Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic

Abstract

The Cryogenian period (~720–635 Ma) is marked by extensive Snowball Earth glaciations. These have previously been linked to CO₂ draw-down, but the severe cold climates of the Cryogenian have never been replicated during the Phanerozoic despite similar, and sometimes more dramatic changes to carbon sinks. Here we quantify the total CO₂ input rate, both by measuring the global length of subduction zones in plate tectonic reconstructions, and by sea-level inversion. Our results indicate that degassing rates were anomalously low during the Late Neoproterozoic, roughly doubled by the Early Phanerozoic, and remained comparatively high until the Cenozoic. Our carbon cycle modelling identifies the Cryogenian as a unique period during which low surface temperature was more easily achieved, and shows that the shift towards greater CO₂ input rates after the Cryogenian helped prevent severe glaciation during the Phanerozoic. Such a shift appears essential for the development of complex animal life.

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Item Type:	Article
Authors/Creators:	Mills, BJW https://orcid.org/0000-0002-9141-0931 Scotese, CR Walding, NG Shields, GA Lenton, TM
Copyright, Publisher and Additional Information:	(c) 2017, The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.
Dates:	Accepted: 18 September 2017 Published (online): 24 October 2017 Published: 24 October 2017
Institution:	The University of Leeds
Academic Units:	The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds)
Depositing User:	Symplectic Publications
Date Deposited:	29 Sep 2017 08:29
Last Modified:	06 Jul 2018 10:18
Status:	Published
Publisher:	Nature Publishing Group
Identification Number:	10.1038/s41467-017-01456-w
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:121800

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Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic

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