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| Titel |
Fabric along the NEEM ice core, Greenland, and its comparison with GRIP and NGRIP ice cores |
| VerfasserIn |
M. Montagnat, N. Azuma, D. Dahl-Jensen, J. Eichler, S. Fujita, F. Gillet-Chaulet, S. Kipfstuhl, D. Samyn, A. Svensson, I. Weikusat |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2014-07-01), S.1129-1138 |
| Datensatznummer |
250116237
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| Publikation (Nr.) |
 copernicus.org/tc-8-1129-2014.pdf |
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| Zusammenfassung |
| Fabric (distribution of crystallographic orientations) along the full NEEM
ice core, Greenland was measured in the field by an automatic ice texture
analyzer every 10 m, from 33 m down to 2461 m depth. The fabric evolves
from a slightly anisotropic fabric at the top, toward a strong single maximum
at about 2300 m, which is typical of a deformation pattern mostly driven by
uniaxial compression and simple shearing. A sharp increase in the fabric
strengthening rate is observed at the Holocene to Wisconsin (HW) climatic
transition. From a simple model we estimate that this depth is located at a
transition from a state dominated by vertical compression to a state
dominated by vertical shear. Comparisons are made to two others ice cores
drilled along the same ridge; the GRIP ice core, drilled at the summit of the
ice sheet, and the NGRIP ice core, drilled 325 km to the NNW of the summit
along the ridge, and 365 km upstream from NEEM. This comparison tends to
demonstrate that the ice viscosity change with the HW climatic transition
must be associated with the shear-dominated state to induce the abrupt fabric
strengthening observed at NEEM. This comparison therefore reflects the
increasing role of shear deformation on the coring site when moving NW along
the ridge from GRIP to NGRIP and NEEM. The difference in fabric profiles
between NEEM and NGRIP also evidences a stronger lateral extension associated
with a sharper ridge at NGRIP. Further along the core, centimeter scale
abrupt texture (fabric and microstructure) variations are observed in the
bottom part of the core. Their positions are in good agreement with the
observed folding layers in Dahl-Jensen et al. (2013). |
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