Properties of internal tides and vertical mixing observed on the continental slope of the southwestern East Sea

Abstract

Internal tides and their impact on vertical mixing near the continental slope of the southwestern East Sea were investigated using 3 sets of CTD, LADCP, and free falling Microstructure shear profiler (TurboMAP) measurements collected for 26 hours in 2-hour interval. The profiles span the whole water column from the surface to near bottom (~ 260 m). Semi-diurnal internal tide was the strongest below the main thermocline (150-200 m) where 5ºC isotherm displacements larger than 30 m were observed. Turbulence dissipation rate ε and vertical diffusivity K_z estimated using shear profiles reveal the presence of mixing events below the main thermocline as well as in the mixed layer. The value of K_z below the main thermocline reached in the range of 10-3&#8210 10-2 m2 s-1 order of 2 higher than that in the open ocean, which seems to be associated with vertical mixing induced by internal tides. Mean value of K_z through the whole water column was 8ｘ10-4 m2 s-1 and that under the thermocline (about 70 m to bottom) was 3ｘ10-4 m2 s-1. Methods of vertical diffusivity assessment based on TurboMAP shear profiles and on density inversion calculated from temperature and salinity profiles were compared.