Seasonal variation of counterclockwise eddies downstream of the Tsushima Islands

The seasonal variation of counterclockwise eddies downstream of the Tsushima Islands in the Tsushima Straits was investigated from 2004 to 2008 using long-term acoustic Doppler current profiler (ADCP) data. Eddy activity was high from summer to autumn (July–November). The eddies were formed in short-term intervals of 5–8 days, almost corresponding to the formation cycle of Karman vortices. The eddy activity varied on a longer time period (about 13 days). The mean kinetic energy (MKE) converted to eddy kinetic energy (EKE) at current shears between the eastern and western channels of the Tsushima Straits. The counterclockwise eddies that formed downstream of the Tsushima Islands were intensified and maintained by energy conversion from MKE to EKE at the northern shear of the current core in the eastern channel. The countercurrent east of the Tsushima Islands from summer to autumn was intensified by energy conversion from EKE to MKE.