Transport of reactive materials in the Sea of Japan: Implications from fine-resolution surface distribution of 228Th/228Ra ratio. (15th May 2022)

• Record Type: Journal Article
• Authors: Inoue, Mutsuo; Shirotani, Yuhei; Morokado, Toshiki; Hanaki, Shotaro; Kameyama, Hiroaki; Kofuji, Hisaki; Okino, Akira; Yoshida, Masa-aki; Miki, Shizuho; Shikata, Takafumi; Honda, Naoto; Takikawa, Tetsutaro; Morita, Masaya; Nagao, Seiya
• Is Part Of: Continental shelf research. Volume 241(2022)
• Publication Date: 2022-05-15
• Subjects: 228Th/228Ra ratio -- 228Ra/226Ra ratio -- Sea of Japan -- Reactive materials -- Ocean scavenging; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2022.104749
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: This study aimed to explore the transport patterns of reactive materials under the Tsushima Warm Current (TWC) in the Sea of Japan. Fine-resolution seasonal and lateral variations in 228 Th/ 228 Ra activity ratio were examined along with 228 Ra/ 226 Ra ratio in surface seawater samples from the Sea of Japan, East China Sea (ECS), and Pacific Ocean in 2015–2020. Significant 228 Th/ 228 Ra ratio variations were observed in surface seawaters (<∼0.02–0.3), which partially correlated with the mixing ratios of the low- 228 Th/ 228 Ra continental shelf side waters from the western ECS and high- 228 Th/ 228 Ra Kuroshio Warm Current of the Pacific Ocean, in addition to the contributions of the subarctic current of the northern Sea of Japan. Conversely, in the Sea of Japan, local variation of 228 Th/ 228 Ra ratios were observed in samples with a similar fraction of the ECS continental shelf side waters. It is reasonable to speculate that these variations are due to local scavenging during the TWC circulation. Highlights: Seasonal and lateral 228 Th/ 228 Ra ratio variations in the Sea of Japan were studied. Surface 228 Th/ 228 Ra ratio partially reflects the mixing ratio of ECS shelf water. High 228 Th/ 228 Ra ratio in the northern area suggests mixing of subarctic current. Inhomogeneous lateral distributions of the ratio were ascribed to local scavenging.