Shear Instability and Turbulent Mixing by Kuroshio Intrusion Into the Changjiang River Plume

Junbiao Tu¹, Jiaxue Wu^{2, *} , Daidu Fan¹ , Zhiyu Liu³ , Qianjiang Zhang⁴ , and William Smyth^{5, *}

¹State Key Laboratory of Marine Geology, Tongji University, Shanghai, China 

²School of Marine Sciences, Sun Yat-sen University, Zhuhai, China 

³State Key Laboratory of Marine Environmental Science, and Department of Physical Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China 

⁴State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, China 

⁵College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA

*Corresponding author. 

E-mail address: wujiaxue@mail.sysu.edu.cn (J. Wu); smyth@coas.oregonstate.edu; bill. smyth@oregonstate.edu (W. Smyth)

Abstract

Shear instability is a dominant mechanism for mixing in the stratified oceans and coastal seas. For the first time, we present fine-scale, direct measurements of shear instabilities in the bottom front generated by the Kuroshio intrusion into the Changjiang (Yangtze) river plume. Shear instabilities were identified using a shipboard echo‐sounder and the resulting turbulent mixing was quantified using a turbulence microstructure profiler. The shear instabilities generate vigorous turbulent mixing with dissipation rate and vertical diffusivity up to O (10− 4 m2 s− 3) and O (10− 1 m2 s− 1), respectively, comparable to values associated with shear instabilities observed in river plumes and western boundary currents but several orders of magnitude larger than typical values in the open ocean. The enhanced turbulence may contribute significantly to mixing between the Kuroshio water and coastal water and thereby alter the coastal biogeochemistry cycles

Full article：https://doi.org/10.1029/2024GL110957

Fig. Bathymetry of the Changjiang River estuary and its adjacent sea. The mooring site is marked by a red triangle.