Pluriannual thermal behavior of low elevation cold talus slopes in western Switzerland

Abstract. The internal and reversible mechanism of air circulation (chimney effect) throughout a porous debris accumulation acts as an efficient advective conveyor of heat, which strongly influences its thermal balance during the whole year. Ground temperature monitoring carried out at eight sites located below the timberline in western Switzerland since 1997 indicates the major role played by winter air temperature conditions in the thermal regime of low elevation talus slopes and relict rock glaciers. In contrast, both snow depth and summer air temperatures have far less influence. The temperature monitoring at these sites offers the longest time series world-wide. Borehole temperature monitoring indicates the presence and growth of permafrost at one particular site from 2004–2006, with its consequent thawing again in 2007.