Process and Mechanisms of Cross-Topographic Transport Induced by Coastal Trapped Waves along the Western South Yellow Sea in Winter
Zehao Qiu¹, Qi Quan^1*
1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China

Abstract: Coastal trapped waves (CTWs) are important low-frequency dynamical processes regulating shelf circulation and cross-isobath exchange. However, their role in driving cross-topographic transport over the complex coastal topography of the western South Yellow Sea remains insufficiently understood. This study focuses on the Jiangsu coast, the radial sand ridge system, and the adjacent shelf area in winter. A high-resolution three-dimensional SCHISM model, together with ADCP observations and satellite sea surface temperature data, is used to investigate the propagation characteristics of CTWs and their associated transport mechanisms. Methods include EEMD and wavelet analysis, 40–960 h band-pass filtering, velocity projection along bathymetric gradients, cross-isobath transport calculation, Ertel potential vorticity diagnosis, and eddy buoyancy/salt flux analysis. Preliminary results show that during active CTW events, low-frequency cross-isobath velocities are significantly enhanced, forming alternating offshore and onshore transport pathways near the outer radial sand ridges and the transition zone between the Jiangsu coast and the outer shelf. Regions of dynamical instability correspond well with enhanced eddy buoyancy and salt fluxes, suggesting that CTW-induced shear and topographic modulation can promote local mixing and cross-shelf material exchange. This study highlights a coupled wave–topography–instability mechanism for enhanced cross-isobath transport along the western South Yellow Sea.
Keywords: coastal trapped waves, cross-isobath transport, South Yellow Sea, radial sand ridges, dynamical instability