Circulation of the East China Sea, a numerical study

Abstract

A three-dimensional, primitive-equation model is developed to study how the Kuroshio, the monsoon, the Yangtze River outflow and the buoyancy forcing from the South China Sea affect the circulation of the East China Sea. It is found that the Kuroshio water usually intrudes into the East China Sea from both sides of Taiwan Island. Winter winds enhance the Kuroshio intrusion from northeast of Taiwan, but weaken it from the Taiwan Strait. Summer winds act in the opposite way. The increased presence of the Kuroshio water in the East China Sea in winter can be largely attributed to the shoreward surface Ekman drift associated with the northerly wind. In summer, theΩ-shaped plume emanating from the Taiwan Strait is, to a large extent, produced by the buoyancy forcing from the South China Sea. In summer, the bimodal distribution of the Yangtze River outflow is initially produced by the upwelling-favorable wind. Away from the Yangtze River, the far-field dispersal of the fresher water depends on the strength of the Kuroshio. A stronger Kuroshio enhances the seaward dispersal of the northern branch of the Yangtze outflow north of Taiwan, but reduces the southward penetration of the southern branch. In winter, downwelling-favorable winds confine the Yangtze River outflow to a narrow band forming nearshore coastal jet penetrating southward. The northern tip of Taiwan acts as a conduit, channeling the seaward dispersal of the fresher water. The model results interpret the observed circulation patterns.