GloGEMflow10 is a state-of-the-art global glacier evolution model used in a wide range of studies, including the second phase of GlacierMIP7,8. This allows us to assess the MB models responses at a regional scale to changes in individual predictors (Fig. With a secondary role, glacier model uncertainty decreases over time, but it represents the greatest source of uncertainty until the middle of the century8. Swiss glaciers have displayed less negative MB rates than French glaciers during the last decades, thus likely introducing a bias in simulations specific to the French Alps. Geophys. At present, using complex surface energy balance models for large-scale glacier projections is not feasible yet, mainly due to the lack of input data. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. The mountain has three major peaks: Liberty Cap, Point Success, and Columbia Crest (the latter is the summit, located on the rim of the caldera). is central to a glacier's response: Fig.2ashows 1L.t/for a warming trend of 1 C per century, for three glaciers with dierent (and fixed ). Our results indicate that these uncertainties might be even larger than we previously thought, as linear MB models are introducing additional biases under the extreme climatic conditions of the late 21st and 22nd centuries. Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface mass balance of Saint-Sorlin Glacier (French Alps). This behaviour is particularly clear for summer snowfall, for which the differences are the largest (Fig. The vast majority of glaciers in the French Alps are very small glaciers (<0.01km2), that are mainly remnants from the Little Ice Age, with a strong imbalance with the current climate15. The ice thickness data for two of the largest glaciers in the French Alps were modified in order to improve data quality. Data 12, 19731983 (2020). 3). The increase in glacier altitude also causes the solid to liquid precipitation ratio to remain relatively constant. A comprehensive bibliography of scientific publications relating to the glacier is included. Water resources provided by glaciers sustain around 10% of the worlds population living near mountains and the contiguous plains4, depending on them for agriculture, hydropower generation5, industry or domestic use. For this, a newly-developed state-of-the-art modelling framework based on a deep learning mass balance component and glacier-specific parametrizations of glacier changes is used. Glacier topography is a crucial driver of future glacier projections and is expected to play an important role in determining the magnitude that nonlinearities will have on the mass balance signal: ice caps and large flatter glaciers are expected to be more influenced by these nonlinear sensitivities than steep mountain glaciers in a warming climate. The training was performed with an RMSprop optimizer, batch normalization46, and we used both dropout and Gaussian noise in order to regularize it. 41, 153160 (1995). Through synthetic experiments, we showed that the associated uncertainties are likely to be even more pronounced for ice caps, which host the largest reserves of ice outside the two main ice sheets32. Multiple copies of this dataset were created, and for each individual copy a single predictor (i.e. Moreover, these differences between nonlinear and linear models appear to come from an over-sensitivity of linear models to increasing ablation season air temperatures, when ice is exposed in a large fraction of glaciers. Jordi Bolibar. provided glacier mass balance data and performed the glaciological analyses. Slider with three articles shown per slide. 2a and S3). Partitioning the uncertainty of ensemble projections of global glacier mass change. This work was funded by the Labex OSUG@2020 (Investissements davenir, ANR10 LABX56) and the Auvergne-Rhne-Alpes region through the BERGER project. The Karakoram and the Himalayan mountain range accommodate a large number of glaciers and are the major source of several perennial rivers downstream. Model Dev. The initial glacier ice thickness data for the year 2003 also differs slightly between both models. Bolibar, J. et al. J. Hosp. Consequently, a simple MB model with a single DDF (e.g. However, to further investigate these findings, experiments designed more towards ice caps, and including crucial mechanisms such as ice-ocean interactions and thermodynamics, should be used for this purpose. Immerzeel, W. W. et al. Huss, M., Jouvet, G., Farinotti, D. & Bauder, A. Thus, glacier sensitivity to a step change in climate , glacier response to climate trends , and glacier variance driven by stochastic climate fluctuations are all proportional to , making an important number to constrain. Reanalysis of 47 Years of Climate in the French Alps (19582005): Climatology and Trends for Snow Cover. Greenland's melting glaciers, which plunge into Arctic waters via steep-sided inlets, or fjords, are among the main contributors to global sea level rise in response to climate change. Such ice caps cannot retreat to higher elevations in a warming climate, which inhibits this positive impact on MB40 (Fig. Rackauckas, C. et al. Winter tourism under climate change in the Pyrenees and the French Alps: relevance of snowmaking as a technical adaptation. Bolibar, J., Rabatel, A., Gouttevin, I. This has the strongest impact under RCP 2.6, where positive MB rates are more frequent (Fig. Our results point out that this lack of topographical feedback leads to an increased frequency of extreme negative MB rates and to more pronounced differences between the nonlinear and linear MB models (Figs. For these 32 glaciers, a total of 1048 annual glacier-wide MB values are available, covering the 19672015 period with gaps. This removes the topographical feedback typical from mountain glaciers, and reproduces the more extreme climate conditions that ice caps are likely to endure through the 21st century40. Overall, the evolving glaciers are expected to undergo rather stable climate conditions under RCP 4.5, but increasingly higher temperatures and rainfall under RCP 8.5 (Fig. Average cumulative MB projections of French Alpine glaciers with a nonlinear deep learning vs. a linear Lasso model for 29 climate scenarios; a with topographical feedback (allowing for glacier retreat) and e without topographical feedback (synthetic experiment with constant mean glacier altitude). Despite the existence of a wide variety of different approaches to simulate glacier dynamics, all glacier models in GlacierMIP rely on MB models with linear relationships between PDDs and melt, and precipitation and accumulation. 4). These bulges, called kinematic waves, form when higher than normal snowfall builds up in the accumulation area of the glacier (c). https://doi.org/10.1016/B978-0-12-821575-3.00009-8. "The Patagonia Icefields are dominated by so-called 'calving' glaciers," Rignot said. (Photograph by Klaus J. Bayr, Keene State College, 1990) One method of measuring glaciers is to send researchers onto the ice with . This type of model uses a calibrated linear relationship between positive degree-days (PDDs) and the melt of ice or snow11. 4e). Kinematic waves on glaciers move as several times the speed of the ice as a whole, and are subtle in topographic expression. Our previous work31 has shown that linear MB models can be correctly calibrated for data around the mean temperature and precipitation values used during training, giving similar results and performance to deep learning. Spandre, P. et al. (a) Topographical predictors were computed based on the glaciers annually updated digital elevation model (DEM). Ioffe, S. & Szegedy, C. Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift (2015). The source code of the glacier model can be freely accessed in the following repository: https://github.com/JordiBolibar/ALPGM. 1). All authors provided inputs to the paper and helped to write it. Google Scholar. 3c). We further assessed the effect of MB nonlinearities by comparing our simulated glacier changes with those obtained from other glacier evolution studies from the literature, which rely on temperature-index models for MB modelling. Paul, F., Kb, A., Maisch, M., Kellenberger, T. & Haeberli, W. Rapid disintegration of Alpine glaciers observed with satellite data: disintegration of alpine glaciers. In order to avoid overfitting, MB models were thoroughly cross-validated using all data for the 19672015 period in order to ensure a correct out-of-sample performance. Correspondence to Six, D. & Vincent, C. Sensitivity of mass balance and equilibrium-line altitude to climate change in the French Alps. In that study, a temperature-index model with a separate degree-day factor (DDF) for snow and ice is used, resulting in piecewise linear functions able to partially reproduce nonlinear MB dynamics. Years in white in c-e indicate the disappearance of all glaciers in a given massif. A similar trend is under way. IPCC. Res. This dataset applies a statistical adjustment specific to French mountain regions based on the SAFRAN dataset, to EURO-CORDEX26 GCM-RCM-RCP members, covering a total of 29 different future climate scenarios for the 20052100 period. 2015 IEEE Int. Braithwaite, R. J. During the last decade, various global glacier evolution models have been used to provide estimates on the future sea-level contribution from glaciers7,8. Nonlinear deep learning response and linear Lasso response to a Cumulative positive degree days (CPDD) anomalies, b winter snowfall, and c summer snowfall. Together with recent findings by another study41 highlighting the increased uncertainties in ice thickness distribution estimates of ice caps compared to mountain glaciers, our results raise further awareness on the important uncertainties in glacier projections for ice caps. Hock, R. Temperature index melt modelling in mountain areas. Both MB models were trained with exactly the same data, and all other glacier model parameters were unchanged in order to allow isolating the effects of the nonlinearities in the MB. J. Geophys. Analyses were made of the annual photographs . (2019) https://doi.org/10.18750/MASSBALANCE.2019.R2019. Sci. 58, 267288 (1996). In this study, we investigate the future evolution of glaciers in the French Alps and their nonlinear response to multiple climate scenarios. ADAMONT provides climate data at 300m altitudinal bands and different slope aspects, thus having a significantly higher spatial resolution than the 0.11 from EURO-CORDEX.
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