However, this is not correct in details. The small-scale meander generated off Kyushu usually increases its east-west width, and only the eastern edge travels to east. Just after the eastern edge of the elongated meander passes by Cape Muroto, the eastern portion of the meander is separated and a new small-scale meander is generated just off the Kii Channel. This new meander is rapidly developed there and then passes by Cape Shionomisaki to form the Kuroshio Large meander (Fujita et al., 1998; Nagata et al., 1999a).
(2) Along the southwest coast of the Kii Peninsula, a bifurcation current (the Kii Bifurcation Current) often appears, and its occurrence frequency is about 70% in the period from 1988 to 1996. Its occurrence frequency is especially high when the Kuroshio takes the straight path (Takeuchi et al., 1998a, 1998b).
(3) Structure of the Kii Bifurcation Current and its short-period variation were examined. The Kii Bifurcation Current is very stable when the current zone of the Kuroshio touches the coast and bottom slope just off Cape Shionomisaki. The current is weakened when the current zone leaves the coast even tentatively, according to the passage of small-scale meanders (or eddies) by Cape Shionomisaki . This variation nature can be monitored by the daily averaged sea level difference between Kushimoto and Uragami, and the threshold value of 25 cm is also applicable for the short-period variation having the time scale from a few days to several days. (It was suggested that even the hourly variation of the sea level difference may indicate the sea state variation just off Cape Shionomisaki to a certain extent.) It was observed that, when the daily sea level difference dropped tentatively below 25 cm, the Kii Bifurcation current disappeared (Uchida et al., 2000).
(4) The detailed oceanic observation was carried out in the vicinity of Cape Shionomisaki when the Kuroshio took the typical straight path. It was shown that the current zone of the Kuroshio touched the coast and bottom slope just off Shionomisaki, and that the coastal water to the west of the cape was completely separated from that to the east. It was also observed that the offshore warm Kuroshio Water penetrated into the coastal area to the west of the cape. These oceanographic features seems to explain why the flow path of the Kuroshio can be monitored by the sea level difference between Kushimoto and Uragami though the distance between these tide gauge stations is only 14 km. The Kuroshio flows out eastward into the open ocean after passing by Cape Shionomisaki, even though the strong current of the Kuroshio extends to the bottom slope off Cape Shionomisaki and though the conversation law of vorticity may require the barotropic flow to follow the bottom contours. The reason why the Kuroshio flows into the shelf region and leaves there was investigated by Nagata et al., (1999b).
In this paper, we shall introduce the interesting current natures in the vicinity of Cape Shionomisaki, mainly based on Nagata et al, (1999b).
