ABSTRACT The typical seasonal (summer and winter) residual circulation in the Bohai Sea is studied with the ODEM 3-D flow model. There are many vortexes rather than one big vortex in the Bohai Sea which constitute the tidal residual circulation system. The topography and the shape of coastal line induce the coastal tidal residual circulation pattern. The effects of seasonal wind on tidal residual current and local thermally-driven current on tide-induced current are analyzed. The relationship between the structure of residual circulation and ability of water exchange are presented. The corresponding mechanisms and the interaction of tide, wind and heat exchange are discussed based on the vertical distribution of residual current under different computation cases.
INTRODUCTION The Bohai Sea is a semi-enclosed inland sea located at the northernmost end of eastern Chinese mainland. The sea extends 480 km north and 346 km east to west. It is rather shallow except for the submerged valley with a maximum depth of 70 m near the north of the Bohai Strait, which is approximately 100 km wide, and connects the Bohai Sea with the Yellow Sea. The Bohai Sea contains three main bays, namely Liaodong Bay in the northeast, Bohai Bay in the west and Laizhou Bay in the south. In Liaodong Bay, the averaged water depth is 30 m. The topography of the water bottom in Bohai Bay is rather flat. The water depth in most parts is less than 20 m, except for the northern part wherethe water depth is more than 30 m. Laizhou Bay is the shallowest bay in the Bohai Sea. The water depth is less than 10 m in most parts of the bay, and the average water depth is 18 m.