Seasonal Changes of Baroclinic Circulation and Water Exchange in the Bohai Sea

In four principal sea areas in China, accelerated water pollution has recently become more widespread and severe with rapid economic growth. In enclosed areas such as the Bohai Sea, "red tides" are occurring with greater frequency, degrading ecosystems and causing eutrophication. As the first step in clarifying the mechanisms of ecosystem and coastal eutrophication and for considering concrete enforcement measures to reduce the damage, the present study focuses on physical phenomena such as hydrodynamics and transport processes. First, the flow structure and density field in the Bohai Sea are examined using a three-dimensional baroclinic flow model. Second, the seasonal change of wind and surface heat transfer on the residual current system and the water exchange through the Bohai Strait are examined using a Lagrangian particle tracking method. This computation makes clear that the residual currents in the majority of the Bohai Sea are very weak, less than 0.05m/s. The effect of seasonal winds on hydrodynamics such as residual currents in the Bohai Sea, water exchange between the Bohai Sea and the Yellow Sea, and stratification induced by heat transfer at the sea/water surface are studied.