Vertical mixing as a controller of biogeochemical materials’ distribution in the East China Sea

Abstract

The data collected from microstructure profiler (MSP) in the East China Sea in summer show high turbulent energy dissipation rates near the bottom and within the thermocline, with typical value of O(10-7 Wkg-1). Corresponding vertical eddy diffusivities reach to 10-2 m2s-1. High values of dissipation rate are consistent with high turbidity or enhanced chl a concentration. The data also show good correlation between the enhanced bottom mixed layer and the phase of tidal current indicating that near bottom vertical mixing occurs mainly due to the tidal stirring. During internal wave episodes, high-frequency fluctuations of all components of the velocity occur for almost entire water column suggesting the possibility of vertical transport of suspended materials across the pycnocline. This implies that near bottom mixing and internal mixing within the thermocline are key physical processes for the subsurface chlorophyll maximum layer.diffusivities reach to 10-2 m2s-1. High values of dissipation rate are consistent with high turbidity or enhanced chl a concentration. The data also show good correlation between the enhanced bottom mixed layer and the phase of tidal current indicating that near bottom vertical mixing occurs mainly due to the tidal stirring. During internal wave episodes, high-frequency fluctuations of all components of the velocity occur for almost entire water column suggesting the possibility of vertical transport of suspended materials across the pycnocline. This implies that near bottom mixing and internal mixing within the thermocline are key physical processes for the subsurface chlorophyll maximum layer.