Numerical investigation of the generation of continental shelf waves and their role in the westward shift of the Yellow Sea Warm Current

Abstract

The Yellow Sea Warm Current (YSWC), which carries warm, saline water into the Yellow Sea (YS), exhibits a typical northward (upwind) flow during winter. Observations have shown that the path of the YSWC has shifted to the west from the deep trough, and it has been suggested that continental shelf waves (CSWs) may play an important role in this westward shift. However, the source of southward propagating CSWs that drive the westward shift of the YSWC remains unclear. The objective of this study is to reveal the generative mechanism of CSWs and their role in driving the westward shift of the YSWC. Numerical models with an idealised topography show that the westward shift of the northward flow propagates southward along the western slope offshore of China, with a typical speed of 2.99 ms-1, comparable to the theoretical phase speed of a first mode CSW. CSWs driving the westward shift are generated on the northern slope, primarily by the scattering of Kelvin waves that develop due to northerly winds and propagate northward into the YS along the eastern boundary of the Korean Peninsula. Model experiments with a realistic topography consistently support the idea that Kelvin wave scattering is a primary source of the southward propagation of the CSWs that drive the westward shift of the YSWC.