Turbulent mixing and Chlorophyll maximum layer in the East China Sea in summer

Abstract

The layered structure of the Chlorophyll maximum and vertical mixing in the northern East China Sea in summer is examined by analyzing data obtained in 2003-2007. The subsurface Chlorophyll-a maximum (SCM) layer appears in large parts of studied area. The SCM layer gets shallow toward the west and leads to the surface Chlorophyll maximum in the Changjiang bank where the low salinity water appears. The results of numerical simulation support that the lateral dependence of the SCM layer depth is a common summertime feature in the region. The turbulent energy dissipation rates estimated based on the microstructure profiler measurements show high within the thermocline, with typical value of O(10^-7 W/kg) and occasionally close to 10^-6 W/kg. Corresponding vertical eddy diffusivities reach to 10-2 m^2/s. Such high values of dissipation rate and vertical diffusivity match with the SCM layer. The SCM layer gets shallow toward the west and leads to the surface Chlorophyll maximum in the Changjiang bank where the low salinity water appears.