The Influence of Glacier Randkluft Systems on Rockfall (CirqueMonHT)

Funding Agency: ARGE-Alp (2017-2019)

Principle Investigators: Dr. Markus Keuschnig, Georesearch, Gerald Valentin, Landesgeologie Salzburg

Project Team: Landesgeologie Salzburg, Technical University Munich (TUM), University of Salzburg, Institute for Interdisciplinary Mountain Research (IGF), imBERG CONSULT GmbH

Glacierized cirques are defining high-alpine landscape elements which react particularly sensitively to climatic changes such as rising temperatures or an increase in the proportion of liquid precipitation. Most cirque glaciers are thinning rapidly, and hence, are constantly exposing fresh headwall sections, often featuring drastically changed thermal and rock mechanical boundary conditions. For such freshly exposed sections which frequently are oversteepened and underlain by permafrost, rockfall activity has been documented to be particularly high and hence, poses a considerable risk factor for man and infrastructure which is expected to only increase in the foreseeable future. However, due to the complete lack of robust, long-term data, further assessment of this risk factor is subject to considerable uncertainty.

To address this knowledge gap, CirqueMonHT has established an extensive environmental monitoring system at the Ödenwinkelkar (Stubach valley, Salzburg), a glacial cirque typical of the Hohe Tauern range. Stability relevant temperature changes in bedrock surfaces exposed by recent glacier retreat are monitored in various measurement transects. To simultaneously monitor bedrock stresses, joint aperture changes are recorded in selected locations. High-precision remote sensing techniques, such as laserscanning and photogrammetry, are used to localize and quantify rockfall release zones. Ice temperature and ice velocity measurements are employed to analyze glacial ablation dynamics, enabling an accurate estimation of future glacier behavior close to the headwall. The meso climate within the cirque is recorded by several weather stations, allowing to assess the significant influence of topographic shading effects and local wind conditions.

The consequences of climate change usually become apparent only after long response times. Thus, a comprehensive understanding of increased rockfall activity in freshly exposed headwall sections requires monitoring periods of sufficient length. CirqueMonHT therefore explicitly strives towards a long-term monitoring of relevant processes at decadal scale and towards the integration of existing glaciological and hydrological datasets.