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| Titel |
Changing basal conditions during the speed-up of Jakobshavn Isbræ, Greenland |
| VerfasserIn |
M. Habermann, M. Truffer, D. Maxwell |
| 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 ; 7, no. 6 ; Nr. 7, no. 6 (2013-11-07), S.1679-1692 |
| Datensatznummer |
250085176
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| Publikation (Nr.) |
 copernicus.org/tc-7-1679-2013.pdf |
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| Zusammenfassung |
| Ice-sheet outlet glaciers can undergo dynamic changes such as the
rapid speed-up of Jakobshavn Isbræ following the disintegration
of its floating ice tongue. These changes are associated with
stress changes on the boundary of the ice mass. We invert for basal
conditions from surface velocity data throughout a well-observed
period of rapid change and evaluate parameterizations
currently used in ice-sheet models. A Tikhonov inverse method with a shallow-shelf approximation
forward model is used for diagnostic inversions for the years 1985,
2000, 2005, 2006 and 2008. Our ice-softness, model norm, and
regularization parameter choices are justified using the data-model
misfit metric and the L curve method. The sensitivity of the
inversion results to these parameter choices is explored. We find
a lowering of effective basal yield stress in the first 7 km upstream from the
2008 grounding line and no significant changes higher upstream. The
temporal evolution in the fast flow area is in broad agreement with
a Mohr–Coulomb parameterization of basal shear stress, but with
a till friction angle much lower than has been measured for till
samples. The lowering of effective basal yield stress is significant within
the uncertainties of the inversion, but it cannot be ruled out that
there are other significant contributors to the acceleration of the
glacier. |
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