Ninth International Conference on Permafrost ... - IARC Research

Snowpack Evolution on Permafrost, Non-Permafrost Soils, and Glaciers in theMonte Rosa Massif (Northwest Alps, Italy)M. FreppazDi.Va.P.R.A. - LNSA, Università di Torino, Grugliasco (TO), ItalyM. MaggioniDi.Va.P.R.A. - LNSA, Università di Torino, Grugliasco (TO), ItalyS. GandinoComando Truppe Alpine - Servizio Meteomont, Bolzano, ItalyE. ZaniniDi.Va.P.R.A. - LNSA, Università di Torino, Grugliasco (TO), ItalyIntroductionSnow cover evolution is governed by several variables,such as meteorological factors, local topography, and snowcharacteristics. Different types of substrata might presentdifferent surface temperatures, influencing therefore thetemperature gradient within the snowpack and its evolution.In non-permafrost soils, a thick early winter snow covermaintains soil temperature close to 0°C, independently fromair temperature (Edwards et al. 2007). In permafrost soils,beneath at least a 1 m cover of snow, the ground temperatureduring February and March is below -2 to -3°C (Haeberli1973, Hoelzle 1992). For glaciers, less literature exists.Kuhn et al. (1998) found an interface temperature betweensnow and ice of about -5°C.The aim of this study is to follow the evolution of thesnow cover on three different substrata (permafrost, nonpermafrostsoils, and glacier) in the Monte Rosa Massif onthe Italian Northwest Alps.Materials and MethodsStudy areaThe three study sites are located in the area of the MonteRosa Massif in the northwestern Italian Alps. The permafrostsite is at an elevation of 2910 m a.s.l. on a northwest-orientedslope of about 10° of inclination; the non-permafrost siteis placed at an elevation of 2900 m a.s.l., on horizontalterrain; and the glacier site is located on Indren Glacier at anelevation of 3400 m a.s.l., with a southwest aspect and about10° of inclination.Nivometeorological dataSnow pits were dug periodically, according to theaccessibility of the sites, from December 2006 to July2007: 9 surveys at the permafrost site, 8 surveys at thenon-permafrost site, and 6 surveys at the glacier site. Snowtemperature was measured every 10 cm with 10 cm longdial stem thermometers. Snow density measurements weremade using a 0.5 L stainless steel core in each layer ofthe snowpack, where also grain type and dimension wererecorded. Continuous measurements of the temperature atthe interface between snow and the three different substratahave been made through dataloggers (UTL-1).Meteorological data in the area, such as wind speed anddirection, air temperature, and humidity, were registered byan automatic station of the Italian Army (Comando TruppeAlpine-Servizio Meteomont) located at 2901 m a.s.l. nearthe three sites.Results and DiscussionIn the study area, winter 2006–2007 was characterizedby a lack of snow cover in the early winter and relativelyhigh air temperature, with a minimum of -17.9°C recordedon January 26. As in Phillips & Schweizer (2006), thecharacteristics of the snow cover above the three differentsubstrata are summarized in Table 1 and described briefly inthe following sections.Non-permafrost siteIn the non-permafrost site, the maximum snow depthwas recorded on April 4 (180 cm), while until the end ofFebruary, the amount of snow was less than 80 cm. Seventyfivepercent of the snow profiles were weak-based, with abottom layer of faceted and depth hoar crystals due to themedium-high temperature gradient recorded mainly inthe early winter season. The average snow/soil interfacetemperature was greater than -1°C.Permafrost siteIn the permafrost site, the maximum snow depth wasrecorded on May 7, greater than in the other two sites. Fiftysixpercent of the snow profiles were characterized by facetedand depth hoar crystals, due to the high temperature gradient(recorded especially during March) closely related to thelow air temperature, as this site is on a northwest-orientedslope. But 22% of the snow profiles were also characterizedby small rounded crystals, typical of an equi-temperaturegradient, revealing how the lower ground temperature mayinduce a lower temperature gradient (Keller & Gubler 1993).The average snow/permafrost interface temperature was-5.1°C, 4.2° colder than the interface temperature betweensnow and non-permafrost soil.Glacier siteIn the glacier site, the maximum snow depth was recordedon May 16. Except for the last snow profile, the snow coverwas characterized by a bottom layer of faceted crystals,79