Effects of climate change on high Alpine mountain environments: Evolution of mountaineering routes in the Mont Blanc massif (Western Alps) over half a century

International audienceIn high alpine environments, glacial shrinkage and permafrost warming due to climate change have significant consequences on mountaineering routes. Few research projects have studied the relationship between climate change and mountaineering; this study attempts to characterize and explain the evolution over the past 40 years of the routes described in The Mont Blanc Massif: The 100 Finest Routes, Gaston Rébuffat's emblematic guidebook, published in 1973.The main elements studied were the geomorphic and cryospheric changes at work and their impacts on the itinerary's climbing parameters, determining the manner and possibility for an itinerary to be climbed. Thirty-one interviews, and comparison with other guidebooks, led to the identification of 25 geomorphic and cryospheric changes related to climate change that are affecting mountaineering itineraries. On average, an itinerary has been affected by nine changes. Among the 95 itineraries studied, 93 have been affected by the effects of climate change-26 of them have been greatly affected; and three no longer exist. Moreover, periods during which these itineraries can be climbed in good conditions in summer have tended to become less predictable and periods of optimal conditions have shifted toward spring and fall, because the itineraries have become more dangerous and technically more challenging

Neige et Glace de Montagne : Reconstitution, dynamique, pratiques

Collection edytem n°8International audienceLes cahiers (de géographie, géologie et paléoenvironnement) de la Collection EDYTEM visent à faire connaître les recherches menées au sein du laboratoire EDYTEM ou de programmes dans lequel nous sommes impliqués. Si la priorité est la diffusion de nos travaux dans les revues majeures de nos communautés et les congrès internationaux, il nous paraît également important de mettre en avant la transversalité des recherches du laboratoire qui mobilise plusieurs champs disciplinaires autour de mêmes objets d'étude. Il est, en effet, difficile de mettre en avant cette dimension par le seul biais des publications dans des revues ou des communications qui répondent avant tout à des logiques disciplinaires. La Collection EDYTEM a cette mission : rendre visible la démarche interdisciplinaire du laboratoire autour d'entrées fédératrices : les systèmes hydrothermaux de montagne, les systèmes nivo-glaciaires et les systèmes karstiques. Trois entrées qui caractérisent les objets privilégiés d'étude du laboratoire. Après le numéro dédié à l'Aven d'Orgnac porté par " l'axe karst ", ce nouveau numéro illustre les recherches menées sur la haute montagne et les systèmes nivo-glaciaires. Le prochain numéro également prévu en 2009 traitera de l'hydrothermalisme de montagne. Soulignons que ces trois axes ont été mis en place il y a un peu plus de deux ans. Le fait que chacun d'entre eux produise en peu de temps des synthèses originales, reflète la rapide mobilisation des différents champs disciplinaires du laboratoire sur ces objets de recherche. Ce numéro " Neige et glace " illustre parfaitement cette dynamique. La participation très active des doctorants, comme contributeurs mais aussi animateurs des réunions de travail et de chantiers de recherche en est un bon exemple. Tout comme la structuration du numéro, qui aborde les reconstitutions paléoenvironnementales (de la dernière grande glaciation au Petit Âge Glaciaire), les dynamiques actuelles, à la fois reflets et indicateurs du changement climatique, et les incidences de ce changement sur le tourisme hivernal, les risques en montagne. Ces trois entrées illustrent les apports respectifs des trois équipes du laboratoire. Les 21 contributions originales de ce cahier reflètent la dynamique du laboratoire sur la montagne et les priorités mises à la fois sur les outils (laserscanning, métrologie, dendrochronologie, photogrammétrie, imagerie, modélisation...), les recherches doctorales (T. Barth, N. Cayla, S. Coutterand, P. Paccard, L. Ravanel et M. Le Roy) et l'accueil de chercheurs et de post-doct étrangers (S. Gruber, M. Kirkbride). Ce numéro a le mérite de poser clairement les recherches menées par le laboratoire sur la haute montagne, la neige et les glaciers et sa contribution dans les sciences de l'environnement

Paraglacial Rock Slope Adjustment Beneath a High Mountain Infrastructure—The Pilatte Hut Case Study (Écrins Mountain Range, France)

Landslides triggered by shrinking glaciers are an expected outcome of global climate change and they pose a significant threat to inhabitants and infrastructure in mountain valleys. In this study we document the rock slope movement that has affected the Pilatte hut (2,572 m a.s.l.) in the Écrins range (French alps) since the 1980s. We reconstructed the geometry of the unstable rock mass using Terrestrial Laser Scanning and quantified the unstable volume (~400,000 m3). Field observations and annual crack surveys have been used to identify the dynamics of past movements. These movements initiated in the late 1980s and have accelerated since 2000. The current trend seems to be toward a relative stabilization. Reconstruction of the glacier surface using past images taken since 1960 and “Structure from Motion” photogrammetry showed that the glacier probably applied stresses to the rock slope during its short-lived advance during the 1980s, followed by debuttressing caused by rapid surface lowering until the present day. The relationship between observed crack propagation and glacier surface change suggests that the rock slope instability is a paraglacial response to glacier surface changes, and highlights that such responses can occur within a decade of glacier change

Investigation of a cold-based ice apron on a high-mountain permafrost rock wall using ice texture analysis and micro-14C dating : a case study of the Triangle du Tacul ice apron (Mont Blanc massif, France)

This study is part of the ANR 14-CE03-0006 VIP Mont Blanc and the EU ALCOTRA AdaPT Mont Blanc project.The current paper studies the dynamics and age of the Triangle du Tacul (TDT) ice apron, a massive ice volume lying on a steep high-mountain rock wall in the French side of the Mont-Blanc massif at an altitude close to 3640 m a.s.l. Three 60 cm long ice cores were drilled to bedrock (i.e. the rock wall) in 2018 and 2019 at the TDT ice apron. Texture (microstructure and lattice-preferred orientation, LPO) analyses were performed on one core. The two remaining cores were used for radiocarbon dating of the particulate organic carbon fraction (three samples in total). Microstructure and LPO do not substantially vary with along the axis of the ice core. Throughout the core, irregularly shaped grains, associated with strain-induced grain boundary migration and strong single maximum LPO, were observed. Measurements indicate that at the TDT ice deforms under a low strain-rate simple shear regime, with a shear plane parallel to the surface slope of the ice apron. Dynamic recrystallization stands out as the major mechanism for grain growth. Micro-radiocarbon dating indicates that the TDT ice becomes older with depth perpendicular to the ice surface. We observed ice ages older than 600 year BP and at the base of the lowest 30 cm older than 3000 years.Publisher PDFPeer reviewe

Seeing the Ice. An Overview of Alpine Glacier Tourism Sites, Between Post- and Hyper-Modernity

Glaciers have been popular tourist attractions for almost two centuries. However, current climate change is now posing a new threat. In this context, this paper aims to question the tourism forms which are currently identifiable within Alpine glacier tourism sites. An inventory carried out on an Alpine scale shows that different tourist practices (contemplation, visit of ice caves, recreational activities, environmental education, and luxury) can coexist. The analysis of the way various sites function demonstrates that these practices can be related to the different forms of tourism that exist in the scientific literature: modern, post-modern and hyper-modern tourism. The coexistence of these forms of tourism at glacier sites reveals six possible combinations, i.e. six types of sites: contemplative, experiential, recreational, interpretative, premium and distinctive. Spatial analysis also shows that the premium and distinctive sites are mainly located around the major Alpine tourist destinations (Chamonix, Zermatt and Grindelwald), while the others are more homogeneously distributed. These results raise questions about the way in which these sites was and will develop and the role climate change plays, both of which constitute potential research topics for the future

Effects of topographic and meteorological parameters on the surface area loss of ice aprons in the Mont Blanc massif (European Alps)

Ice aprons (IAs) are part of the critical components of the Alpine cryosphere. As a result of the changing climate over the past few decades, deglaciation has resulted in a surface decrease of IAs, which has not yet been documented out of a few specific examples. In this study, we quantify the effects of climate change on IAs since the mid-20th Century in the Mont-Blanc massif (western European Alps). We then evaluate the role of climate forcing parameters and the local topography in the behaviour of IAs. For this, we precisely mapped the surface areas of 200 IAs using high-resolution aerial and satellite photographs from 1952, 2001, 2012 and 2019. From the latter inventory, the surface area of the present individual IAs ranges from 0.001 to 0.04 km2. IAs have lost their surface area over the past 70 years, with an alarming increase since the early 2000s. The total area, from 7.93 km2 in 1952, was reduced to 5.91 km2 in 2001 (-25.5 %) before collapsing to 4.21 km2 in 2019 (-47 % since 1952). We performed a regression analysis using temperature and precipitation proxies to understand better the effects of climate forcing parameters on IA surface area variations. We found a strong correlation between both proxies and the relative area loss of IAs, indicating the significant influence of the changing climate on the evolution of IAs. We also evaluated the role of the local topographic factors in the IAs area loss. At a regional scale, factors like direct solar radiation and elevation have an important influence on the behaviour of IAs, while others like curvature, slope, and size of the IAs seem to be rather important on a local scale.</p

Les versants englacés de la haute montagne alpine : Évolution holocène et impacts de la crise climatique actuelle

Coups de chaud sur la haute montagne alpineAprès les coups de semonce des étés 2003 et 2015 et leur retentissement médiatique, la succession des étés 2022 et 2023 constitue un troisième palier et un coup d’accélérateur évident du réchauffement et de la morphodynamique de la haute montagne alpine. À Chamonix, au pied du mont Blanc, ces quatre années occupent respectivement les troisième, quatrième, première et deuxième positions des saisons les plus chaudes depuis le début des mesures en 1934..

The Glaciated Slopes of the High Alpine Mountains: Holocene Evolution and Impacts of the Current Climate Crisis

Hot Flush on the Alpine MountainsAfter the wake-up calls of the summers of 2003 and 2015, along with their significant media impact, the succession of the summers of 2022 and 2023 represents a third stage and a clear acceleration in the warming and morphodynamics of the high Alpine mountains. In Chamonix, at the foot of Mont Blanc, these four years respectively rank as the third, fourth, first, and second-hottest summer seasons since measurements began in 1934 (MétéoFrance data). The morphod..

Estimating surface water availability in high mountain rock slopes using a numerical energy balance model

Water takes part in most physical processes that shape the mountainous periglacial landscapes and initiation of mass wasting. An observed increase in rockfall activity in several mountainous regions was previously linked to permafrost degradation in high mountains, and water that infiltrates into rock fractures is one of the likely drivers of these processes. However, there is very little knowledge on the quantity and timing of water availability for infiltration in steep rock slopes. This knowledge gap originates from the complex meteorological, hydrological and thermal processes that control snowmelt, and also the challenging access and data acquisition in the extreme alpine environments. Here we use field measurement and numerical modeling to simulate the energy balance and hydrological fluxes in a steep high elevation permafrost affected rock slope at Aiguille du Midi (3842 m a.s.l), in the Mont-Blanc massif. Our results provide new information about water balance at the surface of steep rock slopes. Model results suggest that only ~25 % of the snowfall accumulates in our study site, the remaining ~75 % are redistributed by wind and gravity. Snow accumulation depth is inversely correlated with surface slopes between 40&deg; to 70&deg;. Snowmelt occurs between spring and late summer and most of it does not reach the rock surface due to the formation of an impermeable ice layer at the base of the snowpack. The annual effective snowmelt, that is available for infiltration, is highly variable and ranges over a factor of six with values between 0.05&ndash;0.28 m in the years 1959&ndash;2021. The onset of the effective snowmelt occurs between May and August, and ends before October. It precedes the first rainfall by one month on average. Sublimation is the main process of snowpack mass loss in our study site. Model simulations at varying elevations show that effective snowmelt is the main source of water for infiltration above 3600 m a.s.l.; below, direct rainfall is the dominant source. The change from snowmelt-dominated to rainfall-dominated water availability is nonlinear and characterized by a rapid increase in water availability for infiltration. We suggest that this elevation of water availability transition is highly sensitive to climate change, if snowmelt-dominated permafrost-affected slopes experience an abrupt increase in water input that can initiate rock slope failure.</p

Late Glacial-Holocene cirque glacier chronology on sub-Antarctic Kerguelen Archipelago (49°S) based on cosmogenic 36Cl exposure dating

Sub-Antarctic glacier chronologies can provide valuable information about the past variability of climate dynamics in the Southern Ocean region. The Kerguelen Archipelago (49°S) is advantageously located under the influence of the Southern Hemisphere's westerly wind belt, thus fluctuations of climate-sensitive glaciers on Kerguelen can provide a baseline for understanding the behavior of this atmospheric regime in response to climatic forcings. We present 17 36Cl exposure ages of moraine and erratic boulders to provide chronological constraints to paleoglacier extents of the Guynemer cirque glacier, located just north of the Cook Ice Cap. Erratic boulders show ice thinning in the Guynemer region started to occur in the Late Glacial by 13.5 ka and continued past 12.4 ka. Ice retreat was punctuated by the formation of two moraine stages, the outermost at 11.5 ± 0.4 ka followed by another at 10.4 ± 1.2 ka, which are indicative of Early Holocene glacier advances/standstills. A glacial advance occurred at 1.4 ± 0.3 ka, which corroborates other Late Holocene re-advances elsewhere on the archipelago. Finally, three undated moraine stages are found between 1.4 ka and the 1960s. The lack of moraines after 10.4 ka and through the Mid-Holocene suggests that the Guynemer glacier was significantly smaller during this extended period of the Holocene compared to its Early Holocene as well as its Late Holocene limits. The Guynemer glacier history provides unique evidence of Early Holocene moraines on Kerguelen, which have not been discovered thus far on the archipelago. Similar to glaciers in Patagonia, New Zealand and South Georgia, the Guynemer glacier was at its largest Holocene extent in the Early Holocene. However, while other southern mid-latitude glacier chronologies show progressively smaller glacial extents throughout the Mid- to Late Holocene, the Late Holocene re-advance of the Guynemer glacier, like other Kerguelen glaciers, likely exceeded its Mid-Holocene extent