Numerical Study of a Kyucho and a Bottom Intrusion in the Bungo Channel, Japan: Disturbances Generated by the Kuroshio Small Meanders
The generation and propagation mechanisms of a Kyucho and a bottom intrusion in the Bungo Channel, Japan, have been studied numerically using the hydrostatic primitive equations by assuming density stratification during summer. The experiments are designed to generate a Kuroshio small meander in Hyuga-Nada, which acts as a trigger for these disturbances. After the current speed of the Kuroshio is changed, a small meander is generated. At the head of the small meander, warm Kuroshio water is engulfed, and encounters the southwest coast of Shikoku. However, convergence of heat flux on the bump off Cape Ashizuri suppresses the generation of a warm disturbance, if the current speed is large. As the cold eddy associated with the small meander approaches Cape Ashizuri, the heat flux diverges on the bump. This heat source forces a warm disturbance, which intrudes along the east coast of the Bungo Channel as a baroclinic Kelvin wave (a Kyucho). After the cold eddy passes off Cape Ashizuri, the Kuroshio approaches the bump again. Strong convergence of heat flux then occurs on the bump, which forces a cold disturbance. This disturbance propagates as a topographic Rossby wave along the shelf break at the mouth of the channel. After the topographic wave reaches the west end of the shelf break, it intrudes along the bottom layer of the channel as a density current (a bottom intrusion). These results suggest that a Kyucho and a bottom intrusion are successive events associated with the propagation of the small meander.
KeywordsKyucho bottom intrusion baroclinic Kelvin wave density current Kuroshio small meander Bungo Channel Cape Ashizuri
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- Akitomo, K., S. Masuda and T. Awaji (1997): Kuroshio path variation south of Japan: Stability of the paths in a multiple equilibrium regime. J. Oceanogr., 53, 129–142.Google Scholar
- Beckman, A. and. D. B. Haidvogel (1993): Numerical simulation of flow around a tall isolated seamount. Part I: Problem formulation and model accuracy. J. Phys. Oceanogr., 23, 1736–1753.Google Scholar
- LeBlond, P. H. and L. A. Mysak (1978): Waves in the Ocean. Elsevier Scientific Publishing Company, Amsterdam, 602 pp.Google Scholar
- Lee, T. N., L. P. Atkinson and R. Legeckis (1981): Observations of a Gulf Stream frontal eddy on the Georgia continental shelf, April 1977. Deep-Sea Res., 28A, 347–378.Google Scholar
- Lilly, D. K. (1965): On the computational stability of numerical solutions of time-dependent non-linear geophysical fluid dynamics problems. Mon. Wea. Rev., 93, 11–26.Google Scholar
- Takeoka, H. and T. Yoshimura (1988): The Kyucho in Uwajima Bay. J. Oceanogr. Soc. Japan, 44, 6–16.Google Scholar
- Takeoka, H., H. Akiyama and T. Kikuchi (1993): The Kyucho in the Bungo Channel, Japan—Periodic intrusion of oceanic warm water. J. Oceanogr., 49, 369–382.Google Scholar
- Takeoka, H., Y. Koizumi and A. Kaneda (2000): Year-to-year variation of a kyucho and a bottom intrusion in the Bungo Channel, Japan. p. 197–215. In Interactions between Estuaries, Coastal Seas and Shelf Seas, ed. by T. Yanagi, Terra Scientific Publishing Company, Tokyo.Google Scholar
- Yamagata, T. (1980): A theory for propagation of an oceanic warm front with application to Sagami Bay. Tellus, 32, 73–76.Google Scholar