The Roles of Kuroshio Intrusion and Mesoscale Eddy in Upper Mixing in the Northern South China Sea

Upper mixing in the northern South China Sea (SCS) is derived from Argo profiles from 2006 to 2012, using the Gregg-Henyey-Polzin parameterization. Temporal and spatial mean estimates reveal clear spatial patterns of mixing over the northern SCS. Enhanced diffusivity on an order of 10(-3) m(2) s(-1). exists in the Luzon Strait and adjacent areas. South of 20 degrees N, diffusivity is one order of magnitude smaller on average than it is near the Luzon Strait. Such observations suggest that other than internal tides, both Kuroshio intrusion and mesoscale eddy might be key factors to the enhanced mixing. Shear instability associated with Kuroshio intrusion plays a major role in strengthening the turbulent mixing near the Luzon Strait. In addition, warm eddies could reinforce the downward-propagating near-inertial waves and thus promote the occurrence of strong mixing, whereas cold eddies could reduce this downward-propagating, inhibiting strong mixing. This work facilitates the contributions of mesoscale eddy and Kuroshio intrusion in the northern SCS.