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Global climate stabilisation by chemical weathering during the Hirnantian glaciation

Pogge von Strandmann, PAE; Desrochers, A; Murphy, MJ; Finlay, AJ; Selby, D; Lenton, TM; (2017) Global climate stabilisation by chemical weathering during the Hirnantian glaciation. Geochemical Perspectives Letters , 3 pp. 230-237. 10.7185/geochemlet.1726. Green open access

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Abstract

Chemical weathering of silicate rocks is a primary drawdown mechanism of atmospheric carbon dioxide. The processes that affect weathering are therefore central in controlling global climate. A temperature-controlled “weathering thermostat” has long been proposed in stabilising long-term climate, but without definitive evidence from the geologic record. Here we use lithium isotopes (δ7Li) to assess the impact of silicate weathering across a significant climate-cooling period, the end-Ordovician Hirnantian glaciation (~445 Ma). We find a positive δ7Li excursion, suggestive of a silicate weathering decline. Using a coupled lithium-carbon model, we show that initiation of the glaciation was likely caused by declining CO2 degassing, which triggered abrupt global cooling, and much lower weathering rates. This lower CO2 drawdown during the glaciation allowed climatic recovery and deglaciation. Combined, the data and model provide support from the geological record for the operation of the weathering thermostat.

Type: Article
Title: Global climate stabilisation by chemical weathering during the Hirnantian glaciation
Open access status: An open access version is available from UCL Discovery
DOI: 10.7185/geochemlet.1726
Publisher version: http://doi.org/110.7185/geochemlet.1726
Language: English
Additional information: This work is distributed under the Creative Commons Attribution 4.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Additional information is available at http://www. geochemicalperspectivesletters.org/copyright-and-permissions.
Keywords: silicate weathering, weathering thermostat, mass extinction, Ordovician, carbon cycle
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1567829
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