TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 64 (No. 1), pp. 81-91, 2008

Surface Current and Vertical Thermal Structure on the Continental Slope in Tosa Bay

Hiroshi Kuroda1*, Manabu Shimizu1, Yuuichi Hirota2, Daisuke Ambe1 and Hideki Akiyama1

1National Research Institute of Fisheries Science, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan
2National Research Institute of Fisheries Science, Sanbashi-dori, Kochi 780-8010, Japan

(Received 13 October 2006; in revised form 25 April 2007; accepted 6 September 2007)

Abstract: In order to specify a vertical thermal structure related to surface current variation on the continental slope in Tosa Bay, Japan, we analyzed monthly regular hydrographic measurements in the years 1991-2004. Subsurface temperature below 200 m on the slope was found to vary synchronously with the vertical displacement of the main thermocline around 200 m. It is shown that the vertical-averaged temperature below 200 m is significantly correlated with an along-isobath/southwestward surface current velocity on the slope. This correlation indicates that when a strong (weak) southwestward surface current is observed, temperature below 200 m decreases (increases) simultaneously, that is, isotherms below the 200 m are displaced upward (downward) together with the main thermocline. Moreover, when the strong southwestward flow is detected, across-isobath isotherms around 200 m slope upward toward the offshore direction. Furthermore, it is suggested that as the Kuroshio axis moves offshore south of the bay, the southwestward flow tends to be weakened by the combined effect of other Kuroshio parameters such as transport and stream width as well as the Kuroshio axis position. As a result, it is inferred that the correlation between the surface current and subsurface temperature can be interpreted in terms of the formation and decay of an anticlockwise circulation interacting with a cold eddy.

*Corresponding author E-mail: kurocan@affrc.go.jp

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