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| Titel |
Past surface temperatures at the NorthGRIP drill site from the difference in firn diffusion of water isotopes |
| VerfasserIn |
S. B. Simonsen, S. J. Johnsen, T. J. Popp, B. M. Vinther, V. Gkinis, H. C. Steen-Larsen |
| 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 ; 7, no. 4 ; Nr. 7, no. 4 (2011-12-02), S.1327-1335 |
| Datensatznummer |
250004690
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| Publikation (Nr.) |
 copernicus.org/cp-7-1327-2011.pdf |
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| Zusammenfassung |
A new ice core paleothermometer is introduced based on the temperature
dependent diffusion of the stable water isotopes in the firn. A new parameter
called differential diffusion length is defined as the difference between the
diffusion length of the two stable water isotopologues 2H1H16O and
1H218O. A model treatment of the diffusion process of the firn and
the ice is presented along with a method of retrieving the diffusion signal
from the ice core record of water isotopes using spectral methods. The model
shows how the diffusion process is highly dependent on the inter-annual
variations in the surface temperatures. It results in a diffusion length
longer than if the firn was isothermal. The longer diffusion length can be
explained by the strong nonlinearly behaviour of the saturation pressure over
ice in the range of the surface temperature fluctuations.
The method has been tested on δ18O and δD measurements,
spanning the transition from the last glacial to the holocene, from the
NorthGRIP ice core. The surface temperature reconstruction based on the
differential diffusion resembles other temperature reconstructions for the
NorthGRIP ice core. However, the Allerød warming is seen to be
significantly warmer than observed in other ice core based temperature
reconstructions. The mechanisms behind this behaviour are not fully
understood.
The method shows the need of an expansion of high resolution stable water
isotope datasets from ice cores. However, the new ice core paleothermometer
presented here will give valuable insight into past climate, through the
physical process of isotope diffusion in the firn column of ice sheets. |
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