Mean Circulation of the Japan Sea Waters from Data of Drifter and Satellite Altimetry Observations

Knowledge of the long-term mean over highly variable currents in the Sea of Japan is essential to understanding the regional climate change. The mean position and speed of the major currents of the Sea of Japan were determined from the subsurface drifter observation (Global Drifter Program, 1988–2023) and calculation of absolute geostrophic currents (AVISO satellite altimetry, 1993–2022). The Tsushima Warm Current (TWC), the East Korean Warm Current (EKWC), the Primorye (Liman) Current, Subpolar Front Current, and the Northern Cyclonic Gyre in the northern part of the sea are clearly identified on the maps constructed from data of drifter and satellite observations. A detailed analysis of the surface current field shows that the EKWC in the western part of the Sea of Japan forms three anticyclonic meanders. A pronounced meander (the eastern branch) of this current is observed in the Ulleung Basin. The second meander is formed due to flow separation from the coast in the area of the East Korea Bay. The third anticyclonic meander is observed in the northwestern part of the Sea of Japan. The Liman Current breaks away from the coast of Primorye in the area of the Peter the Great Bay and proceeds to the Subpolar Front. The interaction of the Liman Current with the northwestern meander of the EKWC leads to the formation of the northwestern dynamic front. Analysis of surface circulation shows that the TWC is divided into the nearshore (coastal) branch and the offshore branches. The main TWC offshore flow, in turn, is divided into three branches. Formation of the Subpolar Front Current in the western part of the sea is determined by waters of the EKWT. The Liman Current affects the northern dynamic boundary of this frontal zone. In the central and eastern parts of the Sea of Japan, the Subpolar Front is connected with the TWC. The Northern Cyclonic Gyre is formed by the continuation of the TWC along the coast of Hokkaido Island, the Liman Current, and the Subpolar Front Current. The mean location of major surface currents is related to the bottom relief of the Sea of Japan. A surface circulation scheme obtained with regard to data from drifter and satellite altimetric observations is presented.