WFP Ref. No.: IR4/ICM8
Last Updated:  August 18, 1991

Ship name: R/V SONNE
Cruise No.: SO 73

Principal Investigators: F.Schott
                         IFM Kiel 

                         D. Quadfasel
                         IFM Hamburg

Dates: Dep Goa     23 Dec. 1990
       Arr Colombo 11 Jan. 1991

	Began station work south of Sri Lanka along 80 30'E, worked down to
6 S and back northward along that section.  Station work was terminated
south of Sri Lanka. 

	Three moorings were deployed north of 4 15'N and a total of 41 CTD
stations and 20 Pegasus profiles at ll stations were taken. 

	CTD station separation was generally 30 nm and was better near the
northern border and near the equator.  CTD stations were to the bottom at
full degrees lat., at all Pegasus stations and near the northern boundary. 
Oxygens were analyzed from 24 bottle samples per station.  Freons were
measured by M. Rhein (IFM Kiel) on a subset of the stations. 

	The three moorings, focussing on the Monsoon Current regime, are
part of WOCE array ICM8.  Two of them (K1, K3) carry upward- looking ADCPs
at 250 m depth to measure the near-surface currents; and a total of 14
Aanderaa current meters are deployed, most of them above the 1000 m level,
and some equipped with conductivity sensors. 

	Underway Doppler current measurements were carried out with
shipboard ADCP down to about l80 m, and at some CTD stations current
profiles down to 1500 m were obtained by attaching a self-contained ADCP to
the rosette. 

	The Monsoon Current was found to be confined to the area north of
about 4 N, carrying low-salinity Bay of Bengal water westward with
near-surface velocities exceeding l m s -1.  South of that regime, currents
were quite variable but with a persistent westward undercurrent in the
depth range 50 - 150 m in the equatorial band. 

Since R/V Sonne is not returning to the Indian Ocean in time for mooring
retrieval, we are looking for a vessel in the time frame December 1991 -
April 1992.  One possibility explored at present is charter of a Sri Lanka
fishing vessel; another one is the Indian R/V Sagar Kanya passing by
there in late 1991.  We are also trying to arrange Pegasus measurements
on a smaller vessel out of Sri Lanka.  Any other suggestion we could pursue
would be welcome. 

Funding requests to extend array ICM8 southward and to repeat the section
work will be submitted shortly to the FRG-WOCE program.