Spatio-temporal structure of the East India Coastal Current from satellite altimetry

Abstract

We use a newly processed altimeter data set to present a hitherto unprecedented description of the spatiotemporal structure of the East India Coastal Current (EICC): the data set resolves timescales ranging from a few months to a few years, and the high along-track resolution yields the first description of the cross-shore structure of the current. The seasonal cycle dominates the variability, but the nonannual timescales have similar energy levels all along the EICC path. There are short-lived, intense intraseasonal bursts. In contrast to the seasonal cycle, the interannual and intraseasonal components are decorrelated along the coast, and possible mechanisms for the decorrelation (discontinuity in the flow) are discussed. In the cross-shore direction, the current is highly correlated at all timescales: the EICC is trapped against the shelf with the current offshore flowing in the opposite direction at most locations. The EICC appears as an inherently discontinuous flow, taking the form of a few recirculating loops along the EICC path, with a typical cross-shore spatial scale of 150-200 km. The loops are highly variable in direction at all timescales from intraseasonal to interannual. This discontinuity of the EICC in space and time implies that the basic pathways and advective timescales for the interbasin exchange of water masses between the Bay of Bengal and the Arabian Sea are not robust when the full spatiotemporal variability of the EICC is considered.