A. Cruise Narrative

A.1 Highlights

WOCE AR15, AR04W and AR04E, R/V LE NOROIT, Cruise ETAMBOT 1

Expedition designation (EXPOCODE): 35LLETAMBOT1

Chief of Project: Claude Oudot
Chief Scientist:  Yves Gouriou
                  Centre ORSTOM
                  B.P. 70
                  29280 Plouzane
                  France
                  Telephone: (33) 02 98 22 45 10
                  Telefax:   (33) 02 98 22 45 14
                  e.mail:    gouriou@orstom.fr

Ship:             R/V LE NOROIT

Port of Call:     1st leg: Cayenne (French Guiana) to Natal (Brazil)
                  2nd leg: Natal (Brazil) to Cayenne (French Guiana)

Cruises Date:     September 9, 1995 to October 11, 1995

A.2 Cruise Summary

Cruise Track

The cruise track and station locations are shown in Figure 1.

First leg:  Cayenne (4 51'N-52 15'W) to 35 W-3 S.
Second leg: Natal (5 48'S-35 18'W) to 35 W-3 S, transit to 
            0 23'N-45 06'W, then 0 23'N-45 06'W to Cayenne.

Number of station

A total of 85 CTD/rosette stations were occupied using a General Oceanics 24 
bottle rosette equipped with:
  24 8-liter Niskin water sample bottles .
  a NIBS Mark IIIa CTD equipped with an oxygen sensor, and bottom proximity 
    alarm.
  a 12 kHz MORS pinger.
  a 150 KHz-RDI L-ADCP (Lowered Acoustic Doppler Current Profiler).

To install the L-ADCP, 2 Niskin bottles have been removed from the rosette.

Due to bad weather condition, there is no station at 35 W-3 S. 

Sampling

Double casts were performed for deep stations (bottom > 4500 m). During the 
first cast 6 water samples were taken between the surface and 500 m, and during 
the second cast 22 water samples were taken between 500 m and the bottom. The 
number of water samples per station is distributed as follows:

15 shallow stations with less than 22 water samples.
37 stations with 22 water samples.
18 stations with 24 water samples (L-ADCP removed from the rosette).
11 stations with 28 water samples (double casts).
3 stations with 30 water samples (double casts and L-ADCP removed from the 
rosette).

Salinity, dissolved oxygen, nutrients (nitrate, nitrite, silicate, phosphate) 
have been measured for every sample, at every station.

Freons (11 and 12) measurements were performed at every station. Between 800 m 
       and the bottom for 75 stations, and between the surface and the bottom 
       for 10 stations.
Total dissolved CO2 and pH measurements were carried out for all the closed 
       bottles every other station (47 stations).
Surface sampling were carried out at each station to determine CO2 fugacity and 
       chlorophyll.

Test stations:

Station N 25: all the bottles closed at 1000 m depth.
Station N 85: 12 bottles closed at 1000 m depth, and 12 bottles closed at 
2000 m depth.

At every station 2 bottles were closed at the same depth.

Floats, Drifters, and Moorings

No floats, drifters, or moorings were deployed on this cruise.

A.3 List of Principal Investigators

TABLE 1: Principal investigators

Name                  Responsibility    Institution
---------------------------------------------------
Chantal Andrie        Freons            ORSTOM
Bernard Bourles       S-ADCP, Salinity  ORSTOM
Yves Gouriou          CTD, L-ADCP       ORSTOM
Claude Oudot          Nutrients - O2    ORSTOM
Jean-Francois Ternon  CO2 parameters    ORSTOM

A.4 Scientific Program and Methods

The principal objectives of the cruise were:

To estimate the inter-hemispheric transport of heat, freshwater, nutrients, CO2, 
   and CFCs in a key region of the Atlantic ocean.
To estimate the seasonal variability of the deep circulation. A second cruise, 
   ETAMBOT 2, have been made in an opposite season.
To repeat the survey of the western equatorial Atlantic ocean made during the 
   CITHER 1 cruise in January-March 1993 (Western part of the A6 section).

The instruments employed in the measurement program consisted of a NBIS Mark 
IIIa CTD and General Oceanics rosette. Subsidiary instrumentation consisted of a 
12 kHz pinger, a bottom proximity alarm, and a L-ADCP. 6 SIS reversing pressure 
meters and 6 SIS reversing thermometers were installed on the bottles.

After a cast the rosette was placed on the deck and secured. The rosette, the 
frame, sensors and L-ADCP were watered with fresh water. L-ADCP binary data were 
downloaded to a PC. Digital instrumentation was read and samples were drawn in 
the following order:

Freons,  oxygen, CO2 parameters, nutrients, and salinity.

The rosette was stored on deck throughout the cruise and all sampling was 
performed there.

Acoustic Doppler Current Profiler (ADCP) measurements were made continuously 
employing a hull mounting 150 kHz unit manufactured by RDI.

No continuous water depth measurements were performed along the track of the 
ship. A deep sounder was used to locate the rosette during the cast.

A. 5 Major Problems Encountered on the Cruise

One station, at 3 S-35 W, has been cancelled due to bad weather 
condition. Consequently we did not finish the 35 W section and we sailed to 
Natal (Brazil). After the call in Natal we carried out the stations between 
5 S-35 W and 3 30'S-35 W. Again we were not able to make the 
station at 3 S.

Due to a failure of two L-ADCP acoustic transponders, deep velocity profiles 
were made only from station N 2 to station N 32 (i.e. 31 velocity 
profiles).

2 SIS reversing pressure meters and 1 reversing thermometers failed during the 
cruise. 

A. 6 List of Cruise Participants

TABLE 2: Cruise participant

Name                  Responsibilities            Affiliation  Leg
------------------------------------------------------------------
Chantal Andrie        CFCs                        ORSTOM       1-2
Francois Baurand      Nutrients                   ORSTOM       1-2
Jean-Michel Bore      Elec. Engineer/CTD/L-ADCP   ORSTOM       1-2
Bernard Bourles       CTD/S-ADCP                  ORSTOM       1-2
Elisabete Braga       Nutrients                   IOUSP        1-2
Remy Chuchla          Oxygen                      ORSTOM       1-2
Christian Colin       CTD                         ORSTOM         2
Denis Diverres        CO2                         ORSTOM       1-2
Gerard Eldin          CTD/S-ADCP                  ORSTOM       1
Philippe Fournier     Salinity                    ORSTOM       1-2
Yves Gouriou          Chief Scientist/CTD/L-ADCP  ORSTOM       1-2
David Nowicki         CTD/L-ADCP                  ORSTOM       1-2
Claude Oudot          CO2                         ORSTOM       1-2
Jean-Francois Ternon  CFCs                        ORSTOM       1-2

ORSTOM: Institut Francais de Recherche Scientifique pour le Developpement en 
Cooperation
IOUSP:  University of Sao paulo

B. Underway Measurements

B.1 Navigation
    By B.Bourles

Navigation data (time, position, course and speed over ground, and fix quality 
information) were acquired throughout the ETAMBOT-1 cruise, from the 09/09/1995 
at 11h05 TU, every 15 seconds with a Magnavox MX4200 Global Positioning System 
(GPS). Due to a failure of this GPS, the vessel NALNO GPS was used during the 
second part of the cruise, from the 09/28/1995 at 13h30 TU to the 10/10/1995 at 
15h45 TU. 

B.2 Echosounding

None.

B.3 Acoustic Doppler Current Profiler (ADCP)
    By B.Bourles

The Ship mounted Acoustic Doppler Current Profiler (S-ADCP) system on board the 
N/O LE NOROIT is a 153 kHz RD-VM150 Instruments unit with a hull mounted 
transducer. The four-beam transducer is mounted in a well, filled with fresh 
water and closed by a Kevlar acoustic window, and located to the port side 
around the vessel centerline at 4 meters depth. It is connected by cable to a 
deck box, containing the processing equipment, and connected to a Personnal 
Computer (AT-286) dedicated to measurement acquisition. Ship's gyrocompass 
information are collected by the deck box through a synchro to digital 
interface. Data were collected using the RDI Data Acquisition Software (version 
2.48). Information exchanges between the S-ADCP and the acquisition PC were 
managed by the 'ENSOUT' RDI software. Navigation data (time, position, course 
and speed over ground, and fix quality information) were aquired with a Magnavox 
MX4200 Global Positioning System (GPS) during the first part of the cruise, and 
with the vessel NALNO GPS during the second part. Standard setup parameters used 
were: 8 meter bin and pulse lengths, 4 meter blanking, and 5 minutes ensemble 
averaging. A reference layer was defined between bins 5 to 15. The first bin was 
centered on 16 meter depth.

The S-ADCP data processing has been made using the Common Oceanographic Data 
Access System (CODAS-3, version 3) of the Hawaii University (Bahr et al., 1990). 
The PC-clock drift is first determined by comparing PC time with GPS time. This 
time drift did not exceed 2 to 3 seconds per day. The corrected time is then 
included in the data base. Navigation and transducer temperature are first 
checked. 'Noisy' bins or profiles are suppressed. Navigation and S-ADCP 
measurements are combined in order to obtain absolute current values. The 
currents velocity is calibrated using the Pollard and Read (1989) standard 
procedure.
 
Absolute velocity profiles were obtained down to about 300 m depth on station, 
and down to 190 m depth when steaming (the vertical extension is defined by the 
depth where the percentage of good bins per ensemble becomes inferior to 30%). 
The original 5 minutes profiles have been averaged into 'in stations', 'between 
stations', '1/4 degree' and 'hourly' profiles. Standard deviation of velocity 
mean profiles is of the order of 3 cm s-1.

References:

Bahr, F., E. Firing and S. Jiang, Acoustic Doppler current profiling in the 
    western Pacific during the US-PRC TOGA Cruises 5 and 6, JIMAR Contr. 90-
    0228, U. of Hawaii, 162 pp., 1990.
Pollard, R. and J. Read, A method for calibrating ship-mounted acoustic Doppler 
    profilers, and the limitations of gyro compasses, J. Atmos. Oceanic 
    Technol., 6, 859-865, 1989.

B.4 L-ADCP measurements
    By B.Bourles,Y.Gouriou, R.Chuchla

The Lowered Acoustic Doppler Current Profiler (L-ADCP) allows to provide 
absolute currents over the whole water column. We used a BroadBand 150 kHz RD 
Instruments ADCP. It was attached to the 'rosette', and two water bottles were 
removed from the 'rosette' frame for L-ADCP installation. The L-ADCP acquires 
velocity profiles during the down and up casts, simultaneously to the CTD-O2 
system. The CTD-O2/L-ADCP package was lowered and rised at a nominal speed of 1 
m s-1, except during the upcast when the package was stopped to fire the 
bottles. We used the following setup parameters: one second sampling rate, one 
ping per ensemble, 19 bins per ensemble, 16 meter bins width, sea water salinity 
of 35 and sound velocity of 1500 m s-1. Thus, a velocity profile of about 300 m 
vertical extent is acquired every second. Each ensemble contains the precise 
time, internal sensor temperature, heading, pitch and roll angles, and vertical 
velocity of the rosette. Data of each bin contain the three velocity components 
in earth coordinates, velocity error estimate, backscattered energy and quality 
parameters (e.g., 'percent good'). Data have been processed following the method 
described by Fischer and Visbeck (1993), and adapted by Gouriou and Hemon 
(1997). As the L-ADCP did not have pressure sensor, the depth of each cell was 
computed using the vertical velocity measurements. Then, all the individual 
profiles were combined in a unique velocity profile over the whole water. At 
depth, data perturbed by the bottom reflections were suppressed. The reference 
velocity was determined using the GPS time and position at the beginning and at 
the end of the profile. Error due to this reference velocity determination is 
estimated to 1 cm s-1 (Fischer and Visbeck, 1993). However, the precision of the 
L-ADCP measurements is difficult to evaluate at this stage, except in the 
surface layers by comparison with Ship mounted Acoustic Doppler Current Profiler 
measurements, where maximum mean differences reach 5 cm s-1. Due to the failure 
of two of the four L-ADCP transducer beams, thirty-two (over eighty-five CTD-O2 
casts) absolute velocity profiles were acquired at the beginning of the Etambot-
1 cruise.

References:

Fischer, J., and M. Visbeck: Deep velocity profiling with self-contained ADCPs, 
    J. Atmos. Oceanic Technol, 10(5), 764-773, 1993.
Gouriou, Y., and C. Hemon: Traitement des donnees L-ADCP, Centre ORSTOM de 
    Cayenne, documents scientifiques n  O.P. 21, 56pp, 1997.

B.5 Thermosalinograph measurements

None

B.6 XBTs

B.7 Meteorological Measurements
    By B. Bourles

Meteorological measurements were recorded every three hours, from the 
09/09/1995-12h00 TU to the 10/10/1995-18h00 TU, by the deck officer of the R/V 
LE NOROIT. These measurements are the following: date, time, position, dry 
thermometer temperature ( C), moist thermometer temperature ( C), dew 
point temperature ( C), sea level pressure (mbar), sea level temperature 
( C), and relative humidity (%). Weather, clouds and sea level conditions 
have not been recorded. Wind measurements were erroneous due to direction 
correction problems.

C. Hydrographic Measurements Techniques and Calibrations

C.1 Sample Salinity Measurements
    By P.Fournier and C.Oudot

Salinity analysis of samples collected during ETAMBOT 1 were carried out onboard 
with a GuildlineTM PortasalTM salinometer model 8410, equipped with an OSI 
(Ocean Scientific International) peristaltic-type sample intake pump. The 
instrument was operated in the container-laboratory kept at a constant 
temperature of 23 C. The bath temperature of the salinometer was adjusted to 
24 C. Standardization was effected by use of IAPSO Standard Seawater batch P123 
(K15 = 0.99994). Every day, the standardization was adjusted before one run of 
analysis and the standardization drift was checked every two stations (44 
samples). The drift was very low: on the average it was - 0.00002  .00045 
psu.Quality control of the salinity data were performed using repeated 
measurements from replicate samples (bottles fired at the same depth at station 
N 25 and N 85) and duplicate samples (two different bottles fired at the same 
depth, sixty-nine times). The standard deviations of the three groups of 
replicate samples are given in the Table 3 below.

TABLE 3: Salinity replicate statistics
-----------------------------------------
Station number           25       85
Pressure (dbar)          997      2001
Number of bottles        12       12
Mean salinity (psu)      34.7542  34.9779
Maximum deviation (psu)  .0008    0.0010
Standard deviation       .0004    .0006

The standard deviation of the sixty-nine sample pairs (duplicate), taken at 
different depths, is  0.0009 psu.

C.2 Sample Oxygen Measurements
    By P.Fournier and C.Oudot

Sampling and techniques Oxygen samples were taken in calibrated clear glass 
bottles (capacity = 120 cm3) immediately after the drawing of samples for CFCs. 
The temperature of the water at the time of sampling was measured to allow the 
conversion of the concentration unit per volume into per mass. The fixing of the 
dissolved oxygen is immediately performed with reagents before the closure of 
the glass bottle, according to the method recommended in the WOCE Operations 
Manual (Culberson, 1991). The samples were stored in the container-laboratory 
(controlled temperature of 23 C) where analyses were carried out, according to 
the Winkler whole bottle method.

All volumes of glassware to collect samples and to dispense solutions were 
calibrated by weight, and corrections were made for changes in volume with 
temperature.

The end-point was determined by automatic potentiometric method with a MetrohmTM 
TitratorTM model 682 and a DosimatTM 665 burette (10 cm3).

The concentration of oxygen dissolved in seawater was converted to mass fraction 
by use of the following relationship:

               [mol kg-1] = (44.660 / rho-sw) * O2 [cm3 dm-3]

where rho-sw is the density of the seawater corresponding to the temperature at 
the sampling time (Millero and Poisson, 1981).

Reproducibility of measurements

The precision of measurements was estimated from analysis of three groups of 
replicate (taken from different bottles fired at the same depth) samples and a 
large number (sixty-nine) of duplicate (two bottles fired at the same depth, 
changing from one station to the other) samples during successive stations. 
Table 4 gives the statistics of replicates.

TABLE 4: Oxygen replicate statistics

Station number                     25     85
-----------------------------------------------
Pressure (dbar)                    997    2001
Number of bottles                  22     12
Mean O2 concentration (mol kg-1)  153.3  252.1
Maximum deviation (mol kg-1)      1.8    1.0
Standard deviation (mol kg-1)     0.8    0.4

The standard deviation of the sixty-nine sample pairs (duplicate) is 0.4 mol 
kg-1, i.e a value not significantly different from reproducibility of 
replicates, excepted the first station (# 0), carried out as a trial station.

Comparisons with historical data

Comparisons of ETAMBOT 1 data with historical data (SAVE Leg 6, 1989 and TTO-
TAS, 1983) are shown in Figure 2. The right insets exhibit the deepest levels. 
Excepted differences in the upper layers resulting from changes in water masses 
in the region, principally in bottom pannel (TTO-TAS) where the latitude range 
is wider, the agreement is satisfactory.

References

Culberson C.H., 1991. Dissoved oxygen in the WOCE Operations Manual. Vol. 3, 
     Part 3.1.3: WHP Operations and Methods. WHP Office Report WHPO 91-1, WOCE 
     Report N  68/91.
Millero F. J. and  A. Poisson, 1981. International one-atmosphere equation of 
     state of Sea Water. Deep Sea Res., 28, 625-629.

C.3 Nutrients 
    By F.Baurand and C.Oudot

Equipment and techniques

Nutrient analyses were performed on a Braun & LuebbeTM AutoAnalyzerTMII type 
TechniconTM (continuous flow analyzer), according to classical methods  (Murphy 
and Riley, 1955 for silicate - Murphy and Riley, 1962 for phosphate - Wood et 
al., 1967 for nitrate and nitrite) as described in the Manual of Treguer and Le 
Corre (1975). Colorimeter signals were processed with an IBM computer using a 
home-made software (Lechauve et al., 1992).

Sampling for nutrient analysis followed those for gases (freons, oxygen, CO2 
fugacity, total CO2 and pH) and were carried out in Nalgene bottle (125 cm3). 
Samples were stored until analysis (the maximum delay is six hours) in the 
container-laboratory controlled in temperature (22 C). The Nalgene bottles were 
put on the special sample tray of the AutoAnalyzer in such a way as the samples 
were directly taken from the sampling bottles without transfer via traditional 
polystyrene cups.

Calibration and standards

Volumes of glassware (volumetric flasks and MetrohmTM automatic burette model 
DosimateTM 665) to prepare standards were checked by weight in the shore-
laboratory, at a temperature near that in the container-laboratory (22 C). 

Nutrient primary standards were prepared from salts (BakerTM, anal. grade., 
certified 99.99 %, for phosphate, nitrate and nitrite ; Carlo ErbaTM, high 
purity for silicate) dried at 105 C for two hours. Four primary standards were 
prepared ashore prior the cruise by dissolving:

  0.85056 g of potassium dihydrogenophosphate in 1 liter of ultrapure water
  12.63875 g of potassium nitrate in 1 liter of ultrapure water
  8.62500 g of sodium nitrite in 1 liter of ultrapure water
  2.35075 g sodium silica fluoride in 5 liters of ultrapure water

No buoyancy correction were applied to the nominal weights. The ultrapure water 
was deionized water with a resistivity of 18 M. The primary standard solutions 
were preserved with chloroform (2 ml per liter).

A mixed secondary standard for phosphate + nitrate and a single secondary 
standard for nitrite were prepared weekly by dilution with deionized water. 
Seven working standards were prepared every day in artificial water. 
Concentrations (mol l-1) were: 0, 10, 20, 40, 60, 90, 120 for silicate ; 0, 
0.25, 0.50, 1.00, 1.50, 2.50, 3.00 for phosphate ; 0, 5, 10, 20, 30, 40 for 
nitrate ; 0, 0.50, 1.00, 1.50, 2.00 for nitrite. The artificial seawater was a 
40 %o solution of analytical grade sodium chloride.

The linearity of the calibration curve (Beer's Law) was not valid beyond 20 mol 
l-1 for silicate and nitrate. So, a polynomial (cubic) relationship was chosen 
for those nutrients.

Quality control

The precision of measurements was estimated from analysis of three groups of 
replicate (taken from different bottles fired at the same depth, during three 
test stations) samples and a large number (seventy) of duplicate (two bottles 
fired at the same depth, changing from one station to the other) samples during 
successive stations. Table 5 gives the statistics of replicates. The percent 
standard deviations (vs full range) are 0.1 for silicate, 0.5 for phosphate and 
0.3 for nitrate, in agreement with WHP recommendations (WOCE, 1994).

TABLE 5: Nutrients replicate statistics

Silicate

Station number                            25     85     85
------------------------------------------------------------
Pressure (dbar)                           997    2001   997
Number of bottles                         22     12     12
Mean silicate concentration (mol kg-1)   27.18  17.43  27.95
Standard deviation (mol kg-1)            0.13   0.05   0.12
Percent standard deviation                0.46   0.27   0.43
Percent standard deviation
(vs full range, 120 mol kg-1)            0.11   0.04   0.10

Phosphate

Station number                            25     85     85
------------------------------------------------------------
Pressure (dbar)                           997    2001   997
Number of bottles                         22     12     12
Mean phosphate concentration (mol kg-1)  2.12   1.28   2.26
Standard deviation (mol kg-1)            0.01   0.00   0.01
Percent standard deviation                0.68   0.35   0.70
Percent standard deviation
(vs full range, 3 mol kg-1)              0.48   0.15   0.53

Nitrate

Station number                            25     85     85
-------------------------------------------------------------
Pressure (dbar)                           997    2001   997
Number of bottles                         22     12     12
Mean nitrate concentration (mol kg-1)    30.98  19.39  33.17
Standard deviation (mol kg-1)            0.12   0.03   0.06
Percent standard deviation                0.39   0.17   0.18
Percent standard deviation
(vs full range, 40 mol kg-1)             0.30   0.08   0.15

The standard deviation of the seventy sample pairs (duplicate) is 0.4 mol kg-1 
for silicate, 0.02 mol kg-1 for phosphate and 0.3 mol kg-1 for nitrate.

The consistency of phosphate and nitrate data is shown in Figure 3 by the strong 
correlation between these two nutrients (R2 = 0.9914). The slope of the 
regression line (15.016) is in good agreement with the Redfield ratio.

Comparisons with historical data

Comparisons of ETAMBOT 1 data with historical data (SAVE Leg 6, 1989 and TTO-
TAS, 1983) are shown in Figure 4. The right insets exhibit the deepest levels. 
Excepted differences in the upper layers resulting from changes in water masses 
in the region, principally in bottom panel (TTO-TAS) where the latitude range is 
wider, the agreement is satisfactory.

References

Lechauve J.J., Baurand F. and C. Oudot, 1992. Manuel d'utilisation ASTECH 
    (Analyse du Signal TECHnicon). Doc. Techn. Centre ORSTOM de Brest, n  
    67, 35 p.
Mullin J.B. and J.P. Riley, 1955. The spectrophotometric determination of 
    silicate-silicon in natural waters with special reference to sea water. 
    Anal. Chim. Acta, 12: 162-170. 
Murphy J. and J.P. Riley, 1962. A modified simple solution method for the 
    determination of phosphate in natural waters. Anal. Chim. Acta, 27: 31-36.
Treguer P. and P. Le Corre, 1975. Manuel d'analyse des sels nutritifs dans l'eau 
    dde mer (utilisation del'AutoAnalyzer II Technicon). Universite de Bretagne 
    Occidentale, Brest, 2eme edition., 110 p.
WOCE , 1994. WOCE Operations Manual. Vol. 3, Part 3.1.3: WHP Operations and 
    Methods. WHP Office Report WHPO 91-1, WOCE Report N  68/91, Revision 1, 
    November 1994.
Wood E.D., Armstrong F.A.J. and F.A. Richards, 1967. Determination of nitrate in 
    sea-water by cadmium-copper reduction to nitrite. J. Mar . Biol. Ass. U.K., 
    47 : 23-31.

C.4 CFC-11, CFC-12
    by C.Andrie

Work on board 

During the cruise, two people had in charge sampling and analysis of water 
samples for CFC measurements.

Sea water samples were directly  taken from Niskin bottles  using syringes with 
metallic stopcocks. All of the samples at the surface and  samples corresponding 
to depths greater than 800 m have been taken. This corresponds to at least 17 
samples per profile or 22 when double casts have been realized for bottom depth 
greater than 4500 m. Complete profiles have been realized for 11 stations 
(stations 5, 6, 36, 42, 57, 64, 65, 67, 69, 70, 81).

Atmospheric measurements have been realized every two days, from syringe 
samples. Globally, 2580 analyses have been realized, including standards and 
atmospheric analyses.

The usual precautions have been taken before and during the boarding: Niskin 
bottles cleaned and stored in a ventilated area in Cayenne before the cruise and 
then Decon washed on board, bottles rings heated (60 C) and degased in an oven 
just at the beginning of the cruise.

Analyses and data validation 

The gas chromatographic method with electron capture detection is described in 
Bullister and Weiss (1988), with some minor modifications. The gas vector is 
ultrapure nitrogen. Validation has been done, for each station, from vertical 
F11 and F12 profiles and F11/F12 diagrams. Seven F12 data have been rejected 
(all F11 data have been kept).

The atmospheric secondary standard has been calibrated against a SIO primary 
standard during four times during the cruise. CFC concentrations are reported in 
the SIO 1986 scale. The reproducibility, for the standard, for the whole cruise, 
was  0.9% for F12 and  2.2% for F11. Mean atmospheric mixing ratio were 514 
ppt ( 1.6 ) for F12 and 270 ppt ( 3.4 %) for F11.

The atmospheric distribution shows an inter-hemispheric gradient around 0.46 
ppt/  lat for F12 and 0.3 ppt/ lat for F11. Reproducibility over all 
the measurements is 2% for F12, 3.5% for F11, 3.2% for F11/F12.

Calibration has been done using a 6 levels x2 curve.

Analytical performances 

The detection limit of the method is obtained during test-stations where all the 
bottles have been closed at the same level, corresponding to a near-zero CFC 
content. There is not true CFC-free waters in the ETAMBOT area. Our mean 
contamination level has been determined through a statistical method of the 
test-stations, the CFC content evolution at 1000 m depth (low CFC Upper 
Circumpolar Water) and a comparison with CITHER1 (A6 and A7 WHP lines) results.

The detection limit determined through the standard deviation over the test-
stations at 1000 m (stations 25 and 85) is around 0.004 pmol.kg-1 for F12 and 
0.01 pmol.kg-1 for F11.

We have examined the evolution of the F11/F12 ratio at the 1000m level in order 
to separate the part of bottles contamination to the part of the sampled water. 
Two groups of stations are identified:
  stations 5 to 23 with high F11/F12 ratio (7.3  3): for this set, an important 
  contamination part is evident. 

The respective contamination levels are 0.002 pmol.kg-1 for F12 et 0.033 
pmol.kg-1 pour F11.
  stations 24 to 84 with lower F11/F12 ratio (2.7  1). For this set the mean 
  contamination levels are  0.002 pmol.kg-1 for F12 and 0.007 pmol.kg-1 for F11.

These contamination levels have been systematically removed from the CFC values.

References 

Bullister, J.L., and R.F. Weiss, Determination of CCl3F and CCl2F2 in seawater 
    and air, Deep-Sea Res., 35, 839-853, 1988.

C.5 Samples Taken for Other Chemical Measurements

CO2 system parameters
    by J.F. Ternon and C.Oudot

Total inorganic carbon (TCO2)

Measurements of TCO2 were made by gas chromatography, according to the method 
described by Oudot and Wauthy (1978). The method basically consists of gas 
stripping of the seawater sample (1 cm3) after acidification, and of the gas 
chromatographic analysis of the gas mixture allowing the TCO2 separation and 
quantification. Routine calibration of the measurements was performed using 
liquid standard solutions prepared at the laboratory prior the cruise, according 
to a procedure adapted from the Goyet and Hacker (1992) technique. Primary 
calibration is done by using the Certified Reference Material delivered by A.G. 
Dickson (Scripps Institution of Oceanography).

Samples were taken from the surface to bottom, every two stations.

Quality control of TCO2 data has been performed using repeated measurements 
(duplicate) at each station (two bottles fired at the same depth ; different 
depth at each station), and "test" stations (all of the bottles closed at the 
same depth). Results for test stations are shown in Table 6.

TABLE 6: TCO2 replicate statistics

Station number     25      85      85
-----------------------------------------
Depth (dbar)       997     2001    997
Number of bottles  22      12      11
TCO2 (mol kg-1)   2196.1  2197.7  2121.6
Standard deviation
(mol kg-1)        8.2     10.3    8.4

Repeatability of TCO2 measurements was determined from statistical anlysis of 
duplicate results, according to the relationship (Dickson and Goyet, 1994):

                           S = (Sigma-di2 / 2n)1/2

where di = difference for pair i and n = number of pairs (32). For Etambot 1 
cruise S = 6.8 mol kg-1.

pH

The pH measurements were performed according to the potentiometric method on the 
total hydrogen ion concentration pH scale (Dickson (1993). The total hydrogen 
ion concentration, [H+], is expressed as moles per kilogram of sea water.

Measurements were made using a combination glass/reference electrode ORION(TM) 
type ROSS(TM) and a pHmeter ORION(TM) model 720A (resolution = 0.1 mv, i.e. 
0.0017 pH units). The Nernst response of the electrode was checked in the shore-
based laboratory before and after the cruise with two buffers: 'Tris' and '2-
aminopyridine'.

The pH electrode was calibrated against the 'Tris' buffer before every serial of 
measurements (every station), and the drift was estimated during each station 
(22 samples) for correction. The mean drift during a station, throughout the 
cruise, was 0.1-0.2 mV, i.e. 0.002-0.003 pH units. Seawater samples and buffers 
were thermostated at 25 C and the temperature was measured with a platine probe 
( 0.01 C).

Then, pH data were corrected to in situ conditions (temperature and pressure) 
according to the relationships of Millero (1995) for temperature and Millero 
(1979) for pressure.

Samples were taken from the surface to bottom, every two stations.

Quality control of pH data has been performed using repeated measurements 
(duplicate) at each station (two bottles fired at the same depth ; different 
depth at each station), and "test" stations (all of the bottles closed at the 
same depth). Results for test stations are shown in Table 7.

TABLE 7: pH replicate statistics

Station number      25      85      85
------------------------------------------
Depth (dbar)        997     2001    997
Number of bottles   21      11      12
PH                  7.983   8.041   7.880
Standard deviation  0.0020  0.0014  0.0027

Repeatability of pH measurements was determined from statistical analysis of 
duplicate results, according to the relationship (Dickson and Goyet, 1994):

                          S = (Sigma-di2 / 2n)1/2

where di = difference for pair i and n = number of pairs (33). For Etambot 1 
cruise S = 0.002 pH units.

Total alkalinity

Total alkalinity, AT, is defined as the number of moles of hydrogen ion 
equivalent to the excess of following bases formed from weak acids in one 
kilogram of sample:

           AT = [HCO3-] + 2 [CO32-] + [B(OH)4-] + [OH-] - [H+]

AT, expressed in eq kg-1, was estimated as the sum of the components of the 
right member of the previous relationship, calculated from TCO2 and pH 
measurements. The used equilibrium equations and thermodynamic data for carbonic 
acid, boric acid and water are identical to those reported in Dikson and Goyet 
(1994).

Samples were taken from the surface to bottom, every two stations.

Quality control of AT data has been performed using repeated measurements 
(duplicate) at each station (two bottles fired at the same depth ; different 
depth at each station), and "test" stations (all of the bottles closed at the 
same depth). Results for test stations are shown in Table 8.

TABLE 8: AT replicate statistics

Station number                 25      85      85
-----------------------------------------------------
Depth (dbar)                   997     2001    997
Number of bottles              21      12      11
AT (eql kg-1)                 2307.7  2294.8  2303.8
Standard deviation (eq kg-1)  7.8     8.1     10.9

Repeatability of AT measurements was determined from statistical analysis of 
duplicate results, according to the relationship (Dickson and Goyet, 1994):

                          S = (Sigma-di2 / 2n)1/2

where di = difference for pair i and n = number of pairs (32). For Etambot 1 
cruise S = 7.0 eq kg-1.

CO2 fugacity

The fugacity of CO2 in seawater was determined in air that was in equilibrium 
with a discrete sample of seawater. The fugacity, fCO2, is related to the 
partial pressure, pCO2 , by the relation (Weiss, 1974) to take into account the 
non-ideality of CO2:

                   fCO2 = pCO2 exp{(B + 2delta) patm / RT}

The partial pressure of CO2 in wet air is calculated from the molar fraction of 
CO2 in dry air, xCO2, the atmospheric pressure, P , and the H2O vapor pressure, 
pH2O  (Weiss and Price, 1980):

                       pCO2 = xCO2 p = xCO2 (P - pH2O)

The molar fraction of CO2 in equilibrated air was measured with an IR analyzer 
LI-COR(TM) model LI6262 . The analyzer was calibrated with three standard gases 
(329.0 - 349.6 - 407.7 ppm), produced by a French manufacturer, Air Liquide, in 
agreement with the scale of the Scripps standards. 

During the cruise, duplicate seawater samples were taken from only the surface 
bottle of the General Oceanics rosette and analyzed as described in Oudot et al. 
(1995). Besides, the measurement of atmospheric CO2 concentration was made twice 
a day by pumping an air stream taken at a mast at the bow of the vessel.

Then, the CO2 fugacity measured at 28 C was corrected for in situ 
temperature according to the temperature dependence equation of Copin-Montegut 
(1989).

The reproducibility of fCO2 measurements was determined from statistical 
analysis of 63 pairs of duplicate results, according to the relationship 
(Dickson and Goyet, 1994):

                           S = (Sigma-di2 / 2n)1/2

where di = difference for pair i and n = number of pairs (63). For Etambot 1 
cruise S = 2.9 atm.

Chlorophyll a and Phaeophytin 
   by C. Oudot and J. Neveux

During the cruise, seawater samples were taken from only the surface bottle of 
the General Oceanics rosette for determination of chlorophyll and phaeopigments 
as described in Neveux and Lantoine (1993) by the spectrofluorometric method.

Seawater was filtered on Whatman GF/F filter (diameter = 47 mm, porosity = 0.45 
m). The filters were stored at -25 C until the analysis in the shore-based 
laboratory.

References

Copin-Montegut C., 1989. A new formula for the effect of temperature on the 
    partial pressure of CO2 in seawater. Mar. Chem., 27, 143-144
Dickson A.G., 1993. pH buffers for seawater media based on the total hydrogen 
    ion concentration scale. Deep Sea Res., 40, 107-118.
Dickson A.G. and C. Goyet, 1994. Handbook of Methods for the Analysis of the 
    various Parameters of the Carbon Dioxide System in Srea Water. Version 2, 
    US. DOE, SGRP-89-7A.
Goyet C. and S.D. Hacker, 1992. Procedure for the calibration of a coulometric 
    system used for total inorganic carbon measurements in seawater. Mar. Chem., 
    38, 37-51.
Millero F.J., 1979. The thermodynamic of the carbonate system in seawater. 
    Geochimica et Cosmochimica Acta, 43,1651-1661.
Millero F.J., 1995. Thermodynamics of the carbon dioxide system in the oceans. 
    Geochimica et Cosmochimica Acta, 59, 661-677.
Neveux J. and F. Lantoine, 1993. Spectrofluorometric assay of chlorophylls and 
    phaeopigments using the least squares approximation technique. Deep Sea 
    Res., 40, 1747-1765.
Oudot C. and B. Wauthy, 1978. Adaptation of a gas chromatograph for shipboard 
    measurement of dissolved gases: nitrogen, oxygen and carbon dioxide (in 
    French). Cah. ORSTOM, ser. Oceanogr., 16, 89-102.
Oudot C., J.F. Ternon and J. Lecomte, 1995. Measurements of atmospheric and 
    oceanic CO2 in the tropical Atlantic: 10 years after the 1982-1984 FOCAL 
    cruises.
Weiss R.F., 1974. Carbon dioxide in water and seawater: the solubility of a non-
    ideal gas. Mar. Chem., 2, 203-215.
Weiss R.F. and B.A. Price, 1980. Nitrous oxide solubility in water and seawater. 
    Mar. Chem., 8, 347-359.

C.6 CTD Measurements

The following equipment was deployed on the CTD/multisampler underwater frame:

1. Neil Brown Mark IIIa with a polarographic Beckman sensor
2. General Oceanics 8-liter 24 bottle rosette.
3. 6 SIS digital reversing thermometers and 6 SIS digital reversing pressure 
   meters.
4. MORS 12 kHz pinger
5. A bottom proximity alarm
6. L-ADCP 140kHz RDI. 2 bottles have been removed.

CTD data were acquired through an EG&G demodulator, with the OCEANSOFT 1 
software. Data were stored on a PC. Raw analogic data were stored on DAT system.

The rosette was not equipped with the non-data interrupt rosette firing module.

We had no problems with the rosette and the bottles were fired at the desired 
depths.

C.7 CTD Data Collection and Processing
    By Y. Gouriou

Temperature Calibration

The temperature sensor of the CTD was calibrated before and after the cruise, on 
June 9, 1995 and December 15, 1995. The temperature sensor has been controlled 
for the following temperature: 0 C, 5 C, 10 C, 15 C, 20 C, 25 C, 30 C.

The calibration results are presented on figure 5. Between the pre- and post-
calibration the temperature sensor 
presents a drift of:

  0.010 C in average
  0,012 C at a temperature of 0 C (maximum)
  0.008 C at a temperature of 10 C, 15 C, and 20 C 
    (minimum).

We considered that the incertitude on the temperature measurements is of  
0.005 C.The solid line represents the 5th order polynomial adjustment applied 
to the CTD temperature measurements.

The CTD temperature has been compared to SIS reversing thermometer measurements. 
The SIS thermometers have been calibrated  before and after the cruise, at  the 
same dates than the CTD temperature sensor. The figures 6 show the temperature 
difference between the SIS and CTD measurements. The SIS and CTD temperature 
data  have been calibrated before the comparison. The figures 6 show a drift of 
the temperature difference from the station N 1 to the station N 35. That 
drift is not confirmed by the other comparisons (figures 6). In a first step the 
CTD temperatures have been corrected from that drift, but the calibration of the 
salinity sensor was not satisfactory, as confirmed by the comparisons of the 
theta-S diagrams of the ETAMBOT 1 cruise with the CITHER 1 cruise (WHP Line A7). 
We then decide not to correct the CTD temperatures from the drift observed.Note 
that:

if the CTD temperature sensor presents a drift of 0.011 C (at a 
  laboratory temperature of 5 C) between the pre- and post-calibration, 
  the SIS thermometer also drifted. The SIS thermometer T-106 and the SIS 
  thermometer T-7 present a drift of 0.009 +C and 0.007 C 
  respectively. 
as the rosette was not equipped with a non-data interrupt rosette firing 
  module, the CTD measurements (temperature, conductivity, oxygen) were 
  perturbed when a bottle was closed. It is likely that the precedent 
  comparison suffered  from that deficiency.

Pressure Calibration

The pressure sensor of the CTD was calibrated before and after the cruise, on 
June 9, 1995 and December 15, 
1995.

In order to estimate the hysteresis of the pressure sensor, laboratory 
calibration have been performed:
 
1 - for increasing pressure (down casts)
2 - for decreasing pressure (up casts)

The pressure sensor did not drift a lot during the 6-months interval (2 dbar at 
maximum)  and the difference between the pre-calibration and post-calibration is 
constant at every depth (Figure 7). We fitted the results of the calibration 
with a 5 order polynomial curve.

The CTD down-cast pressure measurements are calibrated by using the coefficients 
obtained in the laboratory for increasing pressure, at a temperature of 20 C. 
For the up casts we used the calibration coefficients obtained in the laboratory 
for decreasing pressure, at a temperature of 15 C. This was an arbitrary 
choice, as we had no means to know the temperature of the pressure CTD sensor. 
The use of two different reference temperatures, for the up- and down-cast 
calibration, induced different pressure values at 6000 m (Figure 7). The 
discrepancy is negligible at 5000 m, the maximum depth of the measurements.

For the shallow casts (depth < 500 m) we used only the calibration coefficients 
obtained for increasing pressure, estimating that the hysteresis is negligible. 

The pressure measured by the CTD can be compared to the SIS digital reversing 
pressure meters. The SIS  have been calibrated in the laboratory before and 
after the cruise at the same date than the CTD pressure sensor. The calibration 
has been made at a temperature of 2 C close to the temperature at which they 
were used. The figures 8 present the pressure difference between the SIS and CTD  
measurements before calibration. The solid line represents the calibration curve 
(SIS+CTD pressure) we should apply to that difference. The comparisons show that 
the SIS corrected pressure and CTD corrected pressure are equal  with an 
incertitude of 5 dbar. 

Salinity Calibration

The calibration of the CTD conductivity sensor is made by comparing the CTD 
conductivity measurements, at the depth where the bottles are closed, to the in-
situ conductivity of the water samples. The CTD conductivity measurements are 
corrected from the temperature and pressure effect on the conductivity cell. The 
CTD conductivity measurements are calibrated using a linear regression. The 
polynomial coefficients are computed iteratively.

IMPORTANTThe rosette was not equipped with a non-data interrupt rosette firing 
module. Due to this deficiency, the conductivity measurements were perturbed 
during the up-cast. We judged the perturbation sufficiently important to modify 
the normal calibration procedure: to find the calibration coefficients, we 
compared the water sample conductivity to the CTD conductivity measurements of 
the DOWN-cast instead of the UP-cast. We used the pressure of the up-cast water 
sample to find the CTD conductivity in the down-cast profile. This method is 
similar to that used for the calibration of the oxygen sensor. That procedure 
gave correct results, but has the disadvantage of eliminating an important 
number of water samples between the surface and 1500 dbar.
CALIBRATION

Note that:
* We used the same CTD conductivity sensor during the whole cruise.
* The CTD conductivity sensor has been cleaned before stations N 20, N 
  50,and N 71.  
* The stations made in shallow water (bottom < 1500 m) are: N 1, N 2, 
  N 3, N 4, N 5, N 58, N 63, N 64, N 65.

TABLE 9: Calibration coefficient for the CTD conductivity sensor

Stations  Number of     Number of         Standard deviation  Coefficients
          used samples  Retained samples  (0 - 6000 m)        C1        C2
--------------------------------------------------------------------------------
 1 -> 14  246           181               0.0039              1.000318  -0.02146
15 -> 21  159           119               0.0019              1.002110   0.07511
22 -> 24  78            64                0.0029              1.003115  -0.12824
26 -> 27  55            45                0.0030              0.999611   0.00476
28 -> 37  243           187               0.0018              1.001014  -0.03890
38 -> 56  413           331               0.0018              1.000381  -0.01719
   57     24            23                0.0065              0.997654   0.06776
58 -> 62  81            54                0.0021              1.000008  -0.00415
63 -> 70  124           104               0.0018              1.000123  -0.01022
71 -> 84  345           264               0.0014              1.000399  -0.02139

1847 water samples have been taken out during the cruise. Eliminated the samples   
of the test stations N 25 and   N 85, as well as the bad measurements, we 
retained 1768 water samples for   the calibration. 1372 comparisons   have been 
retained by the minimization process (77.6% of the measurements).    

The figure 9 shows the resulting conductivity difference after the calibration   
procedure. Only the station N 57   presents an important dispersion as the 
measurements between the surface and   1500 m have not been rejected by   the 
minimization process (that station being calibrated separately). 
 
The difference is lower than 0.001 mmho cm-1 for 23% of the samples.
The difference is lower than 0.003 mmho cm-1 for 60% of the samples.

CONTROL

To control the quality of the calibration, theta-S diagrams have been compared:

1. Between successive stations of the cruise.
2. Between stations made at the same position during the cruise (N 27 and N 
   82).
3. Between different cruises.

1. theta-S diagrams of consecutive stations made during the cruise have been 
   systematically compared. The differences (>= 0.0005), for potential 
   temperature lower than 1.9 C,have been systematically reported in the 
   following table. The difference is positive when the station in the first 
   column has a salinity greater than the station in the second column. 

TABLE 10: Salinity comparison between contiguous profiles of the ETAMBOT 1 
          cruise

ETAMBOT 1       ETAMBOT 1       Salinity 
Station Number  Station Number  Difference 
-------------------------------------------
8               9               0.0020
10              11              0.0010
19              20              0.0005
21              22              0.0020
22              23              0.0005
23              24              0.0010
24              26             -0.0050
30              31              0.0005
34              35              0.0005
37              38             -0.0010
49              50              0.0005
50              51             -0.0005
55              56              0.0005
69              70             -0.0005
70              71              0.0010
71              72             -0.0005

Remarks
* Station N 8 and N 9: the 0.0020 difference is observed above 2 
  C. Other tracers also show properties differences.
* Station N 21 and N 22, and station N 24 and N 26 (station 
  N 25 is a test station): No error have been found in the sample analysis 
  that could explained the observed difference. The comparison between the 
  theta-S diagrams of these stations and  stations made at the same locations 
  during the CITHER 1 cruise (WHP A6 line) confirm the differences observed (see 
  below).

2. The comparison of the stations made at the same position during the cruise (N 
   27 and N 82) show that there are perfectly superimposed for 
   potential temperature smaller than 1.9 C (Figure 10). 

3. Comparison with preceding cruises
   The ETAMBOT 1 cruise repeats exactly the western track of the CITHER 1 
   cruise, along the 7 30'N latitude and 35 W longitude. Excluding 
   shallow stations, about 40 theta-S diagrams have been compared. The 
   result of that visual comparison is shown in the following table. Only the 
   stations where the differences are equal or greater than 0.0005 are reported:

TABLE 11: Salinity comparison between ETAMBOT 1 and CITHER 1 profiles

ETAMBOT 1       CITHER 1        Salinity 
Station Number  Station Number  difference
------------------------------------------
11              129             -0.0010
16              134             -0.0005
19              137              0.0005
22              140             -0.0020
23              141             -0.0035
24              142             -0.0050
35              154             -0.0005
36              155             -0.0005

The comparison is good except for the station N 22, 23, and 24. The 
differences observed for those stations are coherent with the differences 
observed between the stations N 21 and N 22, and the station N 24 
and N 26 of the ETAMBOT 1 cruise.

We then decide to correct the salinity profiles of the stations N 22, N 
23, and N 24:

0.0020 has been added to the CTD salinity profile of station N 22.
0.0035 has been added to the CTD salinity profile of station N 23.
0.0050 has been added to the CTD salinity profile of station N 24.

Furthermore the theta-S diagrams of the repeated-ETAMBOT 1 stations N 27 
and N 82 are perfectly superimposed with the theta-S diagrams of the CITHER 
1 station N 144 (Fig. 11), for potential temperatures lower than 1.9 deg C.

Oxygen Calibration

The same CTD oxygen sensor has been used during the whole cruise.

CTD oxygen were calibrated by fitting to sample values using the method 
described in Owens and Millard [1985] .

1847 oxygen samples have been gathered during the cruise. Excluding the samples 
of the test stations N 25 and N 85 as well as the bad sample analysis, 1777 
samples have been used to calibrate the data. 1667 samples (93.8%) have been 
retained during the fitting process. The following Table shows the results of 
the calibration:

TABLE 12: Calibration result for the oxygen sensor

Station Number  Number of     Number of         Standard deviation 
                used samples  retained samples  (0-5000 m) mol kg-1
--------------------------------------------------------------------------
1 -> 6          72            66                1.7
7 -> 10         88            85                1.8
  11            22            20                0.9
  12            22            22                2.6
  13            22            19                0.7
  14            21            20                1.2
  15            21            21                1.4
  16            22            22                1.1
  17            22            22                1.0
  18            21            21                0.8
  19            22            22                1.3
  20            21            21                0.7
  21            28            28                1.7
  22            28            27                1.7
  23            28            27                1.0
24 -> 26        53            53                1.8
27 -> 30        99            95                1.2
31 -> 35        124           111               1.2
  36            22            20                0.7
37 -> 38        43            42                1.5
  39            22            22                2.4
  40            22            22                1.5
  41            22            21                0.9
  42            21            19                0.4
43 -> 46        86            82                1.6
47 -> 49        64            62                1.5
50 -> 54        108           97                1.1
55 -> 57        70            64                1.6
58 -> 62        81            72                1.8
63 -> 70        130           115               1.3
71 -> 83        326           303               1.7
  84            24            24                1.7

The figures 12 show the differences, in mol kg-1, between the oxygen samples 
and the down-cast CTD measurements.

The difference is lower than 1 mol kg-1 for 33% of the samples .
The difference is lower than 2 mol kg-1 for 74% of the samples .

CONTROL

The figure 13 shows the CTD oxygen profiles of the repeated station N 27 
and N 82. The profiles are well adjusted to the oxygen samples. The 
difference observed at the bottom disappears on the theta-O2 diagram.

As for the salinity profiles, the comparison with the oxygen profiles of the 
CITHER 1 have been made. Along the 7 30'N latitude the comparison is good 
(figure 14). Along the 35 W longitude some systematic differences 
are observed: they are reported in the following Table:

TABLE 13: Oxygen comparison between ETAMBOT 1 and CITHER 1 profiles

ETAMBOT 1       CITHER 1        Oxygen difference 
Station number  Station number  in mol kg-1
-------------------------------------------------
37              119             -3.0
38              118             -3.0
39              117             -4.0
40              116             -4.0
41              115             -3.0
42              114             -1.5
43              113             -2.0
46              111             -3.0
47              110             -3.0
48              109             -2.0
50              107             -1.0
51              106             -1.0
52              105             -2.0
53              104             -2.0
54              103             -1.5
55              102             -2.5

These differences are generally observed between 2000 m and the bottom (Figure 
15a). For every cruise the CTD oxygen profiles are well fitted to the samples. 
The bias observed seemed to be confirmed by the repeated stations performed 
during the CITHER  1 cruise at 7 30'N-35 W, station N 119 and N 156 (Figure 
15b). As fifteen days separates those 2 stations we are not able to say if that 
difference is due to a natural variability.

NOTE

The CTD oxygen profiles have not been de-spiked. Some profiles show important 
spikes in the upper thermocline.The CTD oxygen profiles have not been filtered. 

Acknowledgements

This project has been supported by ORSTOM as part of the Programme National 
d'Etude de la Dynamique du Climat, and its WOCE/France subprogramme.

Figures caption

Figure 1:  Cruise track and station position.

Figure 2:  Oxygen versus salinity for ETAMBOT 1 and historical data (SAVE Leg 6 
           [35 W, 1 N to 1 S] and TTO-TAS [45 W-1 N to 
           41 W-7 30'N]).

Figure 3:  Nitrate - phosphate correlation for ETAMBOT 1 cruise data.

Figure 4:  Silicate versus temperature for ETAMBOT 1 and historical data (SAVE 
           Leg 6 [35 W, 1 N to 1 S] and TTO-TAS [45 W-1 
           N to 41 W-7 30'N]).

Figure 5:  Temperature difference , in  C, between the laboratory reference 
           temperature and the temperature measured by the probe. The solid 
           represent the 5th order polynomial minimizing the differences.(+: 
           calibration before the cruise. *: calibration after the cruise).

Figure 6:  Temperature difference, in  C, between SIS and CTD measurements 
           (after calibration).

Figure 6:  Temperature difference, in  C, between SIS and CTD measurements 
           (after calibration).

Figure 6:  Temperature difference, in  C, between SIS and CTD measurements 
          (after calibration).

Figure 7:  Pressure difference, in dbar, between the laboratory reference 
           pressure and the pressure measured by the probe. The solid represent 
           the 5th order polynomial minimizing the differences. 
  a) calibration for increasing pressure at a 20 C temperature (down cast).
  b) calibration for decreasing pressure at a 15 C temperature (up cast).

Figure 8:  Pressure difference, in dbar, between SIS and CTD measurements 
           (before calibration). The solid line represents the sum of the SIS 
           and CTD pressure correction to add to the pressure difference.

Figure 8:  Pressure difference, in dbar, between SIS and CTD measurements 
           (before calibration). The solid line represents the sum of the SIS 
           and CTD pressure correction to add to the pressure difference.

Figure 9:  Conductivity difference, in mmho/cm, between water sample and CTD 
           measurements, after calibration.
  a) difference as a function of station number.
  b) difference as a function of pressure.

Figure 10: theta-S diagram of repeated ETAMBOT 1 stations N 27 and N 
           82 (41 20'W-7 30'N).

Figure 11: Comparison of the theta-S diagram of ETAMBOT 1 and CITHER 1 stations.
  a) ETAMBOT 1 station N 82 (41 20'W-7 30'N) and CITHER 1 station 
     N 144 (41 20'W-7 30'N)
  b) ETAMBOT 1 station N 27 (41 20'W-7 30'N) and CITHER 1 station 
     N 144 (41 20'W-7 30'N)

Figure 12: Dissolved oxygen difference, in  mol kg-1, between water sample and 
           CTD measurements.
  a) difference as a function of station number.
  b) difference as a function of pressure.

Figure 13: Dissolved oxygen profiles, in  mol kg-1, of repeated stations N 
           27 and N 82 (41 20'W-7 30'N). 
  *: water sample measurement of station N 27
  x: water sample measurement of station N 82

Figure 14: Dissolved oxygen profiles, in  mol kg-1.
  a) ETAMBOT 1 station N 27 (41 20'W-7 30'N) and CITHER 1 station n 144 
     (41 20'W-7 30'N).
  b) ETAMBOT 1 station N 19 (46 W-7 30'N) and CITHER 1 station n 137 
     (46 W-7 30'N).

Figure 15: Dissolved oxygen profiles, in  mol kg-1.
  c) ETAMBOT 1 station N 39 (35 W-7 N) and CITHER 1 station n 117 
     (35 W-7 N).
  d) CITHER 1 station N 119 (35 W-7 30'N) and CITHER 1 station n 156 
     (35 W-7 30'N