Study of the Residual Flow and Salinity during the Spring and Neap Tides at the Seokmo Channel, South Korea

The Seokmo (SM) channel of Gyeonggi Bay, located in the South Korea, exhibits unique and complex estuarine circulation characteristics. This study analyzed the salinity observations, and the cross-sectional variations in the residual current and strengths of stratification by tidal current, along two cross-channels transects, during the 13-hour periods of the spring and neap tides, respectively. The cross-sectional averaged residual velocity, at the northern entrance of the SM channel, showed a seaward directional flow of 0.05 m/s during the neap tide, and 0.21 m/s during spring tide. At the southern entrance, the residual current showed two-layer circulation with a landward flow in the bottom layer, and a seaward flow in the surface layer. The spatial characteristics of the landward residual current, at the southern entrance are different for the eastern and western sides of the channel, depending on the spring and neap tidal cycles. The variation in the location of the observed landward residual current, caused by the changes in spring and neap tidal cycles, and the correlation between this variation and the stratification, were analyzed using the Richardson number. At the northern and southern end of the SM channel, a landward residual current appeared in the location that Richardson number was large. These results suggested that the cross-sectional residual current pattern, at the SM channel, changes depending on freshwater and topographical influences, and is sensitive to tidal changes, such as changes in the spring and neap tidal cycles.