Intensification of the Winter South China Sea Western Boundary Current During 2014–2024

Abstract

Understanding the low‐frequency variability of the western boundary current (WBC) is essential for the redistribution of heat, salt and energy in the South China Sea (SCS). Long‐term acoustic Doppler current profiler (ADCP) mooring observations show a strengthening trend in the winter SCS WBC from 2014 to 2024. Diagnosis of the vorticity budget suggests that the trend is primarily attributed to the enhanced basin‐scale wind stress curl and secondarily to the weakening of the joint effect of baroclinicity and relief (JEBAR), which overall serves as a vorticity sink. The trend of JEBAR is associated with a warming center west of the Luzon Strait, which enhances the baroclinic effect along the northern SCS continental slope, leading to a positive trend of JEBAR and weakening of vorticity consumption.