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| Titel |
Constraints on atmospheric pCO2 during the Great Oxygenation Event inferred from 3-D climate modeling and relevance regarding paleosol studies |
| VerfasserIn |
Yoram Teitler, Guillaume Le Hir, Frédéric Fluteau |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056022
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| Zusammenfassung |
| Geologic records suggest that Earth was warm during most of its early history, except for two
periods where evidences for regional (2.9 Gyr old; Pongola) and global (2.3 Gyr old;
Huronian) glaciations have been identified. In order to constraint the greenhouse CO2 and
CH4gases concentrations (i.e. pCO2, pCH4) required to induce a global glaciation during the
Early Proterozoic (2.3 Ga), a set of 3-D simulations accounting for the paleogeography and a
reduced solar constant has been performed using the general circulation climate model
(GCM) FOAM. Comparison between model outputs and proxies of the 2.4 Ga glaciation
allows defining liable climate states as a function of pCO2 and pCH4. Our model predicts that
Earth can be maintained in an ice-free state while pCO2 is lower than 4.10-2 bar
as constrained by paleosol studies (Sheldon, 2006; Rye et al. 1995). Moreover,
considering a pCH4 of 1000 ppmv during the Late Archean (Pavlov, 2001), the
required pCO2 for maintaining ice-free conditions is about 8.4.10-3 bar, strikingly
close to Sheldon (2006) “best guess” estimation (8.5.10-3 bar). Assuming that the
Great Oxygenation Event is associated with global, we also show that snowball
conditions are reached when pCH4 drops from 1000 to 10 ppmvfor a pCO2 fixed at
8.4.10-3bar. Throughout the Paleoproterozoic, maintenance of mild temperate conditions
comparable with those observed during the Phanerozoic requires at least 1.6 10-2 bar of
CO2 because pCH4 cannot exceed 100 ppmv in a partially oxidized atmosphere |
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