The most direct information about the reaction of mountain permafrost to climate change derives from borehole temperature measurements. Following the equipment for long-term monitoring of the first borehole drilled through an active rock glacier (Haeberli et al. 1988; Vonder Muhll and Haeberli 1990; Vonder Muhll et al. 1998), attempts were made to collect borehole measurements from mountains on several continents (Haeberli et al. 1998). The standardized bedrock boreholes to 100 m depth established by the EU-funded project Permafrost and Climate in Europe (PACE; Fig. 14.2) for climate-related monitoring of mountain permafrost through the European mountains thereby constitute a major contribution to the Global Terrestrial Network for Permafrost (GTN-P) within GTOS/GCOS (Harris et al. 2001).

A real revolution in the systematic observation of thermal conditions at surfaces of remote slopes and rock walls with difficult access (especially in wintertime) was the introduction and installation of a rapidly increasing number of miniature temperature loggers, which provide fundamentally important high-resolution information on surface temperatures and snow-cover effects (Hoelzle et al. 1999, 2003; Gruber et al. 2003).

Modern strategies of long-term permafrost monitoring at high mountain sites now combine measurements of borehole temperature with miniature temperature

Fig. 14.2 Drilling into permafrost at Juvassh0e near Jotunheimen, Norway for long-term monitoring of borehole temperatures. Permafrost temperature at 20 m depth is about -3°C, and permafrost thickness clearly exceeds 100 m (photo: K. Isaksen 2000)

logging at nearby surfaces, geophysical soundings or even time-lapse geophysics (resistivity and seismic tomography) at fixed profiles (Fig. 14.3; Krautblatter and Hauck 2007) and numerical modelling of time-dependent 3D-temperature evolution (Noetzli et al. 2007). Together with observations of temperature evolution through time (Isaksen et al. 2007), the latter is especially important to disentangle topographic and climatic effects on temperature profiles with depth, and to reconstruct past permafrost temperature histories from heat-flow anomalies (Gruber et al. 2004b). Photogrammetry and more recently also differential GPS and INSAR technologies are used to document flow patterns and their changes in time of creeping permafrost within numerous rock glaciers (Haeberli et al. 2006; Strozzi et al. 2004; Delaloye et al. 2008).

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