Lagrangian Approach for a New Separation Index of the East Korea Warm Current

Abstract

In this study, a separation index for the East Korea Warm Current (EKWC) is defined by Lagrangian particle tracking using surface geostrophic currents based on satellite-observed absolute dynamic topography. After determining the main stream from the inflow through the western channel of the Korea Strait, the separation index is obtained by averaging the latitude of the main particle trajectories crossing the meridian along 130.5°E. Although the separation index is obtained from coastal velocity, it describes well the surface circulation patterns in the Ulleung Basin. When it is low (i.e., the EKWC separates at low latitude), the flow toward the Japanese coast is the strongest and the EKWC is weak. In the middle phase of the separation index, a large portion of the EKWC meanders and forms the Ulleung Warm Eddy-like feature. When the separation index is high, the EKWC stretches further northward to almost 40°N. Therefore, the separation index could be used as a simple representation of the surface circulation pattern in the East/Japan Sea.