Philippe Schoeneich

Ice Loss and Slope Stability in High-Mountain Regions

The present time is one significant stage in the adjustment of mountain slopes to climate change, and specifically atmospheric warming. This review examines the state of understanding of the responses of mid-latitude alpine landscapes to recent cryospheric change, and summarizes the variety and complexity of documented landscape responses involving glaciers, moraines, rock and debris slopes, and rock glaciers. These indicate how a common general forcing translates into varied site-specific slope responses according to material structures and properties, thermal and hydrological environments, process rates, and prior slope histories. Warming of permafrost in rock and debris slopes has demonstrably increased instability, manifest as rock glacier acceleration, rock falls, debris flows, and related phenomena. Changes in glacier geometry influence stress fields in rock and debris slopes, and some failures appear to be accelerating toward catastrophic failure. Several sites now require expensive monitoring and modeling to design effective risk-reduction strategies, especially where new lakes as multipliers of hazard potential form, and new activities and infrastructure are developed.

Velocity Changes of Rock Glaciers and Induced Hazards

Recent observations and geodetic measurements in the European Alps show that changes are occurring on rock glacier dynamics, ranging from moderate velocity variations to strong acceleration or even total collapse. These changes can be related to the ground temperature and to climate warming. In most cases, rock glaciers do not represent any serious hazard, except the instability of their surface and local rockfalls at the steep front. The surface movements, though moderate, can nevertheless cause damages to sensible infrastructures like cableways or buildings, if these are not designed to adapt to surface movements. The strong accelerations observed on some rock glaciers, however, induce a change of magnitude, and may threaten in some cases downslope areas. Thus, the presence of active or inactive rock glaciers with high ice content must be considered not only with regard to present conditions and dynamics, but with respect to possible evolutions due to climate change.

Permafrost Favorability Index: Spatial Modeling in the French Alps Using a Rock Glacier Inventory

In the present study we used the first rock glacier inventory for the entire French Alps to model spatial permafrost distribution in the region. The inventory, which does not originally belong to this study, was revised by the authors in order to obtain a database suitable for statistical modelling. Climatic and topographic data evaluated at the rock glacier locations were used as predictor variables in a Generalized Linear Model. Model performances are strong, suggesting that, in agreement with several previous studies, this methodology is able to model accurately rock glacier distribution. A methodology to estimate model uncertainties is proposed, revealing that the subjectivity in the interpretation of rock glacier activity and contours may substantially bias the model. The model highlights a North-South trend in the regional pattern of permafrost distribution which is attributed to the climatic influences of the Atlantic and Mediterranean climates. Further analysis suggest that lower amounts of precipitation in the early winter and a thinner snow cover, as typically found in the Mediterranean area, could contribute to the existence of permafrost at higher temperatures compared to the Northern Alps. A comparison with the Alpine Permafrost Index Map (APIM) shows no major differences with our model, highlighting the very good predictive power of the APIM despite its tendency to slightly overestimate permafrost extension with respect to our database. The use of rock glaciers as indicators of permafrost existence despite their time response to climate change is discussed and an interpretation key is proposed in order to ensure the proper use of the model for research as well as for operational purposes.