Climate change can impact glacial and periglacial environments, which are likely transforming at unprecedented rates during the Holocene. Progressive increases in air temperature and the associated modification in the ground thermal regime and surface energy balance result in increasing active layer thicknesses, ground warming, changing runoff and alterations in the freeze-thaw cycles. As a consequence to these thermal fluxes and their second order impacts to geomorphological processes the potential for slope instabilities changes accordingly. Active layer detachments, thermokarst or increased mass movement frequency due to frost weathering may result in hitherto unknown, or at least under-appreciated hazards because they may not have led to losses in the past. Where the hazard trajectory intercepts vulnerable infrastructure, geohazard risk may change in response. Quantitative geohazard risk assessments rely on frequency-magnitude relationships constructed from compilation and analyses of proxy data or direct observations. These analyses typically assume data stationarity (i.e., no long-term change in the mean and variance of the reconstructed time series), an assumption that is increasingly questioned considering the observed changes in the periglacial belt. This realization demands alternate approaches in risk assessment. In this paper, we present a general framework for assessing changes in geohazard activity within the periglacial environment heralded by changes in permafrost and ground ice conditions. The proposed framework starts with an examination of the effect of changes in air temperature on the ground thermal regime. Hazard probability and consequences are then assessed. By comparing the risk level under current conditions with the risk associated under a projected change in certain climatic parameters, the sensitivity of the slope stability or strength to climate change can be approximated. Despite considerable uncertainties associated with predictions of a third-order effect of climate change, the general approach outlined in this paper provides at least a tool to identify areas and slopes with high vulnerability to climate change and at best offers a systematic tool to evaluate climate change impacts in the periglacial zone.
来源平台:ENGINEERING GEOLOGY FOR SOCIETY AND TERRITORY, VOL 1: CLIMATE CHANGE AND ENGINEERING GEOLOGY