Sediment dynamic responses to a severe typhoon in a stratified continental shelf sea

Abstract

Under the background of global warming, an intensification of severe typhoons has been observed, with a notable trend of these typhoons shifting poleward and shoreward. This study employed a coupled hydrodynamic-sediment model to investigate the hydrodynamic and sediment dynamic responses in the Yellow Sea (YS) to a northward-moving Typhoon Bolaven. The research further elucidates the cross-front transport and underlying mechanisms triggered by the typhoon. The typhoon led substantial resuspension of seabed sediments and rapid changes in bed elevation, a consequence of the extreme waves generated by the typhoon. A cyclonic pattern was identified in both volume and sediment transport within the central and eastern YS. Significant fluctuations in volume and sediment transport were observed near the frontal zone in the western YS during the typhoon's influence. The critical period for cross-front transport was identified as the 24-hour period following the typhoon's passage. The net transport flux of sediment with high concentration from the Subei Coast to the central YS across the front was calculated to be approximately 0.03 Mt, spanning a transport distance of 2∼15 km. This cross-front transport was predominantly propelled by a cross-front flow, which was a result of the seaward barotropic pressure gradient force (PGF) due to the surge near the Subei Coast. The water temperature pattern during summer enlarged the difference of water level difference between the Subei Coast and the central YS, thereby reinforcing the barotropic PGF. This study offers profound insights into the sediment dynamic response to extreme events in a stratified continental shelf sea characterized by front systems.