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This study investigates the turbulent mixing characteristics of Peng-hu Channel, South China Sea along 21¢XN and the Kuroshio region by using CTD/LADCP and MicroRider. Dissipation rate of turbulent kinetic energy or thermal variances is estimated primarily by the Thorpe overturn method, and is compared with the microstructure turbulence from direct measurement as well as those estimated from the parameterization method based on shear and strain spectra. Our results indicate that there are different turbulent characteristics and dynamic mechanisms at these three regions. Because of its funnel-shaped topography and strong semi-diurnal tides in the Peng-hu Channel, the turbulent mixing and eddy diffusivity reach a maximum value at the narrowest part of Peng-hu Channel near its sea bottom and show a clear tidal variation. In the main stream of Kuroshio where the current speed is faster than 0.8 m/s, turbulent mixing is not particularly stronger than non-main stream zone. In the Kuroshio frontal zone between the Kuroshio and the coastal waters off east Taiwan coast, strong turbulent mixing in the surface layer can be detected. Island wake which is formed when Kuroshio runs into the Lan-yu Island is a transient feature. Strong mixing in the upper 100 m accompanied with upwelling and vortices were observed during one event. The topography along the latitude of 21¢XN is rugged and rough in the Luzon Strait which consists of several ridges and seamounts. Due to its complicated topography and generation of strong semi-diurnal internal tides, eddy diffusivity as high as 10^(-2)m^2/s was measured in the bottom layer of the Luzon Strait. |
