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| Titel |
Using simulations of the last millennium to understand climate variability seen in palaeo-observations: similar variation of Iceland–Scotland overflow strength and Atlantic Multidecadal Oscillation |
| VerfasserIn |
K. Lohmann, J. Mignot, H. R. Langehaug, J. H. Jungclaus, D. Matei, O. H. Otterå, Y. Q. Gao, T. L. Mjell, U. S. Ninnemann, H. F. Kleiven |
| 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 ; 11, no. 2 ; Nr. 11, no. 2 (2015-02-10), S.203-216 |
| Datensatznummer |
250117164
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| Publikation (Nr.) |
 copernicus.org/cp-11-203-2015.pdf |
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| Zusammenfassung |
| A recent palaeo-reconstruction of the strength of the Iceland–Scotland
overflow during the last 600 years suggests that its low-frequency
variability exhibits strong similarity with palaeo-reconstructions of the
Atlantic Multidecadal Oscillation (AMO). The underlying mechanism of the
similar variation remains unclear, however, based on palaeo-reconstructions
alone. In this study we use simulations of the last millennium driven by
external forcing reconstructions with three coupled climate models in order
to investigate possible mechanisms underlying the similar variation of
Iceland–Scotland overflow strength and AMO index. Similar variation of the
two time series is also largely found in the model simulations. Our analysis
indicates that the basin-wide AMO index in the externally forced simulations
is dominated by the low-latitude sea surface temperature (SST) variability and is not predominantly
driven by variations in the strength of the Atlantic meridional overturning
circulation (MOC). This result suggests that a large-scale link through the
strength of the MOC is not sufficient to explain the (simulated) similar
variation of Iceland–Scotland overflow strength and AMO index. Rather, a
more local link through the influence of the Nordic seas surface state and
density structure, which are positively correlated with the AMO index, on
the pressure gradient across the Iceland–Scotland ridge is responsible for
the (simulated) similar variation. In the model simulation showing a weaker
correlation between the Iceland–Scotland overflow strength and the AMO
index, the wind stress in the Nordic seas also influences the overflow
strength. Our study demonstrates that palaeo-climate simulations provide a
useful tool to understand mechanisms and large-scale connections associated
with the relatively sparse palaeo-observations. |
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