The determinant of the volume-transport distribution of the Tsushima Warm Current around the Tsushima/Korea Straits

The Tsushima Warm Current (TWC) splits into, at least, two branches in the Japan Sea. One is the Coastal branch flowing along the Japanese coast, and the other is the East Korean Warm Current (EKWC) flowing northward along the Korean coast. This study proposes a mechanism that determines the volume transport distribution between these two branches around the Tsushima/Korea Straits. Results of the hydrographic observations indicate that the stratification in the western channel develops in summer because of the existence of the bottom cold water and the sea surface heating. At the same time, the volume transport of the EKWC increases. Numerical models show that the Jebar (joint effect of baroclinicity and relief) and the topographic vortex stretching (divergence) effect are predominant around the shelf slope in the Tsushima/Korea Straits, where the TWC bifurcates. The Jebar is due to the intrusion of the bottom cold water along the Korean coast. The divergence effect due to the EKWC crossing the shelf slope cancels this Jebar. It increases in summer when the Jebar is intensified.