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| Titel |
Calibration and application of clumped isotopes of G. ruber for high-resolution climate reconstructions of the last 2500 years from the Gulf of Taranto, Mediterranean Sea |
| VerfasserIn |
Anna-Lena Grauel, Thomas W. Schmid, Stefano M. Bernasconi, Gert J. De Lange |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049687
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| Zusammenfassung |
| The aim of this project is to reconstruct climate evolution during the last 2500 years in the
eastern Mediterranean Sea at sub-decadal resolution based on isotope analysis of planktonic
foraminifera. We utilize a newly developed technique for clumped isotope measurements of
small samples (Schmid and Bernasconi, 2010), which allows for the first time to produce
combined high-resolution δ18O and clumped isotope records from sediment cores. The
clumped isotope method provides the opportunity to determine the temperature of the
precipitation of calcite via the abundance of 13C- 18O bonds in carbonate and at the same
time to calculate the δ18O of sea water in which the organism lived via the δ18O of the same
sample.
Here we present δ18O and clumped isotope measurements of G. ruber (white) from a
short sediment core covering the last 500 years and a long sediment core covering the last
2500 years, at 3.5 years resolution. We find that in the last 50 years the obtained
clumped isotope temperatures are in good agreement with measured sea surface
temperatures (SST’s) with an accuracy of ± 2Ë C or better. Thus we show that
this new method is a robust new tool for reconstructing changes in temperature
and δ18O of seawater, and therefore of salinity, on exactly the same sample. We
observed that SST’s did not change significantly over the last 2500 years, but that
changes in salinity in the order of 1-2 PSU are not uncommon, suggesting changes in
circulation and freshwater runoff. Additional analyses on core top samples and
water samples support our calibration of the clumped isotope signatures of G. ruber
(white).
In terms of the climatic evolution our isotopic data and a compilation of regional
historical, geographical and archeological data indicate that during the Roman Classical
Period the conditions were more humid in the Mediterranean and drifted towards drier
conditions during the Medieval Warm Period (MWP). Additional counts of G. ruber
(pink) support the assumption of much drier conditions during the MWP, which
concords with higher δ18O values of G. ruber (white) due to higher salinity. The
results of the short core, covering the LIA, correlate well with global temperature
reconstructions.
This work has been made possible thanks to the support from the European Science
Foundation (ESF) under the EUROCORES Program EuroMARC and from the Swiss SNF. |
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