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

Compared to lowland (polar) regions, permafrost in high mountain areas occurs in a large variety of surface and subsurface materials and textures. This work presents an eight-year (2002-2010) data set of borehole temperatures for five different (sub-) surface materials from a high alpine permafrost area, MurtSl-Corvatsch, Switzerland. The influence of the material on the thermal regime was investigated by borehole temperature data, the temperature at the top of the permafrost (TTOP-concept) and the apparent thermal diffusivity (ATD). The results show that during the last eight years, material-specific temperature changes were more significant than climate-induced temperature trends. At coarse blocky, ice-rich sites, no changes in active layer depth were observed, whereas the bedrock and the fine-grained sites appear to be highly sensitive to changes in the microclimate. The results confirm that the presence and growth of ice as well as a thermally driven air circulation within the subsurface are the key factors for the occurence and preservation of alpine permafrost.