Fig.12. The current distributions at 5 m (upper), 25 m (middle) and 75 m (lower) depths at the time of multi-line observation in Cruise III.
The current divergence of the alongshore component averaged over the central 35 km portion of the line tends to decrease during the repeated observation. The hourly variation of the sea level difference for this period is shown in Fig.14. In contrast to the hourly variations in Cruise II (Fig.7) and in Cruise IV (Fig.11), the curve in Fig.14 contains a conspicuous tidal signal having a semi-diurnal period. However, it is hard to find variations of the tidal periods in the structure of the Kii Bifurcation Current shown in Fig.13.
The relation of the average current divergence values to the raw values of the hourly sea level difference between Kushimoto and Uragami are shown by white dots in Fig.8(b), but the correlation is considerably poorer than in the case of Cruise II (Fig.8(a)). As no variation of tidal periods is recognized in the current profiles shown in Fig.13, it would be reasonable to eliminate tidal signals from the sea level difference curve prior to looking at the correlation. Thus, we calculated the linear trend of the sea level decrease by the least squares method, and the calculated trend is shown with a solid line in Fig.14.
