Rev. ice caps) that are found in other glacierized regions such as the Arctic, where the largest volumes of glacier ice (other than the ice sheets) are stored32, cannot retreat to higher elevations. An enhanced temperature-index glacier melt model including the shortwave radiation balance: development and testing for Haut Glacier dArolla, Switzerland. Deep artificial neural networks (ANNs) are nonlinear models that offer an alternative approach to these classic methods. Robinson, C. T., Thompson, C. & Freestone, M. Ecosystem development of streams lengthened by rapid glacial recession. These are among the cascading effects linked to glacier loss which impact ecosystems and . Nonetheless, a better understanding of the underlying processes guiding these nonlinear behaviours at large geographical scales is needed. S10). 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. 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. Glob. Hock, R. et al. deep artificial neural networks) glacier evolution projections by modelling the regional evolution of French alpine glaciers through the 21st century. 2a). Bolibar, J., Rabatel, A., Gouttevin, I. A consensus estimate for the ice thickness distribution of all glaciers on Earth. a Projected mean glacier altitude evolution between 2015 and 2100. 1). Ice caps in the Canadian Arctic, the Russian Arctic, Svalbard, and parts of the periphery of Greenland are major reservoirs of ice, as well as some of the biggest expected contributors to sea level rise outside the two polar ice sheets7. Meteorol. Glaciers are important for agriculture, hydropower, recreation, tourism, and biological communities. The nonlinearities present in the simulated annual glacier-wide MB values were assessed by running two different glacier simulations with two different MB models. Rainier, Washington. However, both the climate and glacier systems are known to react non-linearly, even to pre-processed forcings like PDDs13, implying that these models can only offer a linearized approximation of climate-glacier relationships. Alluvial landscape response to climate change in glacial rivers and the implications to transportation infrastructure. 36, L23501 (2009). S5h, j, l). Thank you for visiting nature.com. 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 ). An accurate prediction of future glacier evolution will be crucial to successfully adapt socioeconomic models and preserve biodiversity. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (2018). For such cases, we assumed that ice dynamics no longer play an important role, and the mass changes were applied equally throughout the glacier. These bulges, called kinematic waves, form when higher than normal snowfall builds up in the accumulation area of the glacier (c). Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2. Swiss Glacier Mass Balance (release 2019). 3c). 3). Sci. Res. A globally complete, spatially and temporally resolved estimate of glacier mass change: 2000 to 2019. https://meetingorganizer.copernicus.org/EGU2020/EGU2020-20908.html (2020) https://doi.org/10.5194/egusphere-egu2020-20908. The new research suggests that the world's glaciers are disappearing more quickly than scientists previously estimated, and they . 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. 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. GloGEMflow relies on EURO-CORDEX ensembles26, whereas ALPGM uses ADAMONT25, an adjusted version of EURO-CORDEX specifically designed for mountain regions. With this setup, we reproduced the ice cap-like behaviour with a lack of topographical adjustment to higher elevations. For intermediate and pessimistic climate scenarios, no significant differences were found (Fig. This has the strongest impact under RCP 2.6, where positive MB rates are more frequent (Fig. Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. Sci. 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. Simulating these processes at a large geographical scale is challenging, with models requiring several parametrizations and simplifications to operate. Limnol. 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. acknowledges the funding received from a EU Horizon 2020 Marie Skodowska-Curie Individual Fellowship (grant no. Nat. Predicting future glacier evolution is of paramount importance in order to correctly anticipate and mitigate the resulting environmental and social impacts. During the last decade, various global glacier evolution models have been used to provide estimates on the future sea-level contribution from glaciers7,8. This ensures that the model is capable of reproducing MB rates for unseen glaciers and years. In our model, we specifically computed this parameterized function for each individual glacier larger than 0.5km2, representing 80% of the total glacierized area in 2015, using two DEMs covering the whole French Alps: a photogrammetric one in 1979 and a SPOT-5 one in 2011. The first main difference is related to the climate data used to force the models. 60, 11401154 (2014). Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. Climate variations change a glacier's mass balance by affecting ablation and accumulation amounts. Secure .gov websites use HTTPS A lock ( ) or https:// means you've safely connected to the .gov website. 1gi)26 and glaciers shrinking to higher elevations where precipitation rates are higher as a result of orographic precipitation enhancement27. Lett. The initial glacier ice thickness data for the year 2003 also differs slightly between both models. Our synthetic experiment does not account for glacier surface area shrinking either, which might have an impact on the glacier-wide MB signal. 48, 24872512 (2009). Earths Future https://doi.org/10.1029/2019EF001470 (2020). 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 Atmospheres 121, 77107728 (2016). The lower fraction of variance explained by linear models is present under all climate scenarios. Differences in projected glacier changes become more pronounced from the second half of the century, when about half of the initial 2015 ice volume has already been lost independent of the considered scenario. . J. Hydrol. Ten . Simulations for projections in this study were made by generating an ensemble of 60 cross-validated models based on LSYGO. The anomaly in snowfall was evenly distributed for every month in the accumulation (October 1April 31) and ablation seasons, respectively. All these glacier models, independently from their approach, need to resolve the two main processes that determine glacier evolution: (1) glacier mass balance, as the difference between the mass gained via accumulation (e.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). Climatol. Huss, M. & Hock, R. A new model for global glacier change and sea-level rise. On top of that, they happen to be among the glacierized regions with the largest projected uncertainties8. Both DEMs were resampled and aligned at a common spatial resolution of 25m. For each glacier, an individual parameterized function was computed representing the differences in glacier surface elevation with respect to the glaciers altitude within the 19792011 period. Alternatively, the Lasso MB model displayed an RMSE of 0.85m.w.e. However, the use of ANNs remains largely unexplored in glaciology for regression problems, with only a few studies using shallow ANNs for predicting the ice thickness14 or mass balance13 of a single glacier. 51, 313323 (2005). 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). Article 31, n/an/a (2004). Internet Explorer). B Methodol. (b) Climate predictors are based on climatic anomalies computed at the glaciers mean altitude with respect to the 19672015 reference period mean values. Moreover these three aspects of glacier behavior are inextricably interwoven: a high sensitivity to climate change goes hand-in-hand with a large natural variability. Geosci. 0.78m.w.e. As the Earth heats up due to climate change, glaciers are melting. 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. 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. The French Alps, located in the westernmost part of the European Alps, experience some of the strongest glacier retreat in the world15,16,17. Future high-mountain hydrology: a new parameterization of glacier retreat. A dataset of 32 glaciers with direct annual glacier-wide MB observations and remote sensing estimates was used to train the models. Front. Smiatek, G., Kunstmann, H. & Senatore, A. EURO-CORDEX regional climate model analysis for the Greater Alpine Region: performance and expected future change: climate change in the gar area. Scand. 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. 2015 IEEE Int. Since 2005, study finds that surface melt off glaciers in the North has risen by 900%. Nat. A similar trend is under way. P. Kennard, J. 5). J. Glaciol. Ser. We reduced these differences by running simulations with GloGEMflow using exactly the same 29 climate members used by ALPGM in this study (TableS1). Get the most important science stories of the day, free in your inbox. Article These results revealed that the main uncertainties on glacier simulations arise from the initial ice thickness used to initialize the model. IPCC. This suggests that linear MB models are adequate tools for simulating MB of mountain glaciers with important topographical adjustment, with the only exception being the most optimistic climate scenarios and glaciers with long response times. 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. Here, we perform the first-ever glacier evolution projections based on deep learning by modelling the 21st century glacier evolution in the French Alps. 22, 21462160 (2009). contributed to the extraction of nonlinear mass balance responses and to the statistical analysis. Six, D. & Vincent, C. Sensitivity of mass balance and equilibrium-line altitude to climate change in the French Alps. 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. Google Scholar. Sci. 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. 58, 267288 (1996). Front. The original ice thickness estimates of the methods used by both models are different10,32, and for ALPGM we performed some additional modifications to the two largest glaciers in the French Alps (see Glacier geometry evolution for details). 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. Therefore, we were capable of isolating the different behaviours of the nonlinear deep learning model and a linear machine learning model based on the Lasso30. 2013). Despite the existence of slightly different trends during the first half of the century, both the Lasso and the temperature-index model react similarly under RCP 4.5 and 8.5 during the second half of the century, compared to the deep learning model. The processing chain for extracting glacier outlines from images is composed of four steps: (1) calculation of band ratio, (2) selection of threshold value, (3) creation of binary image and (4) manual digitization. volume13, Articlenumber:409 (2022) Nisqually Glacier is perhaps the most visited, best-surveyed glacier on Mount Rainier. In many aspects, it might be too optimistic, as many ice caps will have a negative impact on MB through thinning, bringing their mean surface elevation to lower altitudes, thus further warming their perceived climate. Cite this article. 12, 168173 (2019). Google Scholar. 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. Earth Planet. Interestingly, our analysis indicates that more complex models using separate DDFs for ice, firn and snow might introduce stronger biases than more simple models using a single DDF. Nonlinear sensitivity of glacier mass balance to future climate change unveiled by deep learning. 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. Annu. ADS Massifs without glaciers by 2100 are marked with a cross, b Glacier ice volume distribution per massif, with its remaining fraction by 2100 (with respect to 2015), c Annual glacier-wide MB per massif, d Annual snowfall per massif, e Annual cumulative positive degree-days (CPDD) per massif. 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. MATH CAS The training was performed with an RMSprop optimizer, batch normalization46, and we used both dropout and Gaussian noise in order to regularize it. April 17, 2019. J. Appl. By unravelling nonlinear relationships between climate and glacier MB, we have demonstrated the limitations of linear statistical MB models to represent extreme MB rates in long-term projections. 51, 573587 (2005). These results are in agreement with the main known drivers of glacier mass change in the French Alps28. 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. Nisqually Glacier in Mount Rainier National Park, Wash., covers 2.5 square miles (6.5 square kilometers) (1961) and extends from an altitude of about 14,300 feet (4,400 meters) near the top of Mount Rainier down to 4,700 feet (1,400 meters), in a horizontal distance of 4.1 miles (6.6 kilometers). snowfall, avalanches and refreezing) and the mass lost via different processes of ablation (e.g. An increase in the thickness of ice in the higher portion of the Nisqually Glacier was first observed by Arthur Johnson Reference Johnson 1 about ten years ago, and the progress of this "wave" of increased ice thickness has been measured by Johnson each year since that time. Presentation at 2008 National Hydraulic Engineering . However, glacier projections under low-emission scenarios and the behaviour of flatter glaciers and ice caps are likely to be biased by mass balance models with linear sensitivities, introducing long-term biases in sea-level rise and water resources projections. Ice melt sensitivity to PDDs strongly decreases with increasing summer temperatures, whereas snow melt sensitivity changes at a smaller rate34. Other articles where Nisqually Glacier is discussed: Mount Rainier: from the broad summit, including Nisqually Glacier, whose retreat and advance over the last 150 years has helped scientists determine patterns in the Earth's climate. 3, 16751685 (2019). The smallest best performing architecture was used, in order to find a good balance between predictive power, speed, and extrapolation outside the training data. This results in a higher complexity of the Lasso compared to a temperature-index model. Multiple copies of this dataset were created, and for each individual copy a single predictor (i.e. Rackauckas, C. et al. https://doi.org/10.1038/s41467-022-28033-0, DOI: https://doi.org/10.1038/s41467-022-28033-0. The record, which was started in 1931, shows the glacier's dramatic responses to about half a century of small but significant climatic variations. The effect of glaciers shrinking to smaller extents is not captured by these synthetic experiments, but this effect is less important for flat glaciers that are dominated by thinning (Fig. These differences in the received climate signal are explained by the retreat of glaciers to higher altitudes, which keep up with the warming climate in RCP 4.5 but are outpaced by it under RCP 8.5. a Glacier-wide annual MB, b Ice volume, c Glacier area. We argue that such models can be suitable for steep mountain glaciers. Ice-surface altitude changes of as much as 25 meters occurred between 1944 and 1955. Then in 1884, Allen Mason photographed the glacier for the first time . Tests were performed distributing the CPDD anomalies equally among all months of the year with very similar results. (Photograph by Klaus J. Bayr, Keene State College, 1990) One method of measuring glaciers is to send researchers onto the ice with . Ice thickness data for Argentire glacier (12.27km2 in 2015) was taken from a combination of field observations (seismic, ground-penetrating radar or hot-water drilling53) and simulations32. 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. 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. Dyn. Grenoble Alpes, CNRS, IRD, G-INP, Institut des Gosciences de lEnvironnement, Grenoble, France, INRAE, UR RiverLy, Lyon-Villeurbanne, France, Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, Netherlands, Univ. Clarke, G. K. C., Berthier, E., Schoof, C. G. & Jarosch, A. H. Neural networks applied to estimating subglacial topography and glacier volume. Bolibar, J. ALPGM (ALpine Parameterized Glacier Model) v1.1. Google Scholar. 1a). In order to investigate the effects of MB nonlinearities on flatter glaciers, we conducted a synthetic experiment using the French Alps dataset. S5 and S6). 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. Glacier surface mass changes are commonly modelled by relying on empirical linear relationships between PDDs and snow, firn or ice melt8,9,10,29. The scheme simulates the mass balance as well as changes of the areal . A global synthesis of biodiversity responses to glacier retreat. Earth Sci. This is particularly important for the ablation season and for ice DDFs, which need to accommodate the progressively decreasing role that shortwave radiation will play in the future glacier surface energy budget under warmer conditions. Particularly in Asia, water demand exceeds supply due to rapid population growth, with glacier . a1 and a r2 of 0.69, explaining 69% of the total MB variance. 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. The ice thickness data for two of the largest glaciers in the French Alps were modified in order to improve data quality. For small perturbations, the response time of a glacier to a perturbation in mass balance can be estimated by dividing the maximum thickness of the glacier by the balance rate at the terminus. A glacier flows naturally like a river, only much more slowly. 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. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Braithwaite, R. J. Cross-validation strategies for data with temporal, spatial, hierarchical, or phylogenetic structure. Overall, this results in linear MB models overestimating both extreme positive (Fig. Vertical axes are different for the two analyses. 4a). a1 and an r2 of 0.3531. J. Glaciol. H.Z. We also use this method to extract glacier borderlines from satellite images across the western Lenglongling mountains. Fundam. Ecography 40, 913929 (2017). Lett. Years in white in c-e indicate the disappearance of all glaciers in a given massif. Importance and vulnerability of the worlds water towers. Google Scholar. Zekollari, H., Huss, M. & Farinotti, D. Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble. With this study, we provide new predictions of glacier evolution in a highly populated mountain region, while investigating the role of nonlinearities in the response of glaciers to multiple future climate forcings. The glacier ice volume in the French Alps at the beginning of the 21st century is unevenly distributed, with the Mont-Blanc massif accounting for about 60% of the total ice volume in the year 2015 (7.06 out of 11.64km3, Fig. 3a). Tibshirani, R. Regression Shrinkage and Selection via the Lasso. Res. Interestingly, future warmer temperatures do not affect annual snowfall rates on glaciers as a result of both higher precipitation rates in the EURO-CORDEX ensemble (Fig. By performing glacier projections both with mountain glaciers in the French Alps and a synthetic experiment reproducing ice cap-like behaviour, we argue that the limitations identified here for linear models will also have implications for many other glacierized regions in the world. Earth Syst. Universal Differential Equations for Scientific Machine Learning. Recent efforts have been made to improve the representation of ice flow dynamics in these models, replacing empirical parametrizations with simplified physical models9,10. Despite these differences, the average altitude difference of the glaciers between both models is never greater than 50m (Fig. Despite their limitations, temperature-index models, owing to their simplicity and parsimonious data requirements, have been widely used for large-scale glacier projections7,8. Nonetheless, to represent the glacier mass balance, the vast majority of large-scale glacier evolution models relies on temperature-index models. Grenoble Alpes, CNRS, G-INP, Laboratoire Jean Kuntzmann, Grenoble, France, You can also search for this author in This allows us to assess the MB models responses at a regional scale to changes in individual predictors (Fig. Summer climate is computed between April 1st and September 30th and winter climate between October 1st and March 31st. Geophys. Data 12, 19731983 (2020). New research suggests that climate change-induced melting of the Nisqually Glacier near Seattle, Wash., and other high-elevation glaciers will offset seasonal declines in streamflow until. A comprehensive bibliography of scientific publications relating to the glacier is included. All values correspond to ensemble means under RCP 4.5. glacier length12,14. The images or other third party material in this article are included in the articles Creative Commons license, unless indicated otherwise in a credit line to the material. Conversely, for RCP 8.5, annual glacier-wide MB are estimated to become increasingly negative by the second half of the century, with average MB almost twice as negative as todays average values (Fig. J. Glaciol. J. Clim. Advances occurred from 1963-68 and from 1974-79. GlacierMIP A model intercomparison of global-scale glacier mass-balance models and projections. 3c). CAS Three different types of cross validation were performed: a Leave-One-Glacier-Out (LOGO), a Leave-One-Year-Out (LOYO) and a Leave-Some-Years-and-Glaciers-Out (LSYGO). Verfaillie, D., Dqu, M., Morin, S. & Lafaysse, M. The method ADAMONT v1.0 for statistical adjustment of climate projections applicable to energy balance land surface models. The largest snow depths measured this spring exceeded 10 meters on Nisqually Glacier and 7 meters on Emmons. Rainier is considered by the USGS to be one of the most threatening volcanoes in the Cascade Mountains. Because of easy access and prominent location the glacier has been studied since the mid 1850's. In 1857, Lt. August Kautz crossed Nisqually Glacier during an attempt to climb the summit. Since these flatter glaciers are more likely to go through extreme negative MB rates, nonlinear responses to future warming play a more important role, producing cumulative MB differences of up to 20% by the end of the century (Fig. Slider with three articles shown per slide. Hock, R. & Huss, M. Glaciers and climate change. Alternatively, flatter glaciers (i.e. ice cap-like behaviour). Vis. Several aquatic and terrestrial ecosystems depend on these water resources as well, which ensure a base runoff during the warmest or driest months of the year6. Annual glacier-wide mass balance (MB) is estimated to remain stable at around 1.2m.w.e. Roberts, D. R. et al. This creates an interesting dilemma, with more complex temperature-index MB models generally outperforming simpler models for more climatically homogeneous past periods but introducing important biases for future projections under climate change. The position of the front of the wave will be defined as the transverse line across the glacier where the flow of . When comparing our deep learning simulations with those from the Lasso, we found average cumulative MB differences of up to 17% by the end of the century (Fig. 4a, b) and negative (Fig. J. Glaciol. Our projections show a strong glacier mass loss for all 29 climate members, with average ice volume losses by the end of the century of 75%, 80%, and 88% compared to 2015 under RCP 2.6 (9%, n=3), RCP 4.5 (17% +11%, n=13) and RCP 8.5 (15% +11%, n=13), respectively (Fig. Nisqually Glacier is the lengthiest of any made in North America. When working with spatiotemporal data, it is imperative to respect spatial and temporal data structures during cross-validation in order to correctly assess an accurate model performance48. Source: Mount Rainier National Park Nonetheless, since the main GCM-RCM climate signal is the same, the main large-scale long-term trends are quite similar. Roe, G. H. Orographic precipitation. The main reason for their success comes from their suitability to large-scale studies with a low density of observations, in some cases displaying an even better performance than more complex models12. 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. By submitting a comment you agree to abide by our Terms and Community Guidelines. "It has been pretty much doing this nonstop since the mid-1800s." The Nisqually Glacier is losing nearly a quarter of a mile in length a year, Kennard added.
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