Processes that control permafrost warming in Alpine regions are still not completely understood. Recently, geoelectrical monitoring has emerged as a useful tool to investigate thawing and freezing processes. However, high resistive environments and harsh environmental conditions pose very unfavourable conditions for automated resistivity measurements. Based on the results of several test studies, an improved data acquisition system for geoelectrical monitoring of frozen soils was developed. Furthermore, the implementation of algorithms for statistical analysis of raw data time series led to a significant improvement in the reliability of inversion results. At two Alpine sites, namely Mölltaler Glacier and Magnetköpfl/Kitzsteinhorn, the adapted system was tested at soil temperature conditions between 0°C and -12°C. Data was continuously collected at both locations over nearly a full seasonal cycle. The results showed an almost linear dependency of resistivity and temperature at values above -0.5°C. At lower temperatures, the relation was non-linear, indicating that the reduction of porosity due to the shrinking of connected brine channels was the dominating process that determined the value of resistivity. Based on the derived results, further improvements were suggested, especially for measurements at soil temperatures below -4.5°C as low injection currents make it extremely challenging to gather these. permafrost regions is high priority. The advancement of innovative methods, such as geoelectrical monitoring, allowing all-seasonal, permanent monitoring of remote areas is in demand.The geoelectrical method determines the distribution of the specific electrical resistivity within the subsurface. The specific electrical resistivity mainly depends on porosity, water saturation, conductivity of pore fluid and clay content, and to a minor extent on particle shape and pore geometry. During the process of permafrost thawing and freezing, the volume fraction of the fluid phase (equivalent to a change in porosity), the connectivity of fluid areas and the salinity of the pore fluid is expected to vary. Therefore, geoelectrical monitoring could be an appropriate tool to investigate such processes.

Abstract. The storage of water within the seasonal snow cover is a substantial source of runoff in high mountain catchments. Information about the spatial distribution of snow accumulation is necessary for calibration and validation of hydro-meteorological models. Generally, only a small number of precipitation measurements deliver precipitation input for modelling in mountain areas. The spatial interpolation and extrapolation of measurements of precipitation is still difficult. Multi-temporal application of lidar techniques from aircraft, so-called airborne laser scanning (ALS), provides surface elevations changes even in inaccessible terrain. These ALS surface elevation changes can be used to derive changes in snow depths of the mountain snow cover for seasonal or subseasonal time periods. However, since glacier surfaces are not static over time, ablation, densification of snow, densification of firn and ice flow contribute to surface elevation changes. ALS-derived surface elevation changes were compared to snow depths derived from 35.4 km of ground penetrating radar (GPR) profiles on four glaciers. With this combination of two different data acquisitions, it is possible to evaluate the effect of the summation of these processes on ALS-derived snow depth maps in the high alpine region of the Ötztal Alps (Austria). A Landsat 5 Thematic Mapper image was used to distinguish between snow covered area and bare ice areas of the glaciers at the end of the ablation season. In typical accumulation areas, ALS surface elevation changes differ from snow depths calculated from GPR measurements by −0.4 m on average with a mean standard deviation of 0.34 m. Differences between ALS surface elevation changes and GPR derived snow depths are small along the profiles conducted in areas of bare ice. In these areas, the mean absolute difference of ALS surface elevation changes and GPR snow depths is 0.004 m with a standard deviation of 0.27 m. This study presents a systematic approach to analyze deviations from ALS generated snow depth maps to ground truth measurements on four different glaciers. We could show that ALS can be an important and reliable data source for the spatial distribution of snow depths for most parts of the here investigated glaciers. However, within accumulation areas, just utilizing ALS data may lead to systematic underestimation of total snow depth distribution.

Abstract. In the European Alps, almost half the glacier volume has disappeared over the past 150 years. The loss is reflected in glacier retreat and ice surface lowering even at high altitude. In steep glacial cirques, surface lowering exposes rock to atmospheric conditions probably for the very first time in several millennia. Instability of rockwalls has long been identified as one of the direct consequences of deglaciation, but so far cirque-wide quantification of rockfall at high resolution is missing. Based on terrestrial lidar, a rockfall inventory for the permafrost-affected rockwalls of two rapidly deglaciating cirques in the Central Alps of Austria (Kitzsteinhorn) is established. Over 6 years (2011–2017), 78 rockwall scans were acquired to generate data of high spatial and temporal resolution. Overall, 632 rockfalls were registered, ranging from 0.003 to 879.4 m3, mainly originating from pre-existing structural rock weaknesses. A total of 60 % of the rockfall volume detached from less than 10 vertical metres above the glacier surface, indicating enhanced rockfall activity over tens of years following deglaciation. Debuttressing seems to play a minor effect only. Rather, preconditioning is assumed to start inside the randkluft (void between cirque wall and glacier) where measured sustained freezing and ample supply of liquid water likely cause enhanced physical weathering and high quarrying stresses. Following deglaciation, pronounced thermomechanical strain is induced and an active layer penetrates into the formerly perennially frozen bedrock. These factors likely cause the observed paraglacial rockfall increase close to the glacier surface. This paper, the first of two companion pieces, presents the most extensive dataset of high-alpine rockfall to date and the first systematic documentation of a cirque-wide erosion response of glaciated rockwalls to recent climate warming.