Abstract. The thermal regime of permafrost on scree slopes and rock glaciers is characterized by the importance of air flow driven convective and advective heat transfer processes. These processes are supposed to be part of the energy balance in the active layer of rock glaciers leading to lower subsurface temperatures than would be expected at the lower limit of discontinuous high mountain permafrost. In this study, new parametrizations were introduced in a numerical soil model (the Coup Model) to simulate permafrost temperatures observed in a borehole at the Murtèl rock glacier in the Swiss Alps in the period from 1997 to 2008. A soil heat sink and source layer was implemented within the active layer, which was parametrized experimentally to account for and quantify the contribution of air flow driven heat transfer on the measured permafrost temperatures. The experimental model calibration process yielded a value of about 28.9 Wm −2 for the heat sink during the period from mid September to mid January and one of 26 Wm −2 for the heat source in the period from June to mid September. Energy balance measurements, integrated over a 3.5 m-thick blocky surface layer, showed seasonal deviations between a zero energy balance and the calculated sum of the energy balance components of around 5.5 Wm −2 in fall/winter, −0.9 Wm −2 in winter/spring and around −9.4 Wm −2 in summer. The calculations integrate heat exchange processes including thermal radiation between adjacent blocks, turbulent heat flux and energy storage change in the blocky surface layer. Finally, it is hypothesized that these deviations approximately equal unmeasured freezing and thawing processes within the blocky surface layer.

Abstract. 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)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)) data set of borehole temperatures for five different (sub-) surface materials from a high alpine permafrost area, Murtèl-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.

Continuous monitoring of Electrical Resistivity Tomography (ERT) surveys can be a powerful tool for all kind of long‐term applications in the field of hydrogeophysics and cold‐region geophysics due to its high sensitivity to changes in water and ice content of the near subsurface. However, the large amount of data often calls for autonomous data processing schemes. In this study, a new filter algorithm designed to automatically detect and delete measurement errors from multiple ERT monitoring data is presented. Three successive filter steps were developed in order to eliminate technical errors, overall high‐value outliers and relative outliers within single data levels. The filter procedure is site‐independent and was tested on four different mountain permafrost sites in the Swiss Alps, representing various landforms (talus slope, rock plateau, rock glacier, bedrock). The filter performance is assessed by analysing the effect of the filter procedure on the mean apparent resistivity and on the resulting data misfit of the inversion and both, after the entire filter procedure as well as after each individual filter step. The new filter procedure is expected to yield rapid and high‐quality filtering for monitoring applications. In our study, the procedure is developed to support early detection of electrical resistivity changes associated with freezing and thawing events in permafrost conditions. The filter is applied to 128 ERT data sets from permafrost monitoring stations in Switzerland, including a four year long (2005–2008) ERT monitoring data set from the high‐mountain permafrost monitoring station Stockhorn, which serves as an illustrating example.

Abstract. Different geophysical investigations, such as electrical resistivity tomography (ERT) and refraction seismic tomography (RST), allow for an improved characterization of subsurface conditions in mountain permafrost areas. The knowledge of the permafrost internal composition constitutes a major prerequisite for climate-related modelling studies, for detailed hazard or local infrastructure assessments. To detect the smallscale variations of permafrost characteristics and its varying sensitivity to climate influencing factors, two ERT and RST monitoring profiles were installed in 2009 at two different sites called Chastelets and Murtèl forefield located in the Murtèl-Corvatsch area, Upper Engadin, eastern Swiss Alps. The geophysical profiles extend over four existing boreholes and are characterized by strong small-scale variations of surface as well as subsurface structures such as bedrock, fine material or coarse debris. Here we present ERT measurements carried out in a bimonthly interval during the years of 2009 to 2012 and RST measurements which were performed once a year, normally in August, during the same period. Based on these data sets the so-called four-phase model, based on petrophysical relationships, was applied to determine the volumetric fractions of ice, water and air within the heterogeneous ground, resulting in a relatively precise description of the subsurface material around the existing boreholes.The observations revealed a permafrost occurrence at the Chastelets rock glacier with an estimated icesaturated layer of at least 10 m thickness and the detection of a thawed layer with increased water content in the lower frontal part of the rock glacier within an area of fine material. In the area of the Murtèl forefield the analysis revealed strongly weathered bedrock, which is in the upper part covered by a pronounced layer of coarse debris establishing a thermal regime which is able to sustain permafrost beneath. In addition, the high temporal ERT measurements revealed a seasonal formation of ice during wintertime within the coarseas well as the fine-grained active layer zones. It can be concluded that the combination of existing borehole temperature measurements, the ERT/RST measurements and the application of the four-phase model resulted in an in-depth view of the investigated area, which is a major prerequisite for future modelling studies allowing for a better treatment of the present small-scale spatial ground variabilities.

Abstract. The thermal regime of permafrost in scree slopes and rock glaciers is characterized by the importance of air flow driven convective and advective heat transfer processes. These processes are supposed to be part of the energy balance in the active layer of rock glaciers leading to lower subsurface temperatures than would be expected at the lower limit of discontinues high mountain permafrost. In this study, new parameterizations were introduced in a numerical soil model to simulate permafrost temperatures observed in a borehole at rock glacier Murtèl in the Swiss Alps in the period from 1997 to 2008. A soil heat sink and source layer was implemented within the active layer which was parameterized experimentally to account for and quantify the contribution of air flow driven heat transfer on the measured permafrost temperatures. The experimental model calibration process yielded a value of about 28.9 Wm−2 for the heat sink during the period from mid September to mid January and one of 26 Wm−2 for the heat source in the period from June to mid September. Energy balance measurements, integrated over a 3.5 m thick blocky surface layer, showed seasonal deviations between a zero energy balance and the calculated sum of the energy balance components of around 6.8 Wm−2 in fall/winter, −2.2 Wm−2 in winter/spring and around −5.6 Wm−2 in summer. The calculations integrate heat exchange processes including thermal radiation between adjacent blocks, turbulent heat flux and energy storage change in the blocky surface layer. Finally, it is hypothesized that these deviations approximately equal unmeasured freezing and thawing processes within the blocky surface layer.