Meeting Documents

Revealing the Influence of Tidal Forces on Surface Current and Mesoscale Eddies in the Northern Bay of Bengal: A Modeling Approach

Abstract

The Bay of Bengal (BoB), a tropical basin in the northern Indian Ocean bordered by land on three sides, is shaped by substantial river discharge, wind-driven circulation causing upwelling and downwelling, heavy rainfall, and strong seasonal variations in temperature and salinity. These unique conditions distinguish the BoB from other oceanic regions. Previous studies have examined tides and mesoscale eddies, wind effects, remote forcing from Kelvin and Rossby waves, and runoff-induced changes in temperature and salinity on surface currents and tidal dynamics. However, the direct role of tidal forces in controlling surface currents and mesoscale eddies in the BoB remains poorly understood. This study uses a Regional Ocean Modeling System (ROMS) with a horizontal resolution of 0.25^ox0.25^o and 50 vertical layers to assess the impact of tidal forcing on surface currents and eddy variability. Multivariate Empirical Orthogonal Function (EOF) decomposition, Pearson's correlation, and the Okubo–Weiss parameter are applied to model outputs and observational datasets, including sea surface temperature (SST), salinity (SSS), height (SSH), net surface heat flux (NHF), net freshwater flux (NFF), and surface currents from CMEMS, SMOS, ECCO, QuickSCAT, and WindSAT. The results show that cyclonic and anticyclonic circulation is more pronounced in the southwestern BoB under tidal forcing than in the northwest. Eddy activity significantly increases in March and peaks in June-July, driven by stronger zonal winds and the semi-reversing East India Coastal Current (EICC). These features disappear when tidal forcing is removed. In the eastern BoB, smaller eddies are primarily associated with coastal Kelvin waves and radiated Rossby waves. This study underscores the critical role of tides in modulating eddies, balancing ocean heat and salinity, influencing tropical cyclone patterns, and contributing to global carbon cycling. It also highlights the significance of tidal influences on surface currents in maintaining the oceanic stability and climate regulation of the northern BoB.View Document (AGU) »