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| Titel |
Multiple vegetation states in a warm climate |
| VerfasserIn |
Ulrike Port, Martin Claussen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092177
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| Publikation (Nr.) |
 EGU/EGU2014-6503.pdf |
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| Zusammenfassung |
| Using the Max Planck earth system model, multiple steady states in vegetation cover are
evaluated for preindustrial and Early Eocene boundary conditions. By setting the soil
albedo either to a value similar to vegetation albedo or to a value much higher than
vegetation albedo, the hydrological and the albedo effect of vegetation on climate are
separated.
Considering only the hydrological effect, multiple solutions for the Early Eocene
vegetation cover exist. In central Asia, a desert evolves. This desert is smaller when the
simulation is started with trees on all continents instead of bare soil. Started with trees, the
climate in central Asia is more humid than when started with bare soil. In the more humid
climate, more vegetation grows. For the preindustrial climate, only one solution for
vegetation exists. The atmospheric circulation prevents multiple solutions for vegetation in
the Sahara. Strong subsidence prevails over the Sahara. Under strong subsidence the
hydrological effect becomes ineffective.
Considering the hydrological and the albedo effect of vegetation, only one solution for
Early Eocene and preindustrial vegetation exists. Starting the simulations with trees, the Early
Eocene central Asia and preindustrial Sahara start from a humid climate, but the initial
climate is not humid enough to allow a dense vegetation cover. With shrinking vegetation
cover, surface albedo increases. Increasing albedo amplifies aridification by inducing
the Charney effect. The vegetation cover shrinks further until a dry desert state is
reached.
This study shows that the existence of multiple steady vegetation states depends on the
boundary conditions, such as continent distribution. This result implies that the existence and
the driving mechanisms of multiple stable vegetation states differ for present day, past, and
probably future conditions. |
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