Energetics of Semidiurnal Internal Tides in the Andaman Sea

A detailed energetic estimate of the barotropic and baroclinic semidiurnal internal tides over the Andaman Sea is performed by using the three-dimensional Massachusetts Institute of Technology general circulation model. Model-simulated currents and density fields are validated using in situ observations with high temporal resolution from a buoy located at 10.5 degrees N, 94 degrees E. The generation and dissipation regions of internal tides and their propagation in the domain are identified by quantifying the distribution of total tidal energy among generation, radiation, and dissipation. The model simulation suggests that the internal tides are mainly generated in the north of Sumatra coast, in the Sombrero channel, south of the Car Nicobar Island, and north of the Andaman Island. From these generation sites, a portion of the energy propagates into the Andaman Sea and the remainder propagates toward the southern Bay of Bengal. The depth-integrated baroclinic energy fluxes are found to be a maximum of similar to 30kW/m at the major generation sites in the domain. The model-estimated energy dissipation rates suggest that the maximum amount of energy dissipates near the generation sites themselves. In the region north of the Sumatra coast, almost 87% of the barotropic energy is converted into baroclinic energy and 23% (0.91GW) of the converted baroclinic energy is ultimately radiated out from the generation sites. The barotropic-to-baroclinic conversion rate over the whole domain is estimated to be similar to 23GW, out of which, a major part similar to 18GW (80%) dissipates near the generation sites. This reveals that the local dissipation of baroclinic energy dominates in the Andaman Sea. Internal waves (IWs) in the oceans are ubiquitous phenomena, and they play an important role for a wide range of oceanic processes such as transfer of energy and momentum in the interior of global oceans, sound wave propagation, vertical transport of nutrients, and regional ecosystems. Andaman Sea is known to be an active region in the world's ocean where IWs of exceptionally high amplitudes are observed, but it still remains as one of the least explored regions. In this present study, spatial distribution of generation, propagation, and dissipation of IWs of tidal frequency, that is, internal tides are examined using a numerical model. The detailed energy budget analysis is carried out for this region. The simulated results show that, from the total barotropic-to-baroclinic conversion rate, 80% (similar to 18 GW) of internal tide energy dissipates near the generation sites in the Andaman Sea.