High-mountain slope failures and recent and future warm extreme events

• Main Authors: Huggel, Christian, Salzmann, Nadine, Allen, Simon
• Other Authors: McGuire, Bill, Maslin, Mark A, McGuire, B ( Bill ), Maslin, M A ( Mark A )
• Format: Book Part
• Language: English
• Published: Wiley-Blackwell 2013
• Subjects: Institute of Geography; 910 Geography & travel; glaciers; Ice; permafrost; Alaska
• Online Access: https://www.zora.uzh.ch/id/eprint/76512/; https://www.zora.uzh.ch/id/eprint/76512/1/2013_HuggelC_huggel_etal_slope_instabilities_warm_extremes_wiley13_Kopie_.pdf; https://doi.org/10.5167/uzh-76512; https://doi.org/10.1002/9781118482698.ch2

The number of large slope failures in some high mountain regions such as the European Alps has increased over the past two to three decades. There are a number of indications that ongoing climatic changes cause an increase in slope failures, thus possibly further exacerbating future failure events. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually warm, temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse patterns of meteorological variables in the days and weeks before the failures. Although we did not find one general air temperature pattern, all the studied failures were preceded by unusually warm periods; several happened immediately after temperatures suddenly dropped to freezing level. We assessed the frequency of warm extremes in future by analysing eight regional climate models (RCMs) from the recently completed EU programme ENSEMBLES for the central Swiss Alps. The models show an increase in the frequency of high-temperature events for the period 2001–2050 compared with a 1951–2000 reference period. The 5-, 10- and 30-day warm events are projected to increase about 1.5–4 times by 2050, and in some models by up to 10 times. Warm extremes can trigger large landslides in temperature-sensitive, high mountain environments by increasing occurrence of liquid water due to melt of snow and ice, and by rapid thaw of permafrost. In addition to these climate-induced processes, which can reduce slope strength, local geological, glaciological and topographic parameters of a slope also must be considered for comprehensive analyses.