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| Titel |
Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf |
| VerfasserIn |
C. P. Borstad, E. Rignot, J. Mouginot, M. P. Schodlok |
| 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 (2013-12-18), S.1931-1947 |
| Datensatznummer |
250085194
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| Publikation (Nr.) |
 copernicus.org/tc-7-1931-2013.pdf |
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| Zusammenfassung |
| Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating
ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice
into the ocean, and the presently observed thinning of ice shelves is believed to be reducing
their buttressing capacity and contributing to the acceleration and thinning of the grounded ice
sheet. However, relatively little attention has been paid to the role that fractures play in the
ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new
framework for quantifying the role that fractures play in the creep deformation and buttressing
capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new
analytical relation for the creep of an ice shelf that accounts for the softening influence of
fractures on longitudinal deformation using a state damage variable. We use this new analytical
relation, combined with a temperature calculation for the ice, to partition an inverse method
solution for ice shelf rigidity into independent solutions for softening damage and stabilizing
backstress. Using this new approach, field and remote sensing data can be utilized to monitor the
structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding
line, and thus their indirect contribution to ice sheet mass balance and global sea level. We
apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data,
finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding
line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice
in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in
this area could diminish the backstress transmitted upstream. We model the consequences for the
ice shelf if it loses contact with this small ice rise, finding that flow speeds would increase by
25% or more over an area the size of the former Larsen B ice shelf. Such a perturbation could
potentially destabilize the northern part of Larsen C along pre-existing lines of weakness,
highlighting the importance of the feedback between buttressing and fracturing in an ice shelf. |
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