This synthetic experiment is an approximation of what might occur in other glacierized regions with ice caps. ICCV (2015) https://doi.org/10.1109/iccv.2015.123. Glaciers on Mount Rainier - USGS 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. These different behaviours and resulting biases can potentially induce important consequences in long-term glacier evolution projections. 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. on various mass balance and radiation components) are opening the door for updated and better constrained projections. Earth Syst. a1) over the French Alps. Ice thickness accuracy varied significantly, with an overall correct representation of the ice distribution but with local biases reaching up to 100%. 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. 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. Our results show that the mean elevation is far more variable than the kinematic ELA ( 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. 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. Nature 577, 364369 (2020). Here, with our newly presented approach, we were able for the first time to quantify the effect that stationary parameters in temperature-index mass balance models have on transient glacier evolution. 33, 645671 (2005). 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. Tom R. Andersson, J. Scott Hosking, Emily Shuckburgh, Shfaqat A. Khan, Anders A. Bjrk, Toni Schenk, Romain Hugonnet, Robert McNabb, Andreas Kb, Atanu Bhattacharya, Tobias Bolch, Tandong Yao, Christian Sommer, Philipp Malz, Matthias H. Braun, Romain Millan, Jrmie Mouginot, Mathieu Morlighem, Matthias H. Braun, Philipp Malz, Thorsten C. Seehaus, Nature Communications Climate Change 2013: The Physical Science Basis. 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). Get the most important science stories of the day, free in your inbox. Conversely, the linear MB model appears to be over-sensitive to extreme positive and negative snowfall anomalies. As such, these values reflect both the climatic forcing and the changing glacier geometry. Nature Communications (Nat Commun) Dyn. 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. The Cryosphere 13, 11251146 (2019). Article 4a, b) and negative (Fig. Evol. 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. Glaciers are important for agriculture, hydropower, recreation, tourism, and biological communities. Large glaciers and glaciers flowing slowly down shallow slopes respond more sluggishly to short-term climate changes, as might be expected. Differences for individual glaciers can be much more pronounced, as large and flat glaciers will have topoclimatic configurations that produce more extreme MB rates than small and steep glaciers with a short response time. Article Immerzeel, W. W. et al. 4e). The increase in glacier altitude also causes the solid to liquid precipitation ratio to remain relatively constant. Univ. Huss, M., Jouvet, G., Farinotti, D. & Bauder, A. 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. 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. The projections without glacier geometry adjustment explore the behaviour of glaciers which cannot retreat to higher elevations (i.e. Nonetheless, to represent the glacier mass balance, the vast majority of large-scale glacier evolution models relies on temperature-index models. 799904) and from the Fonds de la Recherche Scientifique FNRS (postdoctoral grant charg de recherches). How Will Melting Glaciers Affect Streamflow? - Eos We compare model runs using a nonlinear deep learning MB model (the reference approach in our study) against a simplified linear machine learning MB model based on the Lasso30, i.e. Source: Mount Rainier National Park By 2100, under RCP 4.5, these two high-altitude massifs are predicted to retain on average 26% and 13% of their 2015 volume, respectively, with most of the ice concentrated in a few larger glaciers (>1km2, Fig. Farinotti, D., Round, V., Huss, M., Compagno, L. & Zekollari, H. Large hydropower and water-storage potential in future glacier-free basins. 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 ). 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. 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. 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. 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. The cumulative positive degree days (CPDD), snowfall and rainfall dl, are at the glaciers annually evolving centroids. The Karakoram and the Himalayan mountain range accommodate a large number of glaciers and are the major source of several perennial rivers downstream. 3c). A comprehensive bibliography of scientific publications relating to the glacier is included. Global-scale hydrological response to future glacier mass loss 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. Toward mountains without permanent snow and ice: mountains without permanent snow and ice. the Open Global Glacier Model - OGGM9) is likely to be less affected by an over-sensitivity to future warming than a more complex model with dedicated DDFs for ice, snow, and firn. Landscape response to climate change and its role in infrastructure As Arctic warms, Canada's glaciers playing major role in sea - CBC https://doi.org/10.5281/zenodo.3609136. A He uniform initialization45 was used for the network parameters. 4 vs.S5). Rainier is considered by the USGS to be one of the most threatening volcanoes in the Cascade Mountains. S5cf), except for the largest glaciers (e.g. This implies that current global glacier mass loss projections are too low for the lowest emissions climate scenarios and too high for the highest emissions ones, which has direct consequences for related sea-level rise and water resources projections. Glob. As the Earth heats up due to climate change, glaciers are melting. 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. S8 and Fig. Cite this article. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. On Mount Rainier, elevation surveys of Nisqually Glacier are regularly made to determine changes in the elevation of the surface. 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. 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. Nat. In this study, we investigate the future evolution of glaciers in the French Alps and their nonlinear response to multiple climate scenarios. and JavaScript. J. Hosp. Such ice caps cannot retreat to higher elevations in a warming climate, which inhibits this positive impact on MB40 (Fig. Due to the statistical nature of the Lasso model, the response to snowfall anomalies is also highly influenced by variations in PDDs (Fig. Here, we compare our results with those from a recent study that focused on the European Alps10. Lett. 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. These conclusions drawn from these synthetic experiments could have large implications given the important sea-level contribution from ice cap-like ice bodies8. 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. Years in white in c-e indicate the disappearance of all glaciers in a given massif. 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. (a) Topographical predictors were computed based on the glaciers annually updated digital elevation model (DEM). S5 and S6). 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. Several differences are present between ALPGM, the model used in this study, and GloGEMflow (TableS2), which hinder a direct meaningful comparison between both. The two recent iterations of the Glacier Model Intercomparison Project (GlacierMIP7,8) have proved a remarkable effort to aggregate, compare and understand global glacier evolution estimates and their associated uncertainties. This ensures that the model is capable of reproducing MB rates for unseen glaciers and years. Gaining a better understanding of how warming ocean water affects these glaciers will help improve predictions of their fate. 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 ). 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. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. performed simulations with another glacier model, provided results for comparison, and contributed to the glaciological analyses. 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. longwave radiation budget, turbulent fluxes), in comparison with a future warmer climate. 22, 21462160 (2009). Tour. A dataset of 32 glaciers with direct annual glacier-wide MB observations and remote sensing estimates was used to train the models. glacier length12,14. H.Z. 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. & Zumbhl, H. J. 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. 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. 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. The Open Global Glacier Model (OGGM) v1.1. Deep artificial neural networks (ANNs) are nonlinear models that offer an alternative approach to these classic methods. Six, D. & Vincent, C. Sensitivity of mass balance and equilibrium-line altitude to climate change in the French Alps. Glacier ice thickness observations are available for four different glaciers in the regions, which were compared to the estimates used in this model. As we have previously shown, these models present a very similar behaviour to the linear statistical MB model from this study (Fig. Fluctuations of the Nisqually Glacier, Mt. Rainier, Washington, since As previously mentioned, here these differences are computed at regional level for a wide variety of glaciers. Using this function, the glacier-specific ice thickness and the DEM are updated every year, adjusting the 3D geometry of each glacier. Glaciers - Mount Rainier National Park (U.S. National Park Service) 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. 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. Alternatively, the Lasso model used here includes 13 DDFs: one for the annual CPDDs and 12 for each month of the hydrological year. Glaciers and ice caps are experiencing strong mass losses worldwide, challenging water availability, hydropower generation, and ecosystems. This adjustment represents a major improvement over most climate data used to force regional and global glacier models. 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. 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. 2008. Monitoring the Seasonal hydrology of alpine wetlands in response to snow cover dynamics and summer climate: a novel approach with sentinel-2. https://zenodo.org/record/5549758. Glaciers are large-scale, highly sensitive climate instruments which, ideally, should be picked up and weighed once a year. Climate change spells disaster for the world's glaciers : NPR 1). 2a). 3). Each one of these models was created by training a deep learning model with the full dataset except all data from a random glacier and year, and evaluating the performance on these hidden values. 6 (2018). 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. 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. Melting Glaciers: Effects on the Environment, Humans, and Biodiversity Bolibar, J. ALPGM (ALpine Parameterized Glacier Model) v1.1. Winter tourism under climate change in the Pyrenees and the French Alps: relevance of snowmaking as a technical adaptation. 3). 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. 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. 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. Response of KarakoramHimalayan glaciers to climate variability and 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). "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. 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. Therefore, an alternative nonlinear parameterization for the reduction in MB sensitivity under increasing air temperatures would be useful. Recent efforts have been made to improve the representation of ice flow dynamics in these models, replacing empirical parametrizations with simplified physical models9,10. "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. 3b). The source code of the glacier model can be freely accessed in the following repository: https://github.com/JordiBolibar/ALPGM. & Funk, M. A comparison of empirical and physically based glacier surface melt models for long-term simulations of glacier response. 5). Climate Change Indicators: Glaciers | US EPA
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