Thermal conditions and kinematics of steep bedrock permafrost
Steep mountain flanks with heterogeneous micro-topography and surface characteristics are typical for high alpine mountain ranges. Permafrost, defined as the subsurface volume remaining at or below 0 °C throughout the year, modifies the hydrological and mechanical conditions of these flanks. Rock fa...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2011
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| Online Access: | https://www.zora.uzh.ch/id/eprint/59731/ https://www.zora.uzh.ch/id/eprint/59731/1/2011_Hasler.pdf https://doi.org/10.5167/uzh-59731 |
| Summary: | Steep mountain flanks with heterogeneous micro-topography and surface characteristics are typical for high alpine mountain ranges. Permafrost, defined as the subsurface volume remaining at or below 0 °C throughout the year, modifies the hydrological and mechanical conditions of these flanks. Rock fall from permafrost bedrock and stability problems of high-alpine infrastructure raise the demand for understanding how these rock faces evolve in response to climate change and where most critical situations may emerge. Diverse studies address this topic and advances in the knowledge of the general permafrost distribution in steep rock faces and in the documentation and investigation of high-alpine rock instabilities have been made in the past decade. However, the processes linking climate change and rock fall are still poorly understood and empirical data is limited. This thesis addresses the corresponding knowledge gap. It is an exploratory study of the thermal, hydrological and mechanical processes in steep bedrock permafrost and its active layer. A large part of the thesis focuses on distributed and extensive in-situ measurements of temperatures, rock movements and hydrological parameters. For this a data acquisition infrastructure based on wireless technology was developed within the consortium PermaSense, which was operated at two field sites (Matterhorn and Jungfraujoch, Swiss Alps) over the past 2–3 years and acquired datasets of novel quality and with new contents. The hydrothermal processes in fractured rock are, however, difficult to observe with field measurements alone. Therefore, laboratory experiments and numerical simulations of a single ice-filled cleft where set up and applied as complementary methods. The main findings of these investigations are: i) a significant cooling effect with respect to snow-free surfaces in radiation-exposed rock faces caused by thin snow cover and air ventilation in clefts; ii) melt water warmed-up before percolation causes high erosion rates of the cleft ice but little ... |
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