Thermo-cryogenic controls of fracture kinematics in permafrost rockwalls

Thermo-cryogenic processes prepare and trigger rockfalls and rockslides in alpine environments. Temporal occurrence, controls, and applied stresses of Thermo-cryogenic processes on rock masses are poorly understood. This paper reports annual crackmeter measurements with 3 h resolution across perennially ice-filled fractures in an unstable rock permafrost crestline. Thermo-cryogenic processes are controlled by snow cover onset and duration. Thermal changes in snow-free periods control expansion and contraction coincident temperature gradients on a daily to seasonal scale. We can show how snow cover promotes sustained temperatures from −9 to −1°C and boosts ice segregation-related fracture opening up to 1 cm in 8 months. During snowmelt, meltwater induces ice erosion and ice relaxation, which occur in the freeze-thaw window close to the thawing point. We hypothesize that Thermo-cryogenic processes and their cyclic repetition can lead to Thermo-cryogenic fatigue preparing rock slope failure and can control type and location of rockfalls in a changing climate.