Atmospheric CO2 estimates for the Miocene to Pleistocene based on foraminiferal δ11B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

Type Article
Acceptance Date 2021 IN PRESS
Language English
Author(s) Guillermic Maxence1, 2, Misra Sambuddha3, 4, Eagle Robert1, 2, Tripati Aradhna1, 2
Affiliation(s) 1 : Department of Atmospheric and Oceanic Sciences, Department of Earth, Planetary, and Space Sciences, Center for Diverse Leadership in Science, Institute of the Environment and Sustainability, University of California – Los Angeles, Los Angeles, CA 90095 USA
2 : Laboratoire Géosciences Océan UMR6538, UBO, Institut Universitaire Européen de la Mer, Rue Dumont d'Urville, 29280, Plouzané, France
3 : The Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, UK
4 : Indian Institute of Science, Centre for Earth Sciences, Bengaluru, Karnataka 560012, India
Source Climate of the Past (1814-9332) (Copernicus GmbH) In Press
DOI 10.5194/cp-2020-158
Abstract

Constraints on the evolution of atmospheric CO2 levels throughout Earth's history are foundational to our understanding of past variations in climate. Despite considerable effort, estimates of past CO2 levels do not always converge and therefore new records and proxies are valuable. Here we reconstruct atmospheric CO2 values across major climate transitions over the past 17 million years using the boron isotopic composition (δ11B) of planktic foraminifera from 89 samples obtained from two sites in the West Pacific Warm Pool, Ocean Drilling Program (ODP) Sites 806 and 807. These sites are in a region that today is in equilibrium with the atmosphere and are thought to have been in equilibrium with the atmosphere for the interval studied. We use high-precision multi-collector inductively-coupled plasma mass spectrometry and show that data from these sites can reproduce the ice core record. Estimates of early Miocene pCO2 are generally higher than published reconstructions from other sites, while values for the Pliocene and Pleistocene are more similar to other datasets. We find evidence for reductions in pCO2 of ~280 µatm during the Middle Miocene Climate Transition, ~270 µatm during Pliocene Glacial Intensification, and ~50 µatm during the Mid-Pleistocene Climate Transition. There is possible evidence for a larger reduction in glacial pCO2 during the Mid-Pleistocene Transition compared to interglacial pCO2, and a minimum in pCO2 during glacial MIS 30. Our results are consistent with a coupling between pCO2, temperature and ice sheet expansion throughout the past 17 million years.

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Guillermic Maxence, Misra Sambuddha, Eagle Robert, Tripati Aradhna Atmospheric CO2 estimates for the Miocene to Pleistocene based on foraminiferal δ11B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific. Climate of the Past IN PRESS. Publisher's official version : https://doi.org/10.5194/cp-2020-158 , Open Access version : https://archimer.ifremer.fr/doc/00678/79045/