TO VIEW PROPERLY YOU MAY NEED TO SET YOUR BROWSER'S CHARACTER ENCODING TO UNICODE 8 OR 16 AND USE YOUR BACK BUTTON TO RE-LOAD CRUISE REPORT: AR04EW / AR15 (Updated FEB 2009) A.1 HIGHLIGHTS CRUISE SUMMARY INFORMATION WOCE section designation AR04EW / AR15 Expedition designation (EXPOCODE) 33LKETAMBOT2_1 Chief Scientist & affiliation Yves Gouriou/ORSTOM* Dates 1996 APR 15 - 1996 May 16 Ship R/V EDWIN LINK Ports of call Leg 1: Cayenne, French Guiana to Natal, Brazil Leg 2: Natal, Brazil to Cayenne, French Guiana Number of stations 95 08°24.03'N Geographic boundaries 34°54.39'W 51°33.85'W 04°46.91'S Floats and drifters deployed 0 Floats, 0 Drifters Moorings deployed or recovered 0 Deployed, 0 recovered Contributing Authors C. Andrié B. Bourlès F. Baurand R. Chuchla P. Fournier Y. Gouriou C. Oudot J.F. Ternon *Yves Gouriou • Centre ORSTOM de Brest IFREMER B.P. 70 Plouzane, 29280 • FRANCE Tel: 33-98-22-4515 • Fax: 33-98-22-4545 • Email: gouriou@orstom.fr 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 Natal (5°48’S-35°18’W). Second leg: Natal (5°48’S-35°18’W) to Cayenne (4°51’N-52°15’W). NUMBER OF STATIONS A total of 95 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. SAMPLING Double casts were performed for deep stations (bottom > 4000 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: 16 shallow stations with less than 22 water samples. 51 stations with 22 water samples. 27 stations with 28 water samples (double casts). 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 the surface and the bottom for 94 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°31: all the bottles closed at 1000 m depth. Station N°42: all the bottles closed at 2000 m depth. Station N°72: all the bottles closed at 2000 m depth. Station N°87: all the bottles closed at 1000 m depth. At every station 2 bottles were closed at the same depth. FLOATS, DRIFTERS, AND MOORINGS No floats, drifters, or moorings were deployed during this cruise. A.3 LIST OF PRINCIPAL INVESTIGATORS TABLE 1. Principal investigators _____________________________________________________ Name Responsibility Institution -------------------- ---------------- ----------- Chantal Andrié Freons ORSTOM Bernard Bourlès S-ADCP, Salinity ORSTOM Yves Gouriou CTD, L-ADCP ORSTOM Claude Oudot Nutrients – O(2) ORSTOM Jean-François 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. An other cruise, ETAMBOT1, has 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. 4 SIS reversing pressure meters and 4 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 on 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.5 MAJOR PROBLEMS ENCOUNTERED ON THE CRUISE (1) The salinity sensor of the first CTD probe (n°2756) stopped working normally at station N°9. That station has been occupied again at the end of the cruise (station N°90). We replaced the probe with the spare one (n°2782) at station N°10. Inspection of the first probe, during the call in Natal, showed that the failure was due to the fast temperature sensor of the probe. (2) The power supply of the first Deck Unit was insufficient to correctly supply the second CTD probe (n°2782). So the conductivity profiles of stations N° 10 to 13 were noisy. We solved that problem at station N°14 by replacing the Deck Unit. The stations N°4 to N°10 and station N°13 have been sampled again at the end of the cruise (stations N°88 to 95). (3) From station N°14 the oxygen sensor of the CTD probe (n°2782) did not work well. Few profiles of oxygen have been made during the first part of the cruise. (4) The salinity sensor of the second CTD probe (n°2782) was deteriorated at our arrival in Natal. We changed the probe after the call, replacing the fast temperature sensor of the probe n°2756 by the sensor of the probe n°2782. This CTD probe (n°2756) worked well during the second part of the cruise (and the oxygen sensor too). (5) The acoustic bases of the deep sounder never worked during the cruise. This failure could have compromised the entire cruise, but: a) the track of the ETAMBOT 2 cruise was similar to the track of the ETAMBOT 1 cruise. So we knew more or less the depth at the station position. b) we used a mechanical system that rings in the laboratory when the rosette is close to the bottom, generally 15 m above, but for this cruise we stopped the rosette about 25 m above the bottom. The vertical penetration of the S-ADCP acoustic signal was only 100 m when the ship was on route. This weak vertical penetration was certainly due to turbulence close to the well where the ADCP was placed in. During the stations, when the ship stopped, the vertical penetration of the measurements was about 300 m. A.6 LIST OF CRUISE PARTICIPANTS TABLE 2. Cruise participant ____________________________________________________________________ Name Responsibilities Affiliation Leg -------------------- -------------------------- ----------- --- Chantal Andrié CFCs ORSTOM 1-2 François Baurand Nutrients ORSTOM 1-2 Jean-Michel Bore Elec. Engineer/CTD/L-ADCP ORSTOM 1-2 Bernard Bourlès CTD/S-ADCP/Salinity ORSTOM 1-2 William Biegun CFCs ORSTOM 1-2 Rémy Chuchla CTD/Salinity ORSTOM 1-2 Denis Diverres CO2 ORSTOM 1-2 Philippe Fournier Oxygen ORSTOM 1-2 Yves Gouriou Chief Scientist/CTD/L-ADCP ORSTOM 1-2 Christophe Le Doare CTD/L-ADCP ORSTOM 1-2 Frédéric Marin CTD/salinity ORSTOM 1-2 Yves Montel Nutrients ORSTOM 1-2 Claude Oudot CO2 ORSTOM 1-2 Jean-François Ternon CFCs ORSTOM 1-2 ____________________________________________________________________ ORSTOM: Institut Français de Recherche Scientifique pour le Développement en Coopération B. UNDERWAY MEASUREMENTS B.1 NAVIGATION (B. Bourlès) Navigation data (time, position, course and speed over ground, and fix quality information) were acquired every 15 seconds throughout the ETAMBOT- 2 cruise, from the 04/15/1996 at 18h50 TU to the 05/16/1996 at 10h55 TU, with the vessel Magnavox MX200 Global Positioning System (GPS). The GPS was located in the bridge, and navigation information were transmitted to a Personal Computer dedicated to navigation and thermosalinograph measurement acquisition, located in the main laboratory. Due to a not clarified network problem between the bridge and the laboratory, the registered time was erroneous, yet the position (latitude and longitude) was correct. As the internal acquisition PC clock, and the internal L-ADCP clock, were perfectly synchronized, we used the acquisition-PC clock for time reference. Thus, we registered this PC time at the beginning and at the end of every CTD-O2 station during the cruise, and used these time reference values to correct the GPS time information, hence the navigation. We first linearly constructed a time reference data base, and then attributed the ‘true’ position to the correct time, using a 2 minutes time filter. Navigation measurements were also acquired by the S- ADCP acquisition system (see chapter B3), using the RDI ‘GPRMC’ software. This software calculates the average of GPS successive information around the velocity acquisition times, and registers ‘mean’ navigation every 5 minutes. The re-calculated navigation data are in very good agreement with this navigation data base (differences are of the order of 1/100 minute), and has been used with confidence for L-ADCP data treatment (see chapter B4). B.2 ECHOSOUNDING None. B.3 ACOUSTIC DOPPLER CURRENT PROFILER (ADCP) ( B. Bourlès) The S-ADCP system on board the R/V EDWIN LINK is a 153 kHz RD-VM150 Instruments unit with a hull mounted transducer. The four-beam transducer is mounted in a open sea well, and located to port side around the vessel centerline at about 3 meters depth. It is connected by cable to a deck box, containing the processing equipment, and connected to a Personal 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 acquired with a Magnavox MX4200 Global Positioning System (GPS). 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 at 16 meter depth. Sea salinity value, necessary to calculate the sound velocity during data acquisition, was fixed to 25 off French Guiana because of the influence of fresh Amazon water, and to 35 or 36 (considering the thermosalinograph measurements) in the open sea. 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. The corrected time is then included in the data base. Navigation and transducer temperature are first checked. ‘Noisy’ bins or profiles are suppressed. Due to the location of the transducer, and to the presence of turbulence along the hull during the vessel course, current velocity profiles were only available during CTD stations, when vessel was stopped. Navigation and S-ADCP measurements are combined in order to obtain absolute current values. The current velocity is calibrated using the Pollard and Read (1989) standard procedure. Absolute velocity profiles were obtained down to about 350 m depth. The original 5 minutes profiles have been averaged into ‘in stations’ profiles; 96 mean velocity profiles are thus available. 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 shipmounted acoustic Doppler profilers, and the limitations of gyro compasses, J. Atmos. Oceanic Technol., 6, 859-865, 1989. B.4 L-ADCP MEASUREMENTS (B. Bourlès, Y. Gouriou, R. Chuchla) The Lowered Acoustic Doppler Current Profiler (L-ADCP) allows to provide absolute currents over the whole water column. The L-ADCP is a BroadBand 150 kHz RD Instruments unit. It was attached to the ‘rosette’, and two water bottles had to be 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 raised at about 1 m s^-1, except during the up-cast when the package was stopped to fire the bottles. Standard setup parameters used were: 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 Hémon (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 of the bins perturbed by the bottom reflections were suppressed. The reference velocity was determined using the precise time and position at the beginning and at the end of the profile, generally known thanks to a Global Positioning System (GPS). Error due to this reference velocity determination is estimated to 1 cm s^-1 (Fischer and Visbeck, 1993). Here, due to GPS time transmission problems (see navigation chapter), we used the time of position recalculated from ‘true’ navigation information. 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. The L-ADCP perfectly worked during all the CTD-O2 casts; hence, ninety-nine absolute velocity profiles were acquired during the Etambot-2 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. Hémon: Traitement des données L-ADCP, Centre ORSTOM de Cayenne, documents scientifiques n° O.P. 21, 56pp, 1997. B.5 THERMOSALINOGRAPH MEASUREMENTS (B. Bourles) Continuous underway measurements of surface salinity and temperature were made with a Seabird SBE-21 shipboard mounted thermosalinograhp (TSG), calibrated one month before the cruise. Waters amples were taken below the sea surface at the forward side of the vesssel, and forwarded thanks to a pump to the thermosalinograph, located in the main acquisition laboratory. TSG measurements were acquired every 15 seconds. As the sampling hole was certainly too close to the surface, air bubbles contamined waters amples during vessel course, due to pitch and roll, when rough sea conditions occurred (mainly at the beginning of the cruise and off the Amazon mouth). There, raw measurements were noisy and exhibited numerous picks or erroneous values. In the same way, due to unpowerfull pumping, salinity linearly decreased on station, when vessel is stopped. Thus, a first visualization allowed to eliminate every erroneous or doubtful TSG measurement. A second step consisted to filter the measurements (temperature and salinity in a same processing), by using a median filter (Henin and Grelet, 1996). We kept the median T/S values over a 15-minute time window, after discarding T/S values more than five standard deviations from the mean calculated over the window. Thus, TSG measurements have been filtered and averaged over 15 mn time intervals. However, a comparison with sample salinity measurements and CTD-O2 temperature measurements is necessary before every quantitative use of the TSG data. REFERENCE Henin, C., and J. Grelet: A merchant ship thermo-salinograph network in the Pacific ocean, Deep-Sea Res., 43, 11-12, 1833-1855, 1996. B.6 XBTs B.7 METEOROLOGICAL MEASUREMENTS (B. Bourlès) Meteorological measurements were recorded at the beginning of every CTD-O2 station. These measurements are the following: date, time, position, wind speed (m s^-1), wind direction (degrees from geographical north), sea level pressure (mbar), sea level temperature (°C), and relative humidity (%). Weather, clouds and sea level conditions have not been recorded. C. HYDROGRAPHIC MEASUREMENTS TECHNIQUES AND CALIBRATIONS C.1 SAMPLE SALINITY MEASUREMENTS (P. Fournier and C. Oudot) Salinity analysis of samples collected during ETAMBOT 2 were carried out onboard with a Guildline(TM) Portasal(TM) 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 (K(15) = 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 (all bottles fired at the same depth, twice) and duplicate samples (two different bottles fired at the same depth, seventy-four times). The standard deviations of the two groups of replicate samples are given in the Table 3 below. TABLE 3. Salinity replicate statistics ________________________________________________ Station number 42 72 ----------------------- --------- --------- Pressure (dbar) 2020 2500 Number of bottles 22 22 Mean salinity (psu) 34.9772 34.9504 Maximum deviation (psu) 0.0013 0.0012 Standard deviation 0.0005 0.0005 _______________________________________________ The standard deviation of the seventy-four sample pairs (duplicate), taken at different depths, is 0.0010 psu. C.2 SAMPLE OXYGEN MEASUREMENTS (P. Fournier and C. Oudot) SAMPLING AND TECHNIQUES Oxygen samples were taken in calibrated clear glass bottles (capacity = 120 cm^3) 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 22 ± 1°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 Metrohm(TM) Titrator(TM) model 682 and a Dosimat(TM) 665 burette (10 cm^3). The concentration of oxygen dissolved in seawater was converted to mass fraction by use of the following relationship: O2 [µmol kg^-1] = (44.660 / ρ(sw)) * O2 [cm^3 dm^-3] where r(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 four groups of replicate (taken from different bottles fired at the same depth) samples and a large number (seventy-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 32 42 72 87 ---------------------------------- ------ ------ ------ ------ Pressure (dbar) 1030 2020 2500 1000 Number of bottles 22 22 22 22 Mean O2 concentration (µmol kg^-1) 152.0 255.1 259.0 153.1 Maximum deviation (µmol kg^-1) 0.7 0.6 0.3 1.7 Standard deviation (µmol kg^-1) 0.7 0.2 0.4 0.6 ____________________________________________________________________ The standard deviation of the seventy-nine sample pairs (duplicate) is 0.5 µmol kg^-1, i.e a value not significantly different from reproducibility of replicates. 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 panel (TTO-TAS) where the latitude range is wider, the agreement is satisfactory. REFERENCES Culberson C.H., 1991. Dissolved 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 (F. Baurand and C. Oudot) EQUIPMENT AND TECHNIQUES Nutrient analyses were performed on a Braun & Luebbe(TM) AutoAnalyzer(TM)II type Technicon (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 Cm^). 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 Metrohm(TM) automatic burette model Dosimate(TM) 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 (Baker(TM), anal. grade., certified 99.99%, for phosphate, nitrate and nitrite; Carlo Erba(TM), 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 Ω. 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 (µmol 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 ‰ solution of analytical grade sodium chloride. The linearity of the calibration curve (Beer’s Law) was not valid beyond 20 µmol 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 four groups of replicate (taken from different bottles fired at the same depth, during four test stations) samples and a large number (seventy-four) 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 0.3% for silicate, 0.4% for phosphate and 0.2% for nitrate, in agreement with WHP recommendations (WOCE, 1994). TABLE 5. Nutrient replicate statistics SILICATE ______________________________________________________________________________ Station number 32 42 72 87 ---------------------------------------- ------- ------- ------- ------- Pressure (dbar) 1000 2000 2500 1000 Number of bottles 22 22 22 22 Mean silicate concentration (µmol kg^-1) 27.32 18.85 23.28 27.19 Standard deviation (µmol kg^-1) 0.13 0.07 0.08 0.35 Percent standard deviation 0.48 0.39 0.35 1.27 Percent standard deviation 0.11 0.06 0.07 0.29 (vs full range, 120 μmol kg^-1) ______________________________________________________________________________ PHOSPHATE _______________________________________________________________________________ Station number 32 42 72 87 ------------------------------------------ ------- ------- ------- ------ Pressure (dbar) 1000 2000 2500 1000 Number of bottles 22 22 22 22 Mean phosphate concentration (µmol kg^-1) 2.09 1.22 1.23 2.08 Standard deviation (µmol kg^-1) 0.01 0.01 0.02 0.01 Percent standard deviation 0.60 0.83 0.38 0.47 Percent standard deviation 0.42 0.33 0.15 0.33 (vs full range, 3 µmol kg^-1) _______________________________________________________________________________ NITRATE ___________________________________________________________________ Station number 32 72 87 --------------------------------------- ------- ------- ------ Pressure (dbar) 1000 2500 997 Number of bottles 22 22 22 Mean nitrate concentration (µmol kg^-1) 31.10 19.00 31.45 Standard deviation (µmol kg^-1) 0.08 0.03 0.05 Percent standard deviation 0.27 0.17 0.15 Percent standard deviation 0.21 0.08 0.12 (vs full range, 40 µmol kg^-1) ___________________________________________________________________ The standard deviation of the seventy-four sample pairs (duplicate) is 0.4 μmol kg^-1 for silicate, 0.02 μmol kg^-1 for phosphate and 0.1 μmol kg^-1 for nitrate. The consistency of phosphate and nitrate data is shown in Figure 3 by the strong correlation between these two nutrients (R^2 = 0.9935). The slope of the regression line (15.092) 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. Tréguer P. and P. Le Corre, 1975. Manuel d’analyse des sels nutritifs dans l’eau de mer (utilisation de l’AutoAnalyzer II Technicon). Université de Bretagne Occidentale, Brest, 2^(eme) édition., 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 (C. Andrié) WORK ON BOARD During the cruise, three 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. Samples from the whole water column have been taken. This corresponds to at least 22 samples per profile. 28 samples have been taken for stations with double casts with bottom depth greater than 4500 m (stations 22 to 26, 28 to 35, 51 to 57 and 79 to 85). Atmospheric measurements have been realized every two days, from syringe samples. Globally, 3725 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 before the first station. Important CFC links have perturbed the first analyses on board. The analytical system has been moved in another laboratory, without air conditioning. Finally, measurements were satisfactory, excepted during station 32 where a high F-12 blank made impossible good measurements. 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. For the whole cruise, the reproducibility for the standard content was ±0.4% for F12 and ±0.4% for F11, so better than for ETAMBOT1. The atmospheric mixing ratios were 524.5 ppt (±1.1%) for F12 and 267.1 ppt (±1.2%) for F11 so in the same order of magnitude than during ETAMBOT1. Calibration has been done using a 6 levels x^2 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. Differently from CITHER 1, 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 results. The detection limit determined through the standard deviation over the test-stations at 1000 m (stations 32 and 87) is around 0.005 pmol.kg^-1 for F12 and 0.008 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: the mean contamination levels are 0.003 pmol.kg^-1 for F12 and 0.025 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 CCl(3)F and CCl(2)F(2) in seawater and air, Deep-Sea Res., 35, 839-853, 1988. C.5 SAMPLES TAKEN FOR OTHER CHEMICAL MEASUREMENTS CO2 SYSTEM PARAMETERS (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 cm^3) after acidification, and of the gas chromatographic analysis of the gas mixture allowing the TCO(2) 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 32 42 72 87 ------------------------------- ------ ------ ------ ------ Depth (dbar) 1000 2000 2500 1000 Number of bottles 21 22 17 22 TCO2 (µmol kg^-1) 2202.3 2215.9 2225.4 2201.6 Standard deviation (μmol kg^-1) 9.1 14.2 7.7 6.1 _________________________________________________________________ Repeatability of TCO2 measurements was determined from statistical analysis of duplicate results, according to the relationship (Dickson and Goyet, 1994): S = (Σd(i)^2/2n)^(1/2) where d(i) = difference for pair i and n = number of pairs (76). For Etambot2 cruise S = 9.7 μmol 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™ 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 32 42 72 87 ------------------ -------- -------- -------- -------- Depth (dbar) 1000 2000 2500 1000 Number of bottles 21 21 22 21 pH 7.880 8.014 8.008 7.881 Standard deviation 0.003 0.003 0.002 0.005 ____________________________________________________________ Repeatability of pH measurements was determined from statistical analysis of duplicate results, according to the relationship (Dickson and Goyet, 1994): S = (∑d(i)^2/2n)^(1/2) with d(i) = difference for pair i and n = number of pairs (76). For Etambot 2 cruise S = 0.003 pH units. TOTAL ALKALINITY Total alkalinity, A(T), 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: A(T) = [HCO(3)^-] + 2 [CO3^(2-)] + [B(OH)(4)^-] + [OH^-] - [H^+] A(T), expressed in μeq 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 A(T) 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. A(T) replicate statistics ________________________________________________________________ Station number 32 42 72 87 ------------------------------ ------ ------ ------ ------ Depth (dbar) 1000 2000 2500 1000 Number of bottles 21 21 17 21 A(T) (µeql kg^-1) 2308.7 2280.4 2397.2 2309.9 Standard deviation (µeq kg^-1) 9.4 15.0 8.3 6.8 ________________________________________________________________ Repeatability of A(T) measurements was determined from statistical analysis of duplicate results, according to the relationship (Dickson and Goyet, 1994): S = (∑d(i)^2/2n)^(1/2) with d(i) = difference for pair i and n = number of pairs (76). For Etambot 2 cruise S = 10.8 µeq 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, ƒCO2, is related to the partial pressure, ρCO2 , by the relation (Weiss, 1974) to take into account the non-ideality of CO2: ƒCO2 = ρCO3 exp{(B + 2δ) ρ(atm)/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, ρ(H2O) (Weiss and Price, 1980) : ρCO2 = xCO2ρ = xCO2 (P – ρ(H2O)) 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 – 360.5 – 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 ƒCO2 measurements was determined from statistical analysis of 86 pairs of duplicate results, according to the relationship (Dickson and Goyet, 1994): S = (∑d(i)^2/2n)^(1/2) where d(i) = difference for pair i and n = number of pairs (86). For Etambot 2 cruise S = 2.2 µatm. REFERENCES Copin-Montégut 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 Sea 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. 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, sér. Océanogr., 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 150kHz 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 Two CTD-O2 Neil Brown Mark IIIa probes have been used during the cruise. The N°2756 probe has been used for stations N°1 to N°9. Due to a failure of the fast temperature sensor at station N°9, the N°2782 probe has been used from station N°10 to station N°64. For these stations, the oxygen sensor worked only for a few stations. The N°2756 probe has been repaired at the Natal (Brazil) port of call and used for stations N°65 to N°95. Due to a too weak power supply, conductivity and oxygen profiles of stations N°10 to N°13 are noisy. The problem was solved at station N°14. TEMPERATURE CALIBRATION The temperature sensors of the two CTD probes were calibrated before and after the cruise. The N°2756 probe has been calibrated on December 15, 1995, and on October 30, 1996. The N°2782 probe has been calibrated on December 6, 1995, and on October 1, 1996. The temperature sensors have been controlled for the following temperature: 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C. PROBE N°2756 The calibration results for the N°2756 are presented on figure 5a. Between the pre- and post-calibration the temperature sensor presents a drift of: • 0.006°C in average • 0.008°C at a temperature of 0°C (maximum) • 0.000°C at a temperature of 10°C (minimum). We considered that the incertitude on the temperature measurements is of ±0.003°C. The solid line represents the 5th order polynomial adjustment applied to the CTD temperature measurements. PROBE N°2782 The calibration results for the N°2782 probe are presented on figure 5b. Between the pre- and post-calibration the temperature sensor presents a drift of: • 0.002°C in average • 0.005°C at a temperature of 5°C (maximum) • 0.000°C at a temperature of 10°C (minimum). We considered that the incertitude on the temperature measurements is of ±0.001°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 that there is a bias between the two types of measurements: a bias of +0.017°C for the N°T_216 thermometer and +0.007°C for the N°T_707 thermometer. The laboratory calibrations point out an important drift at the 0°C temperature reference (+0.025°C for the N°T-216 thermometer and +0.015°C for the T_707 thermometer) for the SIS thermometers. The observed bias was constant during the whole cruise, and does not depend on the probe we used. We are thus confident in the probe measurements and we attributed the observed bias to the SIS thermometer measurements. PRESSURE CALIBRATION The pressure sensor of the CTD was calibrated before and after the cruise. The N°2756 probe has been calibrated on December 15, 1995, and on October 30, 1996. The N°2782 probe has been calibrated on December 6, 1995, and on October 1, 1996. 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) PROBE N°2756 (Figure 7) The pressure sensor did not drift a lot during the 6-months interval (less than 2 dbar) 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. PROBE N°2782 (Figure 8) The calibration coefficient of the N°2782 probe have been computed by A.Billant of the Laboratoire d’Océanographie Physique of the IFREMER center in Brest. 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 9 present the pressure difference between the SIS and CTD measurements after calibration. 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. IMPORTANT The 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 profile. 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: • the CTD n°2756 has been used for stations N°1 to N°9 and for stations N°65 to N°95 • CTD conductivity are unusable below 2580 dbar for the station N°8. • CTD conductivity are unusable below 1500 dbar for the station N°9. • CTD conductivity profiles of station N°10, N°11, N°12, N°13 are unusable. • The CTD conductivity sensor has been cleaned before stations N°20, N°36, n°49, n°65, n°80. • The stations made in shallow water (bottom < 1500 m) are : N°1, N°2, N°3, N°4, N°5, N°63, N°64, N°65, N°66, N°94, N°95. TABLE 9. Calibration coefficient for the CTD conductivity sensor _________________________________________________________________ Stations Number Number of Standard of used retained deviation Coefficients samples samples (0–6000 m) C1 C2 -------- ------- --------- ---------- -------- -------- 1 -> 7 75 59 0.0085 1.000496 -0.02704 8 19 19 0.0121 1.000926 -0.03716 14 -> 19 129 94 0.0023 0.999995 -0.00495 20 22 20 0.0037 0.999848 -0.00924 21 -> 22 56 51 0.0028 0.999738 -0.00472 23 28 23 0.0014 0.999909 -0.01206 24 28 26 0.0052 0.999938 -0.01093 25 -> 27 78 59 0.0024 0.999903 -0.01145 28 -> 29 56 38 0.0014 0.999920 -0.00792 30 28 24 0.0038 0.999940 -0.01248 31 22 21 0.0044 1.000356 -0.02149 33 27 26 0.0023 0.999975 -0.01149 34 28 26 0.0037 0.999534 0.00674 35 -> 37 70 57 0.0040 0.999981 -0.01047 38 -> 44 128 94 0.0022 0.999910 -0.01056 45 -> 46 44 38 0.0045 0.999969 -0.01034 47 -> 48 44 36 0.0032 0.999912 -0.01009 49 -> 56 216 178 0.0023 0.999624 -0.01279 57 -> 64 153 114 0.0029 0.999248 0.01352 65 -> 71 118 86 0.0026 1.004005 -0.01560 73 -> 77 108 81 0.0019 0.999951 -0.01345 78 -> 94 355 266 0.0022 0.999925 -0.01986 _________________________________________________________________ 2043 water samples have been taken out during the cruise. Eliminating the samples of the test stations N°32, N°42, N°72, and N°87, of stations N°9, N°10, N°11, N°12, and N°13 as well as the bad measurements, we retained 1832 water samples for the calibration. 1436 comparisons have been retained by the minimization process (78.2% of the measurements). The figure 10 shows the resulting conductivity difference after the calibration procedure. The difference is lower than 0.001 mmho cm^-1 for 17% of the samples. The difference is lower than 0.003 mmho cm^-1 for 50% of the samples. CONTROL To control the quality of the calibration, θ-S diagrams have been compared: (1) Between successive stations of the cruise. (2) Between stations made at the same position during the cruise (N°26 and N°84). (3) Between different cruises. (1) θ-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 2 cruise ____________________________________________ ETAMBOT 2 ETAMBOT 2 Salinity Station Number Station Number Difference -------------- -------------- ---------- 14 15 0.0020 15 16 -0.0020 16 17 0.0015 17 18 -0.0010 20 21 0.0015 34 35 0.0010 47 48 -0.0020 48 49 0.0020 57 58 -0.0010 58 59 0.0020 73 74 -0.0020 75 76 0.0010 ____________________________________________ The comparison is satisfactory. Only 8 comparisons show a difference greater then 0.0010. No correction have been made to these salinity profiles. (2) During the ETAMBOT 2 cruise, 9 stations have been made at the same geographical position, but only the stations N°26 and N°84 (41°20’W- 7°30’N) are sufficiently deep to allow a meaningful comparison. The comparison is reported on Figure 11. On the θ-S diagrams the salinity difference, for a given temperature, does not exceed 0.0010, below the potential temperature 1.9°C. (3) The ETAMBOT 2 cruise exactly repeats the cruise track of the ETAMBOT1 cruise and the western part of the CITHER 1 cruise (WHP A6 and A7 lines). Omitting the shallow stations, 80 θ-S diagrams of the ETAMBOT1 and ETAMBOT2 cruises have been compared. The differences, 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 11. Salinity comparison between ETAMBOT 1 and ETAMBOT 2 profiles ____________________________________________ ETAMBOT 2 ETAMBOT 2 Salinity Station Number Station Number Difference -------------- -------------- ---------- 15 15 -0.0020 20 20 0.0010 24 24 -0.0010 33 33 0.0010 36 36 0.0010 43 42 -0.0020 49 48 -0.0010 51 50 0.0010 69 68 0.0020 73 71 0.0010 74 72 0.0020 75 73 0.0010 86 84 -0.0020 ____________________________________________ Likewise 40 θ-S diagrams of the ETAMBOT 2 and CITHER 1 cruise have been compared. The salinity differences are reported in the following table. TABLE 12. Salinity comparison between ETAMBOT 2 and CITHER 1 profiles ____________________________________________ ETAMBOT2 CITHER1 Salinity Station Number Station Number Difference -------------- -------------- ---------- 15 133 -0.0030 19 137 -0.0010 20 138 0.0010 33 151 0.0020 34 153 0.0010 43 114 -0.0010 48 110 0.0010 52 106 0.0010 ____________________________________________ The difference observed at the ETAMBOT2 station N°15 has not been corrected. OXYGEN CALIBRATION CTD oxygen were calibrated by fitting to sample values using the method described in Owens and Millard [1985]. During the cruise the oxygen sensor worked for stations N°14 to N°22, N°29 to N°36 using the N°2782 probe, and for stations N°1 to N°8, N°65 to N°95 using the N°2756 probe. Furthermore several oxygen profiles are noisy. All these profiles have been calibrated but they must be used with cautious. 1041 samples have been used to calibrate the data. 966 samples (92.7%) have been retained during the fitting process. The following Table shows the results of the calibration: TABLE 13. Calibration results for the oxygen sensor ____________________________________________ Standard Number Number of deviation Station of used retained (0 – 5000 m) Number samples samples μmol kg^-1 -------- ------- --------- ------------ 1 -> 8 94 92 3.0 14 -> 22 20 181 1.5 29 28 28 2.9 30 28 28 2.8 31 22 22 1.6 33 28 26 0.8 34 28 27 1.6 36 22 20 1.9 65 -> 71 118 111 1.6 73 -> 86 347 322 1.8 88 -> 94 119 109 1.5 ____________________________________________ The figures 12 show the differences, in µmol kg^-1, between the oxygen samples and the down-cast CTD measurements. The difference is lower than 1 µmol kg^-1 for 27% of the samples . The difference is lower than 2 µmol kg^-1 for 65% of the samples . CONTROL As for the salinity profiles, the comparison with the oxygen profiles of the ETAMBOT1 have been made. TABLE 14: Oxygen comparison between ETAMBOT 1 and ETAMBOT 2 profiles _________________________________________________ N° de station N° de station Oxygen difference ETAMBOT 2 ETAMBOT 1 μmol kg^-1 ------------- ------------- ----------------- 14 14 -2.0 19 19 -1.0 20 20 -1.0 30 31 -1.0 73 71 -1.0 80 78 -1.0 _________________________________________________ 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. Figure captions Figure 1: Cruise track and station position. Figure 2: Oxygen versus salinity for ETAMBOT 2 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 2 cruise data. Figure 4: Silicate versus temperature for ETAMBOT 2 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 results for the N°2756 CTD probe calibration results for the N°2782 CTD probe 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 N°2756 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: Calibration curve for the pressure sensor of the N°2782 CTD probe a) calibration for increasing pressure (down cast). b) calibration for decreasing pressure (up cast). Figure 9: Pressure difference, in dbar, between SIS and CTD measurements (after calibration). Figure 10: 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 11: θ-S diagram of repeated ETAMBOT 2 stations N°26 and N°84 (41°40’W-7°30’N). Figure 12: Dissolved oxygen difference, in μmol kg-1, between water sample and CTD measurements. a) difference as a function of station number. b) difference as a function of pressure. WHPO DATA PROCESSING NOTES Date Contact Data Type Event Summary -------- ---------- ----------------- ------------------------------------ 04/23/98 Gouriou Cruise Report Submitted (hard copy) 04/28/98 Gouriou CTD/BTL/SUM Submitted for DQE 03/10/99 Bartolacci CTD/BTL/SUM* Website Updated 02/14/00 Gouriou CTD/BTL/SUM Status changed to Public 06/02/00 Huynh Cruise Report pdf, txt versions online, 08/04/00 Huynh Cruise Report new pdf w/ figs online 01/01/08 Bartolacci BTL/Cruise Report Small edits made It was brought to our attention by a user that the station 42 of the bottle file for ar04_hhy.txt was missing the column of values for FCO2. PH and QUALT1 columns were shifted over. QUALT1 column was missing quality byte for this column as well. • Added -9.0 values in the FCO2 column, and added a 5 quality byte (not reported) to the QUALT1 column. • Added place holding zeros to all leading decimal values (eg. .07 to 0.07). • Added place holding zeros to all trailing decimal values (eg. 1. to 1.0) • Realigned first three data columns and headers. • Realigned and corrected spelling of QUALT1 header. • edited date/name stamp (previous stamp was: 20010323SIOUCSD this is incorrect). • ran wocecvt with no errors. • replaced online version with newly edited file and RCS'd this action. 01/10/02 Bartolacci BTL Reformatted data online I have edited the file to correct the missalignment of the missing station data and also the other columns as well. There is a new file for this cruise online now. My student and I are also working on the others on your list you sent to Steve to see why they haven't get gotten into exchange. It's usually just minor reformatting that keeps these cruises in the exchange queue. Karla is going to investigate and generate the easier exchange files. I'll tackle any remaining ones, and we'll keep you posted on our progress, or you can keep checking the website for updated files. On Fri, 21 Dec 2001, Tom Haine wrote: Steve, I've been looking at the repeat .txt files. I think the FCO2 data are missing from STNNBR 042 in ar04_hhy.txt. At least, there's 1 less column for this station. 01/11/02 Uribe BTL Exchange file online Bottle file has been converted to exchange and put online. 03/04/02 Uribe CTD Exchange file online CTD has been converted to exchange and put online. 04/10/02 Lebel CFCs Final CFC data submitted The file: ar04h.dat - 305211 bytes has been saved as: 20020410.124051_LEBEL_AR04F_ar04h.dat in the directory: 20020410.124051_LEBEL_AR04F The data disposition is: Public The file format is: Plain Text (ASCII) The archive type is: NONE - Individual File The data type(s) is: Other: final CFC data The file contains these water sample identifiers: Cast Number (CASTNO) Station Number (STATNO) Bottle Number (BTLNBR) Sample Number (SAMPNO) LEBEL, DEBORAH would like the following action(s) taken on the data: Merge Data Place Data Online Update Parameters Any additional notes are: These are the finalized CFC data for Etambot2 (AR04H). Scale is SIO98, units are pmol/kg. Includes QUALT2 word. 07/23/02 Buck CTD Expocode edited to reflect HYD Changed expocode in CTD file from 35LKETAMBOT2 to 33LKETAMBOT2 to match SUM file and HYD file. 02/10/03 Bartolacci CTD lat/lon inconsistent For some time now we have been trying to clean up the last of the repeat cruises and incorporating current meter cruise data has fallen into this category. We were forwarded CTD data and two email correspondences by Jim Crease for the KN04 cruise. I am working on formatting these CTD files into a WOCE CTD format and a summary file. I am having some difficulties with the inconsistant lat/lon values recorded in the files. The values in the files that we obtained are are of differring precision and in some cases exceed any possible lat/lon value. Can you please help? We have no cruise or data documentation for these files and presently do not even know who the Chief Scientist was on cruise! Could you please forward a data contact with whom I might correspond to regarding these matters? We would like to button this up as soon as possible and any information you could give us would be greatly appreciated. WOCE AR15, AR04W and AR04E, R/V EDWIN LINK, Cruise ETAMBOT 2