16:30 〜 16:45
[SGC54-11] サンゴ骨格を用いた高時間分解能放射性炭素濃度測定による西太平洋海洋環境復元
キーワード：放射性炭素、サンゴ骨格、西太平洋、北太平洋西岸境界流
High-resolution measurements of radiocarbon (14C) in corals can be used to reconstruct past variability in ocean conditions. However, the conventional 14C measurement requires more than 10 mg of carbonate samples even for Accelerator Mass Spectrometry (AMS), which prevent us to establish a history of high-resolution seawater properties.
We established a new 14C analytical method, which requires smaller amount of carbonates using AMS at the Atmosphere and Ocean Research Institute, The University of Tokyo. Using our new method, we report seasonal Δ14C changes in coral from Ishigaki Island and compare with previously reported data from Palau and Guam. Our data clearly indicate a significant increase in Δ14C from 1947 to 1998 related to atmospheric nuclear bomb testing. Additionally, the existence of three early Δ14C spikes of nuclear bomb tests in 1950s was confirmed in the North Pacific western boundary current area. After 1976, variability in the Mindanao Dome region related to North Equatorial Current bifurcation latitude migration affected the Δ14C difference between Palau and Guam, whereas difference between Ishigaki and Guam was not correlated with the bifurcation latitude. The Δ14C difference between Ishigaki and Guam may be owing to mesoscale eddies in the Kuroshio area. On decadal scale, evidence suggests that stronger transport by the Kuroshio around the Luzon Strait resulted in less upwelling, which may be represented by a smaller Δ14C difference between Ishigaki and Guam after 1976.
We established a new 14C analytical method, which requires smaller amount of carbonates using AMS at the Atmosphere and Ocean Research Institute, The University of Tokyo. Using our new method, we report seasonal Δ14C changes in coral from Ishigaki Island and compare with previously reported data from Palau and Guam. Our data clearly indicate a significant increase in Δ14C from 1947 to 1998 related to atmospheric nuclear bomb testing. Additionally, the existence of three early Δ14C spikes of nuclear bomb tests in 1950s was confirmed in the North Pacific western boundary current area. After 1976, variability in the Mindanao Dome region related to North Equatorial Current bifurcation latitude migration affected the Δ14C difference between Palau and Guam, whereas difference between Ishigaki and Guam was not correlated with the bifurcation latitude. The Δ14C difference between Ishigaki and Guam may be owing to mesoscale eddies in the Kuroshio area. On decadal scale, evidence suggests that stronger transport by the Kuroshio around the Luzon Strait resulted in less upwelling, which may be represented by a smaller Δ14C difference between Ishigaki and Guam after 1976.