SEPARATION OF THE KUROSHIO WATER AND ITS PENETRATION ONTO THE CONTINENTAL-SHELF WEST OF KYUSHU

The separation of Kuroshio water west of Kyushu and its penetration on to the continental shelf of the East China Sea were investigated by an alyzing trajectories of satellite-tracked surface drifters deployed du ring 1989-1996. Conductivity, temperature, and depth (CTD) data collec ted in the eastern East China Sea in December 1993 and late April/earl y May 1995 were also analyzed. Composite trajectories of 172 drogued d rifters provided direct evidence of the separation of the northeastwar d flowing Kuroshio into two parts at the western mouth of the deep tro ugh southwest of Kyushu. The Kuroshio main stream turns to the east to ward the Tokara Strait, and a northward flowing branch current penetra tes onto the shelf across the continental slope west of the trough. An alysis of the CTD data and drifter trajectories, concurrently observed , shows that the branch current was part of the inshore Kuroshio, just upstream before its separation. During the periods of CTD observation s, the separated, inshore Kuroshio water intruded northward in a tongu e shape along the shelf break of the trough and penetrated onto the sh elf after crossing obliquely the western continental slope of the trou gh. The water that penetrated onto the shelf continued to flow northwa rd toward the Korea Strait. The main path of this water was easily tra ced by its high salinity, which is characteristic of the inshore Kuros hio water. Application of an inverse method to the observed CTD data a lso supports the separation and penetration of the Kuroshio and calcul ates the volume transport of the northward branch to be about 4.0 x 10 (6) m(3)/s for the two different surveys. The tongue-shaped intrusion of the inshore Kuroshio water onto the outer shelf may take place in c lose association with the eastward turning of the Kuroshio main stream and it might be caused by the vorticity adjustment created by the eas tward turning of the Kuroshio.