Description on variability of shelf-edge hydrography and current structure of the South Eastern Arabian Sea during summer and winter monsoons.

Abstract

The paper describes the hydrography and vertical current structure along the shelf edge of South East Arabian Sea (SEAS) during summer and winter monsoons based on current profiles from moving Acoustic Doppler Current Profiler (ADCP). During summer monsoon, SEAS was characterized by upwelling with low saline water at the surface along the southern sector (8° N to 11° N). During winter, thermal structure was vertically homogeneous in the upper 80 m, and intrusion of low saline Bay of Bengal waters were found up to 14° N. In the southern sector, turbidity was more than the northern sector during winter and summer seasons. ADCP-derived current profiles during summer along 200-m isobath show dominant northward flow in the south, and southeasterly in the north as part of the West India Coastal Current (WICC). A comparison between ADCP current profiles and Ekman currents during summer indicates dominance of remote forcing (coastal Kelvin waves) over the local wind forcing in the 8-9° N sector whereas a combined influence of both remote forcing and wind in the 9-15° N sector. During winter, the direction of surface current reversed and was poleward generally except at the southern sector (7-8° N) where the flow was southwestward. Sector-wise comparison of ADCP and Ekman current showed less influence of wind on current fields throughout the sector except at south; wind has a major role in the current generation, whereas along the 8-15° N sector, the remote forcing dominates over the wind.