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| Titel |
Understanding climate variability in Greenland ice cores for the last two centuries: insights from the weather regime approach |
| VerfasserIn |
Pablo Ortega, Didier Swingedouw, Valérie Masson-Delmotte, Camille Risi, Pascal Yiou, Robert Vautard, Kei Yoshimura, Bo Vinther |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081082
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| Zusammenfassung |
| Greenland ice cores offer highly resolved (seasonal to annual) δ18O reconstructions over the
last few centuries to millennia. Previous analyses relate multidecadal variability in these
reconstructions to changes in Arctic temperature, the North Atlantic Oscillation, the Atlantic
Multidecadal Oscillation and also to blocking activity in the North Atlantic. However, the
relative weight of each driver remains unclear. In this study, we analyse the regional imprints
of different large-scale modes of variability as well as external forcings on δ18O
reconstructions from Greenland ice cores. For this purpose, a compilation of 20 different
shallow ice-core reconstructions over Greenland has been considered to provide the best
spatial coverage possible within the instrumental era, all covering the period from 1767 to
1967AD. This guarantees an overlap of about a century with several instrumental indices of
climate variability (NAO, AMO and Southwest Greenland temperatures), large-scale
climate datasets (SSTs and sea-ice cover from HadISST), and also with the second
version of the Twentieth Century atmospheric Reanalysis (20CRv2), which spans
from 1871 to 2008AD. This latter reanalysis is used to assess the impact of daily
atmospheric variability on ice core records, through the calculation of the North
Atlantic weather regimes (using clustering techniques) and the respective changes
in their time of occurrence. In particular, we investigate if the fraction of δ18O
variance explained by the common climate indices can be improved by considering
the weather regimes and by taking into account both the changes in their seasonal
frequency of occurrence and the spatial shifts in their centers of action. Finally,
the link between water isotopes and weather regimes is further explored by using
two isotope simulations with the IsoGSM and LMDZ-iso models, both nudged
to the 20th century reanalysis. This allows to further evaluating the relationship
between isotopes and other climate variables like temperature and precipitation. |
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