Thermo-cryogenic controls of fracture kinematics in permafrost rockwalls

Titelangaben

Draebing, Daniel ; Krautblatter, Michael ; Hoffmann, Thomas:
Thermo-cryogenic controls of fracture kinematics in permafrost rockwalls.
In: Geophysical Research Letters. Bd. 44 (2017) Heft 8 . - S. 3535-3544.
ISSN 1944-8007
DOI: https://doi.org/10.1002/2016GL072050

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Abstract

Abstract 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.