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| Titel |
Transient thermal effects in Alpine permafrost |
| VerfasserIn |
J. Noetzli, S. Gruber |
| 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 ; 3, no. 1 ; Nr. 3, no. 1 (2009-04-27), S.85-99 |
| Datensatznummer |
250000787
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| Publikation (Nr.) |
 copernicus.org/tc-3-85-2009.pdf |
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| Zusammenfassung |
| In high mountain areas, permafrost is important because it influences the
occurrence of natural hazards, because it has to be considered in
construction practices, and because it is sensitive to climate change. The
assessment of its distribution and evolution is challenging because of
highly variable conditions at and below the surface, steep topography and
varying climatic conditions. This paper presents a systematic investigation
of effects of topography and climate variability that are important for
subsurface temperatures in Alpine bedrock permafrost. We studied the effects
of both, past and projected future ground surface temperature variations on
the basis of numerical experimentation with simplified mountain topography
in order to demonstrate the principal effects. The modeling approach applied
combines a distributed surface energy balance model and a three-dimensional
subsurface heat conduction scheme. Results show that the past climate
variations that essentially influence present-day permafrost temperatures at
depth of the idealized mountains are the last glacial period and the major
fluctuations in the past millennium. Transient effects from projected future
warming, however, are likely larger than those from past climate conditions
because larger temperature changes at the surface occur in shorter time
periods. We further demonstrate the accelerating influence of multi-lateral
warming in steep and complex topography for a temperature signal entering
the subsurface as compared to the situation in flat areas. The effects of
varying and uncertain material properties (i.e., thermal properties,
porosity, and freezing characteristics) on the subsurface temperature field
were examined in sensitivity studies. A considerable influence of latent
heat due to water in low-porosity bedrock was only shown for simulations
over time periods of decades to centuries. At the end, the model was applied
to the topographic setting of the Matterhorn (Switzerland). Results from
idealized geometries are compared to this first example of real topography,
and possibilities as well as limitations of the model application are
discussed. |
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