Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tTable 1. Snow cover characteristics for the three sites. Except forsnow depth and the snow/substratum interface temperature, theother parameters are average values computed on data from manualsnow profiles (N = 8 at non-permafrost site, N = 9 at permafrostsite, N = 6 at glacier site).Parameter NonpermafrostPermafrost Glaciermax snow depth (cm) 180 230 125grain type in bottomlayer of snowpackmaximum grain sizein bottom layer (mm)hand hardness indexin bottom layersnow/substratuminterfacetemperature* (°C)temperature gradientwithin the snowpack(°C/m)density(Mg/m 3 )Effective heatconductivity (W/mK)5a, 4a 5a, 4a, 3a 4c2.4 1.8 1.71.8 2.2 5.0-0.9 -5.1 -4.8-6.5 -7.4 -2.10.305 0.273 0.3890.131 0.116 0.257* average values computed on data recorded by dataloggers(12/29/2006–04/20/2007).often well bonded together. The snow hardness was veryhigh (level 5), higher than in the other sites. The averagesnow/glacier interface temperature was -4.8 °C.The main differences between the three sites can besummarized in the following points:• A very hard bottom layer was present on the glacier inrespect to a snow hardness of 2 for the other two sites; theassumption is that the cold temperature of the glacier surfacetogether with the high density and low gradient might creategood conditions for the snow crystals to bond well together.• The permafrost and glacier sites presented similarinterface temperatures, close to -5°C, before reachingisothermal conditions.• The average temperature gradient at the glacier sitewas lower than in the other two sites. The possible reason isthat the air temperature was higher, as this site is southwestexposed, resulting then in a lower temperature gradient.In all the sites, the interface temperature remainedconstant around a certain value (non-permafrost soil -0.9°C,permafrost -5.1°C, glacier -4.8°C) without great oscillationswhen the snow cover was deep enough to insulate thesubstrata.might generate appreciable differences in the snow covercharacteristics.Our results shows that the main differences in the evolutionof the snow cover on permafrost, non-permafrost, and glaciersubstrata are related to hand hardness in the bottom layer(higher on glacier), snow/substrata interface temperature(higher on non-permafrost soil), and temperature gradient(lower on glacier).Moreover, an important outcome of this work is that thetemperature at the snow/substrata interface remains constantaround certain values, without oscillating in relation toair temperature, when enough snow covers the substrata,showing the important insulating effect of the snow.AcknowledgmentsFot the technical support we thank MonterosaSki, RobertoCilenti, Corpo Guide Alpine di Alagna Valsesia, RegioneAutonoma Valle d’Aosta-Ufficio Neve e Valanghe, HervèJaccond, Emil Squinobal, and Antoine Brulport.ReferencesEdwards, A.C., Scalenghe, R. & Freppaz, M. 2007. Changesin the seasonal snow cover of alpine regions andits effect on soil processes: A review. Quaternary<strong>International</strong> 162-163: 172-181.Haeberli, W. 1973. Die Basis-Temperatur der winterlichenSchneedecke als morfologischer Indikator fuer dieVerbreitung von Permafrost in den Alpen. Zeitschriftfuer Gletscherkunde und Glazialgeologie 9: 221–227.Hoelzle, M. 1992. Permafrost occurrence from BTSmeasurements and climatic parameters in the EasternSwiss Alps. Permafrost and Periglacial Processes 3:143-147.Keller, F. & Gubler, H. 1993. Interaction between snow coverand high mountain permafrost; Murtèl/Corvatsch,Swiss Alps. Proceedings of the Sixth <strong>International</strong><strong>Conference</strong> on Permafrost, Beijing, China, 5-9 July1993. Proceedings. Guangzhou, China: South ChinaUniversity of Technology Press, 1: 332-337.Kuhn, M., Haslhofer, J., Nickus, U. & Schellander, H. 1998.Seasonal development of ion concentration in a highalpine snow pack. Atmospheric Environment 32(23):4041-4051.Phillips, M. & Schweizer, J. 2007. Effect of mountainpermafrost on snowpack stability. Cold RegionsScience and Technology 47: 43-49.ConclusionsThe main purpose of this work was to analyze the evolutionof the snow cover on different substrata to understand if they80