DISTRIBUTION AND EVOLUTION OF ICE APRONS IN A CHANGING CLIMATE IN THE MONT-BLANC MASSIF (WESTERN EUROPEAN ALPS)

Rock glaciers are landforms generated by the creep of frozen ground (permafrost) in cold-climate mountains. Mapping rock glaciers contributes to documenting the distribution and the dynamics of mountain permafrost. We compiled inventories documenting the location, the characteristics, and the extent of rock glaciers in 12 mountain regions around the world. In each region, a team of operators performed the work following common rules and agreed on final solutions when discrepancies were identified.

We studied how water moves through fractured rock walls in a high mountain area in the Alps. Using sensors and tracers over two years, in a high-altitude site, we tracked where the water came from and when it flowed. Most of it came from melting snow, but some came from rain and older ice. The results show that heat and water flow can speed up the melting of frozen ground, which may affect mountain stability. This helps us understand how climate change influences these fragile environments.

This study presents a robust methodological approach to detect and analyse rock glacier kinematics using Landsat 7/Landsat 8 imagery. In the semiarid Andes, 382 landforms were monitored, showing an average velocity of 0.37 ± 0.07 m yr⁻¹ over 24 years, with rock glaciers moving 23 % faster. Results demonstrate the feasibility of using medium-resolution optical imagery, combined with radar interferometry, to monitor rock glacier kinematics with widely available satellite datasets.

Permafrost dynamics at Aiguille du Midi in the French Alps was investigated using Automated Electrical Resistivity Tomography (A-ERT) during four years. A-ERT reveals seasonal and multi-year permafrost changes. Temperatures estimated using resistivity measurements provide a good agreement with measured temperature in borehole in frozen zone. Variations in active layer thickness across different faces were observed, along with a slight decrease in permafrost resistivity suggesting warming.

Quantitative knowledge of water availability on high mountain rock slopes is very limited. We use a numerical model and field measurements to estimate the water balance at a steep rock wall site. We show that snowmelt is the main source of water at elevations >3600 m and that snowpack hydrology and sublimation are key factors. The new information presented here can be used to improve the understanding of thermal, hydrogeological, and mechanical processes on steep mountain rock slopes.