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| Titel |
600 yr High-Resolution Climate Reconstruction of the Atlantic Multidecadal Oscillation deduced from a Puerto Rican Speleothem |
| VerfasserIn |
Rolf Vieten, Amos Winter, Denis Scholz, David Black, Christoph Spoetl, Sophie Winterhalder, Gabriella Koltai, Andrea Schroeder-Ritzrau, Stefan Terzer, Davide Zanchettin, Augusto Mangini |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121475
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| Publikation (Nr.) |
 EGU/EGU2016-216.pdf |
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| Zusammenfassung |
| A multi-proxy speleothem study tracks the regional hydrological variability in Puerto Rico
and highlights its close relation to the Atlantic Multidecadal Oscillation (AMO) describing
low-frequency sea-surface temperature (SST) variability in the North Atlantic ocean. Our
proxy record extends instrumental observations 600 years into the past, and reveals the
range of natural hydrologic variability for the region. A detailed interpretation and
understanding of the speleothem climate record is achieved by the combination of
multi-proxy measurements, thin section petrography, XRD analysis and cave monitoring
results.
The speleothem was collected in Cueva Larga, a one mile-long cave system that has been
monitored since 2012. MC-ICPMS 230Th/U-dating reveals that the speleothem grew
constantly over the last 600 years. Trace element ratios (Sr/Ca and Mg/Ca) as well as stable
isotope ratios (δ18O and δ13C) elucidate significant changes in atmospheric precipitation at
the site.
Monthly cave monitoring results demonstrate that the epikarst system responds to
multi-annual changes in seepage water recharge. The drip water isotope and trace element
composition lack short term or seasonal variability. This hydrological system creates
favorable conditions to deduce decadal climate variability from Cueva Larga’s climate record.
The speleothem time series mimics the most recent AMO reconstruction over the last 200
years (Svendsen et al., 2014) with a time lag of 10-20 years. The lag seems to results from
slow atmospheric signal transmission through the epikarst but the effect of dating
uncertainties cannot be ruled out. Warm SSTs in the North Atlantic are related to drier
conditions in Puerto Rico. During times of decreased rainfall a relative increase in
prior calcite precipitation seems to be the main process causing increased Mg/Ca
trace element ratios. High trace element ratios correlate to higher δ13C values.
The increase in both proxies indicates a shift towards time periods of decreased
rainfall.
Before 1800 there were two intervals of increased Mg/Ca and δ13C values (dryer
conditions) lasting several decades in our speleothem record centered around 1680
CE and 1470 CE. The elevated ratios indicate that drier conditions than present
may have occurred in the region during periods of warm Atlantic surface waters. |
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