Impact of Mesoscale Eddies on Mixed Layer Dynamics in The Bay of Bengal

Abstract

The present study aims to understand the mesoscale eddies induced mixed layer and barrier layer dynamics in the Bay of Bengal (BoB). Mesoscale eddies in the BoB are identified using an autonomous eddy identification and tracking algorithm, which is employed to weekly gridded multi-mission altimeter sea surface height anomalies (SSHA) data for of 20 years (1997-2016) period. The weekly mixed layer depth (MLD) and barrier layer thickness (BLT) are estimated based on variable density criteria from the ARMOR3D high resolution data provided by Copernicus Marine and Environment Monitoring Services. Composite analysis suggest that over the warm (cold) eddy regions anomalous deeper (shallower) MLD variations are depicted. These variations are predominant during the winter seasons with dipole surface variations. Results also reveal that the center of warm (cold) eddies having the maximum (minimum) magnitude which is further decreased (increased) towards the periphery of eddies. To quantify the role of eddy induced surface temperature and salinity variations, we examine the mixed layer dynamics over the eddy regions by employing a diagnostic mixed layer heat and salinity budget models. Analysis reveal that the eddy induced surface variations are primarily attributed by the horizontal advection and entrainment process for both cold and warm eddies. Findings from the present analysis are important to understand the internal upper ocean dynamics of BoB.