Surface current and vertical thermal structure on the continental slope in Tosa Bay |
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| Authors: | Hiroshi Kuroda Manabu Shimizu Yuuichi Hirota Daisuke Ambe Hideki Akiyama |
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| Institution: | (1) National Research Institute of Fisheries Science, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan;(2) National Research Institute of Fisheries Science, Sanbashi-dori, Kochi 780-8010, Japan |
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| 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. |
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| Keywords: | Tosa Bay continental slope surface current main thermocline Kuroshio anticlockwise circulation |
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