Long-term historical interactions between French society and glaciers have developed a dependency of society on them for water resources, agriculture, tourism18particularly the ski business19and hydropower generation. Earths Future https://doi.org/10.1029/2019EF001470 (2020). Climate Change 2013: The Physical Science Basis. Glaciers with the greatest degree of seasonality in their flow behavior, such as Nisqually and Shoestring glaciers, responded most rapidly. Nature 575, 341344 (2019). 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. The climatic forcing comes from high-resolution climate ensemble projections from 29 combinations of global climate models (GCMs) and regional climate models (RCMs) adjusted for mountain regions for three Representative Concentration Pathway (RCP) scenarios: 2.6, 4.5, and 8.525. South American Glaciers Melting Faster, Changing Sea Level 5). 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. C.G. Photographs taken by Simo Rsnen (Bossons glacier, European Alps, CC BY-SA 3.0) and Doug Hardy (Quelccaya ice cap, Andes, CC BY-SA 4.0). Climate variations change a glacier's mass balance by affecting ablation and accumulation amounts. As climate changes, so do glaciers | PNAS 4e). Additionally, the specific responses of the deep learning and Lasso MB models to air temperature and snowfall were extracted by performing a model sensitivity analysis. The Elements of Statistical Learning. Importance and vulnerability of the worlds water towers. 31, n/an/a (2004). 3). 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. Since these two glaciers are expected to be some of the few large glaciers that will survive the 21st century climate, an accurate representation of their initial ice thickness has an important effect on the estimates of remaining ice. Soc. Uncertainties of existing projections of future glacier evolution are particularly large for the second half of the 21st century due to a large uncertainty on future climatic conditions. Gardent, M., Rabatel, A., Dedieu, J.-P. & Deline, P. Multitemporal glacier inventory of the French Alps from the late 1960s to the late 2000s. a1 and a r2 of 0.69, explaining 69% of the total MB variance. MB rates only begin to approach equilibrium towards the end of the century under RCP 2.6, for which glaciers could potentially stabilize with the climate in the first decades of the 22nd century depending on their response time (Fig. Nature Communications (Nat Commun) 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. Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. 3c), which is directly linked to summer air temperatures and has a strong influence on surface albedo. ALPGM uses a feed-forward fully connected multilayer perceptron, with an architecture (40-20-10-5-1) with Leaky-ReLu44 activation functions and a single linear function at the output. Glacier variations in response to climate change from 1972 to 2007 in J. Glaciol. Some of these models use a single DDF, while others have separate DDFs for snow and ice, producing a piecewise function composed of two linear sub-functions that can partially account for nonlinear MB dynamics depending on the snowpack. Rainier is considered by the USGS to be one of the most threatening volcanoes in the Cascade Mountains. Nature Geosciences, https://doi.org/10.1038/s41561-021-00885-z (2022). Huss, M., Funk, M. & Ohmura, A. Deep learning captures a nonlinear response of glaciers to air temperature and precipitation, improving the representation of extreme mass balance rates compared to linear statistical and temperature-index models. Using this function, the glacier-specific ice thickness and the DEM are updated every year, adjusting the 3D geometry of each glacier. Since in ALPGM the climate forcing of glaciers is extracted at the mean glacier altitude, we do not expect these altitude differences to drive important MB differences between models. Model Dev. Alternatively, the Lasso MB model displayed an RMSE of 0.85m.w.e. Nature Communications thanks Mohd Anul Haq, Lauren Vargo, and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Google Scholar. Nisqually Glacier is the lengthiest of any made in North America. Positive degree-day factors for ablation on the Greenland ice sheet studied by energy-balance modelling. 3 (2015). 47 (2020). Therefore, linear MB models present more limitations for projections of ice caps, showing a tendency to negative MB biases. A physically-based method for mapping glacial debris-cover thickness from ASTER satellite imagery: development and testing at Miage Glacier, Italian Alps Discovery - the University of Dundee Research Portal Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2. Braithwaite, R. J. Summer climate is computed between April 1st and September 30th and winter climate between October 1st and March 31st. Gaining a better understanding of how warming ocean water affects these glaciers will help improve predictions of their fate. In order to investigate the effects of MB nonlinearities on ice caps, we performed the same type of comparison between simulations, but the glacier geometry update module described in the Glacier geometry evolution section was deactivated. Ecography 40, 913929 (2017). The Cryosphere 13, 13251347 (2019). This behaviour has already been observed for the European Alps, with a reduction in DDFs for snow during the ablation season of 7% per decade34. 2a). The model output data generated in this study have been deposited in netCDF and CSV format in a Zenodo repository under accession code Creative Commons Attribution 4.0 International. Res. b, c, d and f, g, h annual glacier-wide MB probability distribution functions for all n scenarios in each RCP. Fr Hydrobiol. Xu, B., Wang, N., Chen, T. & Li, M. Empirical Evaluation of Rectified Activations in Convolutional Network. Since both MB models also include monthly temperature data as predictors, this CPDD anomaly was distributed evenly between the ablation season (April 1September 30), following the expected increase in mostly summer temperatures instead of winter temperatures in the future (Fig. Kinematic waves on glaciers move as several times the speed of the ice as a whole, and are subtle in topographic expression. J. Clim. a1) over the French Alps. By the end of the century, we predict a glacier volume loss between 75 and 88%. 3). Then, we ran multiple simulations for this same period by altering the initial ice thickness by 30% and the glacier geometry update parametrizations by 10%, according to the estimated uncertainties of each of the two methods31. Simulations for projections in this study were made by generating an ensemble of 60 cross-validated models based on LSYGO. Rainier, Washington. Despite these differences, the average altitude difference of the glaciers between both models is never greater than 50m (Fig. Nonetheless, since they are both linear, their calibrated parameters establishing the sensitivity of melt and glacier-wide MB to temperature variations remain constant over time. Our results also highlight the important role played by glacier geometry adjustment under changing climatic conditions, which is typical of mountain glaciers38. 12, 909931 (2019). Earth Sci. (b) Climate predictors are based on climatic anomalies computed at the glaciers mean altitude with respect to the 19672015 reference period mean values. Glacier response to climate change Jim Salinger, Trevor Chinn, Andrew Willsman, and how fluctuations in New Zealand glaciers reflect regional climate change. 36, L23501 (2009). These bulges, called kinematic waves, form when higher than normal snowfall builds up in the accumulation area of the glacier (c). J. Glaciol. As for the MB modelling approach, a detailed explanation on this method can be found in a previous dedicated paper on the methods31. Bolibar, J., Rabatel, A., Gouttevin, I. Publishers note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Article In order to investigate the implications of these results for flat glaciers, we performed additional synthetic experiments in order to reproduce this lack of topographical feedback (Fig. The lower fraction of variance explained by linear models is present under all climate scenarios. Activity 13.3 Nisqually Glacier Response to Climate Change Course/Section Date: Name: Nisqually Glacier is a mountain glacier located on the south side of Mt. Interestingly, this matches the nonlinear, less sensitive response to summer snowfall in the ablation season of our deep learning model (Fig. Article Each one of these models was created by training a deep learning model with the full dataset except all data from a random glacier and year, and evaluating the performance on these hidden values. A dataset of 32 glaciers with direct annual glacier-wide MB observations and remote sensing estimates was used to train the models. Hock, R. & Huss, M. Glaciers and climate change. The main uncertainties in future glacier estimates stem from future climate projections and levels of greenhouse gas emissions (differences between RCPs, GCMs, and RCMs), whose relative importance progressively increases throughout the 21st century. The advantage of this method is that by only changing the MB model, we can keep the rest of the model components (glacier dynamics and climate forcing) and parameters the same in order to have a controlled environment for our experiment. This means that these flatter ice bodies, under a warming climate, will be subject to higher temperatures than their steeper counterparts. Both models agree around the average values seen during training (i.e. Glacier landscapes are expected to see important changes throughout the French Alps, with the average glacier altitude becoming 300m (RCP 4.5) and 400m (RCP 8.5) higher than nowadays (Fig. Park, and S. Beason. 51, 313323 (2005). J. Glaciol. Therefore, an alternative nonlinear parameterization for the reduction in MB sensitivity under increasing air temperatures would be useful. Map-based methods for estimating glacier equilibrium-line altitudes 1 and S1). Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. Annu. A similar trend is under way. The dataset of initial glacier ice thickness, available for the year 2003, determines the starting point of our simulations. Summer melt was also above average. Geophys. Glaciers and ice caps are experiencing strong mass losses worldwide, challenging water availability, hydropower generation, and ecosystems. 3). Sci. Res. This results in a higher complexity of the Lasso compared to a temperature-index model. B Methodol. Simulations were then performed by averaging the outputs of each one of the 60 ensemble members. Fundam. Durand, Y. et al. Despite the differences in the two modelling approaches (TableS2), both regional glacier volume projections present relatively similar results by the end of the century, with volume differences ranging between 14% for RCP 2.6 to less than 2% for RCP 4.5 (Fig. 2) and RCP 8.5 by the end of the century. The largest snow depths measured this spring exceeded 10 meters on Nisqually Glacier and 7 meters on Emmons. For these 32 glaciers, a total of 1048 annual glacier-wide MB values are available, covering the 19672015 period with gaps. 15 - Response of glaciers to climate change - Cambridge Core Toward mountains without permanent snow and ice: mountains without permanent snow and ice. 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. 3). By submitting a comment you agree to abide by our Terms and Community Guidelines. Future high-mountain hydrology: a new parameterization of glacier retreat. Despite their limitations, temperature-index models, owing to their simplicity and parsimonious data requirements, have been widely used for large-scale glacier projections7,8.
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