Estimates of Reynolds Stress and TKE Production in the Seasonally Stratified East China Sea

• Published in: Journal of Ocean University of China 2013-12, Vol.12 (4), p.549-556
• Main Authors: Yang, Wei, Zhao, Liang, Xu, Peng, Feng, Jianlong, Wang, Tao, Quan, Qi, Jiang, Wensheng
• Format: Article
• Language: English
• Subjects: Boundary layers; Diurnal variations; Earth and Environmental Science; Earth Sciences; Kinetic energy; Marine; Meteorology; Ocean currents; Ocean floor; Oceanography; Reynolds number; Spring; Stratigraphy; Summer; Tidal waves; Turbulence; Velocity; Water column; 东中国海; 估计; 季节性; 密度跃层; 应力和; 生产; 速度剪切; 雷诺应力
• ISSN: 1672-5182; 1993-5021; 1672-5174
• DOI: 10.1007/s11802-013-2212-y

During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea （ECS） were measured synchronously by a bottom-mounted fast sampling ADCP （acoustic Doppler current profiler） and a RBR CTD （RBR-620） profiler. While focusing on the tide-induced and stratification＇s impact on mixing, the Reynolds stress and the turbulent kinetic energy （TKE） production rate were calculated using the ‘variance method＇. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoy- ancy frequency of N2~ （1-6）x 10 3 S-2 The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.