Kuroshio fractions in the southwestern sea of Japan; implications from radium isotopes. (1st February 2021)

• Record Type: Journal Article
• Authors: Inoue, Mutsuo; Shirotani, Yuhei; Morokado, Toshiki; Hanaki, Shotaro; Ito, Masashi; Kameyama, Hiroaki; Kofuji, Hisaki; Okino, Akira; Shikata, Takafumi; Yoshida, Masa-aki; Nagao, Seiya
• Is Part Of: Continental shelf research. Volume 214(2021)
• Publication Date: 2021-02-01
• Subjects: Radium isotopes -- Radiocesium -- Sea surface -- Tsushima warm current -- Sea of Japan; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2020.104328
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: To understand complicated current systems, we examined the 228 Ra activities and 228 Ra/ 226 Ra activity ratios in 290 surface waters in the southwestern Sea of Japan from 2015 to 2020. The 228 Ra/ 226 Ra ratios exhibited large seasonal variation, showing higher ratios in July–September (1.5–2.5) than in other months. The fractions of the Kuroshio Current from the Pacific Ocean ( f K ), based on the 228 Ra activities and salinity, in the western part of the study area were lowest in July after the steep decrease in the f K from May to July (0.95–0.6). This is due to the water mixing ratio of the East China Sea continental shelf side waters to the Kuroshio Current, reflecting the seasonal change and local water circulations. Highlights: Fine-resolution 228 Ra distributions were examined in southwestern Sea of Japan. 228 Ra at the surface showed large seasonal variation reflecting Kuroshio fractions. Kuroshio fractions were 0.6–0.95, showing a steep decrease from May to July. Kuroshio fractions were tightly coupled to radiocesium concentrations.