A SUMMARY OF RESULTS ON THERMOHALINE VARIABILITY IN THE UPPER LAYERS OF THE EAST CENTRAL ARABIAN SEA AND BAY OF BENGAL DURING SUMMER MONSOON EXPERIMENTS

Some important features of thermohaline variability emerged from sever al case studies carried out utilising short time series measurements o f surface marine meteorological parameters, vertical profiles of tempe rature and salinity, and currents. These were measured at discrete dep ths at selected stations in the east central Arabian Sea, the Bay of B engal and the equatorial Indian Ocean from USSR and Indian Ships durin g the field experiments of ISMEX-73, MONSOON-77 and MONEX-79. The obse rved changes in the variable surface meteorological forcing, response characteristics of the mixed layer and thermohaloclines in the east ce ntral Arabian Sea under the onset and progress of the summer monsoon a re documented and described. The efficacy of a simple one-dimensional numerical model in simulating the mixed layer cooling and deepening is evaluated. In the Bay of Bengal the evidence for a suggestive relatio nship between an accumulation of heat in the upper layers and the gene sis of monsoon depression/cyclonic storms is presented. The role of a severe cyclonic storm in producing dramatic transient variations in th e upper layer characteristics is highlighted. The observed eastward de pression in the thermocline along the equator is described.