The temperature-index model includes up to three different DDFs, for ice, firn and snow, resulting in three parameters. Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface mass balance of Saint-Sorlin Glacier (French Alps). Article In the meantime, to ensure continued support, we are displaying the site without styles Recent efforts have been made to improve the representation of ice flow dynamics in these models, replacing empirical parametrizations with simplified physical models9,10. 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. 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. The Cryosphere 13, 13251347 (2019). This will reduce the importance of shortwave radiation for future ablation rates, and it is expected to result in a reduction in values of degree-day factors (DDFs) and therefore a significant change in melt sensitivity to air temperature variations36. Therefore, their sensitivities to the projected 21st century increase in PDDs are linear. Rainier, Washington. J.B. developed the main glacier model, performed the simulations, analysed the results, and wrote the paper. 799904) and from the Fonds de la Recherche Scientifique FNRS (postdoctoral grant charg de recherches). Due to the statistical nature of the Lasso model, the response to snowfall anomalies is also highly influenced by variations in PDDs (Fig. Geosci. We acknowledge the more than 50 years of glaciological monitoring performed by the GLACIOCLIM French National Observatory (https://glacioclim.osug.fr), which provided essential observations for our modelling study. ADS Finally, there are differences as well in the glacier dynamics of both models, with ALPGM using a glacier-specific parameterized approach and GloGEMflow explicitly reproducing the ice flow dynamics. 5). 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. 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. 22, 21462160 (2009). Huss, M., Funk, M. & Ohmura, A. Rev. Simulating these processes at a large geographical scale is challenging, with models requiring several parametrizations and simplifications to operate. For such cases, we assumed that ice dynamics no longer play an important role, and the mass changes were applied equally throughout the glacier. 4 vs.S5). Canada's glaciers and ice caps are now a major contributor to sea level change, a new UCI study shows. Secure .gov websites use HTTPS A lock ( ) or https:// means you've safely connected to the .gov website. 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. Pellicciotti, F. et al. 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). 4e). 58, 267288 (1996). Marzeion, B. et al. 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. Since these two glaciers are expected to be some of the few large glaciers that will survive the 21st century climate, an accurate representation of their initial ice thickness has an important effect on the estimates of remaining ice. Additionally, glacier surface area was found to be a minor predictor in our MB models31. 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. Summer climate is computed between April 1st and September 30th and winter climate between October 1st and March 31st. By Carol Rasmussen,NASA's Earth Science News Team. 1). 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. 12, 909931 (2019). 2013). 4a, b) and negative (Fig. Hock, R. Temperature index melt modelling in mountain areas. The Nisqually Glacier, Mount Rainier, Washington, 1857-1979: A summary This allows us to assess the MB models responses at a regional scale to changes in individual predictors (Fig. (a) Topographical predictors were computed based on the glaciers annually updated digital elevation model (DEM). Glacier surface mass changes are commonly modelled by relying on empirical linear relationships between PDDs and snow, firn or ice melt8,9,10,29. How Will Melting Glaciers Affect Streamflow? - Eos Moreover these three aspects of glacier behavior are inextricably interwoven: a high sensitivity to climate change goes hand-in-hand with a large natural variability. 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.
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