A numerical investigation on seasonal variations of mass transport between Bohai and Yellow Seas, China

Water exchange and mass transport between Bohai Sea and Yellow Sea, through the Bohai Strait, are strongly influenced by wind, heat flux, tide, and basin-scale circulations. However, which processes are responsible for the prominent seasonal variability of the bay-shelf exchange across the strait is yet well understood. In this study, conservative passive tracers and Lagrangian particle tracking method were used in a 3D high-resolution ocean model (ROMS) to investigate the spatial-temporal characteristics of the particles transport pathways and to evaluate the relative contributions of different mechanisms. Results show that water exchange in the strait is characterized by the general structure of “north-in and south-out” in summer and winter. Tide-induced residual current modulates the exchange pattern, especially in the northern channel of the strait. In summer, the basin-scale cyclonic circulation due to the southerly monsoon and well-developed stratification lead to a two-layered bidirectional flow structure at the bay-shelf interface. In winter, water exchange is predominately determined by the barotropic response to the strong northwesterly wind, which strongly enhances the water exchange. This study highlights that the seasonal variation of water exchange in a coupled bay-shelf system is closely related to the monsoon reversal.