Japan Geoscience Union Meeting 2016

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Symbol M (Multidisciplinary and Interdisciplinary) » M-TT Technology & Techniques

[M-TT28] Frontiers in Geochemistry : Prospect for geochemistry and cosmochemistry in future

Sun. May 22, 2016 10:45 AM - 12:15 PM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Hajime Obata(Marine inorganic chemistry division, Atmosphere and Ocean Research Institute, University of Tokyo), Hirochika Sumino(Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo), Tetsuya Yokoyama(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Takafumi Hirata(Graduate School of Science, Kyoto University), Urumu Tsunogai(Graduate School of Environmental Studies, Nagoya University), Yoshio Takahashi(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Shogo Tachibana(Department of Natural History Scieces, Hokkaido University), Katsuhiko Suzuki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Gen Shimoda(Geological Survey of Japan, AIST), Hiroyuki Kagi(Geochemical Research Center, Graduate School of Science, University of Tokyo), Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo), Chair:Hirochika Sumino(Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo), Tetsuya Yokoyama, Hajime Obata(Marine inorganic chemistry division, Atmosphere and Ocean Research Institute, University of Tokyo)

11:15 AM - 11:30 AM

[MTT28-09] Δ14C variability obtained from high-resolution radiocarbon measurements in coral skeletons from the western Pacific

*Shoko Hirabayashi1,2, Yusuke Yokoyama1,2, Atsushi Suzuki3, Yosuke Miyairi1, Takahiro AZE1 (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Graduate School of Science, The University of Tokyo, 3.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST))

Keywords:Radiocarbon, Δ14C variability, ΔR, coral, sea surface water

Corals skeletons consistent with calcium carbonate and are widely used as archives of paleoenvironments such as sea surface temperature reconstruction. Radiocarbon (14C) in coral skeletons is used as a tracer of ocean circulation because corals take dissolved inorganic carbon (DIC) of seawater in their skeletons. Sample size requirement for conventional 14C measurement, however, need more than 10 mg of CaCO3 (1 mgC), which prevent us to establish a history of high-resolution seawater properties.
In this study, we established a new 14C analytical method, which requires smaller amount of carbonate samples using the accelerator mass spectrometry (AMS) at the Atmosphere and Ocean Research Institute, The University of Tokyo (YS-AMS). Coral skeletons along the Kuroshio trajectory were used to understand the variations of Kuroshio, which were compared with published radiocarbon ratio (Δ14C) data in the western Pacific.
Our results showed that Δ14C in Luzon, Ishigaki and Kikai Is, along Kuroshio current, were similar after 1950 (Post-bomb period). Before 1950 (Pre-Bomb period), our data showed that Δ14C in 1940s were different from Δ14C in 1900s previously reported by Yoneda et al. (2007). It is suggested that sea surface Δ14C fluctuates during a short period of time in the western Pacific. This variability would influence significantly to the calibration of local marine reservoir effects when calibrating 14C ages to calendar ages.