Characteristics of the Discontinuity of Western Boundary Current in the Bay of Bengal

Abstract

AbstractThe western boundary current in the Bay of Bengal, also known as East India Coastal Current, is northward (southward) and continuous during pre‐ (post‐) Indian Summer Monsoon (ISM) but discontinuous during ISM (June–September). This study investigates the features of this discontinuity and role of eddies, local winds, and southern open boundary lateral forcing using AVISO TOPEX Poseidon, ERS, and Jason1 combined sea surface height anomaly, Ocean Surface Current Analysis Real‐time (OSCAR) surface currents and high‐resolution Regional Ocean Modelling System simulations. The study shows that the discontinuity is governed by westward and southwestward propagating eddies between two opposite facing flows along the boundary, northward of 10°N and southward of 21°N. This northward flow of 10°N is wind driven with lateral influence during September. The southward flow of 21°N is influenced by the Summer Monsoon Current, but the local wind influence starts from July onward. During ISM, about 79% cyclonic and 77% anticyclonic eddies move westward, while 68% cyclonic and 69% anticyclonic eddies move southward. Three highly active eddy genesis areas, having more than 50% activities during ISM, are identified: northern and southwestern bay for cyclonic and off Visakhapatnam (17.68°N, 83.21°E) coast for anticyclonic eddies. The pre‐ISM (post‐ISM) is dominated by anticyclonic (cyclonic) eddies, which are found across the western Bay of Bengal and away from northward (southward) East India Coastal Current. The ISM is dominated by westward and southwestward moving both cyclonic and anticyclonic eddies, which are confined to the boundary, where discontinuity is generally observed.