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| Titel |
The variability of the North Atlantic Oscillation throughout the Holocene |
| VerfasserIn |
Jasper Wassenburg, Stephan Dietrich, Jan Fietzke, Jens Fohlmeister, Wei Wei, Klaus Peter Jochum, Denis Scholz, Detlev Richter, Abdellah Sabaoui, Gerrit Lohmann, Meinrat Andreae, Adrian Immenhauser |
| 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 |
250072328
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| Zusammenfassung |
| The North Atlantic Oscillation (NAO) has a major impact on Northern Hemisphere winter
climate. Trouet et al. (2009) reconstructed the NAO for the last millennium based on a
Moroccan tree ring PDSI (Palmer Drought Severity Index) reconstruction and a Scottish
speleothem record. More recently, Olsen et al. (2012) extended the NAO record back to 5.2
ka BP based on a lake record from West Greenland. It is, however, well known that the NAO
exhibits non-stationary behavior and the use of a single location for a NAO reconstruction
may not capture the complete variability. In addition, the imprint of the NAO on
European rainfall patterns in the Early and Mid Holocene on (multi-) centennial
timescales is still largely unknown. This is related to difficulties in establishing
robust correlations between different proxy records and the fact that proxies may
not only reflect winter conditions (i.e., the season when the NAO has the largest
influence).
Here we present a precisely dated, high resolution speleothem δ18O record from NW
Morocco covering the complete Early and Mid Holocene. Carbon and oxygen isotopes were
measured at a resolution of 15 years. A multi-proxy approach provides solid evidence that
speleothem δ18O values reflect changes in past rainfall intensity. The Moroccan record shows
a significant correlation with a speleothem rainfall record from western Germany, which
covers the entire Holocene (Fohlmeister et al., 2012). The combination with the extended
speleothem record from Scotland, speleothem records from north Italy and the NAO
reconstruction from West Greenland (Olsen et al., 2012) allows us to study the variability of
the NAO during the entire Holocene. The relation between West German and Northwest
Moroccan rainfall has not been stationary, which is evident from the changing signs of
correlation. The Early Holocene is characterized by a positive correlation, which
changes between 9 and 8 ka BP into a negative correlation. Simulations with the
state-of-the-art earth system model COSMOS for the Early and Mid Holocene
(Wei and Lohmann, 2012) indicate that this change in the NAO teleconnection is
related to large-scale circulation changes due to the ice sheet configuration and
deglaciation.
References:
Fohlmeister, J., Schroder-Ritzrau, A., Scholz, D., Riechelmann, D.F.C., Mudelsee, M.,
Wackerbarth, A., Gerdes, A., Riechelmann, S., Immenhauser, A., Richter, D.K., Mangini, A.,
2012. Bunker Cave stalagmites: an archive for central European Holocene climate variability.
Climate of the Past 8, 1751-1764.
Olsen, J., Anderson, J.N., Knudsen, M.F., 2012. Variability of the North Atlantic
Oscillation over the past 5,200 years. Nature Geoscience DOI:10.1038/NGEO1589,
Trouet, V., Esper, J., Graham, N.E., Baker, A., Scourse, J.D., Frank, D.C., 2009.
Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate
Anomaly. Science 324, 78-80.
Wei, W., Lohmann, G., 2012. Simulated Atlantic Multidecadal Oscillation during the
Holocene. Journal of Climate 6989-7002. |
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