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| Titel |
Influence of anisotropy on velocity and age distribution at Scharffenbergbotnen blue ice area |
| VerfasserIn |
T. Zwinger, M. Schäfer, C. Martin, J. C. Moore |
| 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. 2 ; Nr. 8, no. 2 (2014-04-10), S.607-621 |
| Datensatznummer |
250116089
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| Publikation (Nr.) |
 copernicus.org/tc-8-607-2014.pdf |
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| Zusammenfassung |
| We use a full-Stokes thermo-mechanically coupled ice-flow model to study the
dynamics of the glacier inside Scharffenbergbotnen valley, Dronning Maud
Land, Antarctica. The domain encompasses a high accumulation rate region and,
downstream, a sublimation-dominated bare ice ablation area. The ablation ice
area is notable for having old ice at its surface since the vertical velocity
is upwards, and horizontal velocities are almost stagnant there. We compare
the model simulation with field observations of velocities and the age
distribution of the surface ice. No satisfactory match using an isotropic
flow law could be found because of too high vertical velocities and much too
high horizontal ones in simulations despite varying enhancement factor,
geothermal heat flux and surface temperatures over large ranges. However, the
existence of a pronounced ice fabric may explain the observed present-day
surface velocity and mass balance distribution in the inner
Scharffenbergbotnen blue ice area. Near absence of data on the temporal
evolution of Scharffenbergbotnen since the Late Glacial Maximum necessitates
exploration of the impact of anisotropy using prescribed ice fabrics:
isotropic, single maximum, and linear variation with depth, in both
two-dimensional and three-dimensional flow models. The realistic velocity
field simulated with a noncollinear orthotropic flow law, however, produced
surface ages in significant disagreement with the few reliable age
measurements and suggests that the age field is not in a steady state and
that the present distribution is a result of a flow reorganization at about
15 000 yr BP. In order to fully understand the surface age
distribution, a transient simulation starting from the Late Glacial Maximum
including the correct initial conditions for geometry, age, fabric and
temperature distribution would be needed. This is the first time that the
importance of anisotropy has been demonstrated in the ice dynamics of a blue
ice area and demonstrates the need to understand ice flow in order to better
interpret archives of ancient ice for paleoclimate research. |
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