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| Titel |
Cornice dynamics and meteorological control at Gruvefjellet, Central Svalbard |
| VerfasserIn |
S. Vogel, M. Eckerstorfer, H. H. Christiansen |
| 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 ; 6, no. 1 ; Nr. 6, no. 1 (2012-02-08), S.157-171 |
| Datensatznummer |
250003382
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| Publikation (Nr.) |
 copernicus.org/tc-6-157-2012.pdf |
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| Zusammenfassung |
| Cornice fall avalanches endanger life and infrastructure in Nybyen, a part
of Svalbard's main settlement Longyearbyen, located at 78° N in the High
Arctic. Thus, cornice dynamics – accretion, cracking and eventual failure –
and their controlling meteorological factors were studied along the
ridgeline of the Gruvefjellet plateau mountain above Nybyen in the period
2008–2010. Using two automatic time-lapse cameras and hourly
meteorological data in combination with intensive field observations on the
Gruvefjellet plateau, cornice process dynamics were investigated in larger
detail than previously possible. Cornice accretion starts directly following
the first snowfall in late September and October, and proceeds throughout
the entire snow season under a wide range of air temperature conditions that
the maritime winter climate of Svalbard provides. Cornice accretion is
particularly controlled by distinct storm events, with a prevailing wind
direction perpendicular to the ridge line and average wind speeds from 12 m s−1. Particularly high wind speeds in excess of 30 m s−1 towards the plateau
ridgeline lead to cornice scouring and reduce the cornice mass both
vertically and horizontally. Induced by pronounced air temperature
fluctuations which might reach above freezing and lead to midwinter rainfall
events, tension cracks develop between the cornice mass and the plateau. Our
measurements indicate a linear crack opening due to snow creep and tilt of
the cornice around a pivot point. Four to five weeks elapsed between the
first observations of a cornice crack until cornice failure. Throughout the
two snow seasons studied, 180 cornice failures were recorded, of which 70
failures were categorized as distinctive cornice fall avalanches. A clear
temporal pattern with the majority of cornice failures in June was found.
Thus only daily air temperature could determine avalanche from non-avalanche
days. Seven large cornice fall avalanches reached the avalanche fans on
which the Nybyen settlement is located. The size of the avalanches was
primarily determined by the size of the cornice that detached. The improved
process understanding of the cornice dynamics provides a first step towards
a better predictability of this natural hazard, but also highlights that any
type of warning based on meteorological factors is not an adequate measure
to ensure safety of the housing at risk. |
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