Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS10] Paleoclimatology and paleoceanography

Thu. May 24, 2018 3:30 PM - 5:00 PM A07 (Tokyo Bay Makuhari Hall)

convener:Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Atsuhiko Isobe(Research Institute for Applied Mechanics, Kyushu University), Akihisa Kitamura(静岡大学理学部地球科学教室, 共同), Masaki Sano(Faculty of Human Sciences, Waseda University), Hitoshi Hasegawa(Faculty of Science and Technology, Kochi University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Michinobu Kuwae(Center for Marine Environmental Studies), Chairperson:Kuwae Michinobu(愛媛大学沿岸環境科学研究センター)

4:30 PM - 4:45 PM

[MIS10-33] Unique properties of stalagmite oxygen isotopic records in Japan

*Akihiro Kano1, Hirokazu Kato1, Shota Amekawa1, Taiki Mori2 (1.Graduate School of Science, The University of Tokyo, 2.Graduate School of Integrated Science for Global Sciety, Kyushu University)

Keywords:stalagmite, oxygen isotopes, terrestrial paleoclimate

Stalagmite paleoclimatology has reconstructed climate conditions in the past mainly by oxygen isotopes. This is because O-isotopes of stalagmite calcite are principally controlled by two factors; temperature and O-isotope of drip water, which represent the mean air temperature and the mean isotopic value of meteoric water at the cave location. However, studies in south China have emphasized the control of meteoric O-isotopes because the temperature change cannot reasonably explain the large amplitude of change in the stalagmite O-isotopes (> 8‰) in the late Pleistocene-Holocene time window. Interpretation of the Chinese records relies on a model based on isotopic fractionation in a route from seawater evaporation to rainwater precipitation, which may changes with intensity of East Asian summer monsoon.
We have been analyzed O-isotopes of the stalagmites collected from Hiroshima, Niigata, Gifu, and Mie Prefectures. Except for the material from Niigata indicating the intensity change of the East Asian winter monsoon, the stalagmites from other three caves generally indicate a similar patter of change with the Chinese stalagmites, but indicate much smaller amplitude of change. Another feature of these Japanese stalagmites is long-term trends that follow to the O-isotope record of seawater. Another model is required for these trends. The seawater O-isotope can explain 1/3 of the change in the stalagmites, and the remaining 2/3 likely associated with the temperature change. This model estimates that the range of warming from the LGM and mid-Holocene was 9 degree and that the maximum cooling during Heinrich event was -3 degree, and these estimates are consistent with some of the previous studies. We also suggest that the rainfall intensity and the water-vapor fractionation did not largely reflect on the Japanese stalagmite records. These unique features of the isotopic records of the Japanese stalagmites are due to the geographic position at the vicinity of the moisture source, Kuroshio warm current.