Dynamics of Surface Cold Patch off the Korean Peninsula Cape: Driven by Upwelling

Abstract

Surface cold patches (SCPs) are important hydrological phenomena in the Yellow Sea (YS). We investigate the dynamics behind the appearance of the SCP off the Korean Peninsula Cape during summer. The numerical model results revealed that upwelling is the primary mechanism of SCP formation in this region. On one hand, the 3D vorticity balance of the dynamic processes of the SCP indicated that the combined effect of the tides and the baroclinic pressure gradient enhances dissipation in the bottom boundary layer, leading to seawater convergence in the bottom layer west of the tidal front and divergence east of the tidal front, forming a stable frontal secondary circulation and resulting in the formation of upwelling. On the other hand, the offshore transport, which is triggered by the Jeju Warm Current and persists throughout the year in the strait, leads to a divergence of seawater within the region. The joint effect of the above two processes ultimately contributes to the generation of upwelling. The presence of upwelling forces the thermocline to be changed. Strong tidal upwelling triggers the upward ventilating of the thermocline, which can bring cold water to the surface, and the dome-like upwarp of the thermocline isotherms caused by the current-induced upwelling, together lead to the formation of the SCP.