ON THE ORIGIN OF THE TSUSHIMA WARM CURRENT

The origin of the Tsushima Warm Current (referred to as TWC) was inves tigated by surface drifter experiments and conductivity, temperature, and depth (CTD) surveys in the northeastern East China Sea (ECS) at th ree different times: July 1991, and April and November 1992. Trajector ies of 10 satellite-tracked drifters provide direct information for th e first time on the surface how patterns in each season, and CTD obser vations allow identification of warm and saline TWC waters. The result s of the experiments argue against two historical concepts of TWC orig ins, i.e., (1) a northward flow transporting warm and saline water thr ough the deep trough southwest of Kyushu toward the Korea Strait after separation from the Kuroshio and (2) a northeastward continuation of the Taiwan Current (TC) on the shelf of ECS after passing through the Taiwan Strait. A persistent northward current was found to exist both on the shelf west of the trough and on the western flank of the trough . The northward flow seems to bifurcate around the northwestern corner of the trough, splitting into a northward continuing flow on the shel f of 100-150 m and an eastward flow along the northern wall of the tro ugh. The northward flow on the shelf, which might be the shore fringe of the Kuroshio, corresponds to the origin of TWC entering the Korea S trait. The eastward flow on the northern slope turned back to the sout h along the west coast of Kyushu and eventually joined the Kuroshio. T his structure was accompanied by an anticyclonic eddy in the northern trough. The second concept, that of TWC originating from TC, contradic ts the observed differences in physical properties between TWC and TC waters. The saline water in the Taiwan Strait flows out intermittently only during late winter-early spring, and its salinity during other s easons is lower than that of the TWC water in the Korea Strait. Experi ments also indicated a seasonal shift of drifter paths in the northeas tern ECS and coexistence of cyclonic and anticyclonic eddies in the tr ough during the cold season.