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| Titel |
Medieval climate anomaly and little ice age as recorded in speleothem and tree-ring data from the Middle Atlas in Morocco |
| VerfasserIn |
J. A. Wassenburg, A. Immenhauser, D. K. Richter, J. Fietzke, D. Scholz, K. P. Jochum, D. F. C. Riechelmann, L. Schneider, J. Esper |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065410
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| Zusammenfassung |
| Progress has recently been made in assessing the spatial extend and timing of the
Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) on hemispheric and
global scales (Graham et al. 2011). Uncertainties still exist, however, since the
transition from the MCA into the LIA seems to be diachronous, and in many cases,
reconstructions are based on single climate archives (e.g., speleothems, tree-rings, or pollen
data). In Morocco, cedar trees from the Middle and High Atlas have been used to
reconstruct the Palmer Drought Severity Index (PDSI) back to 1049 AD (Esper
et al., 2007), a metric integrating the evaporation-precipitation balance and soil
properties. According to Graham et al. (2011), the MCA/LIA transition recorded
in Moroccan tree rings occurred rather late (around 1400 AD) in comparison to
the reconstructed winter temperature in the European Alps (e.g., Mangini et al.,
2005), which show substantial changes about 50 years earlier. Here we compare
precisely dated speleothem δ13C and trace element records from the Middle Atlas
with an updated version of the tree-ring based PDSI reconstruction from Esper et
al. (2007). Both stalagmite δ13C and strontium records support the prevalence of
exceptionally dry conditions during the MCA and relatively wet conditions during the LIA.
These changes have formerly been suggested to be related to persistent positive
and negative phases of the North Atlantic Oscillation (Trouet et al., 2009). The
speleothem based reconstruction extends back to 700 AD and, thus, provides insight on
the precise timing of the driest period during the MCA in the Moroccan Middle
Atlas.
References:
Esper, J., Frank, D., Buntgen, U., Verstege, A. and Luterbacher, J. 2007. Long-term
drought severity variations in Morocco. Geophysical Research Letters, 34, doi:
10.1029/2007GL030844.
Graham, N.E., Ammann, C.M., Fleitmann, D., Cobb, K.M. and Luterbacher, J. 2011.
Support for global climate reorganization during the "Medieval Climate Anomaly". Climate
Dynamics, 37: 1217-1245.
Mangini, A., Spotl, C., and Verdes, P., 2005. Reconstruction of temperature in the Central
Alps during the past 2000 yr from a delta O-18 stalagmite record. Earth Planet. Sci. Lett.
235, 741-751.
Trouet, V., Esper, J., Graham, N. E., Baker, A., Scourse, J. D., and Frank, D. C., 2009.
Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate
Anomaly. Science 324, 78-80. |
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