Impact of interannual variation in surface heat flux on the variability of the upper layer circulation in the East Sea (Sea of Japan)

The Intrinsic variability in the East Sea (Sea of Japan), excluding the influence of external forcings on interannual variation, is distributed mainly in the southern region, especially in the Ulleung and Yamato Basins. In this study, the effects of interannual variations in surface heat flux on upper layer circulation in the East Sea are analyzed via numerical experiments. The interannual variations in the surface heat flux amplify variability in the Yamato Basin, not in the Ulleung Basin. The variability in the water temperature in the northern region is highly correlated with the variability in the surface heat flux with one month time lag. Winter surface cooling facilitates cold water formation in the northern regions, and it extends toward the Yamato Basin. As the cold water region expands (contracts), the meandering (straight) path of the Tsushima Warm Current flows northeastward due to increasing baroclinic instability. However, the surface heat flux does not significantly impact the separation latitude of the East Korea Warm Current. Instead, the separation latitude of the East Korea Warm Current is influenced primarily by strong winter positive wind stress curl anomalies in the northern region and greatly affects the southward flow of cold water along the Korean coast.