Modeled sensitivity of two alpine permafrost sites to RCM‐based climate scenarios

Abstract

Climate change as projected by contemporary general circulation models (GCMs) and regional climate models (RCMs) will have a great impact on high latitude and high mountain permafrost. A process‐based one‐dimensional permafrost model is used to evaluate the sensitivity of two characteristic alpine permafrost sites to changes in climate for a 110 year time period starting 1991 and ending 2100 using output time series of six different GCM‐RCM model chains. Statistical analysis of the RCM climate variables and output of the impact model has been conducted to gain insight into the sensitivity of the active layer to changes in climatic conditions. Strong sensitivity to climate change was found for the active layer thickness (ALT) at Schilthorn, which increased by up to 100% before most of the models pointed to a degradation of the permafrost around the year 2020. The sensitivity of the ALT at the rock glacier site Murtèl is less pronounced; permafrost degradation is slower and sets in only around 2070. At both sites, the thermal evolution is linked to an increase in unfrozen water content within the permafrost body. Multiple linear regression analysis shows a strong model dependency of ALT on ice content and summer soil surface temperatures and to a less significant degree on snow cover timing and duration. The ALT at Schilthorn is influenced by the ALT of the preceding year, while at Murtèl, the ALT is influenced by the ALT of up to 15 preceding years.