On the Nature of the Kuroshio Waters off the Kii Peninsula and Its Relation with the Kii Bifurcation Current and Coastal Sea Level
J. TAKEUCHI1, Y. MORIKAWA2 and Y. NAGATA3
1 Wakayama Research Center of Agriculture. Forestry and Fisheries, 1551 Kushimoto-cho, Nishimuro-gun, Wakayama 649-6503, Japan
2 Faculty of Bioresources, Mie University, 1515 Kamihama-cho, Tsu-shi, Mie 514-8507, Japan
3 Marine Information Research Center. JHA. Mishima Bldg. 5F, 7-15-4 Ginza, Chuo-ku, Tokyo 104-0061, Japan
e-mail:nagata@mirc.jha.or.jp
Abstract. The detailed nature of the Kuroshio Waters and its relation with the Kii Bifurcation Current and the sea level difference between Kushimoto and Uragami are discussed by using the recent observations and referring the recent investigations conducted by our group. The current zone of the Kuroshio touches the coast and the bottom just off Cape Shionomisaki at the time of the straight path of the Kuroshio. The current zone separates the coastal water to the west of Cape Shionomisaki from that to the east. The warm Kuroshio Water intrudes well into the coastal region to the west, but the water to the east remains to be occupied by the relatively cold and original coastal water. Resulted contrast between the coastal waters produces the large sea level difference between Kushimoto and Uragami, which are separated only by 14 km. The Kii Bifurcation Current, which is often found along the southwest coast of the Kii Peninsula at the time of the straight path of the Kuroshio, appears to be related to the mechanism to draw the Kuroshio Water into the coastal region. Even though the current zone intrudes into the shelf region near the Shionomisaki, it leaves the shelf just to the east of the cape. The centrifugal force, which would be produced if the current follows bottom contours, would give an explanation why the current leaves the shelf.
INTRODUCTION
One of the peculiarities of the Kuroshio is that it has two stable path patterns at the south of Honshu, Japan: a straight path and a large meander path (Fig.1). Each of the pattern persists from several months to several years when it takes place (e,g., Shoji, 1972; Taft, 1972). It was shown that the flow pattern of the Kuroshio can be monitored by watching the sea level difference between two tide gauge stations, Kushimoto and Uragami (e.g., Kawabe, 1980), which are located only 14 km apart to each other (see Fig.5 for the locations of these tide stations and see Fig.3 for the region under consideration). Fujita (1997) and Sekine and Fujita (1999) analyzed the data taken at two routine observation stations Sta.25 just off Kushimoto and Sta. 31 just off Uragami: see Fig.5 also their locations) of the Wakayama Prefectural Fisheries Experimental Station (its present name is the Wakayama Research Center of Agriculture, Forestry and Fisheries).
