The effects of wind-stress curl on the Japan/East Sea circulation

Abstract

Abstract The wind-driven ocean circulation of the Japan/East Sea (JES) is studied using a primitive-equation two-layer model forced by monthly mean climatological wind of ECMWF. The modeled circulation in the upper layer is characterized by a large basin-wide cyclonic circulation generated by the positive wind-stress curl occupying most of the JES in winter and four small gyres inside of the large circulation. One of the four small gyres is cyclonic and located along the Primorskii coast. Two other small gyres located off Vladivostok form a dipole with a cylonic gyre to the east and anti-cyclonic gyre to the west. The remaining small gyre is cyclonic and located around the East Korean Bay (EKB). The gyre dipole off Vladivostok is generated by the dipole of wind-stress curl off Vladivostok. The cyclonic gyre of the dipole does not change its strength so much seasonally and plays an important role in separating the low-salinity coastal water from the coast and advecting it eastward along the Subpolar Front as subsurface low-salinity core, which spreads into the subsurface of the Tsushima Warm Current Region as the Japan/East Sea Intermediate Water. The anti-cyclonic gyre west of the cyclonic gyre of the dipole off Vladivostok generated in winter decreases much in amplitude or disappears until summer depending on parameters, interfacial friction, vertical stability, and topographic constraint. The coastal current reversal from southwestward to northeastward along the North Korean coast suggested by the ARGOS buoy deployed in summer in 1994 during the CREAMS cruise appears to be closely related with the development of this anti-cyclonic gyre. The cyclonic gyre in the EKB is generated by a dipole of wind-stress curl off the EKB and might be important for the separation of the East Korean Warm Current. The cyclonic gyre along the Primorskii coast is generated by the positive wind-stress curl northwest of Hokkaido and persists to exist throughout a year with a volume transport more than 1.0 Sv, and may explain the track of the ARGOS buoy deployed in summer in 1994 during the CREAMS cruise. It is concluded that the wind-driven surface circulation account for an important part of the circulation of the Northern JES since the modeled surface circulation seems to capture many characteristic features of the circulation in the northern JES, and the amount of volume transport of modeled circulations and gyres is comparable to the inflow transport at the Tsushima Straits.