Climate change leads to more alpine hazards

From rockfall to ice avalanches: Climate change is intensifying natural hazards in the mountains in many places, posing particular challenges for the Alpine region. This is the result of a study jointly coordinated by glaciologist Mylène Jacquemart and permafrost expert Samuel Weber from ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. The international team has evaluated more than three hundred scientific papers from the past three decades.

Rockfall, landslides, debris flows, snow and ice avalanches
Mass movements such as rockfall, landslides, debris flows, snow and ice avalanches have always characterised alpine landscapes. (Graphic: Jacquemart and Weber et al. / Earth-Science Reviews 2024)

The study focuses on the most common natural hazards in the Alps: rockfall, landslide, debris flow, ice and snow avalanche. The results:

  • Rockfall: Activity has increased in recent decades, but only in the high Alpine region. There, the permafrost is thawing (see box) and the glaciers are retreating. This weakens the rock on a widespread basis and encourages the release of stones and rock masses.
  • Rock avalanche: There is comparatively little data available for these major events. "Even if a clear statement is not yet possible, there are many indications that large rock avalanches occur more frequently today," says Weber.
  • Debris flows: The number of heavy precipitation events that can trigger debris flows has clearly increased. "But only half of the studies examined indicate an increase in debris flows," says Jacquemart. However, there are signs of more activity above the tree line and in areas not previously affected. Due to the retreat of the glaciers and increased rockfall, there is more loose material available that rainfalls can set in motion.
  • Avalanches: "Activity is declining at low altitudes because the amount of snow is decreasing. At high altitudes, on the other hand, avalanche activity has increased slightly," explains Weber. At the same time, the avalanches are changing their characteristics. Dry avalanches occur less frequently on average these days, while wet snow avalanches are more common.
  • Ice avalanches: In many places, ice avalanches are disappearing along with the glaciers. However, regional observations indicate that larger ice avalanches have been occurring more frequently since the turn of the millennium. "Where and how exactly ice avalanches are changing needs to be investigated further," admits Jacquemart.
Enlarged view: Diagram of the processes
Rising temperatures are the (I) primary cause for the observed increase of rockfall (a) in alpine regions. Above treeline, increased sediment availability and increased intense precipitation (II) lead to increased debris-flow activity, potentially in locations without historical precedence (b). Warmer winters are leading to scarcer snow conditions (III) at low elevations and a transient state of increased snowfall at high elevations. This shift is leading to more avalanches with wet snow (c), fewer and smaller avalanches (d) at low and mid elevations, and increased avalanche activity at high elevations (e). (Graphic: Jacquemart and Weber et al. / Earth-Science Reviews 2024)

None of this comes as a surprise. Jacquemart and Weber refer to the first IPCC assessment report from 1990, which had already predicted an increase in alpine hazards due to climate change. The researchers expect snow and ice avalanches to become rarer by the end of the 21st century as warming continues. At the same time, the permafrost will continue to warm, even at high altitudes. The researchers therefore assume that rockfalls, debris flows and landslides will become more frequent. "This change poses major challenges for society in the Alpine region," emphasize Jacquemart and Weber.

The study was carried out as part of the WSL research programme external page CCAMM.

What is Permafrost?

Permafrost is ground such as rock, debris or moraine that has temperatures below 0°C throughout and is therefore permanently frozen. Permafrost covers some five percent of Switzerland’s territory and is mainly found in scree slopes and rock walls in cold locations at elevations above 2,500 metres above sea level.

Reference

Mylène Jacquemart & Samuel Weber, Marta Chiarle, Małgorzata Chmiel, Alessandro Cicoira, Christophe Corona, Nicolas Eckert, Johan Gaume, Florie Giacona, Jacob Hirschberg, Roland Kaitna, Florence Magnin, Stepanhie Mayer, Christine Moos, Alec van Herwijnen, Mrakus Stoffel
external page Detecting the impact of climate change on alpine mass movements in observational records from the European Alps
Earth Science Reviews (October 2024), doi: 10.1016/j.earscirev.2024.104886

Contact

Dr. Mylène Jacquemart, Scientific staff member, Chair of Glaciology, ETH Zürich, +41 44 632 41 62,

Dr. Samuel Weber, Scientific staff member, Institute for Snow and Avalanche Research SLF, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, +41 81 4170 376,

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