Current Structure of the Japan Sea Proper Water

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1. As part of the International Scientific Research Program (Joint Research), a basin-wide observation was conducted in the Sea of Japan in summer 1995. The main contents of the observation were moorings, CTD casts and water sampling for chemistry. The observation provided the following new findings :(1) Strong, barotropic currents occur in the mid and deep layrs of the Japan Basin in spring (March-April). The maximum current speed exceeded 30 cm/s in the interior region of the western Japan Basin. In summer and fall, the deep water is almost stagnant.(2) There are two salinity minimum layrs. The shallow one is located beneathe the Tsushima Warm Water south of the polar front, which has been known as the Japan Sea Intermediate Water. The deep salinity minimum was found at all stations in the Japan Basin. Its potential temperature was between 0.10-0.15ﾟC and salinity between 34.066-34.068psu. Below thedeep salinity minimum layr dissolved oxygen has its minimum, which is similar to the vertical sturucture beneath the North Pacific Intermediate Water. These results suggest that the Japan Sea Proper Water is not a single water mass as known in the past, but made of at least two waters of different sources.A fine resolution, primitive equation general circulation model was constructed. The simulated deep circulation shows a consistent pattern with the main features of the deep circulation as suggested from previous observations (Nitani, 1972).3. An international symposium on the material and water circulation in the Sea of Japan was held in Feb. 1996 at Vladivostok, Russia, in which all results of this project were presented together with related research work. Future plan of an international cooperative study on the Sea of Japan was also discussed.