An Eddy Pair in the Northwestern Bay of Bengal: Characteristics, Dynamics and Interannual Variability

Abstract

Mesoscale eddies are active in the Bay of Bengal and have profound effects on the dynamic conditions, the transport of heat and salt, and the primary productivity. We report a pair of periodic eddies in the Bay of Bengal and examine their characteristics, dynamic mechanisms and interannual variability based on satellite observations and a nonlinear 1.5‐layer reduced‐gravity model. The eddy pair mainly occupies the northwestern Bay of Bengal from March to May and consists of a cyclonic eddy in the north and an anticyclonic eddy in the south. The anticyclonic eddy is generated by local wind forcing, whereas the cyclonic eddy is significantly contributed by equatorial and coastal Kelvin waves. On an interannual scale, the eddy pair was exceptionally weak in 1999, 2000 and 2008 due to the extreme La Niña events in these years when the westerly wind anomaly over the equatorial Indian Ocean weakened the local wind forcing and coastal Kelvin waves. This study provides new knowledge on periodic eddies in the Bay of Bengal and advances our understanding of the dynamic connections between this marginal sea and the equator.