Internal tides and ocean mixing on the ontinental shelf of the southwestern East/Japan Sea from observation and simulation

Abstract

We investigate internal tides and ocean mixing near the continental slope of the southwestern East/Japan Sea using two sets of 25-hr long hourly CTD and LADCP profiles and numerical imulations. The time series of profiles span the whole water column from the surface to about 260 m during spring and neap tidal periods. Our observations reveal strong semi-diurnal internal tides below the main thermocline (150-200 m) where the 5¨&not C-isotherm displaces more than 50 m. The Richardson numbers calculated from the observations show low values (0-0.25) in layers where large vertical displacements exist, suggesting internal tide induced mixing. Numerical simulations using an idealized vertical 2.5-dimensional numerical model based on the ROMS reveal that semi-diurnal internal tide is dominantly generated on the continental slope. Simulations using different configurations are conducted for further understanding of internal tide generation mechanism and its impact on ocean mixing in this region.er column from the surface to about 260 m during spring and neap tidal periods. Our observations reveal strong semi-diurnal internal tides below the main thermocline (150-200 m) where the 5¨&not C-isotherm displaces more than 50 m. The Richardson numbers calculated from the observations show low values (0-0.25) in layers where large vertical displacements exist, suggesting internal tide induced mixing. Numerical simulations using an idealized vertical 2.5-dimensional numerical model based on the ROMS reveal that semi-diurnal internal tide is dominantly generated on the continental slope. Simulations using different configurations are conducted for further understanding of internal tide generation mechanism and its impact on ocean mixing in this region.