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Déclin des deux plus grands glaciers des Alpes françaises au cours du XXIe siècle : Argentière et Mer de Glace
Abstract and Figures
Des modélisations ont été réalisées sur les deux plus grands glaciers des Alpes françaises afin d’estimer leur évolution au cours du XXI esiècle.Pour un scénario climatique intermédiaire avec réduction des émissions de gaz à effet de serreavant la fin du XXI esiècle (RCP 4.5), les simulations indiquent que le glacier d’Argentière devrait disparaître vers la fin du XXI esiècleet que la surface de la Mer de Glace pourrait diminuer de 80 %. Dans l’hypothèse la plus pessimiste d’une croissance ininterrompue des émissions de gaz à effet de serre (RCP 8.5), la Mer de Glace pourrait disparaître avant 2100 et le glacier d’Argentière une vingtaine d’années plus tôt.
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... For larger glaciers such as the Mer de Glace (Figure 5), their state at the end of the century depends on the emission scenario. The Mer de glace would loose 80% of its surface area in 2100 under the intermediate emission scenario (RCP 4.5), while it would disappear before 2100 under the high emission scenario (RCP 8.5) (Vincent, Peyaud, et al., 2019). In contrast to the seasonal snow cover that mostly evolves in response to the meteorological conditions of the current year, the time evolution of glaciers results from a cumulative process by which glaciers gain or lose mass on an annual scale-most often lose, in the past decades, because of their negative annual mass balance under current climate conditions. ...
Mountain areas crown their surrounding landscapes and host a great diversity of ecosystems and human activities. Due to their high altitudes and low temperatures, mountains, in many regions of the world, including Europe, allow the existence of the solid phase of water, ice, seasonally or perennially, which is found in glaciers, snow cover and permafrost, key components of the cryosphere. In the European Alps, the air temperature has increased by about 2 °C compared to the pre-industrial period (end of 19th century), alongside with a slight change in the seasonality of precipitation. Both are projected to intensify in the future. The increase in temperature induces profound changes for the mountain cryosphere with in particular the scarcity of snow cover, the retreat of glaciers and the thawing of permafrost. These changes are causing a cascade of upheavals for the water cycle, mountain ecosystems, the economic and touristic activity of mountain societies. They also induce changes in the natural hazards associated with the cryosphere such as avalanches, risks of glacial and peri-glacial origins as well as floods and droughts. Thus, in a changing climate, the fragile beauty and balance of the European Alps is undergoing profound disruptions whose consequences extend to the lowlands. These will continue to intensify as long as the temperature continues to rise and this is why every increment of temperature matters for the state of the European mountains.
... The two main glaciers are the Argentière glacier and the Mer de Glace, in the Mont Blanc massif. Vincent et al. (2019) showed that, due to climate change, these two glaciers lost 34 and 45 m of water-equivalent depth, respectively, since the beginning of 20th century, representing 25 % and 32 % of their thickness, respectively. Some other glaciers are located in the Écrins and Vanoise massifs. ...
Over the last decade, large-sample approaches, i.e., based on large catchment sets, have become increasingly popular in hydrological studies. Efforts were made to assemble and disseminate national catchment datasets. This article aims to make a contribution to the construction of a large international database of catchments by proposing the CAMELS-FR dataset, a contribution to the CAMELS (Catchment Attributes and MEteorology for Large-sample Studies) initiative. The first version presented here gathers hydroclimatic data and physical attributes for a set of 654 catchments in France. These catchments cover a wide spectrum of hydroclimatic conditions (from oceanic to continental, mountainous, or Mediterranean conditions) and are considered to have limited human influence. Data include time series of daily streamflow (with at least 30 years over the 1970–2021 period, also aggregated to monthly and yearly time steps) and of 11 catchment-scale daily climate variables (including precipitation, potential evaporation, and air temperature), as well as a total of 255 catchment attributes organized into 10 classes (e.g., geology, soil, land cover). River flow time series were quality-checked. Along with the database itself, two graphical tools are proposed, namely dynamic graphs to visualize time series and graphical fact sheets to summarize the main catchment characteristics. Care was taken to provide as many metadata as possible to help users interpret their results based on this dataset. We intend to update the database regularly to include new available data and account for end users' feedback. CAMELS-FR is available at https://doi.org/10.57745/WH7FJR.
Over the last decade, large-sample approaches, i.e. based on large catchment sets, have become increasingly popular in hydrological studies. Efforts were made to assemble and disseminate national catchment datasets. This article aims to add a stone to the construction of a large international database of catchments by proposing the CAMELS-FR dataset, a contribution to the CAMELS initiative (Catchment attributes and meteorology for large-sample studies). The first version presented here gathers hydroclimatic data and physical attributes for a set of 654 catchments in France. These catchments cover a wide spectrum of hydroclimatic conditions (from oceanic to continental, mountainous or Mediterranean conditions), and are considered to have limited human influence. Data include time series of daily streamflow (with at least 30 years over the 1970–2021 period; also aggregated to monthly and yearly time steps) and of eleven catchment-scale daily climate variables (including precipitation, potential evaporation, and air temperature), as well as a total of 255 catchments attributes organised in ten classes (e.g. geology, soil, land cover, etc.). River flow time series were quality-checked. Along with the database itself, two graphical tools are proposed, namely dynamic graphs to visualize time series and graphical fact sheets to summarize the main catchments characteristics. Care was taken to provide as many metadata as possible to help users interpret their results based on this dataset. We intend to update the database regularly to include new available data and account for end-users' feedbacks.
One of the most complete, spectacular and most thoroughly documented sections of Ordovician cool to temperate water limestones, globally. It is significant in understanding the Ordovician world.
Entering the Anthropocene, defined as the era during which human activities have become forces capable of influencing the climate and the environment on a planetary scale, raises many questions for tourism. Glacier tourism sites and practices, although not uniquely, are changing along with their environment. These changes raise the question of how climate change influences the motivations of those involved in tourism and, more specifically, allow us to envisage the emergence of reflexive tourism. Reflexive tourism is understood to be an awareness by tourists themselves of the issues - in this case, environmental issues - raised by current lifestyles, and offers a broader approach to the contradictions faced by societies in the context of the challenges of ecological transition. By analysing the implementation of the project to rehabilitate one of France’s most famous glacier sites, Montenvers and its Mer de Glace, this article aims to examine the rationale behind the development of tourism in such a site, while highlighting its contradictions. Interviews with site and project stakeholders reveal a clear tension between a logic of sustainability leading to reflexive tourism, and an economic logic of investment and the quest for profitability. Beyond this case study, this work considers more generally the figure of tourism as a symbol of societal contradictions between discourse and practice in the Anthropocene.
L’entrée dans l’Anthropocène, défini comme l’ère dans laquelle les activités humaines deviennent des forces à même d’influencer le climat et l’environnement à l’échelle planétaire, induit de nombreuses questions pour le tourisme. S’ils ne sont pas les seuls, les sites touristiques glaciaires, et les pratiques afférentes, se transforment avec leur environnement. Ces transformations posent la question de l’influence du changement climatique sur les motivations des acteurs touristiques et permettent d’envisager plus spécifiquement l’avènement d’un tourisme réflexif. Entendu comme une prise de conscience par les touristes eux-mêmes des enjeux – ici, environnementaux – soulevés par les modes de vie actuels, le tourisme réflexif permet plus largement d’aborder les contradictions auxquelles sont confrontées les sociétés dans le cadre des défis de la transition écologique. À travers l’analyse de la mise en œuvre du projet de réhabilitation de l’un des sites glaciaires les plus connus de France, le Montenvers et sa Mer de Glace, cet article entend interroger les logiques du développement touristique d’un tel site tout en soulignant ses contradictions. Les entretiens menés avec les parties prenantes du site et du projet montrent une tension claire entre une logique de durabilité menant au tourisme réflexif et une logique économique d’investissement et de quête de rentabilité. Au-delà de ce cas d’étude, ce travail questionne plus généralement la figure du tourisme comme symbole des contradictions sociétales entre discours et pratiques à l’heure de l’Anthropocène.
Climate change is causing profound changes in high mountain environments, including the rapid retreat of glaciers. The retreat and potential disappearance of Alpine glaciers during the twenty-first century raises questions about the future of glacier tourism sites. This perspective article reflects on these changes with a desk-based approach to suggest three possible ways glacier tourism can adapt to anticipated glacier loss. These three strategies include further developing geotourism, transforming last-chance tourism into “dark tourism,” and using virtual reality to “virtually” reconstruct disappearing glaciers. This paper draws on three cases to discuss the potential of these strategies. The first is the Aletsch Glacier, the largest in the Alps, which is listed as a UNESCO World Heritage Site. It has also been the subject of recent work on geotourism. The second case is Mer de Glace, the largest glacier at the Montenvers site in France. This glacier has been studied in the context of last-chance tourism. The final case is the Mortaretsch Glacier in Switzerland, which can be reached from Diavolezza and has not been the subject of many studies. However, this site is one of the first to incorporate virtual reality technology into the tourist experience of the glacier.
The Infierno Glacier is located in Aragon (Spain), Pyrenees Mountain range, the only one in this country that still preserves white glaciers. These are the southernmost glaciers in Europe and are currently in rapid decline. The work analyzes the evolution of the glacier between 2016 and 2022 and provides data, for this period, which lacked this information, in an area bordering the glacial ice survival. In addition to the observations on the glacier itself, the variables (precipitation, temperature, snow volume and thickness) that allow an understanding of this evolution are studied. The results show a setback of the glacier (thickness losses: 4.6 m; front retreat; 14.9 m). The evolution has frequent trend changes, linked to the interannual climatic irregularity characteristic of the Pyrenees. The main explanatory factor is the thermal increase. The thermal anomalies with respect to the average reference values have increased, in this period, by +0.55 °C. The year 2022 has been particularly warm and has recorded the greatest losses for this glacier. With respect to precipitation, it has an irregular behavior and shows a tendency to decrease (−9% in the same period). This work has the additional interest of analyzing a glacier in the terminal phase, which if current trends continue, evolves into dead ice.
The Infierno glacier is located in Aragon (Spain), Pyrenees mountain range, southern slope, the only one in this country that still preserves white glaciers. These are the southernmost glaciers in Europe and are currently in rapid regression. The work analyzes the evolution of the glacier between 2016 and 2022 (taking as "year zero" or starting point, 2015). In addition to the observations on the glacier itself, the variables (precipitation, temperatures, snow volumes and thicknesses) that allow understanding this evolution are studied. The results offer strong regression, with thickness losses in that period of 4.6 m and retreat of its front of 14.9 m. The evolution has frequent trend changes, linked to the interannual climatic irregularity characteristic of this mountain range. The main explanatory factor is the thermal increase. The thermal anomalies with respect to the average reference values have increased, in this period, +0.55° C. The year 2022 has been particularly warm and has recorded the greatest regression of the glacier (between May and August, the thermal anomalies were between +4° C and +2° C). Regarding precipitations, they have irregular tendencies and show a decreasing trend (-9% in the same period of time).
After being perceived negatively by the inhabitants of mountain areas, glaciers have been promoted as a tourist attraction for over two centuries. The first visits to the Arveyron Arch (Chamonix) in the 18th century were followed by cog railways and cable cars that allow access to the largest glaciers in the Alps and in the world in just a few dozen minutes. Thus, glacier tourism today includes practices and touristic sites that are emblematic of certain mountain territories. However, rising temperatures and the extremely rapid glacier retreat also make these glacier sites markers of climate change. The Mer de Glace in France, the Rhone glacier in Switzerland and the Pasterze glacier in Austria are among the major glacier tourist sites that are experiencing the full force of landscape changes linked to the retreat of the cryosphere. What do these changes imply for the operators of these glacier tourism sites? And for their visitors? Using mixed methodologies, this PhD thesis attempts to answer these two questions for six major Alpine glacier tourism sites. In essence, the results show that glacial tourism sites are largely impacted by climate change and the glaciological and geomorphological changes it brings to mountain territories. These impacts lead to difficulties in site management, itinerary issues, difficulties in carrying out certain activities which may become more dangerous, or a decrease in the attractiveness of the sites through less attractive glacial activities or through a "landscape degradation" feared by the site managers. However, our results with visitors to the sites show that this "degradation" of the landscape does not drastically reduce visitors' satisfaction with the glacial landscape: the negative judgements are limited to glaciers or paraglacial forms, but only slightly affect visitors' general appreciation of the landscape. At the same time, a new form of tourism - last chance tourism - is developing around glaciers and shows that they are now considered as "endangered species". Furthermore, the site managers in question are implementing strategies for adapting to climate change that are mainly reactive and which raise the question of their long-term sustainability. This question is even more important as glacier modelling for the year 2050 suggests that current adaptations will not be sufficient.
The largest collection so far of glaciological and geodetic observations suggests that glaciers contributed about 27 millimetres to sea-level rise from 1961 to 2016, at rates of ice loss that could see the disappearance of many glaciers this century.
In north-western Tibet (34.0∘ N, 82.2∘ E) near lake Aru Co, the entire ablation areas of two glaciers (Aru-1 and Aru-2) suddenly collapsed on 17 July and 21 September 2016. The masses transformed into ice avalanches with volumes of 68 and 83×106 m3 and ran out up to 7 km in horizontal distance, killing nine people. The only similar event currently documented is the 130×106 m3 Kolka Glacier rock and ice avalanche of 2002 (Caucasus Mountains). Using climatic reanalysis, remote sensing, and three-dimensional thermo-mechanical modelling, we reconstructed the Aru glaciers' thermal regimes, thicknesses, velocities, basal shear stresses, and ice damage prior to the collapse in detail. Thereby, we highlight the potential of using emergence velocities to constrain basal friction in mountain glacier models. We show that the frictional change leading to the Aru collapses occurred in the temperate areas of the polythermal glaciers and is not related to a rapid thawing of cold-based ice. The two glaciers experienced a similar stress transfer from predominant basal drag towards predominant lateral shearing in the detachment areas and during the 5–6 years before the collapses. A high-friction patch is found under the Aru-2 glacier tongue, but not under the Aru-1 glacier. This difference led to disparate behaviour of both glaciers, making the development of the instability more visible for the Aru-1 glacier through enhanced crevassing and terminus advance over a longer period. In comparison, these signs were observable only over a few days to weeks (crevasses) or were absent (advance) for the Aru-2 glacier. Field investigations reveal that those two glaciers were underlain by soft, highly erodible, and fine-grained sedimentary lithologies. We propose that the specific bedrock lithology played a key role in the two Tibet and the Caucasus Mountains giant glacier collapses documented to date by producing low bed roughness and large amounts of till, rich in clay and silt with a low friction angle. The twin 2016 Aru collapses would thus have been driven by a failing basal substrate linked to increasing pore water pressure in the subglacial drainage system in response to increases in surface melting and rain during the 5–6 years preceding the collapse dates.
Glacier thickness distribution is a prerequisite to simulate the future of glaciers. Inaccurate thicknesses may lead to significant uncertainties in the timing of future changes to glaciers and their consequences for water resources or sea level rise. Unfortunately, glacier thickness distribution is rarely measured and consequently has to be estimated. In this study, we present an approach developed on the well documented Argentière Glacier (French Alps) that uses surface mass balance (SMB) together with surface flow velocity data to quantify glacier thickness distribution over the entire surface of the glacier. We compare the results of our approach to those obtained applying Farinotti et al. (2009) approach. Our results show that glacier thickness distribution are significantly biased when the glacier SMB profile used to quantify the ice fluxes is not constrained with in situ measurements. We also show that even with SMB measurements available on the studied glacier, ice flux estimates can be inaccurate. This inability to correctly estimate ice fluxes from the apparent SMB may be due to the steady state assumption that is not respected from the available glacier surface topography data. Therefore, ice thickness measurements on few cross sections (four are used in this study) are required to constrain the ice flux estimates and lead to an overall agreement between the ice thickness estimations and measurements. Using our approach, the ice thicknesses only differ by 10% from observations in average, but can differ by up to 150 m (or 30%) locally. We also show that approaches that use the glacier surface slope can lead to large uncertainties given that the quantification of the slope is highly uncertain. The approach presented here does not pretend to be applied globally but rather as a tool to quantify ice thickness distribution over the entire surface of glaciers for which a few in situ surface mass balance and thickness data are available together with surface flow velocities that can be obtained for example from remote sensing.
This study focuses on simulations of the seasonal and annual surface mass balance (SMB) of Saint-Sorlin Glacier (French Alps) for the period 1996–2015 using the detailed SURFEX/ISBA-Crocus snowpack model. The model is forced by SAFRAN meteorological reanalysis data, adjusted with automatic weather station (AWS) measurements to ensure that simulations of all the energy balance components, in particular turbulent fluxes, are accurately represented with respect to the measured energy balance. Results indicate good model performance for the simulation of summer SMB when using meteorological forcing adjusted with in situ measurements. Model performance however strongly decreases without in situ meteorological measurements. The sensitivity of the model to meteorological forcing indicates a strong sensitivity to wind speed, higher than the sensitivity to ice albedo. Compared to an empirical approach, the model exhibited better performance for simulations of snow and firn melting in the accumulation area and similar performance in the ablation area when forced with meteorological data adjusted with nearby AWS measurements. When such measurements were not available close to the glacier, the empirical model performed better. Our results suggest that simulations of the evolution of future mass balance using an energy balance model require very accurate meteorological data. Given the uncertainties in the temporal evolution of the relevant meteorological variables and glacier surface properties in the future, empirical approaches based on temperature and precipitation could be more appropriate for simulations of glaciers in the future.
This article investigates the climatic response of a series of indicators for characterizing annual snow conditions and corresponding meteorological drivers at 1500 m altitude in the Chartreuse mountain range in the Northern French Alps. Past and future changes were computed based on reanalysis and observations from 1958 to 2016, and using CMIP5–EURO-CORDEX GCM–RCM pairs spanning historical (1950–2005) and RCP2.6 (4), RCP4.5 and RCP8.5 (13 each) future scenarios (2006–2100). The adjusted climate model runs were used to drive the multiphysics ensemble configuration of the detailed snowpack model Crocus. Uncertainty arising from physical modeling of snow accounts for 20 % typically, although the multiphysics is likely to have a much smaller impact on trends. Ensembles of climate projections are rather similar until the middle of the 21st century, and all show a continuation of the ongoing reduction in average snow conditions, and sustained interannual variability. The impact of the RCPs becomes significant for the second half of the 21st century, with overall stable conditions with RCP2.6, and continued degradation of snow conditions for RCP4.5 and 8.5, the latter leading to more frequent ephemeral snow conditions. Changes in local meteorological and snow conditions show significant correlation with global temperature changes. Global temperature levels 1.5 and 2 ∘C above preindustrial levels correspond to a 25 and 32 % reduction, respectively, of winter mean snow depth with respect to the reference period 1986–2005. Larger reduction rates are expected for global temperature levels exceeding 2 ∘C. The method can address other geographical areas and sectorial indicators, in the field of water resources, mountain tourism or natural hazards.
Worldwide glacier retreat and associated future runoff changes raise major concerns over the sustainability of global water resources, but global-scale assessments of glacier decline and the resulting hydrological consequences are scarce. Here we compute global glacier runoff changes for 56 large-scale glacierized drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual glacier runoff continues to rise until a maximum (‘peak water’) is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger glaciers and higher ice-cover fractions. Typically, future glacier runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to glacier mass loss in at least one month of the melt season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued glacier wastage can be substantial, but the magnitudes vary greatly among basins and throughout the melt season.
Recent record-breaking glacier melt values are attributable to peculiar extreme events and long-term warming trends that shift averages upwards. Analyzing one of the world's longest mass-balance series with extreme value statistics, we show that detrending melt anomalies makes it possible to disentangle these effects, leading to a fairer evaluation of the return period of melt extreme values such as 2003, and to characterize them by a more realistic bounded behavior. Using surface energy balance simulations, we show that three independent drivers control melt: global radiation, latent heat and the amount of snow at the beginning of the melting season. Extremes are governed by large deviations in global radiation combined with sensible heat. Long-term trends are driven by the lengthening of melt duration due to earlier and longer-lasting melting of ice along with melt intensification caused by trends in long-wave irradiance and latent heat due to higher air moisture.
Basal slip accounts for a large part of the flow of ice streams draining ice from Antarctica and Greenland into the ocean. Therefore, an appropriate representation of basal slip in ice flow models is a prerequisite for accurate sea level rise projections. Various friction laws have been proposed to describe basal slip in models. Here, we compare the influence on grounding line (GL) dynamics of four friction laws: the traditional Weertman law and three effective pressure-dependent laws, namely the Schoof, Tsai and Budd laws. It turns out that, even when they are tuned to a common initial reference state, the Weertman, Budd and Schoof laws lead to thoroughly different steady-state positions, although the Schoof and Tsai laws lead to much the same result. In particular, under certain circumstances, it is possible to obtain a steady GL located on a reverse slope area using the Weertman law. Furthermore, the predicted transient evolution of the GL as well as the projected contributions to sea level rise over a 100-year time horizon vary significantly depending on the friction law. We conclude on the importance of choosing an appropriate law for reliable sea level rise projections and emphasise the need for a coupling between ice flow models and physically based subglacial hydrological models.
The quantification of uncertainty sources in ensembles of climate projections obtained from combinations of different scenarios and climate and impact models is a key issue in climate impact studies. The small size of the ensembles of simulation chains and their incomplete sampling of scenario and climate model combinations makes the analysis difficult. In the popular single-time ANOVA approach for instance, a precise estimate of internal variability requires multiple members for each simulation chain (e.g., each emission scenario-climate model combination), but multiple members are typically available for a few chains only. In most ensembles also, a precise partition of model uncertainty components is not possible because the matrix of available scenario/models combinations is incomplete (i.e., projections are missing for many scenario-model combinations). The method we present here, based on data augmentation and Bayesian techniques, overcomes such limitations and makes the statistical analysis possible for single-member and incomplete ensembles. It provides unbiased estimates of climate change responses of all simulation chains and of all uncertainty variables. It additionally propagates uncertainty due to missing information in the estimates. This approach is illustrated for projections of regional precipitation and temperature for four mountain massifs in France. It is applicable for any kind of ensemble of climate projections, including those produced from ad hoc impact models.
Transverse profiles and velocities which have been measured on the ablation zone of Mer de Glace more or less continuously since 1891 contradict the Weertman–Nye theory of glacier kinematic waves. Faint broad waves, which undoubtedly result from fluctuations in the balance, travel down the glacier faster than this theory predicts. (This theory having first been completed by taking changes in width with time and with distance down the glacier into account.) On the other hand, velocity fluctuations are synchronous and more or less the same over the entire length studied (6 km).
These discrepancies result from bottom friction being of the solid type, i.e. independent of sliding velocity. Friction should also be almost insensitive to discharge in subglacial waterways, since in the steady state energy for keeping them open, not entirely flooded, and at atmospheric pressure, is superabundant. The sliding velocities at all cross-profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical. One such controlling zone exists on Mer de Glace owing to the existence of a subglacial transverse shoulder. A new perturbation equation and a new rough expression for wave velocity are given.
Intervals between Forbes’ bands were plotted on seven aerial surveys between 1939 and 1979. Progressive tilting of the slices of blue, dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account. This analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888.