Implications of climatic variations in the fresh water outflow on the wind-induced circulation of the Bay of Bengal

A barotropic model is applied to simulate the large-scale ocean circulation in the Bay of Bengal. The driving mechanisms consist, in general, of wind-stress forcing representative of that applying during the southwest monsoon season (July), and a forced southward transport of water across a northern open boundary that models the fresh water discharge from the northern river system. The model simulations (both with and without northern boundary forcing) are compared with the observed circulation pattern. The simulations provide definitive evidence that, with the simultaneous presence of both a forced fresh water flow and upwelling favourable winds along the east coast of India during the monsoon season, there is formation of a cyclonic gyre at the head Bay and occurrence of downwelling to the north of Machilipatnam along the east coast of India.