the Angola Basin and the Cape Basin to the south. All of the bottom water 
nutrients along this track were significantly lower than along the GEOSECS 
section which was further east. The extreme core values for this section are 
summarized in table 2.


TABLE 2:  Section B Water Mass Extrema

                    Property   AAIW    NADW    AABW   units
                    --------  ------  ------  ------  -----
                    salinity   34.20   34.88   34.67    ‰
                    oxygen    250     240     224     uM/kg
                    AOIJ      152      91     127     uM/kg
                    nitrate    36.8    23.4    35.1   uM/kg
                    phosphate   2.52    1.58    2.47  uM/kg
                    silicate  -60.0    51.0   124.8   uM/kg



SECTION 4C:  STATION 215-235
             30°S 3.75°W - 30°S 15.3°E

This final section of SAVE leg 4 was executed essentially as planned except 
for starting approximately 1 further to the east. Twenty-one stations were 
occupied including 5 full water column large volume stations. In addition, 
one near surface (Sta 226) and one near bottom (Sta 224) large volume 
profiles were obtained by hanging all of the Gerard barrels during the 
planned Argon casts. This proved to be a very good technique to increase LV 
sample density. Figure 7 which shows the large volume sampling density 
demonstrates that horizontal station separation was halved where these two 
casts were made. The time required to hang the extra bottles was small 
relative to wire time. Twenty-eight XBT's were taken between stations. Station 
planning and sampling went very well along this leg thanks in no small part 
to good weather conditions.

Sampling for Section 4C began in the southern part of the Angola Basin, 
continued across the Walvis Ridge and Namibia Abyssal Plain region of the 
Cape Basin and ended at the shelf-slope break on the northern portion of the 
Orange Cone. The main features seen in the thermocline were a general 
shoaling of isolines from west to east and two distinct areas of isoline 
depression (centered at station 220 ~2°E over the Walvis Ridge and between 
stations 223 and 224 ~6.5°E in the central Namibia Abyssal Plain). These 
details are clearly shown in the temperature section (figure 8). The two 
depression areas are probably remnants of rings shed in the Agulhas 
Retroflexion region.

Bottom waters in the Cape Basin were significantly fresher (34.73 vs 34.85‰) 
and colder (0.66 vs 1.82°C) than in the Angola Basin. The Cape Basin bottom 
waters also had the much higher nutrient and AOU levels indicative of AABW 
(see the silicate section figure 9). In the Cape Basin all the isolines 
tended to shoal both toward the Walvis Ridge and toward the African 
continental slope. Within this basin the bottom water extrema were found 
along the flank of the ridge (sta 221) and at the saddle point connecting the 
southeastern and northwestern areas of the Namibia Abyssal Plain. The 
mid-water column (2km - 3km) relative minimum in nutrients and AOU was defined 
more clearly in the Cape Basin than in the Angola Basin (see figure 9). This 
minimum was weaker at stations 223-224 where the isoline depression had been 
noted in the thermocline.

This section passed very close to GEOSECS station 102 (31.5°S 9.5°E). 
Comparison of the data shows the two to be comparable in all major 
characteristics. The extrema core values for this section are shown in table 
three. The GEOSECS East Atlantic section was used to help pick water mass 
cores. Note that the terminology AAIW is used very loosely both here and 
above. For example the AAIW salinity minimum listed below lies significantly 
above the nutrient maximum.


TABLE 3:  Section C Water Mass Extrema

                    Property   AAIW    NADW    AABW   units
                    --------  ------  ------  ------  -----
                    salinity   34.31   34.88   34.73    ‰
                    oxygen    178     239     216     uM/kg
                    AOU       148      92     128     uM/kg
                    nitrate    33.5    23.4    31.0   uM/kg
                    phosphate   2.33    1.54    2.15  uM/kg
                    silicate   63.6    40.8   111.2   uM/kg




LIST OF PARTICIPANTS

Ship's Captain
        Curtis D. Johnson - Scripps Institution of Oceanography

Chief Scientist 
        Robert M. Key 
        Princeton University

Co-chief Scientist
        Alberto R. Piola
        Servicio de Hidrografía Naval - Argentina

Lamont-Doherty Geological Observatory 
        Michael T. Benjamin 
        David W. Chipman 
        Amy Ffield 
        Guy Mathieu 
        Maureen K. Noonan

Princeton University 
        Gerard J. McDonald

Scripps Institution of Oceanography/ODF 
        David L Boa 
        Marie-Claude Beaupre 
        Carol Conway 
        Tim Field 
        Mary C. Johnson 
        Carl W. Mattson 
        Kristin M. Sanborn 
        James A. Wells

Scripps Institution of Oceanography 
        John T. Boaz 
        Leonard T. Lopez 
        Mark J. Warner

Texas A&M University 
        Bret B. Bergland

University of Washington 
        David Straub

Woods Hole Oceanographic Institution 
        Scot P. Birdwhistell




CCHDO DATA PROCESSING NOTES

Date        Person      Date Type  Summary 
----------  ----------  ---------  ------------------------------------------
2011-04-08  Muus, Dave  BTL        Exchange, NetCDF, WOCE files online 
            Notes on Save Leg 4 rosette sample data EXPOCODE 318M19881207 
            110406/dm
            1. Temperature, salinities, oxygen and nutrients taken from ODF 
               data, whprpasave4, dated Aug 25, 2005.
            2. CFCs and CO2 data merged from file SAVEsv.csv received from R. 
               Key Dec 10, 2010.
                 PCO2 values in file but no flags. Added flag 2 for all PCO2s.
            3. Sta 230 Cast 1 Sample 31 leaked. Nutrients not analyzed, 
               Oxygen, Salinity & Alkalinity deleted.     
                 TCARBN & PCO2 values exist but are very low.
                 ODF notes say "Bottle appears to have leaked". Deleted 
                   TCARBN and PCO2.
            4. Deleted Station 173 Cast 2 Bottle 21 from SAVEsv.csv. Cast 2 
               is Gerard cast, Bottle 21 is rosette bottle.
                 Deleted Station 203 Cast 3 Bottle 18 from SAVEsv.csv. Cast 3 
                 is Gerard cast, Bottle 18 is rosette bottle.
            5. CTDTMP units ITS-68 not ITS-90. 



