Estimates of Internal Tide Energetics in the Western Bay of Bengal

Abstract

In this paper, a study is presented on energetics of internal tides using available high temporal resolution in situ data collected during February 19–20, 2012 and MITgcm (M.I.T. General Circulation Model) model simulations in the western Bay of Bengal. The spectral estimate of density indicates that the peak estimate is associated with the semidiurnal frequency at all the depths. The vertical displacement of density, i.e., isopycnal displacement, suggests that about 20-m amplitude of semidiurnal internal tides exist in the pycnocline region in both observations and model simulations. After eliminating the barotropic signal, the baroclinic zonal and meridional components of velocity are found to be in the order of 0.3 and 0.4 m s−1, respectively. The energy flux calculated using the velocity-pressure correlation is predominantly seen in zonal direction from both observations and simulations. The peak magnitude of available potential energy is found to be of the order of 22 J m−3 in the pycnocline region for the semidiurnal tide. As expected, the horizontal kinetic energy values have the maximum at the surface layer. The computed barotropic forcing is found minimal over the shelf-break region as it is converted into internal tides. The internal tides are generated over the shelf-slope region and propagate toward the coast. The energy dissipation is seen to be maximum over the shelf-slope region causes mixing due to internal tides. The available potential energy is found to be maximum in north of the model domain. The internal tides activities are found to be maximum in the northern Bay of Bengal.