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

Abstract

[1] 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.

Ground temperature variations in a talus slope influenced by permafrost: a comparison of field observations and model simulations

“…Results from Schneider (2014) and others indicate that ground cooling in late autumn might be more important (for inter-annual temperature variations) due to its long-lasting effect (Delaloye, 2004;Vonder Mühll et al, 1998) over the whole winter season. But regarding the long-term permafrost evolution, increasing air temperatures in summer and in the annual mean (MAAT) might play the key role IPCC, 2014;Isaksen et al, 2011;Marmy et al, 2013;Scherler et al, 2013).…”

Soil Moisture Data for the Validation of Permafrost Models Using Direct and Indirect Measurement Approaches at Three Alpine Sites

“…The modeled processes of water infiltration into the frozen soil were implemented and described by Stähli et al (1996) and a complete description and test of water infiltration is given by Scherler et al (2010). The model has already been used in many studies focussing on various purposes, including soil moisture (e.g., Noroozvalashedi et al, 2012;Wu and Jansson, 2013) and permafrost (Engelhardt et al, 2010;Marmy et al, 2013Marmy et al, , 2015Scherler et al, 2013Scherler et al, , 2014Staub et al, 2015). Other studies specifically applied the COUP model to simulate the soil moisture in frozen grounds (Scherler et al, 2010;Xarpell et al, 2010;Python, 2015).…”

“…The active layer thickness (ALT) typically varies between 4 and 6 m with maximum of 8.55 m in 2003(PERMOS, 2013. The possible long term evolution of permafrost at Schilthorn was investigated using the COUP model and downscaled RCM scenarios for the next 100 years (Marmy et al, 2013Scherler et al, 2013). According to these studies, permafrost at Schilthorn is comparatively sensitive and will probably start to degrade early within this century.…”

“…To analyze the water and ice content evolution in detail we used the heat and mass transfer model COUP (see Scherler et al, 2010Scherler et al, , 2013Marmy et al, 2013). Due to the complexity of the coupled hydrological and thermal processes in the ground, we used here the semi-automated calibration scheme proposed by Marmy et al (2015).…”

“…The COUP model is currently used in permafrost research for process modeling and long-term transient modeling of the permafrost evolution (Scherler et al, 2010(Scherler et al, , 2014 as well as for sensitivity studies (Engelhardt et al, 2010;Marmy et al, 2013;Staub et al, 2015), whereas the 4PM was selected for its ability to determine the spatial variability of ice content in the ground, which was found to be one of the key factors controlling the sensitivity of mountain permafrost to climate changes (e.g., Harris et al, 2009;Scherler et al, 2013).…”