Seasonal variation in material exchange through the Bohai Strait

The seasonal variation in material exchange through the Bohai Strait (BS) was examined using the climatological mean outputs from the Regional Ocean Modelling Systems and in-situ observations from two acoustic Doppler current profilers at two typical stations in the Strait from July 2017 to June 2018. The suspended sediment concentration (SSC) was retrieved from ocean color remote sensing data. The long-term mean numerical results and the one-year observations suggest that the volume and suspended sediment flux in the BS section exhibit distinct seasonal variations. The annual mean net outflow of the suspended sediment through the BS section is estimated to be 15.8 Mt/yr in the climatological state. The observations further reveal the circulation structure, with inflow in the north and outflow in the south. Freshwater from the Yellow Sea discharged sediment into the Bohai Sea in the deep northern channel at a rate of 0.4 Mt/yr, whereas turbid water discharged sediment into the Yellow Sea in the shallow southern channel at a rate of 0.19 Mt/yr. Several factors determine the seasonal variation in the sediment flux. In the winter half-year, variation in SSC plays a dominant role, while in summer, the primary influence on sediment flux is current velocity. Moreover, SSC significantly influences the southern shallow and deep northern channels, while the current velocity is dominant in the central channel. In addition, the meridional wind displays a close relationship with the seasonal variation of the sediment exchange through the BS by dominating both the current and SSC.