著者

Fang Xiaorong Isoda Yutaka

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.25-40, 2020-08-24

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A multi-layered numerical model driven by seasonal change in sea surface heat flux with excess cooling was used to investigate the dynamics of a cooling induced current (CIC) in the Japan Sea. The original idea of the CIC was proposed by Isoda (1999) (Journal of Oceanography, 55, 585-596) as follows : eastward thermal flow in the interior region, i.e., Tsushima Warm Current (TWC), accompanied with meridional thermal gradient on the planetary-β plane would be determined by the heat balance between net heat loss at the sea surface and lateral heat transport from the southern entrance into the Japan Sea. The CIC model produced a significant meandering TWC with an east-west wave number of three, based on the property of a standing Rossby wave, only under the model condition that coexisted with seasonal disturbances of heat. A positive heat supply from the southern entrance to the Japan Sea occurred in late winter, extended slowly to the TWC region as the offshore advection of meandering patchiness in summer, and then contributed to the heat loss by sea surface cooling in the following winter. The whole TWC region was cooled not only at the sea surface in winter, but also by eastward advection of upwelled cold waters originating from the western boundary area in summer to autumn. The meandering flow was stably confined to the southern part because of the dominant southward eddy momentum fluxes, which were caused by the northwest-southeast inclinations of meandering ridge-axes. Owing to such seasonal change in the lateral transports of momentum and heat, the meandering TWC (or CIC) flow pattern was maintained as a “dynamic equilibrium state”.