Climate Change, Mountain Permafrost Degradation and Geotechnical Hazard

Abstract

The IPA Circum-Polar Permafrost Map (Brown et al. 1997) shows discontinuous and sporadic permafrost in the mountains of Europe, including Scandinavia, the Alps, the Pyrenees, and further east in the Urals. In general, the lower altitudinal limit of mountain permafrost increases with decreasing latitude, from sea level in Svalbard, to around 1500 m in Southern Norway, to above 2500 m in the southern Swiss Alps. Many of these low-latitude mountain regions have permafrost temperatures that are only a few degrees below zero, so that a slight shift in energy flux at the ground surface is likely to cause a significant increase in the depth of summer thawing and, in consequence, widespread permafrost degradation. Where permafrost is ice-rich, degradation caused by global warming is likely to be associated with increased magnitude and frequency of mountain slope instability (Harris et al. 2001a). Traditional landslide hazard assessment approaches, based on forward projection of historical data on distribution and magnitude-frequency relationships (Varnes 1984), may therefore become increasingly inappropriate if climate change leads to a significant change in the thresholds of processes within the permafrost geomorphic system. In this paper, approaches to the assessment of geotechnical hazards associated with mountain permafrost in a warming climate are outlined in the context of recent European collaborative research. A critical first stage is the early detection of permafrost responses to climate change through integrated monitoring systems.