 |
| Titel |
Initiation of a Marinoan Snowball Earth in a state-of-the-art atmosphere-ocean general circulation model |
| VerfasserIn |
A. Voigt, D. S. Abbot, R. T. Pierrehumbert, J. Marotzke |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 7, no. 1 ; Nr. 7, no. 1 (2011-03-10), S.249-263 |
| Datensatznummer |
250004409
|
| Publikation (Nr.) |
 copernicus.org/cp-7-249-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|