Role of continental shelf waves on the westward shift of the Yellow Sea Warm Current and their generation based on numerical model experiments

The Yellow Sea Warm Current (YSWC), which supplies warm and saline water into the Yellow Sea (YS), is a typical upwind flow in winter. Observations have presented that the path of the YSWC has shifted to the western flank of the YS. Previous studies proposed that continental shelf waves (CSWs) could play a key role in the westward shift of the YSWC. However, the source and generation process of CSWs that drive the westward shift of the YSWC remains unclear. The aim of this study is to reveal the generation and propagation of CSWs driving the westward shift of the YSWC. Numerical model experiments with idealized topography present that the westward shift of the upwind flow propagates southward along the western slope off China with a typical speed of 2.99 m/s, which is significantly similar with the theoretical phase speed of a first-mode CSW estimated using an analytical model. CSWs driving the westward shift are generated on the northern slope mainly by scattering of barotropic Kelvin waves that develop due to northerly winds and propagate northward into the YS along the eastern boundary off Korea. Model experiments with realistic topography consistently support the idea that scattering of Kelvin waves is a primary source of the southward propagating CSWs that drive the westward shift of the YSWC.