Seasonal Variation And Distribution Of Suspended Sediment In The Yellow Sea

Based on suspended-sediment concentration (SSC) and CTD data collected in spring,summer, autumn and winter in the Yellow Sea from2010to2011, combined with the MODISL1B remote-sensing data, an empirical model was established using band4data to retrieveSSC from the MODIS imagery. The seasonal variation and distribution of suspendedsediment in the Yellow Sea was studied based on the in-situ data and monthly averaged SSCretrieved from the monthly averaged MODIS data. The pathways of suspended-sedimentdispersal in different seasons were illustrated by analyzing the distribution of suspendedsediment along nine key transects. The dynamic mechanisms of seasonal distribution ofsuspended sediment and its dispersal pathways were discussed as well. The results show that:1. Three high SSC areas were observed in the Yellow Sea, namely, around the Subei shoal,the Chengshantou cape off the Shandong Peninsula and the north coast of the ShandongPeninsula. The high SSC areas around the Subei shoal and the Chengshantou cape wereresulted from the resuspension of the sediment in seabed, while the high SSC area in thenorth coast of the Shandong Peninsula was formed due to the highly turbid wateroriginated from the coast of the Huanghe delta transported through the Bohai strait.2. The suspended sediment in the Yellow Sea presented significant seasonal variation anddistribution. Three notably high SSC areas caused by the strong waves and coastalcurrents due to winter storm were found in the Subei shoal, the Chengshantou off theShandong Peninsula and the north coast of the Shandong Peninsula in winter. Thesuspended sediment originated from the coast of the Huanghe delta was delivered throughthe Bohai strait to the Chengshantou and formed a highly turbid water belt along the northcoast of the Shandong Peninsula. The high SSC water in the Subei shoal deliveredsouthwards by the Subei coastal current and turned southeastly around the north of theChangjiang estuary and a cross-shelf dispersal pathway of suspended sediment wasformed. The SSC in the Yellow Sea decreased considerably due to the weaken waves andcoastal currents in spring. The highly turbid water originated from the coast of the Huanghe delta retreated back to the west of122°E. The cross-shelf transport of thesuspended sediment from the Subei shoal almost disappeared. In summer, only one highSSC area was formed in the Subei shoal due to the strong tidal currents in this area. TheSSC as well as the extent of highly turbid water in the Yellow Sea increased significantlyin autumn due to the increasing of the intensity of the northerly storms. The winter patternof suspended-sediment distribution was formed since late autumn in the Yellow Sea.3. Influenced by the seasonal variation of the marine dynamic environment, the ShandongPeninsula muddy deposit shifts accordingly. In winter, strong wave and coastal currentgenerate abundant resuspension in the Yellow River delta and they impel the suspendedsediment to move along the northern coast of the Shandong Peninsula. Then thesuspended sediment bypasses the Chengshantou and moves on toward the south,providing plentiful sediments for the Shandong Peninsula muddy deposit. In spring andautumn, with the strength of waves and current in the Northern-Shandong Peninsulaweakening, the supply of the Yellow River Estuary suspended sediments reduces sharply.Meanwhile, the Shandong Peninsula muddy deposit was partially resuspended due to thetides and waves, and transported southward around the external area of the ShandongPeninsula muddy deposit, changing the shape of the Shandong Peninsula muddy deposit.4. The band4data of MODIS L1b imagery are highly correlated with the SSC and can beused for the retrieval of SSC based on MODIS imagery. A method on how to generate thereal monthly averaged MODIS L1b imagery was created in this study. The seasonalvariation and distribution of the suspended sediment retrieved based on empirical modelestablished in this study and the monthly averaged MODIS imagery were consist with theobserved data. Therefore, the SSC retrieval model and monthly averaged MODIS datacan be used for quantitative estimation of seasonal variation and distribution of thesuspended sediment in the Yellow Sea.