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| Titel |
Individual and combined effects of ice sheets and precession on MIS-13 climate |
| VerfasserIn |
Q. Z. Yin, A. Berger, M. Crucifix |
| 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 (2009-06-24), S.229-243 |
| Datensatznummer |
250002399
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| Publikation (Nr.) |
 copernicus.org/cp-5-229-2009.pdf |
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| Zusammenfassung |
| An Earth System Model of Intermediate Complexity is used to investigate the
role of insolation and of the size of ice sheets on the regional and global
climate of marine isotope stage (MIS) 13. The astronomical forcing is
selected at two dates with opposite precession, one when northern hemisphere
(NH) summer occurs at perihelion (at 506 ka (1 ka=1000 years) BP), and the
other when it occurs at aphelion (at 495 ka BP). Five different volumes of
the Eurasian ice sheet (EA) and North American ice sheet (NA), ranging from
0 to the Last Glacial Maximum (LGM) one, are used. The global cooling due to
the ice sheets is mainly related to their area, little to their height. The
regional cooling and warming anomalies caused by the ice sheets intensify
with increasing size. Precipitation over different monsoon regions responds
differently to the size of the ice sheets. Over North Africa and India,
precipitation decreases with increasing ice sheet size due to the southward
shift of the Intertropical Convergence Zone (ITCZ), whatever the
astronomical configuration is. However, the situation is more complicated
over East Asia. The ice sheets play a role through both reducing the
land/ocean thermal contrast and generating a wave train which is
topographically induced by the EA ice sheet. This wave train contributes to
amplify the Asian land/ocean pressure gradient in summer and finally
reinforces the precipitation. The presence of this wave train depends on the
combined effect of the ice sheet size and insolation. When NH summer occurs
at perihelion, the EA is able to induce this wave train whatever its size
is, and this wave train plays a more important role than the reduction of
the land/ocean thermal contrast. Therefore, the ice sheets reinforce the
summer precipitation over East China whatever their sizes are. However, when
NH summer occurs at aphelion, there is a threshold in the ice volume beyond
which the wave train is not induced anymore. Therefore, below this
threshold, the wave train effect is dominant and the ice sheets reinforce
precipitation over East China. Beyond this threshold, the ice sheets reduce
the precipitation mainly through reducing the land/ocean thermal contrast. |
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