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| Titel |
Role of CO2 and Southern Ocean winds in glacial abrupt climate change |
| VerfasserIn |
R. Banderas, J. Álvarez-Solas, M. Montoya |
| 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 ; 8, no. 3 ; Nr. 8, no. 3 (2012-06-01), S.1011-1021 |
| Datensatznummer |
250005591
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| Publikation (Nr.) |
 copernicus.org/cp-8-1011-2012.pdf |
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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, the final cause of these reorganisations 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
initial abrupt surface air temperature (SAT) increase over the North Atlantic
by 4 K in less than a decade, followed by a more gradual warming greater
than 10 K on centennial timescales, is simulated in response to increasing
atmospheric CO2 levels and/or enhancing southern westerlies. The
simulated peak 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 a northward
retreat of the sea-ice front in response to higher temperatures. This leads
to enhanced heat loss to the atmosphere as well as reduced freshwater fluxes
via reduced sea-ice import into the region. 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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