The flow in the ECS/YS is dominated by strong semidiurnal M2 tidal currents with superimposition of semidiurnal S2, and diurnal O1 and K1 currents. The low-frequency variability of the current in this region is strongly influenced by river discharges, air-sea interaction, tidal mixing and the Kuroshio. The ECS/YS is surrounded by the largest rivers in Asia, the Hangho (Yellow River) and Changjiang (Yangtzi River) along the east coast of China, and by three relatively small rivers, the Yalu, Han and Keum, along the north coast of China and west coast of Korea (see Chen et al. 1994). The seasonal cycle of freshwater discharge from these rivers dominates the surface distribution of water properties in the ECYBS, especially in summer when the river output is largest. Air-sea interaction is responsible for vertical stratification of water masses in the ECS/YS where the water is mixed vertically by strong surface cooling and wind mixing during winter and re-stratified by strong surface heating during summer. It is well known that the Kuroshio centers the ECS east of Taiwan, flows northeastward along the edge of the continental shelf along the 200-m isobath, and then leaves the ECS through the Tokaro Strait southwest of Kyushu (see Chen et al. 1992). The water exchange between the coastal and Kuroshio waters tends to form a strong frontal zone between the warm and high salinity Kuroshio water and relatively cold and low salinity coastal ECS water at the shelf break. This front exhibits eddies due to baroclinic instability.
Recently the ECS has experienced a serious environmental problem due to the high-frequently occurrence of the harmful algal blooms (HAB) (or red tide) (see Chen et al. 2003). Significant increase in nutrient loading from the Changjiang is believed to be a key physical-biological source to cause the eutrophication. The accumulation of the sediment around the mouth of the Changjiang also continuously make the navigation problems. All these economic and environmental problems call for the intense scientific study of the ECS/YS and Changjiang Estuary.
As Zhijiang Scholar, Dr. Chen has been collaborating with Dr. Pingxing Ding, Director of the State Key Laboratory for Coastal and Estuarine Research at East China Normal University, Shanghai, on developing the East China Sea and Changjiang River Estarine models system by using the stat-of-the-art unstructured grid Finite-Volume Coastal Ocean Model (FVCOM). To nest the Changjiang Estuarine Model with a regional scale ECS and Pactific Ocean, Chen et al. (2005) at Marine Ecosystem Dynamics Modeling Laboratory at University of Massachusetts has developed a new finite-volume flux algorithm that ensure the volume and mass conservation in the control volume that are independent of poleward convergences of longitude and latitude. Dr. Beardsley at Woods Hole Oceanographic Institution, founder of the first US-China Cooperation in the East China Sea about 25 years ago, is working together with Dr. Chen on continuing exploration of the physical and ecosystem process in the ECS and YS. A brief description of our ECS model and some examples of the model reshults are given below.