Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Paleoclimatology and paleoceanography

Tue. May 24, 2016 9:00 AM - 10:30 AM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Akihisa Kitamura(Institute of Geosciences, Faculty of Science, Shizuoka University), Masaki Sano(Research Institute for Humanity and Nature), Ryuji Tada(Department of Earth and Planetary Science, Graduate School of Science, The Univeristy of Tokyo), Takeshi Nakagawa(Ritsumeikan University), Akira Hayashida(Department of Environmental Systems Science, Doshisha University), Chair:Akira Hayashida(Department of Environmental Systems Science, Doshisha University)

10:00 AM - 10:15 AM

[MIS17-17] Fossil coral-based reconstruction of the Mid-Holocene ocean environment in Okinawa-jima, Japan

*Ryuji Asami1, Matsumi Yoshimura1, Shogo Minei1, Chuki Hongo2, Kazuhiko Fujita1 (1.Department of Physics and Earth Sciences, University of the Ryukyus, 2.University of the Ryukyus)

Keywords:coral skeleton, fossil, oxygen isotope composition, carbon isotope composition, paleo-temperature, the Ryukyu Islands

Quaternary paleoclimate records have been extracted from climate proxies such as deep-sea sediments, ice sheets, trees, speleothems, and corals. Continuous long cores from sediments and ice sheets play a leading role in Quaternary paleoclimate reconstructions, although the slow rates of sedimentation frequently preclude them from reconstructions on seasonal and interannual time scales. However, fossil coral archives provide high resolution windows of generally short duration with which to investigate past atmospheric and oceanic conditions at the tropical/subtropical sea surface. Massive Porites corals, living in shallow waters of the tropical to subtropical oceans, precipitate annually banded aragonite skeletons. These colonies provide robust chronological control and allow sub-sampling at monthly-to-seasonal resolution. The ages of fossil corals are determined accurately by radiocarbon and uranium-series dating methods. Oxygen isotope composition of coral skeleton reflects variations in sea surface temperature and seawater oxygen isotope composition (salinity) with the latter being closely related to the precipitation-evaporation balance at sea surface and changes in water mass transport. Long-lived corals can be a powerful proxy for documenting paleoceanography at seasonal, interannual, and decadal time scale, but only a few long-records of >50-year have been published from fossil corals. Here we present bimonthly resolved oxygen and carbon isotope composition time series from mid-Holocene corals in coral reef sediment cores drilled at the west coast of Okinawa-jima, the Ryukyu Islands, Japan. Our coral-based climate reconstruction significantly shows seasonal-to-decadal time scale variability of thermal and hydrologic conditions in the northwestern subtropical Pacific during the mid-Holocene.