日本海対馬暖流域における海水の酸素同位体比と塩分の関係

The δ¹⁸O_sw (seawater δ¹⁸O) and its relationship with salinity are principal information for analyzing mixing of water masses in the ocean, as well as reconstructing paleo-salinity from biogenic carbonate. Although δ¹⁸O_sw–salinity equations have been reported in the Sea of Japan, it's unclear whether such equations are applicable in the Tsushima Current area. Here, we report 74 δ¹⁸O_sw data in the Tsushima Current area. For shallow seawater samples (≤100 m),data were plotted along the mixing line that connects High Salinity Tsushima Current Water (HSTCW) and low-salinity/low-δ¹⁸O_sw water. In the Tsushima Strait, the source of low-salinity/low-δ¹⁸O_sw water was the Changjiang Diluted Water (CDW).Yet, in the Sea of Japan, the Tsushima Current surface waters exhibited more δ¹⁸O-depleted freshwater sources than the CDW (δ¹⁸O_sw=-9.1+0.27×Salinity).Analysis of the freshwater budget with their δ¹⁸O values in the Tsushima Current surface water reveals that terrestrial water inputs from the Japanese Islands, precipitation, and evaporation were attributable to more δ¹⁸O-depleted freshwater sources. Further, we found that a mixing model for HSTCW, freshwater, and Northern Japan Sea Surface Water can be useful for analyzing provenance and mixing ratios of each surface water mass in the Sea of Japan.