J. Glaciol. Conversely, the linear MB model appears to be over-sensitive to extreme positive and negative snowfall anomalies. S5 and S6). Gabbi, J., Carenzo, M., Pellicciotti, F., Bauder, A. Google Scholar. 0.5) than lower values typical from ice34. (Zenodo, 2020). Partitioning the uncertainty of ensemble projections of global glacier mass change. Steiner, D., Walter, A. 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. Therefore, an alternative nonlinear parameterization for the reduction in MB sensitivity under increasing air temperatures would be useful. An enhanced temperature-index glacier melt model including the shortwave radiation balance: development and testing for Haut Glacier dArolla, Switzerland. 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. 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. 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. Simulations for projections in this study were made by generating an ensemble of 60 cross-validated models based on LSYGO. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. 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. The increase in glacier altitude also causes the solid to liquid precipitation ratio to remain relatively constant. 2008. 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. Lett. 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. Such ice caps cannot retreat to higher elevations in a warming climate, which inhibits this positive impact on MB40 (Fig. From this behavior, inferences of past climate can be drawn. 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 ). 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. All authors provided inputs to the paper and helped to write it. 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. 6 (2018). Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface mass balance of Saint-Sorlin Glacier (French Alps). Our results suggest that, except for the lowest emissions climate scenarios and for large glaciers with long response times, MB models with linear relationships for PDDs and precipitation are suitable for mountain glaciers with a marked topographical feedback. Vertical axes are different for the two analyses. In order to investigate the effects of MB nonlinearities on flatter glaciers, we conducted a synthetic experiment using the French Alps dataset. Recent efforts have been made to improve the representation of ice flow dynamics in these models, replacing empirical parametrizations with simplified physical models9,10. 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. Earth Sci. In the past, shortwave radiation represented a more important fraction in the glacier surface energy budget than the energy fluxes directly related to air temperature (e.g. Glacier-wide MB is simulated annually for individual glaciers using deep learning (i.e. S4). GloGEMflow relies on EURO-CORDEX ensembles26, whereas ALPGM uses ADAMONT25, an adjusted version of EURO-CORDEX specifically designed for mountain regions. 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. On the one hand, MB nonlinearities for mountain glaciers appear to be only relevant for climate scenarios with a reduction in greenhouse gases emissions (Fig. 3, 16751685 (2019). 3). 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. 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. 60, 11401154 (2014). As the Earth heats up due to climate change, glaciers are melting. This behaviour is particularly clear for summer snowfall, for which the differences are the largest (Fig. The anomaly in snowfall was evenly distributed for every month in the accumulation (October 1April 31) and ablation seasons, respectively. 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. 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. Studies have warned about the use of temperature-index models for snow and ice projections under climate change for decades34,35,36. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. 12, 909931 (2019). Front. A.R. Glaciers and ice caps are experiencing strong mass losses worldwide, challenging water availability, hydropower generation, and ecosystems. The cumulative positive degree days (CPDD), snowfall and rainfall dl, are at the glaciers annually evolving centroids. Geosci. 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. deep artificial neural networks) glacier evolution projections by modelling the regional evolution of French alpine glaciers through the 21st century. All climate anomalies are computed with respect to the 19672015 mean values. Data 12, 19731983 (2020). Particularly in Asia, water demand exceeds supply due to rapid population growth, with glacier . A knowledge of the areas once occupied by mountain glaciers reveals at least part of the past behavior of these glaciers. Slider with three articles shown per slide. 1d, g). The record, which was started in 1931, shows the glacier's dramatic responses to about half a century of small but significant climatic variations. S8 and Fig. ADS The Cryosphere 14, 565584 (2020). 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 . J.B. developed the main glacier model, performed the simulations, analysed the results, and wrote the paper. B Methodol. Vis. a1) over the French Alps. 48, 24872512 (2009). Climate variations change a glacier's mass balance by affecting ablation and accumulation amounts. Nonlinear deep learning response and linear Lasso response to a Cumulative positive degree days (CPDD) anomalies, b winter snowfall, and c summer snowfall. On the other hand, ice caps present a different response to future warming, with our results suggesting a negative MB bias by models using linear PDD and accumulation relationships. 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 ). 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. 22, 21462160 (2009). He, K., Zhang, X., Ren, S. & Sun, J. Delving Deep into Rectifiers: Surpassing Human-Level Performance on ImageNet Classification. 1a). Glaciers are large-scale, highly sensitive climate instruments which, ideally, should be picked up and weighed once a year. Huss, M., Jouvet, G., Farinotti, D. & Bauder, A. ADS GlacierMIP A model intercomparison of global-scale glacier mass-balance models and projections. 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. Data 12, 18051821 (2020). Alternatively, the Lasso model used here includes 13 DDFs: one for the annual CPDDs and 12 for each month of the hydrological year. 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. This annual geometry adjustment accounts for the effects of glacier retreat on the climate signal received by glaciers. 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. This means that these flatter ice bodies, under a warming climate, will be subject to higher temperatures than their steeper counterparts. In this study, we investigate the future evolution of glaciers in the French Alps and their nonlinear response to multiple climate scenarios. Fr Hydrobiol. Despite marked differences among regions, the generalized retreat of glaciers is expected to have major environmental and social impacts2,3. Jordi Bolibar. Monitoring the Seasonal hydrology of alpine wetlands in response to snow cover dynamics and summer climate: a novel approach with sentinel-2. & Zumbhl, H. J. 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. Grenoble Alpes, Universit de Toulouse, Mto-France, CNRS, CNRM, Centre dtudes de la Neige, Grenoble, France, Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, Netherlands, Laboratoire de Glaciologie, Universit Libre de Bruxelles, Brussels, Belgium, Univ. Through these surveys "bulges" have been tracked as they travel down the glacier (c). 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. Lett. 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. Our results show that the mean elevation is far more variable than the kinematic ELA ( Fig. In the United States, glaciers can be found in the Rocky Mountains, the Sierra Nevada, the Cascades, and throughout Alaska. Advances occurred from 1963-68 and from 1974-79. 4a, b) and negative (Fig. 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. The lower fraction of variance explained by linear models is present under all climate scenarios. Since 2005, study finds that surface melt off glaciers in the North has risen by 900%. https://doi.org/10.5281/zenodo.3609136. These different behaviours and resulting biases can potentially induce important consequences in long-term glacier evolution projections. Using this function, the glacier-specific ice thickness and the DEM are updated every year, adjusting the 3D geometry of each glacier. This implies that specific climatic differences between massifs can be better captured by ALPGM than GloGEMflow. Universal Differential Equations for Scientific Machine Learning. Glaciers with the greatest degree of seasonality in their flow behavior, such as Nisqually and Shoestring glaciers, responded most rapidly. This modelling approach was described in detail in a previous publication dedicated to the methods, where the ALpine Parameterized Glacier Model (ALPGM43) was presented31. 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. Dyn. Article 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. The maximum downvalley position of the glacier is marked by either a I.G. A global synthesis of biodiversity responses to glacier retreat. "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. CPDD, winter snowfall or summer snowfall) was modified for all glaciers and years. 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. 65, 453467 (2019). Soc. 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. 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. Alternatively, flatter glaciers (i.e. S5b). Meteorol. We argue that such models can be suitable for steep mountain glaciers. Regarding air temperature forcings, the linear Lasso MB model was found to be slightly under-sensitive to extreme positive cumulative PDD (CPDD) and over-sensitive to extreme negative CPDDs. 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. Hock, R. & Huss, M. Glaciers and climate change. 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).

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