Spatial modes of suspended sediment concentration in surface water in Bohai Sea and their temporal variations

A five years (2000-2004) SeaWiFs satellite dataset is used to investigate the overall pattern of suspended sediments in the Bohai Sea Basin. The dataset consists of 354 charts of suspended sediment concentration (SSC) in surface water, which cannot be obtained by the conventional procedure through in-situ sampling. Results show that the 5-year mean seasonal cycle of SSC is constructed for the entire Bohai Sea Basin. The SSC exhibits a character of spatial distributions with higher values from inshore waters and lower values from offshore waters, except for those near Qinhuangdao Island. Furthermore, the SSC in the eastern part of Liaodong Bay is much higher than that of the western part. Highest concentrations occur during winter seasons and followed by spring and autumn seasons. The opposite is true during summers, except for estuary areas where the concentration remains higher during both summers and winters. The empirical orthogonal function decomposition (EOF) analysis is performed to reveal the spatial modes and the corresponding time coefficients in Bohai Sea. Results show that the first EOF mode indicates a basin-wide pattern of SSC in the Bohai Sea with an annual variation of 12-month period. The second mode reveals the influence of the Yellow River runoff on the SSC in the Bohai Sea with a dominant semi-annual (6 months) variation at the estuary of the Yellow River. The third mode indicates that there exists a clear difference in the variation of the SSC in different waters in Bohai Sea.