A NOTE ON POLEWARD UNDERCURRENT ALONG THE SOUTHWEST COAST OF INDIA

A comparative study of currents and hydrography during the monsoon and nonmonsoon periods of 1984, 1985 and 1987 was carried out using data collected on five cruises covering the waters of the west coast of Ind ia from 8 degrees N to 15 degrees N and the inferences on upwelling an d associated features are discussed. Climatological wind analysis indi cate distinct behavioural variation between monsoon (May-September) an d non-monsoon (November-March) periods. Between Cochin and Bhatkal the alongshore wind stress component builds up from May to reach a maximu m during July and then decreases with time. Off Trivandrum the wind st ress increases from 0.4 to 0.8 dynes cm(2). Wind driven surface curren ts are quite organised in the surface 75 m layer and are reversed at a bout 200 m (depth of the 14 degrees C isotherm). Well defined thermal and saline fronts are Visible adjacent to each other and close to the coastline with gradients of 0.06 degrees C km(-1) and 0.04 parts per t housand km(-1), respectively. Strong alongshore wind stress component is associated with maximum offshore transport and remarkable sea surfa ce temperature anomaly. The strong surface wind drift weakens the pole ward undercurrent during the monsoon period and as the undercurrent ga ins strength the surface drift is retarded. Penetration of very low sa linity water mass (<33 parts per thousand) from the Bay of Bengal to t he Arabian Sea during the non-monsoon period has also been observed.