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| Titel |
Glacial abrupt climate change as a result of internal oscillations |
| VerfasserIn |
R. Banderas, J. Álvarez-Solas, M. Montoya |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060849
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| Zusammenfassung |
| The study of Greenland ice cores revealed two decades ago the abrupt character of glacial
millennial-scale climate variability. Several triggering mechanisms have been proposed
and confronted against growing proxy-data evidence. Although the implication of
North Atlantic deep water (NADW) formation reorganisations in glacial abrupt
climate change seems robust nowadays, their final cause remains unclear. Here, the
role of CO2 and Southern Ocean winds is investigated using a coupled model of
intermediate complexity in an experimental setup designed such that the climate
system resides close to a threshold found in previous studies. An abrupt surface air
temperature (SAT) increase over the North Atlantic is simulated in response to increasing
atmospheric CO2 levels and/or enhancing southern westerlies. The simulated abrupt
warming shows a similar pattern and amplitude over Greenland as registered in
ice-core records of Dansgaard-Oeschger (D/O) events. This is accompanied by a
strong Atlantic meridional overturning circulation (AMOC) intensification. The
AMOC strengthening is found to be caused by a northward shift of NADW formation
sites into the Nordic Seas as a result of an increase in sea surface salinity in the
Northeastern Atlantic. The latter is caused by a northward retreat of the sea-ice front in
response to higher temperatures. In this way, a new mechanism that is consistent
with proxy data is identified by which abrupt climate change can be promoted. |
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