Ice aprons on steep high-alpine slopes: insights from the Mont-Blanc massif, Western Alps

• Published in: Journal of Glaciology
• Main Authors: Ravanel, Ludovic, Guillet, Grégoire, Kaushik, Suvrat, Preunkert, Susanne, Malet, Emmanuel, Magnin, Florence, Trouvé, Emmanuel, Montagnat, Maurine, Yan, Yajing, Deline, Philip
• Other Authors: Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), University of St Andrews Scotland, Laboratoire d'Informatique, Systèmes, Traitement de l'Information et de la Connaissance (LISTIC), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry ), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Cold ice; glacial heritage; ice aprons; ice melting; Mont-Blanc massif; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SHS.GEO]Humanities and Social Sciences/Geography; Ice; Journal of Glaciology; permafrost
• Online Access: https://hal.science/hal-04172099; https://hal.science/hal-04172099/document; https://hal.science/hal-04172099/file/ice-aprons-on-steep-high-alpine-slopes-insights-from-the-mont-blanc-massif-western-alps.pdf; https://doi.org/10.1017/jog.2023.15

International audience Ice aprons are defined as very small ice bodies covering steep rock slopes. They have only been the subject of increased scientific interest for a few years, despite the fact that they are a condition for mountaineering and obvious elements in the high-alpine landscapes. However, very little is known about their distribution, evolution and physical characteristics. In this paper, we review the existing knowledge on ice aprons, which have almost exclusively been investigated in the Mont-Blanc massif, Western Alps. We supplement this review with novel results from recent surveys of ice aprons. We used a wide array of methodologies, from remote sensing (multi-source imagery) to in situ (stakes and thermal monitoring) and laboratory (radiocarbon dating and texture analysis) glaciological investigations. In the Mont-Blanc massif, ice aprons occupy 4.2 km 2 within the alpine permafrost zone. Temperature measured at the ice–rock interface is indeed largely negative. Thinness of ice aprons coupled with the cold context implies a quasi-stationary shear regime without basal Sliding. Only ice at the surface can possibly melt in warm periods. After a shrinking period from the end of the Little Ice Age to the mid-to-late-1960s, ice aprons experienced a short period of expansion, followed by an accelerated shrinkage since the beginning of the 21st century. This shrinkage now favours rockfall triggering and poses a serious threat to a glaciological heritage since ice aprons host several-thousand-year-old ice. Finally, we synthesize this information to assess the existing definition of ice aprons, and propose some future research directions.