CHALLENGES WITH ASSESSING GEOHAZARDS RELATED TO DEGRADING PERMAFROST

Mountain environments are generally very dynamic. Recent changes in climate, however, have affected the rates at which glacial and periglacial environments change. Based on current projections, those changes are expected to be even more dramatic in the future. Ground surface conditions and climatic settings influence the stability and dynamics of slopes in permafrost change. An increase in air temperature modifies the ground thermal regime and the surface energy balance resulting in active layer thickening, ground warming, runoff changes and alterations in frost action cycles. In consequence to these thermal fluxes and their second order impacts to geomorphological processes, the hazard potential for slope instabilities to occur from within such zones changes accordingly. Active layer detachments, thermokarst or increased mass movement frequencies may be unknown because they may not have led to impacts in the past. Under such dynamic conditions it is challenging to quantify the hazard from historic events alone. A typical, quantitative geohazard assessment relies on frequency-magnitude relationships determined from analyzing proxy data or direct observations. Such analyses usually assume stationarity in the available data, which means that no long-term changes occur in the time series. Under currently occurring degrading permafrost conditions, which may be unprecedented, such an assumption must be questioned and alternate approaches in geohazard assessments are required.

In this presentation the challenges of geohazard assessments related to degrading permafrost in mountainous environments are highlighted. Based on these challenges a general framework is described. The proposed framework starts with an examination of the effects of changes in climate conditions and how this affects the ground thermal regime. Geohazard probabilities are assessed and compared using current conditions as well as those that may occur in the future. The sensitivity of a geohazard to these projected climatic conditions can then be used as a measure to assess the geohazard’s vulnerability to climate change and may offer a systematic tool to evaluate future hazards from the periglacial belt.