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Scenario for the evolution of atmospheric pCO (sub 2) during a snowball Earth

Guillaume Le Hir, Gilles Ramstein, Yannick Donnadieu and Yves Godderis
Scenario for the evolution of atmospheric pCO (sub 2) during a snowball Earth
Geology (Boulder) (January 2008) 36 (1): 47-50

Abstract

The snowball Earth theory, initially proposed by J. L. Kirschvink to explain the Neoproterozoic glacial episodes, suggests that the Earth was globally ice covered at 720 Ma (Sturtian episode) and 640 Ma (Marinoan episode). The reduction of the water cycle and the growth of large ice sheets led to a collapse of CO (sub 2) consumption through continental weathering and biological carbon pumping. As a consequence, atmospheric CO (sub 2) built up linearly to levels allowing escape from a snowball Earth. In this contribution, we question this assumed linear accumulation of CO (sub 2) into the atmosphere. Using a numerical model of the carbon-alkalinity cycles, we suggest that during global glaciations, even a limited area of open waters (10 (super 3) km (super 2) ) allows an efficient atmospheric CO (sub 2) diffusion into the ocean. This exchange implies that the CO (sub 2) consumption through the low-temperature alteration of the oceanic crust persists throughout the glaciation. Furthermore, our model shows that rising CO (sub 2) during the glaciation increases the efficiency of this sink through the seawater acidification. As a result, the atmospheric CO (sub 2) evolution is asymptotic, limiting the growth rate of the atmospheric carbon reservoir. Even after the maximum estimated duration of the glaciation (30 m.y.), the atmospheric CO (sub 2) is far from reaching the minimum deglaciation threshold (0.29 bar). Accounting for this previously neglected carbon sink, processes that decrease the CO (sub 2) deglaciation threshold must be further explored.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 36
Serial Issue: 1
Title: Scenario for the evolution of atmospheric pCO (sub 2) during a snowball Earth
Affiliation: CEA Saclay, Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette, France
Pages: 47-50
Published: 200801
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 35
Accession Number: 2008-028897
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix; with GSA Data Repository Item 2008013
Illustration Description: illus.
Secondary Affiliation: Observatoire Midi-Pyrenees, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200809
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