[U05-P07] Insight to Western Pacific circulation from coral skeletal radiocarbon
Keywords:Coral, Western Pacific, Radiocarbon, East Asian monsoon, Kuroshio
In this study, high-resolution coral skeletal Δ14C dataset during the Anthropocene and Holocene are reported from the western Pacific. Our Δ14C data indicates a significant increase in Δ14C from 1946 to 1994 related to atmospheric nuclear bomb testing, with more rapid increase in the South China Sea (SCS) than in the Pacific. The unusual, rapid Δ14C increase (early bomb-14C spikes) in the 1950s related to the “close-in fallout” found in our SCS and Ryukyu corals. Although three early bomb-14C spikes have been reported from Guam and from Ishigaki, only one such spike was clearly detected in the SCS. The amplitude of the bomb-14C spike in the SCS was less than half that in Ishigaki, likely due to upwelling around Luzon Island and the Kuroshio intrusion into the SCS. We also calculated ΔR during the Holocene using paired analyses of Δ14C and 230Th on 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 was 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.