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| Titel |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
| VerfasserIn |
M. Jay-Allemand, F. Gillet-Chaulet, O. Gagliardini, M. Nodet |
| 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 ; 5, no. 3 ; Nr. 5, no. 3 (2011-08-23), S.659-672 |
| Datensatznummer |
250002596
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| Publikation (Nr.) |
 copernicus.org/tc-5-659-2011.pdf |
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| Zusammenfassung |
| Variegated Glacier (Alaska) is known to surge periodically after a
sufficient amount of cumulative mass balance is reached, but this observation
is difficult to link with changes in the basal conditions. Here, using a
10-yr dataset, consisting of surface topography and surface velocity
observations along a flow line for 25 dates, we have reconstructed the
evolution of the basal conditions prior to and during the 1982–1983 surge. The
model solves the full-Stokes problem along the central flow line using the
finite element method. For the 25 dates of the dataset, the basal friction
parameter distribution is inferred using the inverse method proposed by
Arthern and Gudmundsson (2010). This method is here slightly modified by incorporating a
regularisation term in the cost function to avoid short wavelength changes
in the friction parameter. Our results indicate that dramatic changes in the
basal conditions occurred between 1973 to 1983. Prior to the surge,
periodic changes can be observed between winter and summer, with a regular
increase of the sliding from 1973 to 1982. During the surge, the basal
friction decreased dramatically and an area of very low friction moved from
the upper part of the glacier to its terminus. Using a more complex friction
law, these changes in basal sliding are then interpreted in terms of basal
water pressure. Our results support that dramatic changes took place in the
subglacial drainage system of Variegated Glacier, moving from a relatively
efficient drainage system prior to the surge to an inefficient one during the
surge. By reconstructing the water pressure evolution at the base of the
glacier it is possible to propose a scenario for the hydrological
history leading to the occurrence of a surge. |
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