Sensitivity of rock permafrost to regional climate change scenarios and implications for rock wall instability
Final Report Abstract
In this project, the sensitivity of rock instabilities in degrading permafrost has been systematically researched. (i) Conceptual models have been developed to decipher multiple likely inputs and their related response times. (ii) The feasibility of geophysical methods (resistivity, p‐wave velocity) to detect frozen bedrock has been demonstrated in the laboratory and temperature relations have been quantified and transformed into empirical models. (iii) The applicability of electrical resistivity tomography and seismic refraction tomography for the spatial and temporal monitoring of permafrost in unstable low‐porosity bedrock has been demonstrated. (iv) Determinants and dynamic displacements patterns of rock creep (precursory to major displacements) could be measured and show significant acceleration patterns in late summer. (v) The sensitivity of rock instabilities in permafrost can presently only be estimated deductively based on the mechanical understanding of rock and ice‐mechanics. Based on literature and experiments, we develop a modified Mohr–Coulomb failure criterion for ice‐filled rock fractures that incorporates fracturing of rock bridges, friction of rough fracture surfaces, ductile creep of ice and detachment mechanisms along rock–ice interfaces. (vi) Novel laboratory setups were developed to assess the temperature dependency of the friction of ice‐free rock–rock interfaces and the shear detachment of rock–ice interfaces. (vii) In degrading permafrost, rock‐mechanical properties may control early stages of destabilization and become more important for higher normal stress, i.e. higher magnitudes of rock–slope failure. Ice‐mechanical properties outbalance the importance of rock‐mechanical components after the deformation accelerates and are more relevant for smaller magnitudes.
Publications
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(2010): Patterns of multiannual aggradation of permafrost in rock walls with and without hydraulic interconnectivity (Steintälli, Valley of Zermatt, Swiss Alps). Lecture Notes in Earth Sciences, 115: 199‐214
Krautblatter, M.
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(2010): Temperature‐ calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps). J. Geophys. Res. ‐ Earth Surface
Krautblatter, M., Verleysdonk, S., Flores‐Orozco, A. and Kemna, A.
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(2011): Neue Forschungsansätze zur räumlichen und zeitlichen Dynamik des Gebirgspermafrostes und dessen Naturgefahrenpotentials. Polarforschung, 81 (1): 57 – 68 (Deutsches Weißbuch Permafrost)
Krautblatter, M. and Hauck, C.
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2011): Sensitivity and path dependence of mountain permafrost systems. Geografiska Annaler, Series A, 93, 113‐135
Verleysdonk, S., Krautblatter, M. and Dikau, R.
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(2012): P‐wave velocity changes in freezing hard low‐ porosity rocks: a laboratory‐based time‐average model. The Cryosphere, 6: 1163–1174
Draebing, D. and Krautblatter, M.
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(2012): Research perspectives for unstable high‐alpine bedrock permafrost: measurement, modelling and process understanding. Permafrost and Periglacial Processes, 23 (1): 80‐88
Krautblatter, M., Huggel, C., Deline P. and Hasler A.
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(2013): Why permafrost rocks become unstable: a rock‐ice‐mechanical model in time and space. Earth Surf. Process. Landforms. Vol. 38, Issue 8, pages 876–887
Krautblatter, M., Funk, D. and Günzel, F.
