Avalanches : unlikely allies of glaciers

Avalanches are often seen as a danger in mountain sports, but they also have a beneficial side in that they supply many high-altitude glaciers with large quantities of snow, which they redistribute by gravity from the surrounding steep slopes.

A team from the Grenoble Institute of Environmental Geosciences (IGE) recently set out to quantify for the first time this avalanche snow supply to Argentière Glacier in the Mt Blanc massif. The difficulty of this study lies in the fact that it is impossible to maintain measuring instruments in these areas, which are regularly swept by avalanches of considerable size. The IGE team therefore relied on a combination of new observation techniques and glacier modelling. Using very high-resolution images from the Pléiades satellites, they were able to estimate the volume of snow redistributed by avalanches over the period 2012-2021.

The results of this study showed that 20% of the snow accumulation on Argentière Glacier comes from avalanches, and that this contribution rises to 60% at the foot of the surrounding mountain headwalls. These avalanches therefore make a very positive contribution to the state of health of Argentière Glacier, and numerical simulations have shown that taking this effect into account results in maintaining twice as much ice by 2100 in an average CO₂ emissions scenario. Nevertheless, the glacier would still lose almost 70% of its current volume.

Reference : Kneib, M., Dehecq, A., Gilbert, A., Basset, A., Miles, E. S., Jouvet, G., Jourdain, B., Ducasse, E., Beraud, L., Rabatel, A., Mouginot, J., Carcanade, G., Laarman, O., Brun, F., and Six, D. : Distributed surface mass balance of an avalanche-fed glacier, The Cryosphere, 18, 5965–5983, https://doi.org/10.5194/tc-18-5965-2024, 2024.

Scientific contact : Amaury Dehecq