Permafrost degradation due to global warming is a widespread phenomenon in recent dec-ades (Lemke et al. 2007), latitudinal as well as altitudinal. Dealing with permafrost related mountain hazards requires knowledge on the exact permafrost distribution throughout mountain areas. Therefore, a monitoring project on European permafrost distribution will be discussed. Furthermore, it has to be determined, what mountain hazards exist in general and which of them could be affected by permafrost degradation in terms of frequency and/or intensity. Two different types of mountain hazards will be examined in detail: rockfall and outburst flood of permafrost dammed lakes.
Moreover, the impact of mountain hazards on the society will be marked. The focus will be on investigations which can be done, before undertaking engineering projects. After that a brief overview on perspectives in terms of climate scenarios and their possible impact on permafrost degradation and mountain hazards will be given. Finally, some concluding statements will be made.
Table of Contents
1. Introduction
2. Permafrost distribution and monitoring in mountain areas
3. Permafrost related hazards
2.1 Mass movements/ Rockfall
2.2 Outburst floods
4. Hazard and risk assessment
5. Perspective
6. Conclusion
Research Objectives and Core Topics
This paper examines the correlation between global warming-induced permafrost degradation and the resulting increase in mountain hazards, specifically focusing on rockfalls and outburst floods of permafrost-dammed lakes. It evaluates monitoring techniques, assesses regional impacts, and explores how shifting climate conditions influence slope stability and infrastructure safety in mountain environments.
- Impact of permafrost degradation on mountain hazard frequency and intensity
- Mechanisms behind rockfall and thermokarst lake outburst floods
- Application of GIS and field survey methods for hazard risk assessment
- Analysis of thermal profiles and permafrost sensitivity to temperature changes
- Future climate scenarios and their implications for mountain infrastructure
Excerpt from the Book
3.1 Mass movements/ Rockfall
Mass movements occur on different temporal and spatial scales. They span a range from solifluction and rock glacier movement with slow velocities to debris flows or rockfall marked by very high velocities.
The thawing reduces the strength of ice-rich sediment and bedrock. That leads to thaw consolidation in ice-rich soils. The slope failure ranges from shallow translational landslides in finer-grained sediment to rapid mudflows and debris flows (Harris 2005). Thereby, the critical issue is the ice-content of the frozen ground (Harris et al. 2001). Slope failure can even dam rivers. This results in the potential of floods as a consequence of sudden release of huge amounts of water in the course of dam failure.
The water percolation in highly fractured rock leads to thicker and earlier development of an active layer. Moreover, a convex topography (ridges, spurs, peaks) is subject to faster and deeper thaw than other areas. The melting of joint bonding ice causes 5 physical processes resulting in destabilization of the bedrock: Loss of bonding, ice segregation, volume expansion, increase in hydrostatic pressure, reduction of shear strength (Gruber &Häberli 2007). A slope steepness of 37° is assumed as a threshold for separation of debris from bedrock slopes (Gruber & Häberli 2007). Warming surface temperatures causes active layer thickening, basal melting (leads to permafrost thinning) and hydrogeological changes in permafrost areas. For the release of a rockfall usually a specific trigger mechanism is required. Common triggers are earthquakes, high precipitation events and – on a different temporal scale – permafrost degradation. However, regarding past rock falls, the triggering mechanism is hard to reconstruct in terms of the exact timing, the initial topography and the rock properties.
Summary of Chapters
1. Introduction: Outlines the phenomenon of permafrost degradation due to climate change and defines the scope of examining specific mountain hazards like rockfalls and outburst floods.
2. Permafrost distribution and monitoring in mountain areas: Explains the factors influencing permafrost and presents the PACE project as a model for monitoring thermal gradients in European mountains.
3. Permafrost related hazards: Analyzes the mechanics of mass movements, specifically rockfall, and the development of thermokarst lakes that lead to outburst floods.
4. Hazard and risk assessment: Details methodological approaches, including GIS and geophysical investigations, to identify and evaluate thaw-sensitive areas and infrastructure risks.
5. Perspective: Discusses the necessity of regional climate scenarios and the potential for future instabilities exceeding historical variability.
6. Conclusion: Summarizes the link between warming, permafrost degradation, and slope instability, emphasizing the need for site-specific risk assessments for planners.
Keywords
Permafrost degradation, Mountain hazards, Rockfall, Outburst floods, Climate change, Slope stability, PACE project, Thermokarst, Risk assessment, Geotechnical hazard, Alpine infrastructure, Active layer, Thermal profiles, GIS, Bedrock.
Frequently Asked Questions
What is the primary focus of this paper?
The paper examines how rising global temperatures cause permafrost degradation in mountain regions, thereby increasing the frequency and intensity of natural hazards such as rockfalls and outburst floods.
What are the main mountain hazards discussed?
The study primarily focuses on mass movements, particularly rockfalls, and the dangers posed by thermokarst lake outburst floods resulting from melting ice.
What is the central research objective?
The goal is to determine the relationship between permafrost degradation and mountain hazards, while assessing how investigative methods and monitoring can help mitigate risks for engineering projects.
Which scientific methods are employed for risk assessment?
The research emphasizes the use of GIS techniques, geophysical surveys (such as seismic and resistivity tomography), and borehole temperature monitoring to analyze ground stability.
What does the main body of the text address?
The main body covers the distribution of permafrost, the PACE monitoring project, the physical processes behind slope failure, and case studies of thermokarst lake growth and drainage.
Which keywords characterize this work?
Key terms include Permafrost degradation, Mountain hazards, Rockfall, Outburst floods, Climate change, Slope stability, and Risk assessment.
Why are northern slopes more vulnerable to rockfall?
Northern slopes exhibit a stronger dependence on air temperature for their thermal state; as air warms, the active layer thaws deeper and faster than on southern slopes, which are instead dominated by direct solar radiation.
How did the 2003 European heatwave impact permafrost?
The 2003 heatwave caused extreme active layer thickening, with thaw depths significantly exceeding the previous 21-year maximum, directly correlating with a high frequency of rockfall events.
What was the outcome for the thermokarst lake on Grubengletscher?
The lake, which grew rapidly during the 1980s and 1990s and posed a threat due to potential outburst floods, was successfully drained in 1995 as a preventative engineering measure.
Why is standard climate modeling insufficient for this study?
Global climate models are too broad; the paper argues that regional climate scenarios are necessary to account for local topography and microclimatic factors that drive mountain permafrost changes.
- Quote paper
- Eric Petermann (Author), 2008, Mountain Hazards associated with Permafrost Degradation, Munich, GRIN Verlag, https://www.grin.com/document/119367
