Interaction of a warm eddy with the coastal current at the eastern boundary area in the Tsushima Current region

Abstract

The Tsushima Current region in the Japan Sea is one of the eddy-rich areas. According to Isoda (1994) ( Journal of Oceanography, 50, 1–15), when an eastward moving warm eddy reached its eastern boundary area, two or three mesoscale eddies frequently evolved and gradually disappeared into the coastal current. Such process associated with the eddy-current interaction are examined numerically using a reduced gravity model on the f-plane. Once a warm (anticyclonic) eddy influences the coastal current, the following two kinds of meanders evolve. In the nonlinear regime, an original eddy moves onshore and becomes part of the seaward meander. Furthermore, this eddy excites another small seaward meander or a new eddy at its northern part due to the vorticity control of the distorted coastal current. After that, a newly formed northern eddy travels downstream with an advective speed of the coastal current, while the potential vorticity of an original eddy becomes to lose within a larger potential vorticity anomaly onshore side of the coastal current.