On the thermal response of the upper central Arabian Sea to the summer monsoonal forcing during Monsoon-77

Abstract

The thermal response of the upper central Arabian Sea to the summer monsoonal forcing is documented with the aid of surface wind and upper ocean temperature data sets collected from a four-ship USSR stationary polygon during Monsoon-77. The near surface mixed layer cooled by about 2°C and 'deepened by about 50 m with the onset and sway of the summer monsoon over a five-week period from 7 June 77. Depth-time sections of temperature, constructed with daily averaged BT data revealed the presence of downwelling phenomenon in the upper thermooline with a decreasing magnitude from June to July. Downward transport of heat in the wake of mixed layer deepening and downwelling below has resulted in a warming of 2° to 3°C below the mixed layer under the sway of the monsoon. A double-cored maxim in the vertical thermal gradient merged into a single core from June to July. Vertical advective processes on these observed time scales mostly govern heat content of the uppermost loom and 200 m slabs.