09:00 〜 09:15
[U13-01] Insight to Western Pacific circulation from coral skeletal radiocarbon during the Anthropocene and Holocene
★Invited Papers
キーワード：放射性炭素、U/Th年代測定、ローカル海洋リザーバー年代、サンゴ、黒潮
Coral skeletal radiocarbon (Δ14C) records can be used as a sensitive proxy of water mass mixing. Compiling coral skeletal Δ14C datasets in the western Pacific will contribute to our understanding of the oceanography of the region and its relationship to climate change such as El Nino-Southern Oscillation.
In this study, high-resolution coral skeletal Δ14C dataset during the Anthropocene and Holocene are reported from the western Pacific. Our Δ14C data indicates the unusual, rapid Δ14C increase (early bomb-14C spikes) in the 1950s related to the “close-in fallout” found in the corals from Ishigaki and Luzon Island. The amplitude of the bomb-14C spike in the Luzon Island was less than half that in Ishigaki, likely due to upwelling around Luzon Island and the Kuroshio intrusion into the South China Sea. We also calculated the local marine reservoir age (R) and the regional offset (ΔR) during the Holocene using paired analyses of Δ14C and 230Th in pristine corals. An abrupt ΔR shift occurred between 5.5 ka BP and 4.0 ka BP in the northwest Pacific. Compared with the previously reported data from the Tropical East Pacific and Great Barrier reef, the timing of the shift is different because the 14C content of the northwestern Pacific was affected by not only the intensity of upwelling at the Peru-Chile coast, but also by the East Asian monsoon.
In this study, high-resolution coral skeletal Δ14C dataset during the Anthropocene and Holocene are reported from the western Pacific. Our Δ14C data indicates the unusual, rapid Δ14C increase (early bomb-14C spikes) in the 1950s related to the “close-in fallout” found in the corals from Ishigaki and Luzon Island. The amplitude of the bomb-14C spike in the Luzon Island was less than half that in Ishigaki, likely due to upwelling around Luzon Island and the Kuroshio intrusion into the South China Sea. We also calculated the local marine reservoir age (R) and the regional offset (ΔR) during the Holocene using paired analyses of Δ14C and 230Th in pristine corals. An abrupt ΔR shift occurred between 5.5 ka BP and 4.0 ka BP in the northwest Pacific. Compared with the previously reported data from the Tropical East Pacific and Great Barrier reef, the timing of the shift is different because the 14C content of the northwestern Pacific was affected by not only the intensity of upwelling at the Peru-Chile coast, but also by the East Asian monsoon.