The features and interannual variability mechanism of mesoscale eddies in the Bay of Bengal

Eddy activity has been examined in many regions of the world ocean. However, the mechanism behind interannual variability of mesoscale eddies remains uncertain. Although eddies can be frequently observed in the Bay of Bengal (BOB), there is no thorough statistical assessment of eddy activity in the bay. Here, we use altimeter data and ocean reanalysis data to show the genesis, propagation, mean properties and the spatiotemporal variability of eddies in the BOB. Energy analysis suggests the interannual variation of eddy kinetic energy (EKE) in the BOB depends on that of perturbation kinetic energy induced by mesoscale eddies. Eddy activity at interannual scale is sensitive to the baroclinic instability of the background flow. When the baroclinic instability is stronger, more energy is converted from the mean flow to the eddy energy, which makes eddies stronger and more stable but fewer in number. The west coast of the BOB is a critical region for eddy-mean flow interaction.

► Eddies are mainly generated along the coasts, especially at the eastern boundary.
► Eddy activity at interannual scale is sensitive to the baroclinic instability.
► The converted energy from the mean flow makes eddies stronger but fewer in number.