Gabbi, J., Carenzo, M., Pellicciotti, F., Bauder, A. 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). At this point, it is important to clarify the different ways of treating PDDs in the Lasso and the temperature-index MB models analysed in this study in order to justify analogies. Glaciers are experiencing important changes throughout the world as a consequence of anthropogenic climate change1. 14, 815829 (2010). b, c, d and f, g, h annual glacier-wide MB probability distribution functions for all n scenarios in each RCP. Scand. Rackauckas, C. et al. All climate anomalies are computed with respect to the 19672015 mean values. Secure .gov websites use HTTPS A lock ( ) or https:// means you've safely connected to the .gov website. Ioffe, S. & Szegedy, C. Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift (2015). By monitoring the change in size of glaciers around the world, scientists can learn about global climate change. ADS Bolibar, J., Rabatel, A., Gouttevin, I. Each one of these cross-validations served to evaluate the model performance for the spatial, temporal and both dimensions, respectively. An enhanced temperature-index glacier melt model including the shortwave radiation balance: development and testing for Haut Glacier dArolla, Switzerland. 51, 313323 (2005). 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. On Mount Rainier, elevation surveys of Nisqually Glacier are regularly made to determine changes in the elevation of the surface. Therefore, their sensitivities to the projected 21st century increase in PDDs are linear. Glacier ice thickness observations are available for four different glaciers in the regions, which were compared to the estimates used in this model. ISSN 2041-1723 (online). Nonetheless, since the main GCM-RCM climate signal is the same, the main large-scale long-term trends are quite similar. 2a). 4e). Future projections of glacier-wide MB evolution were performed using climate projections from ADAMONT25. With a secondary role, glacier model uncertainty decreases over time, but it represents the greatest source of uncertainty until the middle of the century8. Hock, R. & Huss, M. Glaciers and climate change. 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. 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. The vertical blue and red lines indicate the distribution of extreme (top 5%) values for all 21st century projected climate scenarios, with the mean value in the center and 1 indicated by dashed lines. These conclusions drawn from these synthetic experiments could have large implications given the important sea-level contribution from ice cap-like ice bodies8. 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. 1). 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. Earths Future 5, 418435 (2017). In this study, we investigate the future evolution of glaciers in the French Alps and their nonlinear response to multiple climate scenarios. The Cryosphere 14, 565584 (2020). In summary, the linear approximations used by the Lasso manage to correctly fit the main cluster of average values but perform poorly for extreme values31. Nature Communications (Nat Commun) 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. GloGEMflow relies on EURO-CORDEX ensembles26, whereas ALPGM uses ADAMONT25, an adjusted version of EURO-CORDEX specifically designed for mountain regions. a1), but when conditions deviate from this mean training data centroid, the Lasso can only linearly approximate the extremes based on the linear trend set on the main cluster of average values (Fig. a deep artificial neural network) or the Lasso (regularized multilinear regression)30. 1960). Our analysis suggests that due to this positive impact on the MB signal, only relevant differences are observed between nonlinear and linear MB models for the lowest emission climate scenarios (Fig. 4a). Article This adjustment represents a major improvement over most climate data used to force regional and global glacier models. 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. 4a). 1d, g). Glaciers with the greatest degree of seasonality in their flow behavior, such as Nisqually and Shoestring glaciers, responded most rapidly. Hock, R. et al. J. Glaciol. 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. Pellicciotti, F. et al. Importance and vulnerability of the worlds water towers. 4 ). Geomorphology 350, 106913 (2020). The cumulative positive degree days (CPDD), snowfall and rainfall dl, are at the glaciers annually evolving centroids. Simulations were then performed by averaging the outputs of each one of the 60 ensemble members. 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. 22, 21462160 (2009). Gaining a better understanding of how warming ocean water affects these glaciers will help improve predictions of their fate. CoRR abs/1505.00853 (2015). 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. 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. Soc. Reanalysis of 47 Years of Climate in the French Alps (19582005): Climatology and Trends for Snow Cover. 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. Deep artificial neural networks (ANNs) are nonlinear models that offer an alternative approach to these classic methods. 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. 2008. J. Glaciol. Both the Lasso and the temperature-index MB model rely on linear relationships between PDDs, solid precipitation and MB. Google Scholar. Earth Syst. This method has the advantage of including glacier-specific dynamics in the model, encompassing a wide range of different glacier behaviours. 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. In order to overcome these differences, some adaptations were performed to the GloGEMflow output, accompanied with some hypotheses to ensure a realistic comparison. Hastie, T., Tibshirani, R. & Friedman, J. 58, 267288 (1996). "Such glaciers spawn icebergs into the ocean or lakes and have different dynamics from glaciers that end on land and melt at their front ends. This means that these flatter ice bodies, under a warming climate, will be subject to higher temperatures than their steeper counterparts. Toward mountains without permanent snow and ice: mountains without permanent snow and ice. 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. Multiple copies of this dataset were created, and for each individual copy a single predictor (i.e. 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. IPCC. 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. A sensitivity analysis of both MB models revealed nonlinear relationships between PDDs, snowfall (in winter and summer) and glacier-wide MB, which the linear model was only able to approximate (r2=0.41 for the Lasso vs. r2=0.76 for deep learning in cross-validation31; Fig. Universal Differential Equations for Scientific Machine Learning. 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 . Geophys. 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. An analysis of the climate signal at the glaciers mean altitude throughout the century reveals that air temperature, particularly in summer, is expected to be the main driver of glacier mass change in the region (Fig. The training was performed with an RMSprop optimizer, batch normalization46, and we used both dropout and Gaussian noise in order to regularize it. In the meantime, to ensure continued support, we are displaying the site without styles 1a). Nonlinear sensitivity of glacier mass balance to future climate change unveiled by deep learning. ADS Rainier, Washington. 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. Zekollari, H., Huss, M. & Farinotti, D. Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble. how climate change and glacier retreat are reshaping whole aquatic ecosystems, there is a need to develop an integrated understanding spanning multiple taxonomic groups and trophic levels in glacier-fed rivers (e.g., bacteria, protists, fungi, algae, diatoms, invertebrates, mammals, amphibians, and fish; Clitherow et al. Mer de Glace, 29km2 in 2015), which did show important differences under RCP 8.5 (up to 75%), due to their longer response time. CAS If material is not included in the articles Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Geosci. (b) Climate predictors are based on climatic anomalies computed at the glaciers mean altitude with respect to the 19672015 reference period mean values. 2015 IEEE Int. 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. S10). Z. et al. Braithwaite, R. J. 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. Geophys. 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. 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. A recent Northern Hemisphere temperature reconstruction indicates an oscillating temperature drop from A.D. 1000-1850 of about 0.2C with a subsequent and still continuing warming of nearly 0.8C ( 3 ). Spandre, P. et al. 2) and RCP 8.5 by the end of the century. The Karakoram and the Himalayan mountain range accommodate a large number of glaciers and are the major source of several perennial rivers downstream. These trends explored with energy balance models from the literature correspond to the behaviour captured by our deep learning MB model, with a clearly less sensitive response of glacier-wide MB to extreme climate forcings, particularly in summer (Fig. Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. 3). 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. Overall, this results in linear MB models overestimating both extreme positive (Fig. This behaviour is particularly clear for summer snowfall, for which the differences are the largest (Fig. Our results serve as a strong reminder that the outcomes of existing large-scale glacier simulations should be interpreted with care, and that newly available techniques (such as the nonlinear deep learning approach presented here) and observations (e.g. This parametrization reproduces in an empirical manner the changes in glacier geometry due to the combined effects of ice dynamics and MB. A recent study he did found that 80 percent of the glaciers in Alberta and British Columbia could melt in the next 50 years. 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. Cauvy-Frauni, S. & Dangles, O. 0.5) than lower values typical from ice34. MathSciNet a1 and a r2 of 0.69, explaining 69% of the total MB variance. 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. Nisqually Glacier is perhaps the most visited, best-surveyed glacier on Mount Rainier. Planet. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in This has the strongest impact under RCP 2.6, where positive MB rates are more frequent (Fig. 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. . CPDD, winter snowfall or summer snowfall) was modified for all glaciers and years. This synthetic experiment is an approximation of what might occur in other glacierized regions with ice caps. Glacier response to climate change Jim Salinger, Trevor Chinn, Andrew Willsman, and how fluctuations in New Zealand glaciers reflect regional climate change. A He uniform initialization45 was used for the network parameters. Thank you for visiting nature.com. 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. ArXiv200104385 Cs Math Q-Bio Stat (2020). J. Hydrol. Our results show that the mean elevation is far more variable than the kinematic ELA ( Fig. volume13, Articlenumber:409 (2022) The smallest best performing architecture was used, in order to find a good balance between predictive power, speed, and extrapolation outside the training data. A glacier is a large mass of snow and ice that has accumulated over many years and is present year-round. The anomaly in snowfall was evenly distributed for every month in the accumulation (October 1April 31) and ablation seasons, respectively. Indeed, the projected 21st century warming will lead to increasing incoming longwave radiation and turbulent fluxes, with no marked future trends in the evolution of shortwave radiation37. This behaviour is expected for mountain glaciers, as they are capable of retreating to higher altitudes, thus producing a positive impact on their glacier-wide MB (Fig. 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. 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. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. 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. Summer melt was also above average. A small ablation increase may cause . 51, 573587 (2005). Earth Syst. 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. longwave radiation budget, turbulent fluxes), in comparison with a future warmer climate. 6 (2018). a Projected mean glacier altitude evolution between 2015 and 2100. Model Dev. S5h, j, l). Carlson, B. Across the globe, glaciers are decreasing in volume and number in response to climate change. This work was funded by the Labex OSUG@2020 (Investissements davenir, ANR10 LABX56) and the Auvergne-Rhne-Alpes region through the BERGER project. Winter tourism under climate change in the Pyrenees and the French Alps: relevance of snowmaking as a technical adaptation. J. Clim. Res. 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). 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. & Funk, M. A comparison of empirical and physically based glacier surface melt models for long-term simulations of glacier response. Canada's glaciers and ice caps are now a major contributor to sea level change, a new UCI study shows. The lower fraction of variance explained by linear models is present under all climate scenarios. Alternatively, the Lasso model used here includes 13 DDFs: one for the annual CPDDs and 12 for each month of the hydrological year. This oversensitivity directly results from the fact that temperature-index models rely on linear relationships between PDDs and melt and that these models are calibrated with past MB and climate data. Consequently, a simple MB model with a single DDF (e.g. Zemp, M. et al. The record, which was started in 1931, shows the glacier's dramatic responses to about half a century of small but significant climatic variations. 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. Nature Geosciences, https://doi.org/10.1038/s41561-021-00885-z (2022). To obtain 33, 645671 (2005). Vincent, C. et al. Sci. 47 (2020). 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. 3, 16751685 (2019). Lett. 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. 3). Partitioning the uncertainty of ensemble projections of global glacier mass change. Our analyses suggest that these limitations can also be translated to temperature-index MB models, as they share linear relationships between PDDs and melt, as well as precipitation and accumulation. These measurements of surface elevation were begun by personnel of the Tacoma 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. GloGEMflow has been previously applied in a study over the whole European Alps, and its temperature-index model was mainly calibrated with MB data from the Swiss Alps. Nonetheless, to represent the glacier mass balance, the vast majority of large-scale glacier evolution models relies on temperature-index models. 1). 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. deep artificial neural networks) glacier evolution projections by modelling the regional evolution of French alpine glaciers through the 21st century. 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. 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). DDFs are known to vary much less with increasing temperatures for intermediate values of albedo (i.e. Ice melt sensitivity to PDDs strongly decreases with increasing summer temperatures, whereas snow melt sensitivity changes at a smaller rate34. 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. contributed to the extraction of nonlinear mass balance responses and to the statistical analysis. Our results also highlight the important role played by glacier geometry adjustment under changing climatic conditions, which is typical of mountain glaciers38. 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. CAS performed simulations with another glacier model, provided results for comparison, and contributed to the glaciological analyses. During the last decade, various global glacier evolution models have been used to provide estimates on the future sea-level contribution from glaciers7,8. Mt. We previously demonstrated that this period is long enough to represent the secular trend of glacier dynamics in the region31. Nonetheless, a better understanding of the underlying processes guiding these nonlinear behaviours at large geographical scales is needed. Models were trained using the SAFRAN reanalysis dataset47, including observations of mountain regions in France for the 19582015 period. 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 . Thin lines represent each of the 29 individual member runs, while the thick lines represent the average for a given RCP. Years in white in c-e indicate the disappearance of all glaciers in a given massif. Bolibar, J., Rabatel, A., Gouttevin, I. et al. Earths Future https://doi.org/10.1029/2019EF001470 (2020). 36, L23501 (2009). Nisqually Glacier is well known for its kinematic waves ( Meier, 1962 ), but its mass balance has never been measured due to the difficulty of the glacier terrain. ICCV (2015) https://doi.org/10.1109/iccv.2015.123. Farinotti, D. et al. 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. By Carol Rasmussen,NASA's Earth Science News Team. P. Kennard, J. The high spatial resolution enables a detailed representation of mountain weather patterns, which are often undermined by coarser resolution climate datasets. https://doi.org/10.1016/B978-0-12-821575-3.00009-8. In fact, in many cases the surface lowering into warmer air causes this impact on the MB to be negative, further enhancing extreme negative mass balance rates. Glacier surface mass changes are commonly modelled by relying on empirical linear relationships between PDDs and snow, firn or ice melt8,9,10,29. 4a, b) and negative (Fig. A dataset of 32 glaciers with direct annual glacier-wide MB observations and remote sensing estimates was used to train the models. The authors declare no competing interests. 65, 453467 (2019). In order to investigate the effects of MB nonlinearities on flatter glaciers, we conducted a synthetic experiment using the French Alps dataset. 5). Tibshirani, R. Regression Shrinkage and Selection via the Lasso. The source code of the glacier model can be freely accessed in the following repository: https://github.com/JordiBolibar/ALPGM. 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. Marzeion, B. et al. (Springer, New York, 2009). J. R. Stat. The machine learning models used in this study are useful to highlight and quantify how nonlinearities in MB affect climate-glacier interactions, but are limited in terms of process understanding. The linear Lasso MB model suggests a stabilization of glacier evolution, reaching neutral MB rates by the end of the century. Xu, B., Wang, N., Chen, T. & Li, M. Empirical Evaluation of Rectified Activations in Convolutional Network. S6). 4). Cite this article. 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. These are among the cascading effects linked to glacier loss which impact ecosystems and . 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. 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.
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