TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 55 (No. 2), pp. 237-246, 1999

Observations of Eddies in the Japan Basin Interior

Masaki Takematsu1, Alexander G. Ostrovskii1 and Zentaro Nagano2

1Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
2Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 816-8580, Japan

(Received 5 September 1998; in revised form 5 November 1998; accepted 7 November 1998)

Abstract: Eddy features in the Japan Basin have been studied by combining satellite-derived sea surface temperature (SST) images and WOCE drifter tracks with recent current meter data from a deep mooring in the interior of the Basin. SST images indicate that anti-cyclonic eddies often appear around the Subpolar Front in cold seasons and move into the northern cold water region entraining warm water of the frontal zone. The anti-cyclonic eddies "visualized" by the entrained warm water and trajectories of some drifters are typically 30 km in radius and have rotational speeds of 0.15 to 0.3 m/s at the surface. On the other hand, the current meter data of 3-year duration show that vertically coherent eddy-like currents of the order of 0.1 m/s occur every year in cold seasons in the deep (1000 to 3000 m) layer of the Japan Basin interior. An important finding is that available time series of SST patterns are well correlated to the vertically coherent deep currents. This correlation suggests that the anticyclonic eddies indicated by both SST images and drifter tracks are actually barotropic or quasi-barotropic, extending from the surface to the bottom. It is argued that the unique current features in the deep layer of the Japan Basin can be explained in terms of barotropic eddies. A brief discussion is also made of the possible source of the eddy kinetic energy.

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