Title: Pleistocene CO2 variability inferred from the Bay of Bengal leaf-wax carbon isotopes

Authors: Masanobu Yamamoto

Affiliations: Faculty of Environmental Earth Science, Hokkaido University, Japan

Abstract: Atmospheric CO2 and polar ice volume have been strongly coupled over the past 805,000 years. We reconstructed the atmospheric CO2 concentration over the entire Pleistocene by taking advantage of the unique relationship between CO2 concentration and leaf-wax δ13C resulting from changes in the extent of C3 and C4 vegetation in East India. Notably, reconstructed interglacial CO2 concentrations (CO2FA) in the early Pleistocene were lower than the preindustrial level, which agrees with the new result of Antarctic blue ice gas analysis. The CO2FA variation consistently covaries with benthic oxygen isotope variation throughout the Pleistocene, indicating a strong coupling of CO2 and continental ice volume. The CO2FA variation shows the amplitude modulation at the ~400,000-year cycle; the amplitude is larger when the long-term eccentricity is lower. This variation is harmonious with variations in the Antarctic Circumpolar Current strength and the rain ratios (CaCO3/OC, CaCO3/opal, etc.) in subpolar and tropical oceans. We suppose that the ice-CO2 interaction, Southern Ocean upwelling, and biological production regulated CO2 variability in the Pleistocene.

Biography: Masanobu Yamamoto graduated from the master's course at Tohoku University in 1988 and started work in petroleum geology and organic geochemistry in the Geological Survey of Japan as a researcher. Masanobu Yamamoto was awarded a PhD from Nagoya University and moved to Hokkaido University in 2000 as an Associate Professor in paleoceanography and paleoclimatology before becoming a Full Professor. Masanobu Yamamoto worked on SST reconstruction in the Pacific Ocean using UK37 and TEX86 in the 2000s.  He then shifted to the Arctic and Indian Oceans for paleoenvironment and vegetation reconstructions using various biomarkers and their isotopes and works on reconstructing atmospheric CO₂ during the last several million years, as well as understanding the global carbon cycle.