| Summary: | Permafrost and its change in steep high-Alpine rock walls remain insufficiently understood because of the difficulties of in situ measurements. A large proportion of permafrost studies is mainly based on modelling, with a few existing instrumented sites and a resulting lack of process understanding. Yet, a number of rockfalls that occurred in the last decade in the Alps are likely related to climatically-driven permafrost degradation, as indicated by ice in starting zones, increased air temperature, and modelling studies. Starting off in the framework of the French-Italian PERMAdataROC project and presently under development within the EU co-funded project PermaNET (Permafrost long-term monitoring network: www.permanetalpinespace. eu), our investigations at the Aiguille du Midi begin in 2005. The summit (3842 m a.s.l) is accessible from Chamonix by a cable car which was built at the end of the 1950s. Half a million tourists visit the site each year. Because of its elevation, geometry, and year-round accessibility to rock slopes of diverse aspects and to galleries, the site was chosen for: - Monitoring of the thermal regime in steep rock walls. Thermistors were installed at depths of 2, 10, 30 and 55 cm, at all aspects and with slope angles in the range 60–90° (determining e.g. the presence and influence of snow). - Measurements of high altitude climatic data (air temperature and humidity, incoming and outgoing solar radiation, wind speed and direction) perpendicular to the rockwall surface, by movable automatic weather stations. Together with the rock temperature measurements, these data (see Morra et al., poster in session CR4.1) can be used for physically-based model validation (see Pogliotti et al., oral presentation in session CR4.1) or statistical models construction of rock temperature distribution and variability in the rock walls. - Making a 3D-high-resolution DEM by long-range (rock walls) and short-range (galleries) terrestrial laser scanning. - Surveying the distribution of permafrost in the rock mass ...
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