Barotropic current fluctuations coupled with sea level drawdown in Yellow and Bohai Seas

Sub-tidal barotropic current variations coupled with residual sea level fluctuation in the Bohai and Yellow Seas during wintertime are addressed in this study. The temporal evolution and spatial distribution of current fluctuation are investigated using moored acoustic Doppler current profiler data in a three-dimensional numerical model. It is found that a southward current followed by a northward current occurred in the northern Yellow Sea during the fluctuation, concurrent with a significant outflow followed by inflow through the Bohai Strait. The process is consistent from surface to bottom and is coupled with remarkable residual sea level fluctuation. This quasi three-day fluctuation with amplitude 0.2–0.3 m/s leads to 1 m/1.2 m drawdown in the northern Yellow and Bohai Seas, respectively, strongly influencing water exchange between those seas. Because this a prominent feature in the seas, it is necessary to evaluate its effect on fluctuation during winter in future studies, in particular, the northward current during the recovery phase of sea level in the Bohai and Yellow Seas regarding seasonal variation.