Fig. 5. Current field of each repeated run of Cruise II at 5 m depth. The observation period of each run is shown in the rightmost portion of each row of the figure. The bold horizontal line at the bottom of left figures indicates the position where the current divergence was averaged (Table 2 and Figs. 8(a) and (b)). The time required to occupy each repeated line is usually less than 2 hours, and tidal currents appear not to influence the flow pattern. The magnitude of the current vector is indicated at the right-upper corner of the figure.

The distribution of the onshore current component (right panel of Fig. 6) is very variable run by run, and no clear onshore flow can be recognized at the time of Cruise II. This seems to support the statistical result obtained by Takeuchi et al. (1998a) that the fluctuation of the onshore velocity component (perpendicular to the standard line) is usually larger than that of the alongshore velocity component (along the standard line).

Though the basic nature of the bifurcation current appears to be unchanged throughout the repeated observations, there is a small tendency for the magnitude of the current velocity to decrease during the repeated observations: the current profiles in Figs. 5 and 6 indicate that the bifurcation is especially weakened in the last two repeated runs. The divergence values averaged over the central 35 km portion, mentioned above, were calculated for each run and for depths of 5 m and of 25 m. The results are shown in Table 2.

Table 2. The average current divergence along the central segment (35 km length) of the standard line (in 1/s) at 5 m and 25 m depths for each repeated run of Cruise II. The position of the central segment is shown in Fig. 5

　

M. Uchida et al.

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