Distributions of suspended sediment concentration in the Yellow Sea and the East China Sea based on field surveys during the four seasons of 2011

Abstract

The seasonal and spatial variation of the suspended sediment concentration (SSC) in the Yellow Sea and the East China Sea (YSECS) is studied using turbidity, temperature and velocity field data from all seasons of 2011. The important hydrodynamic factors affecting the SSC distribution are discussed, based on the field data. The data provide a picture of the seasonal evolution of the SSC in the YSECS in a single year. The results show that the highest surface layer SSC was measured in spring and winter, while the summer had the lowest surface layer SSC. In the bottom layer, the SSC distribution patterns were similar in all seasons except that a much higher SSC water plume extended from the Subei Shoal to the East China Sea shelf in winter survey. The vertical SSC gradient was stronger in the shallow water area than the deep water area, and it was stronger in summer and autumn than in winter and spring. We argue that wind-induced vertical mixing dominated the SSC distribution in the surface layer while the tidal currents played an important role in the bottom layer and sub-tidal currents dominated the horizontal pattern of the SSC distribution pattern over the shelf area. In particular, the presence of the summer thermocline limited the vertical mixing in summer, decreasing the SSC in the surface layer. The front between the East China Sea Coastal Current and the Taiwan Warm Current appears to prevent the high SSC water from being transported to the shelf. The sediment discharged by the Changjiang River was found to be concentrated in the estuary area and influenced the shelf SSC distribution only through the action of the subtidal currents.