Characteristics of coastal waters of the western Bay of Bengal during different monsoon seasons

Abstract

Physical characteristics of waters along the eastern coast of India up to offshore distances of 400 km have been investigated during the seasons of the north-easterly and south-westerly monsoons in light of relevant observed meteorological forcings. Analysis of wind data for five years (1980-84) showed high magnitudes of onshore-directed wind-stress impulse in the northern region throughout the year. Under the influence of this impulse, surface waters from offshore move towards the coast and sink along the shore under the direct wind setup. This feature is also indicated by negative values of the upwelling index. Fresh water, discharged through multiple outlets along the coast, mixes within the upper 50 m of the water column and spreads south-westward as a lens of low-salinity water. Further, fresh water advects offshore to distances of about 150 km. The transient, cross-shelf, haline frontal zones observed along the western margin of the Bay of Bengal separate the northern dilute waters from the southern saline waters.