Influence of surface and subsurface heterogeneity on observed borehole temperatures at a mountain permafrost site in the Upper Engadine, Swiss Alps

摘要

Compared to lowland (polar) regions, permafrost in high mountain areas occursin a large variety of surface and subsurface materials and textures. This workpresents an eight-year (2002–2010) data set of borehole temperatures forfive different (sub-) surface materials from a high alpine permafrost area,Murtèl-Corvatsch, Switzerland. The influence of the material on thethermal regime was investigated by borehole temperature data, the temperatureat the top of the permafrost (TTOP-concept) and the apparent thermaldiffusivity (ATD). The results show that during the last eight years, material-specific temperature changes were more significant than climate-inducedtemperature trends. At coarse blocky, ice-rich sites, no changes in activelayer depth were observed, whereas the bedrock and the fine-grained sitesappear to be highly sensitive to changes in the microclimate. The resultsconfirm that the presence and growth of ice as well as a thermally drivenair circulation within the subsurface are the key factors for the occurenceand preservation of alpine permafrost.