Decreasing Suspended Sediment Concentration and Flux in the Bohai Sea: Based on Remote Sensing and Numerical Simulation

The Bohai Sea is the region with the highest suspended sediment concentration (SSC) in the world. The transport of suspended sediment from the Bohai Sea to the open sea greatly affects the coastal biogeochemical processes. However, due to the limitations of long-term field observations, the temporal and spatial characteristics and mechanisms of the long-term changes in suspended sediment concentration and flux in the Bohai Sea remain unclear. Remote sensing results and numerical simulation analysis indicate that the transport of suspended sediment from the Bohai Sea to the open sea is decreasing. Further analysis shows that changes in the wind field are the main reason affecting the output of suspended sediment from the Bohai Sea. During the transport process of suspended sediment from the Bohai Sea to the open sea, both the SSC and the range of high concentration suspended sediment are showing a downward trend, with the 15 mg/L isopleth range gradually shrinking at a rate of 7.38 km/yr. The suspended sediment flux (SSF) from the Bohai Sea to the open sea shows a clear downward trend, and the decline rate gradually weakens from west to east, mainly controlled by the weakening of the northwesterly (NW) wind intensity in winter.