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| Titel |
Coherency of European speleothem δ18O records linked to North Atlantic ocean circulation |
| VerfasserIn |
Michael Deininger, Frank McDermott |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125449
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| Publikation (Nr.) |
 EGU/EGU2016-5031.pdf |
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| Zusammenfassung |
| Speleothem δ18O records can provide valuable information about past continental
environmental and climatic conditions. In recent decades a European speleothem network has
been assembled that allows us to reconstruct past climate variability in both space and time.
In particular climate variability during the Holocene was investigated by these studies. The
Holocene is thus an ideal period to apply sophisticated statistical methods to derive
spatio-temporal pattern of common climate variability in the European speleothem
record.
Here we evaluate a compilation of 10 speleothem δ18O records covering the last 4.5 ka for
their shared variability. The selected speleothem δ18O records must satisfy certain
quality criteria to be included: (i) a robust age model; (ii) a temporal intra-sampling
resolution of smaller than 30 years; and (iii) the record should be published. A
Monte Carlo based Principal Component Analysis (MC-PCA) that accounts for
uncertainties in individual speleothem age models and for the different and varying
temporal resolutions of each speleothem δ18O record was used for this purpose. Our
MC-PCA approach allows not only the identification of temporally coherent changes in
δ18O records, but it also facilitates their depiction and evaluation spatially. The
compiled speleothem δ18O records span almost the entire European continent (with the
exception of the circum-Mediterranean region) ranging from the western Margin
of the European continent (stalagmite CC-3, Ireland) to Northern Turkey (SO-1)
and from Northern Italy (CC-26) to Norway (FM-3). For the MC-PCA analysis,
the 4.5 ka period was sub-divided into eight 1 ka long time windows that overlap
the subsequent time window by 500 years to allow a comparison of the temporal
evolution of the common signal. In this study we only interpreted the 1st principal
component (PC) that depict the spatio-temporal pattern with the highest explained
variability of all speleothem δ18O records. Our MC-PCA results demonstrate that a
common signal (expressed by the 1st PCs) is shared by the investigated speleothem
δ18O records for each individual time window and that the 1st PCs agree in the
overlapping periods. This allowed us to construct a common speleothem record (CSR) for
the last 4.5 ka. The CSR shows a strong millennial cyclicity in the investigated
period.
We demonstrate that the large-scale changes in the European CSR, reflected by its millennial
cyclicity, are in phase with the well-known Bond cycles during the last 4.5 ka that reflect
changes of drift ice in the North Atlantic (Bond et al., 2001). Evidence for this link
was also shown by Mangini et al. (2007) using a stalagmite from the Central Alps.
Furthermore, the CSR shows a very good agreement with a recent, independently dated
reconstruction for the strength of the sub-polar gyre (Thornalley et al., 2009) and we
argue that these changes during the last 4.5 ka are likely caused by the variability of
the atmospheric circulation affecting the interplay between the subpolar gyre and
the subtropical gyre in the North Atlantic, as well as European speleothem δ18O
records.
BOND, G., KROMER, B., BEER, J., MUSCHELER, R., EVANS, M. N., SHOWERS, W.,
HOFFMANN, S., LOTTI-BOND, R., HAJDAS, I. & BONANI, G. 2001. Persistent solar
influence on North Atlantic climate during the Holocene. Science, 294, 2130-6.
MANGINI, A., VERDES, P., SPÖTL, C., SCHOLZ, D., VOLLWEILER, N. &
KROMER, B. 2007. Persistent influence of the North Atlantic hydrography on central
European winter temperature during the last 9000 years. Geophysical Research Letters,
34.
THORNALLEY, D. J. R., ELDERFIELD, H. & MCCAVE, I. N. 2009. Holocene oscillations
in temperature and salinity of the surface subpolar North Atlantic. Nature, 457,
711-714. |
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