A Mechanism of Seawater Exchange in Strait-Basin Systems in the Seto Inland Sea, Japan

摘要

The seawater exchange is closely related to the spreading of pollutant and then water quality in coastal seas. The Seto Inland Sea is a semi-enclosed coastal sea which has a series of broad basins and narrow straits. There are several major driving forces of the seawater exchange between a strait and a basin; tide, wind and horizontal gradient of density. In this study, seawater exchange in a strait-basin system in the Seto Inland Sea was quantified by an observation using Acoustic Doppler Current Profiler (ADCP). A numerical model based on Princeton Ocean Model (POM) was also used in order to analyze the mechanisms of the seawater exchange. The observed residual current indicated the existence of the exchange flow across the boundary between the strait and basin; significant outflow from the strait to the surface layer of the basin. The exchange flow was well reproduced using the model which was driven by tide and horizontal density gradient between the strait and basin, suggesting that the seawater exchange was mainly induced by the interaction between tidal stirring and density current.