Oceanographic environment of the Tsushima Island

CTD (Conductivity-Temperature-Depth profiler) observations and bottom water sampling were conducted at 192 sites in the waters surrounding the Tsushima Island during cruise GB23 from October to November in 2023.The survey area is located around the Tsushima Strait, through which the Tsushima Warm Current flows into the Sea of Japan.The observed sea surface water temperature ranged from 18.9 to 23.9 and salinity ranged from 33.7 to 34.6, suggesting the influence of both the Kyushu Coastal Current and the Tsushima Warm Current.The bottom water temperature generally decreased with increasing depth.In the deeper layers south of the Goto Islands, we observed a water mass thought to be North Pacific Subtropical Mode Water, which flowed to this region from the Goto Canyon.A high-turbidity layer was detected in the coastal waters off Kyushu and north of Tsushima Island, likely influenced by the local topography and ocean currents.