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Temperature measured in different boreholes in mountain permafrost in Switzerland 1987-2007

Note: Note: Measured at ca

Data source:

PERMOS, 2007. Permafrost in Switzerland 2002/2003 and 2003/2004. Glaciological Report (Permafrost) 4(5) of the Glaciological Commission of the Swiss Academy of Sciences (SAS) and Department of Geography, University of Zurich

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Temperature distribution within a mountain range containing permafrost

Note: Note: Permafrost is present in the blue area bordered by a black line.

Data source:

Gruber, S. and Haeberli, W., 2007. Permafrost in steep bedrock slopes and its temperature-related destabilization following climate change. Journal of Geophysical Research 112, p. F02S18

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Past trends

Data from a north-south transect of boreholes, 100 m or more deep, extending from Svalbard to the Alps (European PACE-project) indicate a long-term regional warming of permafrost of 0.5-1.0 ^oC during the recent decade (Harris et al., 2003). In Scandinavia and Svalbard, monitoring over 5-7 years shows warming down to 60 m depth and current warming rates at the permafrost  surface of 0.04-0.07 ^oC/year (Isaksen et al., 2007). In Switzerland, a warming trend and increased active-layer depths were observed in 2003, but results varied strongly between borehole locations due to variations in snow cover and ground properties (PERMOS, 2007). At the Murtel-Corvatsch (rock-glacier) borehole in the Swiss Alps, the only long-term data record (20 years), permafrost temperatures in 2001, 2003 and 2004 were only slightly below - 1 ^oC (Figure 1) and were, apart from 1993 and 1994, the highest since measurements began in 1987 (Vonder Muhll et al., 2007). Such data measured at rock-glaciers are difficult to interpret because the sub-surface thermodynamics in ice-rich frozen debris is rather complex. Complementary and clearer signals on thawing permafrost are expected from boreholes drilled directly into bedrock (e.g. Schilthorn, M. Barba Peider; Figure. 2). Corresponding monitoring programmes, such as PACE and PERMOS, however, only started less than a decade ago.

Projections

No specific projections on the behaviour of mountain permafrost are yet available, but changes in mountain permafrost are likely to continue in the near future and the majority of permafrost bodies will experience warming and/or melting. According to recent model calculations based on the regional climate model REMO and following the IPCC SRES-Scenarios A1B, A2 and B1, a warming of up to 4 ^oC by 2100 is projected for the Alpine region (Jacob et al., 2007). Further rises in temperature and melting permafrost could increasingly destabilise mountain walls and increase the frequency of rock falls, posing problems to mountain infrastructure and communities (Gruber et al., 2004a). The warming and thaw of bedrock permafrost can sometimes be rapid and failure along ice-filled joints can occur even at temperatures below 0 ^oC (Davies et al., 2001). Water flowing along linear structures and the advection of heat along joint systems will further accelerate destabilisation (Gruber and Haeberli, 2007).