Spatial distribution of radiocarbon in the southwestern Japan east sea immediately after bottom water renewal

In April 2001, immediately after bottom water renewal in the Japan/East Sea, 7 vertical profiles of radiocarbon were obtained from the area, including the Japan Basin and the Tsushima/Ulleung Basin. The bottom water Δ¹⁴C of the Tsushima/Ulleung Basin increased by 24‰ during 1979-2001 and was 10-15‰ higher than the values reported for the Japan Basin and Yamato Basin during 1995-2002. Within the depth interval 800-2000 m, Δ¹⁴C values at the southernmost station in the Japan Basin were much higher than at other stations, with the maximum difference in Δ¹⁴C values being more than 50‰. Based on a combination of physical observations with analysis of the Δ¹⁴C data, we concluded that the bottom water, which was formed by the sinking of surface water off Vladivostok, Russia, in late January-early February of 2001, had been widely distributed to depths below 2000 m within the southernmost Japan Basin in a timespan shorter than 2 months. However, there was no evidence that the water had been transported into the Tsushima/Ulleung Basin during the same time interval.