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Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2018-21
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
19 Mar 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).
Wet avalanches: long-term evolution in the Western Alps under climate and human forcing
Laurent Fouinat1, Pierre Sabatier1, Fernand David2, Xavier Montet3, Philippe Schoeneich4, Eric Chaumillon5, Jérôme Poulenard1, and Fabien Arnaud1 1EDYTEM, University Savoie Mont Blanc, CNRS, 73376 Le Bourget du Lac Cedex, France
2CEREGE, University Aix-Marseille, 13545 Aix en Provence, France
3University of Geneva Department of Radiology and Medical Informatics Genève, 1211, Switzerland
4IUGA, University Grenoble Alpes, 38100 Grenoble, France
5LIENSs University of La Rochelle, 17 000 La Rochelle, France
Abstract. Understanding wet avalanche intensity and the role of past environmental changes on wet avalanche occurrence is a main concern especially in the context of a warming climate and accelerated environmental mutations. Avalanches are closely related to fast cryosphere changes and may cause major threats to human society. Here, we used the sedimentary archive of the alpine Lake Lauvitel (western French Alps) to establish the first long-term avalanche record in this Alpine region. For this purpose, we used a novel CT scan methodology that allows the precise identification of coarse material – from sand to pebble – transported to the lake and embedded within the finer continuous sedimentation. We identified a total of 166 deposits over the last 3300 yrs cal. BP. In parallel, a detailed pollen analysis gave an independent record of environmental changes. Based on modern observation, lake monitoring, seismic investigations and sedimentological evidences, coarse material deposits were attributed to wet avalanche events. Our results highlight the effect of vegetation cover on the avalanche hazard while a period of strong frequency increase occurred after 780 yrs cal. BP. In Lake Lauvitel, this period corresponds to a major forest clearance induced by the rise of human land-use. Climate forcing on the avalanche hazard was investigated before and after the vegetation shift. On a multi-centennial scale, wet avalanches preferably occur during periods of larger glacier extent, in which higher winter precipitations probably generate a sufficiently thick snow cover. On a sub-centennial scale, avalanches are more frequent during periods of relative warming, resulting in a destabilisation of the same snow cover in spring season. Our results highlight as well the role of forest cover to mitigate wet snow avalanches occurrence. In the context of predicted warmer temperatures, this study raises the question of whether a wet avalanche hazard increase may be expected in the near future especially at higher altitudes.
Citation: Fouinat, L., Sabatier, P., David, F., Montet, X., Schoeneich, P., Chaumillon, E., Poulenard, J., and Arnaud, F.: Wet avalanches: long-term evolution in the Western Alps under climate and human forcing, Clim. Past Discuss., https://doi.org/10.5194/cp-2018-21, in review, 2018.
Laurent Fouinat et al.
Laurent Fouinat et al.

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LAU11-I IEFRA007I
Laurent Fouinat et al.

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Short summary
In the context of a warming climate, mountain environments are especially vulnerable to a change in the risk pattern. Our study focuses on the past evolution of wet avalanches, likely triggered by warmer temperatures destabilizing the snow cover. In the last 3300 years we observed an increase of wet avalanche occurrence related to human activities, intensifying pressure on forest cover; as well as favorable climate conditions such as warmer temperatures coinciding with retreating glacier phases.
In the context of a warming climate, mountain environments are especially vulnerable to a change...
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