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| Titel |
Assimilation of Antarctic velocity observations provides evidence for uncharted pinning points |
| VerfasserIn |
J. J. Fürst, G. Durand, F. Gillet-Chaulet, N. Merino, L. Tavard, J. Mouginot, N. Gourmelen, O. Gagliardini |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2015-08-04), S.1427-1443 |
| Datensatznummer |
250116826
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| Publikation (Nr.) |
 copernicus.org/tc-9-1427-2015.pdf |
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| Zusammenfassung |
| In ice flow modelling, the use of control methods to assimilate the dynamic
and geometric state of an ice body has become common practice. These methods
have primarily focussed on inverting for one of the two least known
properties in glaciology, namely the basal friction coefficient or the ice
viscosity parameter. Here, we present an approach to infer both properties
simultaneously for the whole of the Antarctic ice sheet. After the
assimilation, the root-mean-square deviation between modelled and observed
surface velocities attains 8.7 m a−1 for the entire domain, with
a slightly higher value of 14.0 m a−1 for the ice shelves. An
exception in terms of the velocity mismatch is the Thwaites Glacier Ice
Shelf, where the RMS value is almost 70 m a−1. The reason is that
the underlying Bedmap2 geometry ignores the presence of an ice rise, which
exerts major control on the dynamics of the eastern part of the ice shelf. On
these grounds, we suggest an approach to account for pinning points not
included in Bedmap2 by locally allowing an optimisation of basal friction
during the inversion. In this way, the velocity mismatch on the ice shelf of
Thwaites Glacier is more than halved. A characteristic velocity mismatch
pattern emerges for unaccounted pinning points close to the marine shelf
front. This pattern is exploited to manually identify seven uncharted features
around Antarctica that exert significant resistance to the shelf flow.
Potential pinning points are detected on Fimbul, West, Shackleton, Nickerson
and Venable ice shelves. As pinning points can provide substantial resistance
to shelf flow, with considerable consequences if they became ungrounded in
the future, the model community is in need of detailed bathymetry there. Our
data assimilation points to some of these dynamically important features not
present in Bedmap2 and implicitly quantifies their relevance. |
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