Temporal Change of the Kuroshio in the East China Sea During Several Days

In order to examine temporal changes of the Kuroshio, the observation was carried out twice on March 1-4 and March 7-10, 1997 along three sections across the Kuroshio in the East China Sea by T/V Keitenmaru of Kagoshima University. Two of these sections were located in the continental slope region and one in the Tokara Strait. Horizontal shifts of the surface temperature front (hereafter, called the Kuroshio front) were closely related to those of the position of the maximum surface velocity (hereafter, called the Kuroshio axis) in all cross-sections. However, the former varied with a several times (1.8～7) larger amplitude than the latter. The Kuroshio in the Tokara Strait was focused on, because the Kuroshio axis shifted northward with the large distance of 60km during 8 days. The vertical structure of the Kuroshio in the strait was characterized by the upper- and lower-interfaces. The maximum tilt of the lower-interface geographically corresponded to the Kuroshio axis. On the other hand, the outcropping of the upper-interface corresponded to the Kuroshio front. Since the structure of the lower-interface changed little during the northward migration of the Kuroshio, the surface velocity at the Kuroshio axis was maintained. The structure of the upper-interface changed significantly, and this resulted in the horizontal shift of the Kuroshio front with a twice larger amplitude than the Kuroshio axis. These observations suggest that the fluctuation of the Kuroshio axis is dynamically different from that of the Kuroshio front