Three‐dimensional numerical simulation of M2 internal tides in the East China Sea

Abstract

The East China Sea and adjacent seas are one of the most significant generation regions of the M2 internal tide in the world's oceans. In the present study, we investigate the distribution and energetics of the M2 internal tide around the continental shelf edge in the East China Sea using a three‐dimensional numerical model. The numerical experiment shows that M2 internal tides are effectively generated over prominent topographic features such as the subsurface ridges in the Bashi/Luzon and Tokara Straits, the ridges along the Ryukyu Island chain, and the continental shelf slope in the East China Sea, the former particularly so. All of these topographic features are characterized by steep slopes at the depth of the thermocline onto which the M2 barotropic tide is almost normally incident. The M2 internal tides propagating away from these multiple source regions interfere with each other to create a complicated wave pattern. It is found that the calculated pattern of the M2 internal tide agrees well with TOPEX/Poseidon altimeter observations. The conversion rate from M2 barotropic to baroclinic energy over the whole analyzed model domain is estimated to be 35 GW. Roughly 10% of the energy in the M2 surface tide incident on the prominent topographic features is converted to the M2 internal tide, although about half of the M2 internal tidal energy is subject to local dissipation in close proximity to the generation sites.