Surface current and vertical thermal structure on the continental slope in Tosa Bay

• Published in: Journal of oceanography Vol. 64; no. 1; pp. 81 - 91
• Main Authors: Kuroda, Hiroshi, Shimizu, Manabu, Hirota, Yuuichi, Ambe, Daisuke, Akiyama, Hideki
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.02.2008; Springer Nature B.V
• Subjects: Cartography; Continental slope; Earth and Environmental Science; Earth Sciences; Freshwater & Marine Ecology; Isotherms; Marine; Ocean currents; Ocean temperature; Oceanography; Original Articles; Thermocline; INW, Pacific, Kuroshio Current; INW, Japan, Shikoku, Kochi Prefect., Tosa Bay; continental slope; surface current; Tosa Bay; Kuroshio; main thermocline; anticlockwise circulation
• ISSN: 0916-8370; 1573-868X
• DOI: 10.1007/s10872-008-0006-4

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.