Possible mechanism underlying the millennial scale variation of offshore suspended sediment transport in the North Yellow Sea

Abstract

While terrigenous materials tend to be limited to the inner shelf by coastal fronts in the shelf seas of eastern China, they could still be transported to offshore regions when coastal front is disturbed by winter storms. However, the offshore transport process is still poorly understood because its variation does not have close relation with strength of wind storms. In this study, we took offshore transport in the North Yellow Sea (NYS) as an example to explore the determining factor for amount of offshore transport. The results show that offshore transport in the NYS is positively correlated with the strength of the Kuroshio Current and its branch recorded in water temperature on a millennial scale, but is rarely influenced by winter storms, which is also supported by the instrumental data on interannual and monthly scales. By analyzing modern hydrological and meteorological data, we found that the variation of offshore suspended sediment transport with interannual and monthly scales is controlled by the variation of horizontal density gradient, which supports the possible mechanism underlying the millennial scale variations in sediment core data. One possible mechanism dominating the flux of offshore transport is that the increasing density difference across the coastal front is conductive to cross-front exchange when the frontal instability is triggered.