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| Titel |
Impacts of land surface properties and atmospheric CO2 on the Last Glacial Maximum climate: a factor separation analysis |
| VerfasserIn |
A.-J. Henrot, L. François, S. Brewer, G. Munhoven |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 5, no. 2 ; Nr. 5, no. 2 (2009-06-03), S.183-202 |
| Datensatznummer |
250002396
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| Publikation (Nr.) |
 copernicus.org/cp-5-183-2009.pdf |
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| Zusammenfassung |
Many sensitivity studies have been carried out, using climate models of
different degrees of complexity to test the climate response to Last Glacial
Maximum boundary conditions. Here, instead of adding the forcings
successively as in most previous studies, we applied the separation method of
U. Stein et P. Alpert 1993, in order to determine rigorously the different
contributions of the boundary condition modifications, and isolate the pure
contributions from the interactions among the forcings. We carried out
a series of sensitivity experiments with the model of intermediate complexity
Planet Simulator, investigating the contributions of the ice sheet expansion
and elevation, the lowering of the atmospheric CO2 and of the
vegetation cover change on the LGM climate.
The separation of the ice cover and orographic contributions shows that the
ice albedo effect is the main contributor to the cooling of the Northern
Hemisphere, whereas orography has only a local cooling impact over the ice
sheets. The expansion of ice cover in the Northern Hemisphere causes
a disruption of the tropical precipitation, and a southward shift of the
ITCZ. The orographic forcing mainly contributes to the disruption of the
atmospheric circulation in the Northern Hemisphere, leading to
a redistribution of the precipitation, but weakly impacts the tropics. The
isolated vegetation contribution also induces strong cooling over the
continents of the Northern Hemisphere that further affects the tropical
precipitation and reinforce the southward shift of the ITCZ, when combined
with the ice forcing. The combinations of the forcings generate many
non-linear interactions that reinforce or weaken the pure contributions,
depending on the climatic mechanism involved, but they are generally weaker
than the pure contributions. Finally, the comparison between the LGM
simulated climate and climatic reconstructions over Eurasia suggests that our
results reproduce well the south-west to north-east temperature gradients
over Eurasia. |
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