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| Titel |
A numerical study of glacier advance over deforming till |
| VerfasserIn |
G. J.-M. C. Leysinger Vieli, G. H. Gudmundsson |
| 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 ; 4, no. 3 ; Nr. 4, no. 3 (2010-09-15), S.359-372 |
| Datensatznummer |
250001769
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| Publikation (Nr.) |
 copernicus.org/tc-4-359-2010.pdf |
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| Zusammenfassung |
| The advance of a glacier over a deforming sediment layer is analysed
numerically. We treat this problem as a contact problem involving
two slowly-deforming viscous bodies. The surface evolution of the
two bodies, and of the contact interface between them, is followed
through time. Using various different non-linear till rheologies, we
show how the mode of advance depends on the relative effective
viscosities of ice and till. Three modes of advances are observed:
(1) overriding, where the glacier advances through ice deformation
only and without deforming the sediment; (2) plug-flow, where the
sediment is strongly deformed, the ice moves forward as a block and
a bulge is built in front of the glacier; and (3) mixed-flow, where
the glacier advances through both ice and sediment deformation. For
the cases of both overriding and mixed-flow, an inverse depth-age
relationship within the ice is obtained. A series of model
experiments show the contrast in effective viscosity between ice and
till to be the single most important model parameter defining the
mode of advance and the resulting thickness distribution of the
till. Our model experiments indicate that the thickness of the
deforming till layer is greatest close to the glacier
front. Measurements of till thickness taken in such locations may
not be representative of deforming till thickness elsewhere. Given
sufficiently large contrast in effective viscosity between ice and
till, a sediment bulge is formed in front of the glacier. During
glacier advance, the bulge quickly reaches a steady state form
strongly resembling single-crested push moraines. Inspection of
particle paths within the sediment bulge, shows that particles
within the till travel at a different speed from the bulge itself,
and the push moraine to advance as a form-conserving non-linear
wave. |
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