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Causes of ice-age intensification across the Mid-Pleistocene Transition

Chalk, Thomas B.; Hain, Mathis P.; Foster, Gavin L.; Rohling, Eelco J.; Sexton, Philip F.; Badger, Marcus P.; Cherry, Soraya G.; Hasenfratz, Adam P.; Haug, Gerald H.; Jaccard, Samuel L.; Martínez-García, Alfredo; Pälike, Heiko; Pancost, Richard D. and Wilson, Paul A. (2017). Causes of ice-age intensification across the Mid-Pleistocene Transition. Proceedings of the National Academy of Sciences of the United States of America, 114 pp. 13114–13119.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1073/pnas.1702143114
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Abstract

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.

Item Type: Journal Item
ISSN: 1091-6490
Project Funding Details:
Funded Project NameProject IDFunding Body
Ventilation history of the earth's thermocline (SE-10-079-PS)Not SetThe Leverhulme Trust
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Related URLs:
Item ID: 52671
Depositing User: Philip Sexton
Date Deposited: 13 Dec 2017 17:05
Last Modified: 14 Sep 2018 12:53
URI: http://oro.open.ac.uk/id/eprint/52671
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