In order to clarify the structure and short-period variability of the Kii Bifurcation Current, detailed observations were conducted four times on board the R/V Seisui-maru of Mie University (part of the observational results have already been introduced in Takeuchi et al. ( 1998b) and in Nagata et al. (1999a)). According to the Prompt Report of the Oceanographic Condition published bimonthly by the Hydrographic Department, Maritime Safety Agency of Japan, the Kuroshio was flowing in a straight path during all of these observation periods. However, the structure of the Kii Bifurcation Current was considerably different cruise by cruise. In this paper we make case studies for these observations, and discuss the structure and short-period variations (having time-scales shorter than 15 days) of the Kii Bifurcation Current by referring to the daily and hourly variations of the sea level difference between Kushimoto and Uragami.
Fig. 1 Area discussed in this paper; A: Honshu, B: Shikoku, C: Kyushuu, and D: the Kii Peninsula. The locations of two tide gauge stations of Kushimoto and Uragami are shown by a and b in the lower panel, respectively. In the lower panel, a typical temperature field (in ℃) at 200 m depth is shown (from Nagata et al. , 1999a). Black circles and cross marks indicate the CTD and XBT observation points of the R/V Seisui-maru of Mie University on June ll-14, 1996, and white circles the CTD observation points of the R/V Wakayama of the Wakayarna Prefectural Fisheries Experiment Station, respectively.
Fig. 2 Variation of the daily average value of the sea level difference between Kushimoto and Uragami for the period from October 1996 to December 1997. The horizontal dashed line at 25 cm difference in the figure is the threshold value indicating whether the Kuroshio has the straight path or the large meandering path. The straight path usually occurs if the difference is larger than 25 cm, and the meandering path occurs if it is close to or smaller than 25 cm (Fujita, 1997). The periods of the four cruises are indicated with bold bars under the column.
