THE INFLUENCE OF THE BOTTOM COLD-WATER ON THE SEASONAL VARIABILITY OFTHE TSUSHIMA WARM CURRENT

Previous studies have concluded that the volume transport and surface current velocity of the Tsushima Warm Current are at a maximum between summer and autumn and at a minimum between winter and spring. Each st udy has obtained these results indirectly, using the sea level differe nce across the Tsushima-Korea Strait or dynamic calculation. Numerical experiments are performed to estimate the seasonal variability in the sea level difference caused by the Bottom Cold Water (BCW), which int rudes from the Sea of Japan along the Korean coast in the bottom layer . These experiments basically treat the baroclinic adjustment problem of the BCW in a rectangular cross section perpendicular to the axis (n ortheast-southwest direction) of the Tsushima-Korea Strait. It is a fi ve-layer model for summer and a two-layer model for winter. The initia l conditions and parameters in models are chosen so as to match the ca lculated velocity-density fields with the observed velocity-density fi elds [Isobe A., S. Tawara, A. Kaneko and M. Kawano (1994) Continental Shelf Research, 14, 23-35.]. Consequently, the experiments prove that the observed seasonal variability in the sea level difference across t he Tsushima-Korea Strait largely contains the baroclinic motion caused by the BCW. It should be noted that the position of the BCW also play s an important role in producing a considerable seasonal variation of the sea level difference. It is critical to remove the baroclinic cont ribution from the observed sea level differences across the Tsushima-K orea Strait in order to estimate the seasonal variation in the volume transport of the Tsushima Warm Current.