[AOS09-P15] Mixing over the eastern ridge in the Luzon Strait caused by high-mode internal waves
Keywords:internal waves, Luzon Strait
The cross sections showed wavy structures of isopycnals over the ridge, with 4-7 km of horizontal scale and about 50 m of vertical scale. Velocity distributions by the shipboard ADCP showed strong vertical shear over the ridge, suggesting high-mode internal waves. Froude number of the high-mode internal waves exceeds unity around two summits of the ridge during the periods of strong tidal flow. This suggests that the high-mode internal waves stay over the ridge.
Many temperature inversions, especially large inversions (θ > 0.05 °C) were formed near the ridge (figure). Therefore, energy dissipation rate and vertical diffusivity assuming the model of Osborn (1980) were estimated by calculating Thorpe scale from the temperature profiles. Relatively large energy dissipation rate and vertical diffusivity were distributed over the ridge from surface to the bottom, as well as unstable regions of Ri < 0.25. These results reflect strong mixing over the ridge due to the high-mode internal waves.