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| Titel |
Variations of the Atlantic meridional overturning circulation in control and transient simulations of the last millennium |
| VerfasserIn |
D. Hofer, C. C. Raible, T. F. Stocker |
| 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 ; 7, no. 1 ; Nr. 7, no. 1 (2011-02-28), S.133-150 |
| Datensatznummer |
250004402
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| Publikation (Nr.) |
 copernicus.org/cp-7-133-2011.pdf |
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| Zusammenfassung |
| The variability of the Atlantic meridional overturing circulation (AMOC)
strength is investigated in control experiments and in transient simulations
of up to the last millennium using the low-resolution Community Climate
System Model version 3. In the transient simulations the AMOC exhibits
enhanced low-frequency variability that is mainly caused by infrequent
transitions between two semi-stable circulation states which amount to a 10
percent change of the maximum overturning. One transition is also found in a
control experiment, but the time-varying external forcing significantly
increases the probability of the occurrence of such events though not having
a direct, linear impact on the AMOC. The transition from a high to a low AMOC
state starts with a reduction of the convection in the Labrador and Irminger
Seas and goes along with a changed barotropic circulation of both gyres in
the North Atlantic and a gradual strengthening of the convection in the
Greenland-Iceland-Norwegian (GIN) Seas. In contrast, the transition from a
weak to a strong overturning is induced by decreased mixing in the GIN Seas.
As a consequence of the transition, regional sea surface temperature (SST)
anomalies are found in the midlatitude North Atlantic and in the convection
regions with an amplitude of up to 3 K. The atmospheric response to the SST
forcing associated with the transition indicates a significant impact on the
Scandinavian surface air temperature (SAT) in the order of 1 K. Thus, the
changes of the ocean circulation make a major contribution to the
Scandinavian SAT variability in the last millennium. |
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