Pogge von Strandmann, P. and Desrochers, A. and Murphy, M.J. and Finlay, A.J. and Selby, D. and Lenton, T.M. (2017) 'Global climate stabilisation by chemical weathering during the Hirnantian glaciation.', Geochemical perspectives letters., 3 (2). pp. 230-237.
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.
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|Publisher Web site:||https://doi.org/10.7185/geochemlet.1726|
|Publisher statement:||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.|
|Date accepted:||15 May 2017|
|Date deposited:||07 June 2017|
|Date of first online publication:||15 June 2017|
|Date first made open access:||No date available|
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