current, forming part of the Kuroshio Current, which diverges near the western part of Japan and flows northward into the Yellow Sea at a speed of less than 0.8 km/h. Southward currents prevail near the sea coast, especially in the winter monsoon period.

The water temperature is close to freezing in the northern part in winter, so drift ice patches and continuous ice fields form and hinder navigation between November and March. The water temperature and salinity are homogeneous across the depth.