Summer melt was also above average. 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. energy balance), with differences increasing when the conditions considerably differ from the calibration period33. Consortium, R. G. I. Randolph Glacier Inventory 6.0 (2017) https://doi.org/10.7265/N5-RGI-60. A knowledge of the areas once occupied by mountain glaciers reveals at least part of the past behavior of these glaciers. Sci. A NASA-led, international study finds Asia's high mountain glaciers are flowing more slowly in response to widespread ice loss, affecting freshwater availability downstream in India, Pakistan and China. Cross-validation strategies for data with temporal, spatial, hierarchical, or phylogenetic structure. Temperature-index models are known to be over-sensitive to temperature changes, mainly due to important differences in the processes contributing to future warming. Geophys. Nature Communications thanks Mohd Anul Haq, Lauren Vargo, and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. 31, n/an/a (2004). Source: Mount Rainier National Park 41, 153160 (1995). Glob. 4 ). https://zenodo.org/record/5549758. A glacier is a large mass of snow and ice that has accumulated over many years and is present year-round. For that, a dataset of input predictors covering all the glaciers in the French Alps for the 19672015 period was generated from a past MB reconstruction study15. 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. J.B. developed the main glacier model, performed the simulations, analysed the results, and wrote the paper. Provided by the Springer Nature SharedIt content-sharing initiative. Many studies have investigated the effects of climate change on glacier runoff using observations or modelling, with a recent focus on High Mountain Asia 14,16,17 and the Andes 18,19,20.The degree . contributed to the climate analyses. Therefore, solid precipitation is projected to remain almost constant at the evolving glaciers mean altitude independently from the future climate scenarios, while air temperature is projected to drive future glacier-wide mass changes (Fig. These synthetic experiments suggest that, for equal climatic conditions, flatter glaciers and ice caps will experience substantially more negative MB rates than steeper mountain glaciers. Geosci. Global glacier mass changes and their contributions to sea-level rise from 1961 to 2016. creates a Nisqually Glacier response similar to those seen from its historical waves, suggesting that there are other factors contributing to kinematic wave formation, and 4) the Nisqually . S8 and Fig. Regarding air temperature, a specific CPDD anomaly ranging from 1500 PDD to +1500 PDD in steps of 100 PDD was prescribed to all glaciers for each dataset copy. The rest of the story appears to lie primarily in the unique dynamic response of the region's glaciers to climate change. 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. In order to improve the comparability between both models, a MB bias correction was applied to GloGEMflows simulated MB, based on the average annual MB difference between both models for the 20032015 period (0.4m.w.e. Vertical axes are different for the two analyses. The increase in glacier altitude also causes the solid to liquid precipitation ratio to remain relatively constant. Vis. 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. (2019) https://doi.org/10.18750/MASSBALANCE.2019.R2019. Grenoble Alpes, CNRS, G-INP, Laboratoire Jean Kuntzmann, Grenoble, France, You can also search for this author in Article These results revealed that the main uncertainties on glacier simulations arise from the initial ice thickness used to initialize the model. Particularly in Asia, water demand exceeds supply due to rapid population growth, with glacier . The Open Global Glacier Model (OGGM) v1.1. Analysis of a 24-Year photographic record of Nisqually glacier, Mount 1). melt and sublimation of ice, firn and snow; or calving)9; and (2) ice flow dynamics, characterized by the downward movement of ice due to the effects of gravity in the form of deformation of ice and basal sliding. Magnin, F., Haeberli, W., Linsbauer, A., Deline, P. & Ravanel, L. Estimating glacier-bed overdeepenings as possible sites of future lakes in the de-glaciating Mont Blanc massif (Western European Alps). 3a). Map-based methods for estimating glacier equilibrium-line altitudes Through his research in that area, he's seen firsthand the impact of climate change and has been studying the long-term effects of a warming planet. How Will Melting Glaciers Affect Streamflow? - Eos 60, 867878 (2014). 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. 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. 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. Kinematic waves on glaciers move as several times the speed of the ice as a whole, and are subtle in topographic expression. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. Cite this article. Tests were performed distributing the CPDD anomalies equally among all months of the year with very similar results. The training was performed with an RMSprop optimizer, batch normalization46, and we used both dropout and Gaussian noise in order to regularize it. Researchers analyzed almost 2 million satellite images of the glaciers and found that 94 . H.Z. Data 12, 19731983 (2020). Glaciers and ice caps are experiencing strong mass losses worldwide, challenging water availability, hydropower generation, and ecosystems. Analyses were made of the annual photographs . Geosci. Thin lines represent each of the 29 individual member runs, while the thick lines represent the average for a given RCP. A similar trend is under way. (Springer, New York, 2009). Deep learning applied to glacier evolution modelling. Ice thickness accuracy varied significantly, with an overall correct representation of the ice distribution but with local biases reaching up to 100%. Comput. To interactively describe to response of glaciers to climate change, a glacier parameterization scheme has been developed and implemented into the regional climate model REMO. B Methodol. This enables the recalculation of every topographical predictor used for the MB model, thus updating the mean glacier altitude at which climate data for each glacier are retrieved. a deep artificial neural network) or the Lasso (regularized multilinear regression)30. The temperature-index model includes up to three different DDFs, for ice, firn and snow, resulting in three parameters. As Arctic warms, Canada's glaciers playing major role in sea - CBC 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. 3c), which is directly linked to summer air temperatures and has a strong influence on surface albedo. Glaciers are large-scale, highly sensitive climate instruments which, ideally, should be picked up and weighed once a year. With this cross-validation we determined a deep learning MB model spatiotemporal (LSYGO) RMSE of 0.59m.w.e. A similar behaviour is observed when comparing temperature-index models to more complex models (e.g. Rabatel, A., Sanchez, O., Vincent, C. & Six, D. Estimation of glacier thickness from surface mass balance and ice flow velocities: a case study on Argentire Glacier, France. Therefore, their sensitivities to the projected 21st century increase in PDDs are linear. Relatively minor climate changes during the Little Ice Age (A.D. 1200-1850) impart significant glacial responses. The Nature of Kinematic Waves in Glaciers and their Application to In order to overcome these differences, some adaptations were performed to the GloGEMflow output, accompanied with some hypotheses to ensure a realistic comparison. 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. Since 2005, study finds that surface melt off glaciers in the North has risen by 900%. By the end of the century, we predict a glacier volume loss between 75 and 88%. Google Scholar. As climate changes, so do glaciers | PNAS Glaciers are experiencing important changes throughout the world as a consequence of anthropogenic climate change1. 10, 42574283 (2017). 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. Nisqually Glacier - glaciers.pdx.edu Lett. Swiss Glacier Mass Balance (release 2019). These are among the cascading effects linked to glacier loss which impact ecosystems and . For such cases, we assumed that ice dynamics no longer play an important role, and the mass changes were applied equally throughout the glacier. Nonlinear sensitivity of glacier mass balance to future climate change unveiled by deep learning. "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. Res. Years in white in c-e indicate the disappearance of all glaciers in a given massif. Ioffe, S. & Szegedy, C. Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift (2015). Jordi Bolibar. Nature Geosciences, https://doi.org/10.1038/s41561-021-00885-z (2022). 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. S5b). S5cf), except for the largest glaciers (e.g. 4a). This adjustment represents a major improvement over most climate data used to force regional and global glacier models. Summer climate is computed between April 1st and September 30th and winter climate between October 1st and March 31st. Alternatively, the comparisons against an independent large-scale glacier evolution model were less straightforward to achieve. 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. Article Rising Water Temperatures Could Be A Death Sentence For Pacific Salmon Such glaciers are often remnants of the Little Ice Age, and mainly lose mass via non-dynamic downwasting51. Bolibar, J., Rabatel, A., Gouttevin, I. Huss, M. et al. 60, 11401154 (2014). S5h, j, l). When using the linear MB model (Lasso), glaciers are close to reaching an equilibrium with the climate in the last decades of the century, which is not the case for the nonlinear MB model (deep learning). For intermediate and pessimistic climate scenarios, no significant differences were found (Fig. P. Kennard, J. Despite marked differences among regions, the generalized retreat of glaciers is expected to have major environmental and social impacts2,3. Six, D. & Vincent, C. Sensitivity of mass balance and equilibrium-line altitude to climate change in the French Alps. 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. Nonetheless, these differences have been shown to be rather small, having a lower impact on results than climate forcings or the initial glacier ice thickness10. 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). Models were trained using the SAFRAN reanalysis dataset47, including observations of mountain regions in France for the 19582015 period. On Mount Rainier, elevation surveys of Nisqually Glacier are regularly made to determine changes in the elevation of the surface. South American Glaciers Melting Faster, Changing Sea Level Nonetheless, a close inspection of the annual glacier-wide MB rates from both models reveals similar patterns to those found when comparing deep learning and Lasso approaches (Figs. We performed a validation simulation for the 20032015 period by running our model through this period and comparing the simulated glacier surface area of each of the 32 glaciers with MB to observations from the 2015 glacier inventory16,52. We ran glacier evolution projections for both the deep learning and Lasso MB models, but we kept the glacier geometry constant, thus preserving the glacier centroid where the climate data is computed constant through time. regularized multilinear regression. 2a and S3). (Photograph by Klaus J. Bayr, Keene State College, 1990) One method of measuring glaciers is to send researchers onto the ice with . Marzeion, B. et al. Nonlinear sensitivity of glacier mass balance to future climate change Carlson, B. To obtain As for the MB modelling approach, a detailed explanation on this method can be found in a previous dedicated paper on the methods31. This type of model uses a calibrated linear relationship between positive degree-days (PDDs) and the melt of ice or snow11. Climate variations change a glacier's mass balance by affecting ablation and accumulation amounts. Nat. 4 vs.S5). 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. ADS 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 ice thickness data for two of the largest glaciers in the French Alps were modified in order to improve data quality. The record, which was started in 1931, shows the glacier's dramatic responses to about half a century of small but significant climatic variations. 6 (2018). 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. Paul, F. et al. Both machine learning MB models were trained with exactly the same data coming from the 1048 annual glacier-wide MB values, and both were cross-validated using LSYGO. This reduced sensitivity is captured through the response to summer snowfall anomalies, since the sensitivity to positive CPDD anomalies is quite similar for the linear and nonlinear models, as it encompasses both the accumulation and ablation seasons (Fig. The Elements of Statistical Learning. https://doi.org/10.1016/B978-0-12-821575-3.00009-8. Z. et al. The linear Lasso MB model suggests a stabilization of glacier evolution, reaching neutral MB rates by the end of the century. 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. "Their numbers have gone from regularly exceeding 50,000 adult salmon in the Nisqually to about 5,000 last year." The Nisqually River near its glacial origins. 12, 1959 (2020). Under warmer conditions (RCP 8.5), the differences between the linear and nonlinear MB model become smaller, as the topographical feedback from glacier retreat compensates for an important fraction of the losses induced by the late century warmer climate (Fig. This ensures that the model is capable of reproducing MB rates for unseen glaciers and years. As previously mentioned, here these differences are computed at regional level for a wide variety of glaciers. Envelopes indicate based on results for all 660 glaciers in the French Alps for the 19672015 period. When it was built in the early 1900s, the road into Mount Rainier National Park from the west passed near the foot of the Nisqually Glacier, one of the mountain's longest . The authors declare no competing interests. This is well in agreement with the known uncertainties of glacier evolution models, with glacier ice thickness being the second largest uncertainty after the future GCM-RCM-RCP climate members used to force the model29. In this study, we demonstrated the advantages of using deep learning to model glacier MB at regional scales, both in terms of variance and bias. glacier length12,14. 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. H.Z. The Cryosphere 12, 13671386 (2018). These different behaviours and resulting biases can potentially induce important consequences in long-term glacier evolution projections. 'When the Glaciers Disappear, Those Species Will Go Extinct' Bartk, B. et al. We also use this method to extract glacier borderlines from satellite images across the western Lenglongling mountains. Res. Tibshirani, R. Regression Shrinkage and Selection via the Lasso. Both models agree around the average values seen during training (i.e. Glacier Length Variations and Climate Change: Comparative Glacier Robinson, C. T., Thompson, C. & Freestone, M. Ecosystem development of streams lengthened by rapid glacial recession. 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. In order to do so, we applied a deterministic sampling process as a sensitivity analysis to both the deep learning and the Lasso MB models. PDF Climate Change Glacier response to climate change This translates into a more linear response to air temperature changes compared to the ablation season (Fig. DDFs are known to vary much less with increasing temperatures for intermediate values of albedo (i.e. Canada's glaciers and ice caps are now a major contributor to sea level change, a new UCI study shows. A small ablation increase may cause . 3, 16751685 (2019). On top of that, they happen to be among the glacierized regions with the largest projected uncertainties8. The source code of the glacier model can be freely accessed in the following repository: https://github.com/JordiBolibar/ALPGM. A He uniform initialization45 was used for the network parameters. & Zumbhl, H. J. Simulating these processes at a large geographical scale is challenging, with models requiring several parametrizations and simplifications to operate. Using this function, the glacier-specific ice thickness and the DEM are updated every year, adjusting the 3D geometry of each glacier. Nat. Landscape response to climate change and its role in infrastructure Nisqually Glacier is the lengthiest of any made in North America. I.G. 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. Huss, M., Funk, M. & Ohmura, A. An enhanced temperature-index glacier melt model including the shortwave radiation balance: development and testing for Haut Glacier dArolla, Switzerland. Lett. The largest snow depths measured this spring exceeded 10 meters on Nisqually Glacier and 7 meters on Emmons. ice cap-like behaviour). 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. Simulations were then performed by averaging the outputs of each one of the 60 ensemble members. PDF Centennial glacier retreat as categorical evidence of regional climate Alternatively, flatter glaciers (i.e. The two models with linear MB responses to PDDs and accumulation simulate more positive MB rates under RCP 2.6, highlighting their over-sensitivity to negative air temperature anomalies and positive snowfall anomalies (Fig. This experiment enabled the exploration of the response to specific climate forcings of a wide range of glaciers of different topographical characteristics in a wide range of different climatic setups, determined by all meteorological conditions from the years 19672015 (Fig. All authors provided inputs to the paper and helped to write it. We reduced these differences by running simulations with GloGEMflow using exactly the same 29 climate members used by ALPGM in this study (TableS1). The position of the front of the wave will be defined as the transverse line across the glacier where the flow of . 3). Multiple copies of this dataset were created, and for each individual copy a single predictor (i.e. 2013). Arch. In order to simulate annual glacier-wide MB values, (a) topographical and (b) climate data for those glaciers and years were compiled for each of the 1048 glacier-year values. Res. Predicting future glacier evolution is of paramount importance in order to correctly anticipate and mitigate the resulting environmental and social impacts. Google Scholar. These predictors are composed of: the mean glacier altitude, maximum glacier altitude, slope of the lowermost 20% altitudinal range of the glacier, glacier surface area, latitude, longitude and aspect. Geomorphology 350, 106913 (2020). 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. 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. He, K., Zhang, X., Ren, S. & Sun, J. Delving Deep into Rectifiers: Surpassing Human-Level Performance on ImageNet Classification. 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. The smallest best performing architecture was used, in order to find a good balance between predictive power, speed, and extrapolation outside the training data. 44, 13761383 (2017). Sci. Botanical Evidence of the Modern History of Nisqually Glacier - USGS Alternatively, the Lasso MB model displayed an RMSE of 0.85m.w.e. Glaciers smaller than 0.5km2 often display a high climate imbalance, with their equilibrium line being higher than the glaciers maximum altitude. Cauvy-Frauni, S. & Dangles, O. CAS 5). 65, 453467 (2019). A dataset of 32 glaciers with direct annual glacier-wide MB observations and remote sensing estimates was used to train the models. 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). 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. The 29 RCP-GCM-RCM combinations available, hereafter named climate members, are representative of future climate trajectories with different concentration levels of greenhouse gases (TableS1). At the Edge: Monitoring Glaciers to Watch Global Warming - NASA 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. Steiner, D., Walter, A. Front. S5 and S6). 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. Meteorol.
