Permafrost and climate in Europe - climate change, mountain permafrost degradation and geotechnical hazard (PACE)

The PACE consists of a transect of instrumented permafrost boreholes across the higher mountains of Europe. The transect starts in Svalbard, includes the Scandinavian mountains, the Alps and ends in the Sierra Nevada in southern Spain. The aim of the project is to improve the knowledge on permafrost and, finally, the assessment of related hazards. The project contains several complementary investigations like geophysical surveys, microclimatic investigations, numerical modeling of permafrost distribution and physical modeling of permafrost related slope instability. The first results (Harris et al. 2003) showed that the thermal permafrost gradients are consistent with the 20th century surface warming. Important to notice is further the uniqueness of the thermal profile at each site, which has a huge impact on risk assessment and related investigations required for determining the site specific features. For example, each thermal profile indicates a site specific depth of the lowest temperature as well as different permafrost temperatures and active layer depths. Factors influencing the thermal profiles are geothermal heat flux (warming the permafrost at its bottom), variations in lithology, the ground surface temperature and past changes of surface temperatures as well (Harris et al. 2003). Therefore, a big difficulty in predicting future permafrost changes is that the permafrost/thermal relationship is not in equilibrium, rather it is in part a function of the climate over the last decades and centuries (Harris et al. 2005).