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| Titel |
Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt |
| VerfasserIn |
T. Dunse, T. Schellenberger, J. O. Hagen, A. Kääb, T. V. Schuler, C. H. Reijmer |
| 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. 1 ; Nr. 9, no. 1 (2015-02-05), S.197-215 |
| Datensatznummer |
250116745
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| Publikation (Nr.) |
 copernicus.org/tc-9-197-2015.pdf |
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| Zusammenfassung |
| Mass loss from glaciers and ice sheets currently accounts for
two-thirds of the observed global sea-level rise and has accelerated
since the 1990s, coincident with strong atmospheric warming in the
polar regions. Here we present continuous GPS measurements and
satellite synthetic-aperture-radar-based velocity maps from Basin-3,
the largest drainage basin of the Austfonna ice cap, Svalbard. Our
observations demonstrate strong links between
surface-melt and multiannual ice-flow acceleration. We identify
a hydro-thermodynamic feedback that successively mobilizes stagnant
ice regions, initially frozen to their bed, thereby facilitating
fast basal motion over an expanding area. By autumn 2012, successive
destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg
discharge of 4.2±1.6 Gt a−1 over the period April
2012 to May 2013 triples the calving loss from the entire ice
cap. With the seawater displacement by the terminus advance accounted for, the related
sea-level rise contribution amounts to 7.2±2.6 Gt a−1. This rate
matches the annual ice-mass loss from the entire Svalbard
archipelago over the period 2003–2008, highlighting the importance of dynamic
mass loss for glacier mass balance and sea-level rise. The active role of
surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities.
Given sustained climatic warming and rising significance of surface melt,
we propose a potential impact of the hydro-thermodynamic feedback on the
future stability of ice-sheet regions,
namely at the presence of a cold-based marginal ice plug that restricts fast
drainage of inland ice. The possibility of large-scale dynamic instabilities
such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise. |
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