Identifying mountain permafrost degradation by repeating historicalelectrical resistivity tomography (ERT) measurements

Ongoing global warming intensifies the degradation of permafrost. Permafrostthawing impacts landform evolution, reduces freshwater resources, enhancesthe potential of natural hazards and thus has significant socio-economicimpacts. Electrical resistivity tomography (ERT) has been widely used to mapthe ice-containing permafrost by its resistivity contrast compared to thesurrounding unfrozen medium. This study aims to reveal the effects ofongoing climate warming on mountain permafrost by repeating historical ERTand analyzing the temporal changes in the resistivity distribution. In orderto facilitate the measurements, we introduce and discuss the employment oftextile electrodes. These newly developed electrodes significantly reduceworking effort, are easy to deploy on blocky surfaces and yieldsufficiently low contact resistances. We analyze permafrost evolution onthree periglacial landforms (two rock glaciers and one talus slope) in theSwiss and Austrian Alps by repeating historical surveys after 10, 12 and 16 years, respectively. The resistivity values have been significantly reducedin ice-poor permafrost landforms at all study sites. Interestingly,resistivity values related to ice-rich permafrost in the studied active rockglacier partly increased during the studied time period. To explain thisapparently counterintuitive (in view of increased resistivity) observation,geomorphological circumstances, such as the relief and increased creepvelocity of the active rock glacier, are discussed by using additionalremote sensing data. The present study highlights ice-poor permafrostdegradation in the Alps resulting from ever-accelerating global warming.