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| Titel |
The Medieval Climate Anomaly and the Little Ice Age in the eastern Ecuadorian Andes |
| VerfasserIn |
M.-P. Ledru, V. Jomelli, P. Samaniego, M. Vuille, S. Hidalgo, M. Herrera, C. Ceron |
| 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 ; 9, no. 1 ; Nr. 9, no. 1 (2013-02-05), S.307-321 |
| Datensatznummer |
250017439
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| Publikation (Nr.) |
 copernicus.org/cp-9-307-2013.pdf |
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| Zusammenfassung |
| To better characterize the climate variability of the last millennium in the
high Andes, we analyzed the pollen content of a 1150-yr-old sediment core
collected in a bog located at 3800 m a.s.l. in the páramo in the eastern
Cordillera in Ecuador. An upslope convective index based on the ratio
between cloud transported pollen from the Andean forest to the bog (T) and
Poaceae pollen frequencies, related to the edaphic moisture of the
páramo (P), was defined. This index was used to distinguish changes in
the atmospheric moisture from the soil moisture content of the páramo
and their associated patterns of interdecadal El Niño–Southern
Oscillation (ENSO) variability and South American summer monsoon (SASM)
activity. Results show that between 850 and 1250 AD, the Medieval Climate
Anomaly interval was warm and moist with a high transported pollen/Poaceae
pollen (T/P) index linked to high ENSO variability and weak SASM activity.
Between 1250 and 1550 AD, a dry climate prevailed, characterized by an
abrupt decrease in the T/P index and therefore no upslope cloud convection,
related to lower ENSO variability and with significant impact on the
floristic composition of the páramo. During the Little Ice Age, two
phases were observed: first, a wet phase between 1550 and 1750 AD linked to
low ENSO variability in the Pacific and warm south equatorial Atlantic sea
surface temperatures (SSTs) favored the return of a wet páramo, and then
a cold and dry phase between 1750 and 1800 AD associated with low ENSO
variability and weak SASM activity resulted in drying of the páramo. The
current warm period marks the beginning of a climate characterized by high
convective activity – the highest in the last millennium – and weaker SASM
activity modifying the water storage of the páramo. Our results show
that the páramo is progressively losing its capacity for water storage
and that the interdecadal variability of both tropical Pacific and Atlantic
SSTs matter for Andean climate patterns, although many teleconnection
mechanisms are still poorly understood. |
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