TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 59 (No. 5), pp. 619-627, 2003

Variability of Upper Ocean Heat Balance in the Shikoku Basin during the Ocean Mixed Layer Experiment (OMLET)

Hirotaka Otobe1*, Keisuke Taira2, Shoji Kitagawa3, Tomio Asai4 and Kimio Hanawa5

1International Coastal Research Center, Ocean Research Institute, the University of Tokyo, Akahama, Otsuchi, Iwate 028-1102, Japan
2Japan Society for the Promotion of Science, Ichibancho, Chiyoda-ku, Tokyo 102-8471, Japan
3Ocean Research Institute, the University of Tokyo, Minamidai, Nakano-ku, Tokyo 164-8639, Japan
4Japan Science and Technology Corporation, Toranomon, Minato-ku, Tokyo 105-0001, Japan
5Department of Geophysics, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan

(Received 7 August 2002; in revised form 5 March 2003; accepted 5 March 2003)

Abstract: The heat balance of the surface layer in the vicinity of the former Ocean Weather Station "Tango" (OWS-T; 29°N, 135°E), where a large amount of heat is transported by the Kuroshio and transferred to the atmosphere, was studied by during Ocean Mixed Layer Experiment (OMLET) as an oceanographic component of the Japanese World Climate Research Program (1987-1991). Temperature and velocity in the upper ocean measured using a surface moored buoy system deployed by the Ocean Research Institute, the University of Tokyo, in total 668 days of four time series namely the periods of April 1988-November 1988 (OMELET-88), August 1989-February 1990 (OMLET-89), April 1990-September 1990 (OMLET-901) and September 1990-January 1991 (OMLET-902). We have analyzed the moored buoy data of the upper 100 m for the latter three time series (OMLET-89, -901 and -902) and here we discuss the heat balance of the upper 100 m, in combination with surface heat flux and oceanographic data provided by the Japan Meteorological Agency. A large fluctuation of oceanic heat convergence/divergence of 200-300 W/m2 in amplitude with predominant period of 20-30 days occurred in the first half of OMLET-89 period, which was just the early stage in the formation process of a large meander path of the Kuroshio. A large amount of heat convergence of 71 and 79 W/m2 on average was detected in observation period of OMLET-89 and -901, respectively. During OMLET-902, relatively small heat convergence of 13 W/m2 was obtained. It is suggested that these variations of oceanic heat convergence in this region were closely related to the fluctuation of the Kuroshio axis to the south of Japan.

*Corresponding author E-mail: otobe@wakame.ori.u-tokyo.ac.jp

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