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| Titel |
Dating a tropical ice core by time–frequency analysis of ion concentration depth profiles |
| VerfasserIn |
M. Gay, M. De Angelis, J.-L. Lacoume |
| 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 ; 10, no. 5 ; Nr. 10, no. 5 (2014-09-03), S.1659-1672 |
| Datensatznummer |
250117047
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| Publikation (Nr.) |
 copernicus.org/cp-10-1659-2014.pdf |
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| Zusammenfassung |
| Ice core dating is a key parameter for the interpretation of the ice
archives. However, the relationship between ice depth and ice age generally
cannot be easily established and requires the combination of numerous
investigations and/or modelling
efforts. This paper presents a new approach to ice core dating based on
time–frequency analysis of chemical profiles at a site where seasonal
patterns may be significantly distorted by sporadic events of regional
importance, specifically at the summit area of Nevado Illimani
(6350 m a.s.l.), located in the eastern Bolivian Andes
(16°37' S, 67°46' W). We used ion concentration depth
profiles collected along a 100 m deep ice core. The results of Fourier
time–frequency and wavelet transforms were first compared. Both methods were
applied to a nitrate concentration depth profile. The resulting chronologies
were checked by comparison with the multi-proxy year-by-year dating published
by de Angelis et al. (2003) and with volcanic tie points. With this first
experiment, we demonstrated the efficiency of Fourier time–frequency
analysis when tracking the nitrate natural variability. In addition, we were
able to show spectrum aliasing due to under-sampling below 70 m. In this
article, we propose a method of de-aliasing which significantly improves the
core dating in comparison with annual layer manual counting. Fourier
time–frequency analysis was applied to concentration depth profiles of seven
other ions, providing information on the suitability of each of them for the
dating of tropical Andean ice cores. |
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