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          Institute: MPI für Meteorologie     Collection: Ocean in the Earth System     Display Documents



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ID: 498460.0, MPI für Meteorologie / Ocean in the Earth System
Initiation of a Marnoun Snowball Earth in a state-of-the-art atmosphere-ocean general circulation model
Authors:Voigt, A.; Abbott, D. S.; Pierrehumbert, R.T.; Marotzke, J.
Language:English
Date of Publication (YYYY-MM-DD):2011
Title of Journal:Climate of the Past
Volume:7
Start Page:249
End Page:263
Review Status:Peer-review
Audience:Not Specified
Abstract / Description:We study the initiation of a Marinoan Snowball Earth (~635 million years before present) with the state-of-the-art atmosphere-ocean general circulation model ECHAM5/MPI-OM. This is the most sophisticated model ever applied to Snowball initiation. A comparison with a pre-industrial control climate shows that the change of surface boundary conditions from present-day to Marinoan, including a shift of continents to low latitudes, induces a global-mean cooling of 4.6 K. Two thirds of this cooling can be attributed to increased planetary albedo, the remaining one third to a weaker greenhouse effect. The Marinoan Snowball Earth bifurcation point for pre-industrial atmospheric carbon dioxide is between 95.5 and 96% of the present-day total solar irradiance (TSI), whereas a previous study with the same model found that it was between 91 and 94% for present-day surface boundary conditions. A Snowball Earth for TSI set to its Marinoan value (94% of the present-day TSI) is prevented by doubling carbon dioxide with respect to its pre-industrial level. A zero-dimensional energy balance model is used to predict the Snowball Earth bifurcation point from only the equilibrium global-mean ocean potential temperature for present-day TSI. We do not find stable states with sea-ice cover above 55%, and land conditions are such that glaciers could not grow with sea-ice cover of 55%. Therefore, none of our simulations qualifies as a "slushball" solution. While uncertainties in important processes and parameters such as clouds and sea-ice albedo suggest that the Snowball Earth bifurcation point differs between climate models, our results contradict previous findings that Snowball Earth initiation would require much stronger forcings.
External Publication Status:published
Document Type:Article
Communicated by:Carola Kauhs
Affiliations:MPI für Meteorologie/Ocean in the Earth System
MPI für Meteorologie/IMPRS Earth System Modelling
Identifiers:DOI:10.5194/cpd-7-249-2011
URL:http://www.clim-past.net/7/249/2011/cp-7-249-2011....
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