Mesoscale Eddies in the Western Bay of Bengal as Observed From Satellite Altimetry in 1993–2014: Statistical Characteristics, Variability and Three-Dimensional Properties

A comprehensive study on the statistics, variability, and three-dimensional properties of the mesoscale eddies in the western Bay of Bengal (BOB) using satellite altimetry and Argo floats for the period 1993-2014 is presented. This is a key region characterized by ocean circulation variability at a wide range of scales, including the generation of seasonal boundary currents and mesoscale eddies. A hybrid algorithm based on the physical and geometrical properties of mesoscale eddies is applied to detect the eddies and track their propagation. The potential eddies with radius larger than 50 km and lifespan longer than 30 days are considered for the analysis. Two highly eddy-productive zones are identified: offshore of Visakhapatnam and the northern part of western BOB. It is noticed that the occurrence of anticyclonic eddies (ACEs) dominate the offshore of Visakhapatnam and cyclonic eddies (CEs) in the northern part of western BOB. In general, the ACEs move westward, but the CEs move southwestward and southward along the continental shelf of the western BOB. The ACEs are larger but the CEs have longer lifetime and are more energetic. The eddy genesis is found to be sensitive to the strength of the seasonal wind stress curl. The strong positive wind stress curl during summer favors the formation of more CEs. Investigation on three-dimensional properties of the eddies show that the CEs are generally intensified in the subsurface depths in the western BOB. Both ACEs and CEs have single-core vertical structure with the core at a depth of about 100 dbar.