Seasonal Variability Of Thermohaline Structure And Its Influence On Suspended Sediment Distribution

Transport and distribution of suspended sediment not only exert significant influence on morphology and topography of shelf seas, but also of importance to marine physical, chemical and biological process due to the adsorption effect of suspended sediment to nutrients, heavy metal and other pollutants. Yellow Sea is a system with active sediment transport. Yangtze River, Yellow River and Old Yellow River subaqueous delta provide sufficient terrestrial materials input which make contribution to a large amount of sediment fluxes. Seasonal variability of suspended sediment transport can be ascribed to monsoon actions, circulation, fronts and other factors.Based on hydrology parameters collected during four cruises in 2010 and 2012 which were supported by the public voyage of the National Natural Science Foundation, the hydrological results of HYCOM are evaluated. Combined the data set of suspended sediment concentration with current velocity, significant wave height and topographical data, seasonal variability of suspended sediment’s distribution and the factors which affected its transport path are analyzed. The results show that:In the surface layer, temperature and salinity of offshore water column were relatively low when compared with central part of Yellow Sea while in the bottom layer the offshore water column was characterized by high temperature and low salinity. Vertically, there were not obvious differences of thermohaline structure in spring while in other seasons the differences were outstanding. This phenomenon illustrated that the stratification in April was not notable, but in May, September and November it was strong.There was a high correlation between HYCOM temperature data and in-situ data. Besides, HYCOM(reanalysis) temperature data was better than that of HYCOM(analysis). Nonetheless, HYCOM salinity data differed from in-situ data and there was not conspicuous improvement after data assimilation.High SSC areas in Yellow Sea were observed in Chengshantou cape area and Old Yellow River subaqueous delta, SSC in other areas was extremely low. In summer, SSC was the lowest while it was comparatively high in other seasons. Vertically, SSC in surface layer was lower than that in bottom layer.In spring and summer, the fronts in Shandong Peninsula coastal areas did not exist but they were obvious in fall and winter. Temperature front and hybrid front were distributed along the shoal line. In vertical direction, temperature front was stronger in the bottom layer. Current velocity in spring and summer was lower when compared with that in fall and winter. Surface current velocity was much higher than bottom. Significant wave height in central area of Yellow Sea was higher than that in coastal area. In summer significant wave height was the lowest and in winter it was the highest among all seasons.Temperature front, wave and hybrid front played vital factors which could influence the variability of SSC distribution temporally and spatially in Yellow Sea. Temperature front could confine suspended sediment’s seaward diffusion. In fall and winter, high SSC areas were restricted in the offshore area which located in the western part of temperature front. In summer temperature did not exist, but SSC in summer was comparatively low, thus the total amount of suspended sediment transported seaward was not very large. There was an obvious correlation between seasonal variability of significant wave height and SSC. The ratio between significant wave height and depth had a good linear correlation with SSC, the correlation coefficient was larger than 0.7. Seasonal variability of location of hybrid front also related to the location of high SSC water column in this area.