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| Titel |
A review of the South American monsoon history as recorded in stable isotopic proxies over the past two millennia |
| VerfasserIn |
M. Vuille, S. J. Burns, B. L. Taylor, F. W. Cruz, B. W. Bird, M. B. Abbott, L. C. Kanner, H. Cheng, V. F. Novello |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2012-08-23), S.1309-1321 |
| Datensatznummer |
250005714
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| Publikation (Nr.) |
 copernicus.org/cp-8-1309-2012.pdf |
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| Zusammenfassung |
We review the history of the South American summer monsoon (SASM) over the
past ~2000 yr based on high-resolution stable isotope proxies from
speleothems, ice cores and lake sediments. Our review is complemented by an
analysis of an isotope-enabled atmospheric general circulation model (GCM)
for the past 130 yr. Proxy records from the monsoon belt in the tropical
Andes and SE Brazil show a very coherent behavior over the past 2 millennia
with significant decadal to multidecadal variability superimposed on large
excursions during three key periods: the Medieval Climate Anomaly (MCA), the
Little Ice Age (LIA) and the current warm period (CWP). We interpret these
three periods as times when the SASM's mean state was significantly weakened
(MCA and CWP) and strengthened (LIA), respectively. During the LIA each of
the proxy archives considered contains the most negative δ18O
values recorded during the entire record length. On the other hand, the
monsoon strength is currently rather weak in a 2000-yr historical
perspective, rivaled only by the low intensity during the MCA. Our climatic
interpretation of these archives is consistent with our isotope-based GCM
analysis, which suggests that these sites are sensitive recorders of
large-scale monsoon variations.
We hypothesize that these centennial-scale climate anomalies were at least
partially driven by temperature changes in the Northern Hemisphere and in
particular over the North Atlantic, leading to a latitudinal displacement of
the ITCZ and a change in monsoon intensity (amount of rainfall upstream over
the Amazon Basin). This interpretation is supported by several independent
records from different proxy archives and modeling studies. Although ENSO is
the main forcing for δ18O variability over tropical South
America on interannual time scales, our results suggest that its influence
may be significantly modulated by North Atlantic climate variability on
longer time scales.
Finally, our analyses indicate that isotopic proxies, because of their
ability to integrate climatic information on large spatial scales, could
complement more traditional proxies such as tree rings or documentary
evidence. Future climate reconstruction efforts could potentially benefit
from including isotopic proxies as large-scale predictors in order to better
constrain past changes in the atmospheric circulation. |
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