Circulation in the Japan Basin, the northern part of the Japan Sea

Using the ADCP (acoustic Doppler current profiler) and CTD (conductivity-temperature-depth probe) data obtained in the first CREAMS (Circulation Research of the East Asian Marginal Seas) cruise, we have investigated the cyclonic circulation in the Japan Basin (northern part of the Japan Sea), its volume transport and the spatial distribution of the currents. The current pattern and the distribution of the water mass with low salinity and low potential vorticity reveal the existence of a basin-wide cyclonic circulation in the Japan Basin. Its westward volume transport along the Russian coast from the surface to 300 m depth is estimated to be 1.0-1.5 Sv (1 Sv = 10⁶ m³/sec), increasing as it flows westward. ADCP results show that the cyclonic circulation is found even below the main pycnocline, and its vertical velocity is small there. The water mass with low salinity and low potential vorticity moves along this cyclonic circulation in the intermediate layer. This water mass flows eastward along the isobath of the northern edge of the Yamato Rise. This suggests that the cyclonic circulation is affected by the bottom topography since it reaches the deep layer. Some parts of this water mass move southward above the Yamato Rise.