Enhanced turbulence observed in the East China Sea shelf

Abstract

Turbulence in the central East China Sea is analyzed based on a series of microstructure profiles collected in a drifting vessel in August of 2006. A shallow surface mixed layer, a sharp thermohalocline, and about 20 m thick bottom boundary layer were the main features of summertime stratification. The splitting of upper pycnocline by a warmer, saltier intrusion led to the generation of turbulent patches at the lower, but not at the upper, density interface of this water body, suggesting asymmetry of mixing across the intrusion. In a limited range of the normalized squared buoyancy frequency, , the turbulent kinetic energy dissipation rate decreased sharply as , where ε_m and N_0 are reference values. Measurements in the sharp pycnocline and in lesser-stratified transitional layers between the pycnocline and the surface mixed layer and bottom boundary layer show that the cumulative distribution functions can be modelled by the generalized extreme value distribution or in some cases by lognormal distribution. layer were the main features of summertime stratification. The splitting of upper pycnocline by a warmer, saltier intrusion led to the generation of turbulent patches at the lower, but not at the upper, density interface of this water body, suggesting asymmetry of mixing across the intrusion. In a limited range of the normalized squared buoyancy frequency, , the turbulent kinetic energy dissipation rate decreased sharply as , where ε_m and N_0 are reference values. Measurements in the sharp pycnocline and in lesser-stratified transitional layers between the pycnocline and the surface mixed layer and bottom boundary layer show that the cumulative distribution functions can be modelled by the generalized extreme value distribution or in some cases by lognormal distribution.