To investigate recent permafrost characteristics in detail, quasi‐3D resistivity imaging was applied to map the extent of frozen ground in an area of a glacier forefield in the Engadin/Eastern Swiss Alps. This approach combines a number of parallel and perpendicular electrical resistivity tomography (ERT) profiles into one data set and enables a subsequent 3D inversion and interpretation of geoelectric resistivity results. Spatial information about resistivity distribution within the heterogeneous subsurface of the investigated area is gained and allows a detailed analysis of permafrost occurrence, which is superior to two‐dimensional resistivity surveying. Information about the consistency of the model results is obtained from the modification of the damping parameters during the inversion process. Data sets based on different combinations of ERT profiles and array types were compared to optimize the adequate number and orientation of profiles required for 3D inversion. Our findings show the importance of perpendicular tie lines in improving the image of the subsurface resistivity distribution. Inversion results from a Wenner‐Schlumberger array are regarded as the best trade‐off between accuracy and acquisition time in this periglacial environment. Spatial resistivity data facilitate a good delineation of a distinct permafrost body within the measurement grid. In addition, borehole temperatures are used as ground truth data. Our results show that quasi‐3D resistivity imaging allows a spatial interpretation of ground conditions and thus constitutes an improvement compared to scattered 2D ERT profiles. In particular, single landforms of small‐ to medium‐scale can be regarded as objectives and favour the application of detailed quasi‐3D surveys.

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Frozen ground characteristics resolved by annual, seasonal/monthly and daily electrical resistivity monitoring are presented based on case studies from three alpine sites in the Swiss Alps with different surface conditions and subsurface process dynamics. Data acquisition is achieved by different set-ups ranging from low-cost to automated and more expensive monitoring strategies. To ensure the reproducibility of measurement results a robust setup is required within the rough surface conditions of alpine environments, and this constitutes a fundamental precondition for time-lapse measurements.The selected different monitoring approaches allow for a detection and analysis of processes related to frozen ground dynamics on varying timescales. The interpretation of the geophysical data is improved by temperature measurements from various data loggers and borehole data. All three approaches allowed detection of the interface between frozen and unfrozen ground. The variation of the frequency of measurements enabled exploration of the specific permafrost-related problems. At one site, the multi-annual resistivity distribution at the end of the thawing period revealed fairly stable permafrost conditions, while at the second site, year-round measurements showed extremely divergent evolution of resistivity values in the subsurface throughout the measurement period, which could be ascribed to different site-specific environmental parameters. Using measurements with daily resolution at the third field site, the rapid decrease in subsurface resistivity values due to the infiltration of meltwater in spring could be documented. The presented results show that the different monitoring set-ups have their justification and are able to monitor timedependent subsurface dynamics within the scale of their temporal resolution.The operation of an automated monitoring system allows for very efficient observation especially of short-time processes within the active layer and the frozen ground below, the major advantage in comparison to non-automated monitoring approaches. However, the system is cost-intensive, requires an extensive infrastructure, and is more prone to environmental forces. For monitoring the inter-annual and long-term permafrost evolution, application of a fixed monitoring set-up that is accessible throughout the year and measured manually has proven to be a robust and cost-efficient alternative. Focusing on the long-term permafrost evolution, set-ups using fixed electrodes and measurements conducted as needed with a brought-along cable is a legitimate approach. Hence, for studies in alpine permafrost environments, choice of the monitoring set-up remains a question of the scientific problem, infrastructure facilities, and cost-efficiency.