This chapter presents the results of studies on the currents and hydrography of the waters of the western equatorial Indian Ocean during the period 28 May to 3 June 1973. Studies of hydrographic conditions in the area after about one month (i.e. 25 June to 2 July 1973) are also discussed. Time-series data on horizontal currents were gathered by recording current meters attached to a buoy anchored at the Equator near 60° E during the Indo-Soviet Monsoon Experiment 1973. Hydrographic data were also obtained from repeated Nansen casts at 3-hourly intervals around the buoy. The time variation of currents (3-hour averages) at different depths (75 m, 100 m, 150 m, 200 m, 300 m, 500 m and 800 m) and the vertical time sections of temperature, salinity and density from the surface to 1000 m depth are presented and discussed.

The studies show a complex vertical structure of horizontal currents with predominant easterly components at 75 m and 100 m depth and predominant westerly components at 200 m, 300 m, 500 m and 800 m depth, and a zone of strong current shear between 100 m and 200 m depth. At 150 m depth, the current has been found to be oscillatory with a period of oscillation of about 2 hours. The currents are rather strong even at deeper levels, particularly at 200 m and 800 m depths where westward jets with speeds of the order of 0.35 m s-1 and 0.4 m s-1 respectively have been encountered. […]