Energetics-Based Estimation of the Diapycnal Mixing Induced by Internal Tides in the Andaman Sea

The Andaman Sea (AS) is characterized by surprisingly weak stratification in its deep basin in drastic contrast to the nearby Bay of Bengal (BoB), presumably due to strong diapycnal mixing fertilized by the dissipation of internal tides. Here, we report on the first estimates of tidal mixing in the AS using idealized numerical simulations resolving the generation and evolution of low-mode internal tides. The estimation is based on a diagnostic analysis of the energetics of the simulated internal tides of both local and non-local origins. The results highlight the dominant role of the internal tides generated in the channels along the western boundary island chain in energizing diapycnal mixing in the entire AS. Tidal dissipation and mixing in the deep basin of the AS are found to be highly elevated, with the depth-integrated dissipation rate and the diapycnal diffusivity being O(10(-2)-10 ) W m(-2) and O(10(-3)-10(-2)) m(2) s(-1), respectively, both of which are 1-2 orders of magnitude larger than those in the deep BoB. These model-based estimates of tidal mixing are in general consistent with those from in situ conductivity-temperature-depth (CTD) measurements using the fine-scale parameterization. Our results suggest that the oft-used tidal mixing parameterization considering only local internal tide generation would underestimate the depth-integrated tidal dissipation in the AS by several orders of magnitude, highlighting therefore the necessity of considering contributions of non-local internal tides in parameterizing tidal dissipation and mixing in marginal seas like the AS.