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| Titel |
Estimation and calibration of the water isotope differential diffusion length in ice core records |
| VerfasserIn |
G. Wel, H. Fischer, H. Oerter, H. Meyer, H. A. J. Meijer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 4 ; Nr. 9, no. 4 (2015-08-20), S.1601-1616 |
| Datensatznummer |
250116836
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| Publikation (Nr.) |
 copernicus.org/tc-9-1601-2015.pdf |
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| Zusammenfassung |
| Palaeoclimatic information can be retrieved from the diffusion of the
stable water isotope signal during firnification of snow. The
diffusion length, a measure for the amount of diffusion a layer has
experienced, depends on the firn temperature and the accumulation
rate. We show that the estimation of the diffusion length using power
spectral densities (PSDs) of the record of a single isotope species can
be biased by uncertainties in spectral properties of the isotope signal prior
to diffusion. By using a second water isotope and calculating the
difference in diffusion lengths between the two isotopes, this problem
is circumvented. We study the PSD method applied to two isotopes in
detail and additionally present a new forward diffusion method for
retrieving the differential diffusion length based on the Pearson
correlation between the two isotope signals. The two methods are
discussed and extensively tested on synthetic data which are generated
in a Monte Carlo manner. We show that calibration of the PSD method
with this synthetic data is necessary to be able to objectively
determine the differential diffusion length. The correlation-based
method proves to be a good alternative for the PSD method as it yields
precision equal to or somewhat higher than the PSD method. The use of
synthetic data also allows us to estimate the accuracy and precision
of the two methods and to choose the best sampling strategy to obtain
past temperatures with the required precision. In addition to
application to synthetic data the two methods are tested on
stable-isotope records from the EPICA (European Project for
Ice Coring in Antarctica) ice core drilled in Dronning Maud Land,
Antarctica, showing that reliable firn temperatures can be
reconstructed with a typical uncertainty of 1.5 and
2 °C for the Holocene period and 2 and
2.5 °C for the last glacial period for the correlation
and PSD method, respectively. |
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