Submesoscale-enhanced filaments and frontogenetic mechanism within mesoscale eddies of the South China Sea

被引:5
作者
Zheng, Ruixi [1 ,2 ]
Jing, Zhiyou [1 ,3 ]
机构
[1] Chinese Acad Sci, South China Sea Inst Oceanol, State Key Lab Trop Oceanog, Guangzhou 510301, Peoples R China
[2] Univ Chinese Acad Sci, Beijing 100049, Peoples R China
[3] Southern Marine Sci & Engn Guangdong Lab Guangzho, Guangzhou 511458, Peoples R China
基金
中国国家自然科学基金;
关键词
submesoscale process; vertical exchange; frontogenesis; South China Sea; SYMMETRIC INSTABILITY; VERTICAL PUMP; EDDY; SURFACE; SUBDUCTION; NORTH; VARIABILITY; CIRCULATION; FRONTS; PARAMETERIZATION;
D O I
10.1007/s13131-021-1971-3
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
Submesoscale activity in the upper ocean has received intense studies through simulations and observations in the last decade, but in the eddy-active South China Sea (SCS) the fine-scale dynamical processes of submesoscale behaviors and their potential impacts have not been well understood. This study focuses on the elongated filaments of an eddy field in the northern SCS and investigates submesoscale-enhanced vertical motions and the underlying mechanism using satellite-derived observations and a high-resolution (similar to 500 m) simulation. The satellite images show that the elongated highly productive stripes with a typical lateral scale of similar to 25 km and associated filaments are frequently observed at the periphery of mesoscale eddies. The diagnostic results based on the 500 m-resolution realistic simulation indicate that these submesoscale filaments are characterized by cross-filament vertical secondary circulations with an increased vertical velocity reaching O(100 m/d) due to submesoscale instabilities. The vertical advections of secondary circulations drive a restratified vertical buoyancy flux along filament zones and induce a vertical heat flux up to 110 W/m(2). This result implies a significant submesoscale-enhanced vertical exchange between the ocean surface and interior in the filaments. Frontogenesis that acts to sharpen the lateral buoyancy gradients is detected to be conducive to driving submesoscale instabilities and enhancing secondary circulations through increasing the filament baroclinicity. The further analysis indicates that the filament frontogenesis detected in this study is not only derived from mesoscale straining of the eddy, but also effectively induced by the subsequent submesoscale straining due to ageostrophic convergence. In this context, these submesoscale filaments and associated frontogenetic processes can provide a potential interpretation for the vertical nutrient supply for phytoplankton growth in the high-productive stripes within the mesoscale eddy, as well as enhanced vertical heat transport.
引用
收藏
页码:42 / 53
页数:12
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