Recent efforts have been made to improve the representation of ice flow dynamics in these models, replacing empirical parametrizations with simplified physical models9,10. 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. 3c). Atmospheres 121, 77107728 (2016). Carlson, B. 3). 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. 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 . (b) Climate predictors are based on climatic anomalies computed at the glaciers mean altitude with respect to the 19672015 reference period mean values. Our synthetic experiment does not account for glacier surface area shrinking either, which might have an impact on the glacier-wide MB signal. Rackauckas, C. et al. Thank you for visiting nature.com. deep artificial neural networks) glacier evolution projections by modelling the regional evolution of French alpine glaciers through the 21st century. S10). Earth Syst. 60, 867878 (2014). Front. A.R. Jordi Bolibar. Fr Hydrobiol. Geophys. Nonetheless, a better understanding of the underlying processes guiding these nonlinear behaviours at large geographical scales is needed. Soc. Data 12, 18051821 (2020). Sci. Glacier response to climate change Jim Salinger, Trevor Chinn, Andrew Willsman, and how fluctuations in New Zealand glaciers reflect regional climate change. 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. Loss of glaciers contributes to sea-level rise, creates environmental hazards and can alter aquatic habitats. Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. McKinley, Alaska, change in response to the local climate. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. 22, 21462160 (2009). Universal Differential Equations for Scientific Machine Learning. We reduced these differences by running simulations with GloGEMflow using exactly the same 29 climate members used by ALPGM in this study (TableS1). Salim, E., Ravanel, L., Deline, P. & Gauchon, C. A review of melting ice adaptation strategies in the glacier tourism context. 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. snowfall, avalanches and refreezing) and the mass lost via different processes of ablation (e.g. Graphics inspired by Hock and Huss40. Article Several differences are present between ALPGM, the model used in this study, and GloGEMflow (TableS2), which hinder a direct meaningful comparison between both. 31, n/an/a (2004). To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. 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. CPDD, winter snowfall or summer snowfall) was modified for all glaciers and years. Ice melt sensitivity to PDDs strongly decreases with increasing summer temperatures, whereas snow melt sensitivity changes at a smaller rate34. Farinotti, D., Round, V., Huss, M., Compagno, L. & Zekollari, H. Large hydropower and water-storage potential in future glacier-free basins. Geosci. Durand, Y. et al. 33, 645671 (2005). H.Z. Each one of these cross-validations served to evaluate the model performance for the spatial, temporal and both dimensions, respectively. 2a). 4 vs.S5). He, K., Zhang, X., Ren, S. & Sun, J. Delving Deep into Rectifiers: Surpassing Human-Level Performance on ImageNet Classification. Article 5). Winter tourism under climate change in the Pyrenees and the French Alps: relevance of snowmaking as a technical adaptation. Such glaciers are often remnants of the Little Ice Age, and mainly lose mass via non-dynamic downwasting51. Hastie, T., Tibshirani, R. & Friedman, J. Glaciers with the greatest degree of seasonality in their flow behavior, such as Nisqually and Shoestring glaciers, responded most rapidly. Conversely, during the accumulation season, glaciers are mostly covered by snow, with a much higher albedo and a reduced role of shortwave radiation in the MB that will persist even under climate change. Bolibar, J., Rabatel, A., Gouttevin, I. et al. 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. In that study, a temperature-index model with a separate degree-day factor (DDF) for snow and ice is used, resulting in piecewise linear functions able to partially reproduce nonlinear MB dynamics. B Methodol. https://doi.org/10.5281/zenodo.3609136. As we have previously shown, these models present a very similar behaviour to the linear statistical MB model from this study (Fig. Alluvial landscape response to climate change in glacial rivers and the implications to transportation infrastructure. volume13, Articlenumber:409 (2022) Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2. For intermediate and pessimistic climate scenarios, no significant differences were found (Fig. ICCV (2015) https://doi.org/10.1109/iccv.2015.123. 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. 4e). Zekollari, H., Huss, M. & Farinotti, D. Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble. With this setup, we reproduced the ice cap-like behaviour with a lack of topographical adjustment to higher elevations. Despite their limitations, temperature-index models, owing to their simplicity and parsimonious data requirements, have been widely used for large-scale glacier projections7,8. Lett. 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. Taking into account that for several regions in the world about half of the glacierized volume will be lost during this first half of the 21st century, glacier models play a major role in the correct assessment of future glacier evolution. The vast majority of glaciers in the French Alps are very small glaciers (<0.01km2), that are mainly remnants from the Little Ice Age, with a strong imbalance with the current climate15. This is not the case for the nonlinear deep learning MB model, which captures the nonlinear response of melt and MB to increasing air temperatures, thus reducing the MB sensitivity to extreme positive and negative air temperature and summer snowfall anomalies (Fig. Positive degree-day factors for ablation on the Greenland ice sheet studied by energy-balance modelling. 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 The Nisqually Glacier is one of the larger glaciers on the southwestern face of Mount Rainier in the U.S. state of Washington.The glacier is one of the most easily viewed on the mountain, and is accessible from the Paradise visitor facilities in Mount Rainier National Park.The glacier has had periods of advance and retreat since 1850 when it was much more extensive. 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. Simulations were then performed by averaging the outputs of each one of the 60 ensemble members. 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. J. Clim. Nature Geosciences, https://doi.org/10.1038/s41561-021-00885-z (2022). Google Scholar. Vis. Without these cold water resources during the hottest months of the year, many aquatic and terrestrial ecosystems will be impacted due to changes in runoff, water temperature or habitat humidity6,21,22. Summer melt was also above average. As previously mentioned, here these differences are computed at regional level for a wide variety of glaciers. These results are in agreement with the main known drivers of glacier mass change in the French Alps28. 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. This implies that specific climatic differences between massifs can be better captured by ALPGM than GloGEMflow. 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. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Limnol. Conf. Therefore, an alternative nonlinear parameterization for the reduction in MB sensitivity under increasing air temperatures would be useful. Share sensitive information only on official, secure websites.. Change 120, 2437 (2014). 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). 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. J. Glaciol. Cauvy-Frauni, S. & Dangles, O. Scand. 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. Steiner, D., Walter, A. Maussion, F. et al. Hock, R. & Huss, M. Glaciers and climate change. 5). Res. Nature 577, 364369 (2020). 4e and 5). On the other hand, for flatter glaciers large differences between deep learning and Lasso are obtained for almost all climate scenarios (Fig. Data 12, 19731983 (2020). 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). Park, and S. Beason. 3c). Millan, R., Mouginot, J., Rabatel, A., & Morlighem, M. Ice velocity and thickness of the worlds glaciers. Geophys. Nonetheless, since the main GCM-RCM climate signal is the same, the main large-scale long-term trends are quite similar. Mer de Glace, 29km2 in 2015), which did show important differences under RCP 8.5 (up to 75%), due to their longer response time. Deep artificial neural networks (ANNs) are nonlinear models that offer an alternative approach to these classic methods. Projected changes in surface solar radiation in CMIP5 global climate models and in EURO-CORDEX regional climate models for Europe. Relatively minor climate changes during the Little Ice Age (A.D. 1200-1850) impart significant glacial responses. This synthetic setup allowed us to reproduce the climatic conditions to be undergone by most ice caps, with their mean surface altitude hardly evolving through time. Nat. 1). 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. 12, 168173 (2019). In recent years, shrinking glaciers have contributed to about 30% of global sea level rise 1. 4). Alpine glaciers, like this one near Mt. On the one hand, this improves our confidence in long-term MB projections for steep glaciers made by most GlacierMIP models for intermediate and high emissions climate scenarios. Particularly in Asia, water demand exceeds supply due to rapid population growth, with glacier . The same was done with winter snowfall anomalies, ranging between 1500mm and +1500mm in steps of 100mm, and summer snowfall anomalies, ranging between 1000mm and +1000mm in steps of 100mm. 12, 1959 (2020). 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. The dataset of initial glacier ice thickness, available for the year 2003, determines the starting point of our simulations. In order to investigate the effects of MB nonlinearities on flatter glaciers, we conducted a synthetic experiment using the French Alps dataset. Braithwaite, R. J. However, the impact of different climate configurations, such as a more continental and drier climate or a more oceanic and humid climate, would certainly have an impact on the results, albeit a much less important one than the lack of topographical feedback explored here. 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. 1 and S1). (Photograph by Klaus J. Bayr, Keene State College, 1990) One method of measuring glaciers is to send researchers onto the ice with . 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). Envelopes indicate based on results for all 660 glaciers in the French Alps for the 19672015 period. 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. Our projections highlight the almost complete disappearance of all glaciers outside the Mont-Blanc and Pelvoux (Ecrins region) massifs under RCP 4.5 (Fig. This means that these flatter ice bodies, under a warming climate, will be subject to higher temperatures than their steeper counterparts. 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). Google Scholar. Clarke, G. K. C., Berthier, E., Schoof, C. G. & Jarosch, A. H. Neural networks applied to estimating subglacial topography and glacier volume.
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