[M-IS02] Evolution and variability of the Asian Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS02-P01] A 1.46-million-year record of atmospheric CO₂ from sedimentary leaf wax in the Bay of Bengal

*Masanobu Yamamoto¹, Steven Clemens², Osamu Seki³, Yuko Tsuchiya¹, Yongsong Huang², Ryouta O'ishi⁴, Ayako Abe-Ouchi⁴ (1.Faculty of Environmental Earth Science, Hokkaido University, 2.Brown University, 3.Institute of Low Temperature Science, Hokkaido University, 4.Atmospheric and Ocean Reserach Institute, University of Tokyo)

Keywords:Carbon dioxide, Glacila-interglacial cycles, Mid-Pleistocene Transition

A great deal of effort is now focused on reconstructing atmospheric CO₂ during periods of lower polar ice volume to better constrain carbon cycling under conditions similar to those expected in the future. Here we reconstruct the past 1,460,000 years of atmospheric CO₂ by taking advantage of the unique relationship between CO₂concentration and leaf wax δ¹³C value resulting from changes in the distribution of plant functional types in East India. We find that CO₂ variability is tightly coupled with variability of global ice volume and deep-ocean circulation on glacial–interglacial timescales. However, unexpectedly, interglacial CO₂ concentrations were lower before the mid-Pleistocene transition (MPT; 900,000 years ago) than after it, despite the smaller continental ice volume, while CO₂ showed a similar secular trend with deep-ocean carbon isotopes. A shift in the relative phase of CO₂ and ice volume cycles occurred during the MPT. These findings suggest that deep-ocean circulation controlled the long-term CO₂ trend, and the interaction between CO₂, continental ice, and deep-ocean circulation was reorganized during the MPT.