It is widely recognized that internal tides have a strong influence on the global thermohaline circulation, because they provide energy for turbulent mixing in the deep ocean. The global distribution of internal tide energy is therefore necessary for accurate modeling of the global thermohaline circulation. In the present study, we first examine the distribution of the M2 internal tide in the Pacific Ocean using a three-dimensional numerical model. The numerical model shows that the generation of energetic M2 internal tides is restricted over the prominent topographic features such as the Indonesian Archipelago, the continental shelf edge of the East China Sea, and the Hawaiian Ridge. The calculated spatial pattern of the M2 internal tide around the prominent topographic features agrees reasonably well with the Topex/Poseidon altimetric observation. Reflecting the spatial distribution of the prominent topographies, the energy level of the M2 internal tide in the western Pacific is 2-3 orders of magnitude higher than that in the eastern Pacific. The conversion rate from M2 barotropic to baroclinic tidal motion integrated over the whole Pacific Ocean is estimated to be 338 GW, which amounts to about 15% of the global power required for the turbulent mixing to maintain the meridional overturning circulation estimated by Munk and Wunsch [1998].
We next examine the energetics of the M2 internal tide more in detail by taking up the East China Sea as a representative generation region in the Pacific Ocean. The numerical experiment with a fine-grid local model shows that roughly 10% of the energy in the M2 barotropic tide incident on prominent topographic features in the East China Sea is converted to M2 internal tides, although about half the converted energy is lost due to strong local dissipation in the proximity of the generation sites. |
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