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| Titel |
Glacial climate sensitivity to different states of the Atlantic Meridional Overturning Circulation: results from the IPSL model |
| VerfasserIn |
M. Kageyama, J. Mignot, D. Swingedouw, C. Marzin, R. Alkama, O. Marti |
| 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. 3 ; Nr. 5, no. 3 (2009-09-30), S.551-570 |
| Datensatznummer |
250002552
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| Publikation (Nr.) |
 copernicus.org/cp-5-551-2009.pdf |
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| Zusammenfassung |
| Paleorecords from distant locations on the globe show rapid and large
amplitude climate variations during the last glacial period. Here we
study the global climatic response to different states of the Atlantic
Meridional Overturning Circulation (AMOC) as a potential explanation
for these climate variations and their possible connections. We
analyse three glacial simulations obtained with an atmosphere-ocean
coupled general circulation model and characterised by different AMOC
strengths (18, 15 and 2 Sv) resulting from successive ~0.1 Sv
freshwater perturbations in the North Atlantic. These AMOC states
suggest the existence of a freshwater threshold for which the AMOC
collapses. A weak (18 to 15 Sv) AMOC decrease results in a North
Atlantic and European cooling. This cooling is not homogeneous, with
even a slight warming over the Norwegian Sea. Convection in this area
is active in both experiments, but surprisingly stronger in the 15 Sv
simulation, which appears to be related to interactions with the
atmospheric circulation and sea-ice cover. Far from the North
Atlantic, the climatic response is not significant. The climate
differences for an AMOC collapse (15 to 2 Sv) are much larger and of
global extent. The timing of the climate response to this AMOC
collapse suggests teleconnection mechanisms. Our analyses focus on the
North Atlantic and surrounding regions, the tropical Atlantic and the
Indian monsoon region. The North Atlantic cooling associated with the
AMOC collapse induces a cyclonic atmospheric circulation anomaly
centred over this region, which modulates the eastward advection of
cold air over the Eurasian continent. This can explain why the cooling
is not as strong over western Europe as over the North Atlantic. In
the Tropics, the southward shift of the Inter-Tropical Convergence
Zone appears to be strongest over the Atlantic and Eastern Pacific and
results from an adjustment of the atmospheric and oceanic heat
transports. Finally, the Indian monsoon weakening appears to be
connected to the North Atlantic cooling via that of the troposphere
over Eurasia. Such an understanding of these teleconnections and their
timing could be useful for paleodata interpretation. |
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