Inter‐Annual Variations of the Westward Shift of Yellow Sea Warm Current Controlled by Local Wind Stress Curl

Abstract

AbstractThe Yellow Sea Warm Current (YSWC) transports water from the East China Sea to the Bohai Sea and exhibits a typical westward shifting pathway in winter. Previous studies have attributed this westward shift to changes in local wind stress, defining the YSWC axis by using the warm water tongue from the sea surface temperature (SST). Here we re‐examine the westward shift of the YSWC by defining its pathway dynamically. We use the observed position of the maximum SST along section 35°N and calculate the YSWC pathway from horizontal stream function in a high‐resolution Regional Ocean Modeling System (ROMS) simulation of the East China Sea from 1979 to 2020. It is found that in most years the westward shifted YSWC lies near the 70 m isobath just as the warm tongue axis, but in some years it is closer to the center Yellow Sea, lying near the deep trough. Contrary to previous studies we find no significant correlation between the inter‐annual variability of the shift and the meridional or zonal components of local wind stress in our simulation. Instead, we find that potential vorticity (PV) input by the depth‐averaged wind stress curl dominates the inter‐annual variability of YSWC's westward shift. These changes in PV originate from the realistic wind stress curl in the model that includes spatial inhomogeneity.