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| Titel |
Prediction of alpine glacier sliding instabilities: a new hope |
| VerfasserIn |
J. Faillettaz, M. Funk, D. Sornette |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065057
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| Zusammenfassung |
| Mechanical and sliding instabilities are the two processes which may lead to breaking-off
events of large ice masses. Mechanical instabilities mainly affect unbalanced cold hanging
glaciers. In the latter case, a prediction could be achieved based on data for surface velocities
and seismic activity. The case of sliding instabilities is more problematic. This phenomenon
occurs on temperate glacier tongues. Such instabilities are strongly affected by the subglacial
hydrology: meltwater may cause (i) a lubrication of the bed, and (ii) a decrease
in the effective pressure and consequently a decrease in basal friction. Available
data from Allalingletscher (Valais) indicate that the glacier tongue experienced an
active phase for 2-3 weeks with enhanced basal motion in late summer in most
years.
In order to scrutinize in more detail the processes governing the sliding instabilities, a
numerical model developed to investigate gravitational instabilities in heterogeneous media
was applied to Allalingletscher. This model made it possible to account for various geometric
configurations, interaction between sliding and tension cracking and water flow at the
bedrock.
We could show that both a critical geometrical configuration of the glacier tongue and the
existence of a distributed drainage network were the main causes of this catastrophic
break-off. Moreover, the analysis of the modeling results diagnosed the phenomenon
of recoupling of the glacier to its bed as a potential new precursory sign of the
final break-off. This model casts a gleam of hope for a better understanding of
the ultimate rupture process which results from such glacier sliding instabilities. |
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