Item: On the relation between mountain permafrost and snowpack stability
Title: On the relation between mountain permafrost and snowpack stability
Proceedings: Proceedings of the 2004 International Snow Science Workshop, Jackson Hole, Wyoming
Authors: Marcia Phillips and Jürg Schweizer, Swiss Federal Institute for Snow and Avalanche Research SLF, Davos, Switzerland
Abstract: Many recreational avalanche accidents occur in areas where mountain permafrost exists. Consequently, it has been proposed that the presence of sub-zero ground temperatures favours snowpack instability. In the mainly transitional climate of the Swiss Alps, permafrost prevails in shady slopes above about 2500 m a.s.l. To investigate the effect of mountain permafrost on snowpack stability, over 400 snow profiles with stability tests were analysed, taken in both permafrost-free and permafrost terrain. Snowpack characteristics and stability were compared for the profiles from the two areas. Though basal snowpack characteristics were partly different, no indication was found that permafrost terrain causes the development of an unstable snowpack. However, a shallow snow depth favoured below freezing ground temperatures as well as snowpack instability. The occurrence of many avalanche accidents on permafrost terrain reflects skiing preference - due to better snow conditions on shady slopes- rather than causation, and is therefore merely a coincidence.
Keywords: snowpack stability, stability evaluation, permafrost
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