preliminary data report
may 5, 1995
A.	Cruise Narrative

A.1.	Highlights

A.1.a	WOCE Designation 	ISS1

A.1.b	EXPOCODE		35MF68SUZIL

A.1.c	Chief Scientist		Young-Hyang Park 
				

A.1.d   Ship			M/V Marion Dufresne

A.1.e   Port of Call		Le Port, La Reunion

A.1.f   Cruise Date		April 12 to May 20, 1991


A.2	Cruise Summary

A.2.a	Geographic boundaries
        
The cruise track followed four near-meridional sections cutting across the 
ACC core and a zonal section along 38 S, within the area bounded by 37 - 51 S 
and 50 - 80 E. 

A.2.b	Total number of stations
        
During the cruise, a total of 73 CTD/rosette stations were occupied using a 
12 bottle rosette equipped with 12 l Niskin water sampling bottles.

A.2.c	Floats and drifters deployed

A.2.d	Moorings deployed or recovered

A.3	List of Principal Investigators 

Name                    Responsibility          Affiliation
----------------------------------------------------------------------------
Y. H. Park              CTD, S, 02              Museum National d'Histoire 
						Naturelle (MNHN) 
						Paris, France
-----------------------------------------------------------------------------

A.4	Scientific Programme and Methods

The cruise was carried out in the Crozet Basin area which has recently
been included within the WOCE special study area in the Southwest Indian Ocean 
(ISS1).
        
Our primary goal was to give a detailed description of the frontal structure
and transport associated with the Antarctic Circumpolar Current in the area 
where the bottom topography of the Crozet and Kerguelen Plateaux together with 
the eastward extension of the Agulhas Return Current exert a particularly 
crucial influence on the regional circulation.

A secondary, but still very important, goal was to improve knowledge of 
the water characteristics and circulation at all depths related to the water 
mass exchanges between the Southern Ocean and the Indian Ocean. Specifically, 
this includes the formation and modification of the thermocline water masses 
north of the ACC, the injection of modified waters into the subtropical 
anticyclonic gyre in the South Indian, and the circulation of deep and bottom 
waters within the Crozet Basin.

Water sampling during the cruise included measurements of temperature, 
salinity, and oxygen by CTD,  and water bottle samples for analysis of salinity
and oxygen to calibrate the CTD sensors.

The ship departed Le Port, La Reunion on April 12, 1991, and made on April 13 
a test station near 26 09'S, 55  20'E to test the CTD and its rosette water 
sampling equipment. The first station (Sta. 1) was occupied on April 15 at 
37 S, 55 E, and the last station (Sta. 73) on May 17 at 38 S, 58 30'E. The CTD 
used is Neil Brown Mark III B No 01-1116 equipped with a dissolved oxygen 
sensor. The CTD temperature and pressure sensors were calibrated at the 
IFREMER calibration facility both before and after the cruise. The conductivity
and oxygen sensors were calibrated using data from the on-board analyses of the
salinity and oxygen samples which were collected at each station from PVC 
Niskin bottles mounted on a General Oceanic rosette sampler.

Detailed analysis and interpretation of the cruise data set have been given in 
Park et al. (1992). Selected plots showing property vs property relationships 
within the cruise area and the property sections at 53 E.

A.5	Major Problems and Goals not Achieved

During the early stage of the cruise a problem developed with the General 
Oceanics rosette tripping mechanism which resulted in mis-firings and 
double-tripping of the water sampling bottles. This problem was resolved 
simply by replacing the problematic rosette sampler by a spare one. 

A.6	Other Incidents of Note
A.7	List of Cruise Participants

Name			Responsibility		Institution
-------------------------------------------------------------------------      
Young-Hyang Park        Chief Scientist         MNHN, Paris
Lucien Gamberoni        Salts/Oxygens           MNHN, Paris
Edwige Charriaud        CTD Software            MNHN, Paris
Annie Kartavtseff       CTD Hard & Softwares    LODYC, Paris
Catherine Rouault       CTD Soft ware           LODYC, Paris
Mathilde Nithart        Watch Stander           Univ. Luminy, Marseille
Henri Orengo            Watch Stander           Univ. Luminy, Marseille
Frederic Rigaud         Watch Stander           Lab. Arago, Banyuls s/mer
Jean-Louis Turon        Watch Stander           Univ. Bordeaux
Jean-Jacques Pichon     Watch Stander           Univ. Bordeaux
Fabienne Maret          Watch Stander           Univ. Bordeaux
--------------------------------------------------------------------------

        
C.Measurement Techniques and Calibrations


C.1 CTD Calibration (L. Gamberoni and E. Charriaud)

Temperature 

The calibrations at the IFREMER calibration facility before and after the 
cruise showed a temperature change (in a interval of 15 months) of 0.003 C at 
0 C and 0.001 C at 25 C. Post-cruise temperature calibration consisted of a 
fifth order polynomial curve fit to seven temperature points sampled between 
-2 and 25 C. The polynomial fitting shows a 0.0002 C standard deviation, while
the accuracy of the thermometer standard as claimed by the IFREMER calibration 
facility is 0.002 C. Corrections determined from this polynomial fitting were 
applied to the CTD data.

Pressure 

Pre- and post-cruise calibrations showed a pressure drift of 10 dbar. During 
the post-cruise calibration, data were sampled at 400 db intervals with both 
increasing and decreasing pressure between 0 and 6000 dbar. Corrections were 
determined from a fifth order polynomial curve fit to sixteen pressure points. 
The standard deviation from the polynomial fitting is 0.25 dbar for the 
downcast calibration and 0.14 dbar for the upcast calibration, while the 
accuracy of the pressure tester as claimed by the IFREMER calibration facility 
is ± 1.2 dbar at 6000 dbar. The corrections determined from this polynomial 
fitting were applied to the CTD data from the cruise, with the pressure bias 
term being set equal to the pre-lowering deck unit pressure reading made 
during each CTD cast. 

Conductivity

The conductivity sensor was calibrated with shipboard salinity measurements 
on the maximum 12 water samples collected at each station. The conversion of 
water sample salinities into the corresponding conductivities was made using 
the algorithms of Fofonoff and Millard (1983), with 
C(35, 15, 0) = 42.914 mS/cm. 

The raw conductivities from the CTD were first corrected for temperature and 
pressure effects on the conductivity sensor, using the following algorithm 
proposed by the CTD constructor:
        Cc = Cr [ 1- a (T-15) + b P ]
where Cc and Cr are the corrected and raw conductivities, a is the temperature 
correction coefficient (7 x 10-6  C-1), b is the pressure correction 
coefficient (1.48 x 10-8 dbar-1),and T and P are the calibrated temperature and
pressure. 

The calibration consisted in least-square regression fit of the CTD 
conductivities to their respective water sample data. The data were subdivided 
into two homogeneous groups (Stas. 1-12 and Stas. 13-73) in which the 
differences between water sample and CTD conductivities appeared to have 
homogeneous calibration characteristics. An iterative regression procedure was 
used, discarding successively the outlying observations in excess of 2.8 times 
the standard deviation of the conductivity differences in the station group 
under consideration.The following regression equations were determined from 
the retained data points (about 90 % of the initial data points for each 
homogeneous group), which were used to correct the CTD conductivities:

Stas.  Retained Data Points        Regression Eq.          St. Dev. (mS/cm)

 1-12        72 (91.1 %)       C = 0.00494042 + 1.000110 Cc          0.0032
13-73       552 (90.0 %)       C = 0.01278070 + 0.999841 Cc          0.0026

Finally, the calibrated CTD conductivities were converted into the 
corresponding salinities using the algorithms of Fofonoff and Millard (1983).

Oxygen

The calibration of the CTD oxygen sensor was made against in situ water sample 
oxygen data. The calibration algorithm used here is that of Millard (1982): 

        OX =  Soc*Oc*OXSAT(T, S)*exp{tcor [T +  wt (T0 - T)] + pcor*P} 

where OX is the CTD oxygen in ml/l, Oc is the CTD oxygen current, Soc is the 
oxygen current slope, OXSAT is the oxygen saturation value after Benson and 
Krause (1984), T, S, and P are the calibrated CTD temperature, salinity, and 
pressure, tcor and pcor represent the temperature and pressure corrections, 
T0 is the CTD oxygen prove internal temperature, and wt is the weighting 
fraction of oxygen prove internal temperature. 

The parameters Soc, tcor, wt, and pcor were determined from water sample oxygen values 
by performing a linear least-square regression. The calibration procedure was analogue to that used 
for the conductivity; stations were subdivided into four homogeneous groups (Stas. 1-12, Stas. 13-43,
Stas. 44-58, and Stas. 59-73), and the outlying observations in excess of 2.0 times the standard 
deviation of the oxygen differences in the station group under consideration were discarded
successively from the iterative least-square fits. The resulting parameter values and the standard 
deviation of oxygen differences for each group are shown below.

Stas.   Retained Data Points    Soc       tcor        wt        pcor   St. Dev.
                                                                       (ml/l)
-------------------------------------------------------------------------------
 1-12         55 (83.3 %)     2.6354   - 0.0354      0.818     0.000150  0.046
13-43        202 (70.4 %)     2.6632   - 0.0351      0.680     0.000151  0.038
44-58        101 (78.3 %)     2.6663   - 0.0363      0.844     0.000144  0.046
59-73         78 (63.4 %)     2.6421   - 0.0336      0.817     0.000150  0.034
-------------------------------------------------------------------------------
The conversion of oxygen content in ml/l into that in micromol/kg (as reported 
in Data Files) was made using the following equation from Culberson (1991):
 
        O2 (micromol/kg) = 44.660 x O2(ml/l) / rsw

where rsw  is the density of seawater at the temperature at which the oxygen 
sample was pickled.


C.2.2  Salinity and Oxygen Measurements during the MD 68-SUZIL Cruise

        by:  L. Gamberoni

Salinity

The water sample salinities were measured with a Guildline Portasal Model 8410 
salinometer that was standardized daily with IAPSO Standard Sea Water Batch 
P-110.  The salinity measurements during this cruise were made within a 
temperature controlled (1 C) portable laboratory, generally maintained about 
1-2 C below that of the salinometer water bath.

Oxygen

The dissolved oxygen samples measured during this cruise were analyzed with the
Winkler titration method described by Carritt and Carpenter (1966), with two 
exceptions. The thiosulfate normality was reduced from 0.14 to 0.01, and the 
microburette was replaced by a 20 ml Metrohm Dosimat digital piston buret. 
Potassium hydrogen iodate standard solutions (KH(IO3)2) were previously 
prepared in the laboratory.




D.	Acknowledgments
E.	References

Benson, B., and D. Krause Jr. (1984) The concentration and isotopic fractionation of oxygen 
dissolved in fresh and seawater in equilibrium with the atmosphere. 
Limnol. Oceanogr., 29,         (3), 620-632.

Carritt, D. E., and J. H. Carpenter. (1966) Comparison and evaluation of currently employed 
modifications of the Winkler method for determining dissolved oxygen in seawater; 
a NASCD report. J. Mar. Res., 24, 286-318.

Culberson, C. H. (1991) Dissolved oxygen. WHP Operations and Methods, WHPO 91-1, 
WHP Office, WHOI, Woods Hole.

Fofonoff, N. P., and R. C., Millard. (1983) Algorithms for computation of fundamental properties 
of seawater. Unesco technical papers in marine science No. 44, 53 pp.

Millard, R. C. (1982) CTD calibration and data processing techniques at WHOI using the 1978 
practical salinity scale. 
Proc. Int. STD Conference and Workshop, La Jolla, Mar. Tech.   Soc., 19 pp.

Park, Y. H., L. Gamberoni, and E. Charriaud. Frontal structure, water masses and circulation in 
the Crozet Basin. J. Geophys. Res. (accepted).

Unesco, 1983. International Oceanographic tables. Unesco Technical Papers in 
Marine Science, No. 44.

Unesco, 1991. Processing of Oceanographic Station Data, 1991. By JPOTS
editorial panel.

F.	WHPO Summary


Several data files are associated with this report.  They are the mf68.sum, 
mf68.hyd, mf68.csl and *.wct files.  The mf68.sum file contains a summary of
the location, time, type of parameters sampled, and other pertient
information regarding each hydrographic station.  The mf68.hyd file contains 
the bottle data. The *.wct files are the ctd data for each station.  The *.wct 
files are zipped into one file called mf68wct.zip. The mf68.csl file is a listing
of ctd and calculated values at standard levels.

The *.csl files are not aviliable at this time due to the CTD data files 
being given in non-uniform levels.

G.	Data Quality Evalutation
