NUMERICAL DIAGNOSTIC SIMULATION OF SUMMERTIME TIDE-INDUCED, WIND-DRIVEN AND THERMOHALINE CURRENTS IN THE BOHAI SEA

Abstract

The Bohai Sea is a shallow,semi closed gulf with an average water depth of 18 m. A large number of numerical studies have previously been undertaken on tide and the circulation. However, the interrelationships between tide induced, wind driven and thermohaline currents in summertime are currently poorly understood. Using thermohaline data collected in August 2000 and annual wind field data in the Bohai Sea, a three dimensional ECOMSED model incorporating Mellor Yamada level 2.5 turbulent closure model was used to diagnostically compute tide induced residual currents, wind driven and thermohaline currents in the Bohai Sea with an orthogonal curvilinear grid system. Factual topography and shore shape were both considered. The results were verified using the measured data and previous model results. The results show that there was a clockwise circulation in the middle Bohai Sea during summertime with some counter clockwise circulations in the mouth of Bohai Bay, the middle of Liaodong Bay and the north of Bohai Strait. The trend of the summer circulations in the Bohai Bay is anticlockwise in the north and clockwise in the south, with a `two loop' structure. In addition the differences between tide induced residual currents wind driven and thermohaline currents were compared and analyzed. Tides and tidal currents were well reproduced, showing a high level of agreement with previous research. The model results indicate that in the Bohai Sea during summertime, the tide induced residual currents are weak while the thermohaline currents are strong and dominant.