Bohai Sea Surface Suspended Matter Distribution Variation

Based on 5-year surface suspended sediment concentration with a span from 2000 to 2004, which was inverted from SeaWiFS remote sensing data, Quickscat wind data in the Bohai Sea, and so on, the temporal and spatial distribution of surface suspended sediment concentration and its variation patterns are studied. The main conclusions summarized as follows:1. The distribution of total surface suspended sediment concentration in the Bohai Sea is roughly high inshore, and low offshore, whose isolines are paralleled with the shoreline and isobath. The high-concentration seawater is located at the mouths of the rivers. For example, the highest concentration in the Bohai Sea is in the estuary of the Huanghe River, and the second is at the mouth of the Liao River.2. The distribution of surface suspended sediment concentration in the Bohai Sea has an obviously seasonal variation. The general pattern throughout the year is the highest in winter, while the lowest in summer. However, there are different typical patterns in the different sea areas. The high-concentration sea water appears in the estuary, both in winter and summer, because of the input of large quantity of river fresh water carrying suspended sediment in summer. In the other sea area, the high-concentration sea water appears only in winter. The main reason is the re-suspension of the unsolidated sediment at the sea bottom driven by the winter monsoon.3. There exists obvious correlation-ship between the seasonal variability of surface suspended sediment concentration and the wind velocity in the Bohai Sea, furthermore there is a time lag about 1 to 2 months. The influencing factors of the seasonal variability in different sea areas are so different, which include not only the wind velocity, but also the tide current, the circulation pattern, the water depth, terrestrial sediment and the sediment distribution at the sea bottom. In the Bohai Sea, the correlation coefficient between surface suspended sediment concentration and the wind velocity in the relatively deep sea or near the sediment resources is less than that in the shallow sea or far from the sediment resources.4. The sea water off Qinhuangdao is low concentration throughout the year. There are two main reasons, one is that the input of river sediment has little influence in suspended sediment concentration in flood season, because this area is far from the river mouth. The other is that the tide current is relatively weak in this sea area, therefore generally the re-suspension can't happen even under the role of the large wave-driven current in winter. The another possible reason is that the circulation structure in winter, which consists of a counterclockwise gyre in the Bohai Bay and a clockwise gyre in the Liaodong Bay, has blocked the input of high-concentration water, which comes from the Bohai Bay and Liaodong Bay.