Sensitivity experiments to sea surface temperatures, sea-ice extent and ice-sheet reconstruction, for the Last Glacial Maximum

International audience For the Last Glacial Maximum, (LGM; 21 000 BP), simulations using atmospheric general-circulation models (AGCMs) are very sensitive to the prescribed boundary conditions. Most of the recent numerical experiments have used the CLIMAP (1981) data set for ice-sheet topography, se...

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Bibliographic Details
Published in:Annals of Glaciology
Main Authors: Ramstein, Gilles, Joussaume, Sylvie
Other Authors: Laboratoire de Modélisation du Climat et de l'Environnement (LMCE)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 1995
Subjects:
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean
Atmosphere
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces
environment
Peltier
Annals of Glaciology
Ice Sheet
North Atlantic
Sea ice
Online Access:https://hal.archives-ouvertes.fr/hal-03011873
https://hal.archives-ouvertes.fr/hal-03011873/document
https://hal.archives-ouvertes.fr/hal-03011873/file/ag3.pdf
https://doi.org/10.3189/S0260305500016049
Description
Summary:International audience For the Last Glacial Maximum, (LGM; 21 000 BP), simulations using atmospheric general-circulation models (AGCMs) are very sensitive to the prescribed boundary conditions. Most of the recent numerical experiments have used the CLIMAP (1981) data set for ice-sheet topography, sea-ice extent and sea surface temperatures (SSTs). To demonstrate the impact of ice-sheet reconstruction on the LGM climate, we performed two simulations: one using CLIMAP (1981) ice-sheet topography, the other using the new reconstruction provided by Peltier. We show that, although the geographical structure of the annually averaged temperature is not modified, there are important seasonal and regional impacts on the temperature distribution. In a second step, to analyze the effects of cooler SSTs and sea-ice extent, we performed a simulation using CLIMAP (1981) for the ice-sheet topography, but with present SSTs. We find that the cooling due to ice sheets for the LGM climate is one-third of the global annually averaged cooling, and dial the southward shift of the North Atlantic low in winter is not due to sea-ice extent, but is an orographic effect due to the Laurenride ice sheet. This set of sensitivity experiments allows us also to discriminate between thermal and orographic forcings and to show the impact of the ice-sheet topography and cooler SSTs on the pattern of planetary waves during the LGM climate.

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