Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS06] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

Mon. May 21, 2018 3:30 PM - 5:00 PM 302 (3F International Conference Hall, Makuhari Messe)

convener:Osamu Seki(Institute of Low Temperature Science, Hokkaido University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Ryosuke Makabe(国立極地研究所, 共同), Ryu Uemura(University of the Ryukyus), Chairperson:Fukuda Yoichi(Kyoto University), Oyabu Ikumi(National Institute of Polar Research)

4:00 PM - 4:15 PM

[MIS06-14] A revised chronology of the Dome Fuji ice core from O2/N2 of trapped air

*Ikumi Oyabu1, Kenji Kawamura1,2,3, Kyotaro Kitamura1 (1.National Institute of Polar Research, Research Organization of Information and Systems, 2.SOKENDAI (The Graduate University of Advanced Studies), 3.Japan Agency for Marine Science and Technology )

Keywords:Ice core, Dome Fuji, O2/N2, chronology

Accurate ice core chronology is essential to examine the sequences, durations and phasing of climatic records. A chronology for the Dome Fuji (DF) ice core (DFO-2006, for 340 kyr BP) was constructed by synchronizing variations in O2/N2 of occluded air with local summer insolation, with stated 2σ error of about 2 kyr (Kawamura et al., 2007). However, it was found that DFO-2006 at ~100 kyr BP and ~129 kyr BP (end of Termination II) are older by ~3 kyr and ~2 kyr, respectively, than U-Th radiometric dating of Chinese speleothems with stated 2σ error of <1 kyr (Cheng et al., 2009; Fujita et al., 2015). Poor quality of the O2/N2 data due to diffusive gas loss during core storage in “warm” freezer (-25 °C) may be responsible for the discrepancies. Also, large noise in the O2/N2 data between 220 and 230 kyr BP hampered its use for constraining the time scale, thus the O2/N2 data from the Vostok ice core was used for the chronological tie points at 221.2 and 230.8 kyr BP in DFO-2006. Here we re-analyzed O2/N2 to improve the DF chronology before 80 kyr BP, using the samples stored at -50 °C. After careful tests, we found that ~1-cm-thick surface layer must be removed to eliminate the effect of gas loss for ~20 years. With our new O2/N2 data, the DF chronology was revised with the tuning technique of Kawamura et al. (2007). The new DF chronology between 80 and 165 kyr BP agrees with the speleothem chronology within 1.2 kyr. In particular, the DF age at the end of Termination II agrees with the speleothem chronology and the AICC2012 ice core chronology within ~1 kyr. The results suggest that O2/N2 in the DF core faithfully records local summer insolation, and that the revised chronology greatly improved from DFO-2006. We will extend the O2/N2 record further back in time and show the new data in the presentation.