Transport variability across the Korea/Tsushima Strait and the Tsushima Island wake

Abstract

Abstract Transport variations are calculated across the Korea/Tsushima Strait using continuous current measurements made between May 1999 and March 2000. Twelve bottom-mounted acoustic Doppler current profilers provide velocity profiles along two sections: one section (south line) at the strait entrance southwest (upstream) of Tsushima Island and the other section (north line) at the strait exit northeast (downstream) of Tsushima Island. Transport variations across the strait are large, particularly in the lee of Tsushima Island where a countercurrent commonly exists. The Tsushima Current transport, averaging 2.65 Sverdrups (Sv) (1 Sv = 10 6 m 3 s - 1 ), is split into two cores by Tsushima Island, which divides the strait into eastern and western channels. Transport in the western channel is 23% higher than in the eastern channel over the measurement period. Some seasonality in transport variability is observed for both the western and eastern channels. Transports are largest in fall and smallest during winter. The single-velocity core, observed upstream of Tsushima Island, is estimated to split directly behind Tsushima Island over an aperture of about 31 km along the south line. A wake zone that averages 40 km in width is observed downstream of Tsushima Island and appears to follow island-wake-zone dynamics. Reynolds numbers can range from 22 to 90 in the wake zone, and eddy shedding can occur throughout the year.