Causes of ice age intensification across the Mid-Pleistocene Transition.
- Chalk TB Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom; T.chalk@noc.soton.ac.uk M.P.Hain@soton.ac.uk.
- Hain MP Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom; T.chalk@noc.soton.ac.uk M.P.Hain@soton.ac.uk.
- Foster GL Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom.
- Rohling EJ Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom.
- Sexton PF School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom.
- Badger MPS School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom.
- Cherry SG Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom.
- Hasenfratz AP Geologisches Institut, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland.
- Haug GH Max Planck Institut für Chemie, 55128 Mainz, Germany.
- Jaccard SL Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland.
- Martínez-García A Max Planck Institut für Chemie, 55128 Mainz, Germany.
- Pälike H Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom.
- Pancost RD Organic Geochemistry Unit, School of Chemistry, The Cabot Institute, University of Bristol, Bristol BS8 1TS, United Kingdom.
- Wilson PA Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton SO14 3ZH, United Kingdom.
- 2017-11-29
Published in:
- Proceedings of the National Academy of Sciences of the United States of America. - 2017
English
During the Mid-Pleistocene Transition (MPT; 1,200-800 kya), Earth's orbitally paced ice age cycles intensified, lengthened from ∼40,000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO2 data to show that the glacial to interglacial CO2 difference increased from ∼43 to ∼75 μatm across the MPT, mainly because of lower glacial CO2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship between sea level and CO2-related climate forcing that is suggestive of a change in the dynamics that govern ice sheet stability, such as that expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets.
- Language
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- English
- Open access status
- hybrid
- Identifiers
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- DOI 10.1073/pnas.1702143114
- PMID 29180424
- Persistent URL
- https://folia.unifr.ch/global/documents/201387
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