Article (Scientific journals)
Impacts of land surface properties and atmospheric CO2 on the Last Glacial Maximum climate: a factor separation analysis
Henrot, Alexandra; François, Louis; Brewer, S. et al.
2009In Climate of the Past, 5 (2), p. 183-202
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Keywords :
climate; modelling; Last Glacial Maximum
Abstract :
[en] 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.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Henrot, Alexandra ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
François, Louis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Modélisation du climat et des cycles biogéochimiques
Brewer, S.;  Université de Liège - ULiège > Détartement AGO > UMCCB
Munhoven, Guy ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) - Pétrologie, géochimie endogènes et pétrophysique
Language :
English
Title :
Impacts of land surface properties and atmospheric CO2 on the Last Glacial Maximum climate: a factor separation analysis
Publication date :
2009
Journal title :
Climate of the Past
ISSN :
1814-9324
eISSN :
1814-9332
Publisher :
European Geosciences Union
Volume :
5
Issue :
2
Pages :
183-202
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 19 May 2010

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