Bilan de masse d'un glacier

Résumé

vignette|alt=Histogrammes rouge et bleu et courbe oscillant autour de l'équilibre jusqu'en 1985, puis plongeant vers le bas.|Bilan de masse du Glacier du Silvretta. En bleu clair : bilan hivernal (accumulation). En rouge : bilan estival (ablation). La courbe bleue correspond au bilan total de masse du glacier. La perte est telle que la courbe disparait du diagramme à partir de 2003. La valeur atteinte en 2020 est de -23,7 mètres. Le bilan de masse d'un glacier est la différence entre la masse gagnée, dite accumulation, et la masse perdue par disparition de la neige ou de la glace, dite ablation. Le gain ou la perte de masse totale d'un glacier, d'une calotte glaciaire ou d'un inlandsis au cours d'un cycle hydrologique est appelé bilan de masse total. Le bilan de masse spécifique est la variation de masse sur une période de temps déterminée, spécifique à une zone délimitée du glacier. Le plus souvent, le bilan massique total est déterminé par intégration des différentes données de bi

Source officielle

https://fr.wikipedia.org/wiki/Bilan_de_masse_d'un_glacier

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vignette|Le glacier d'Aletsch (Suisse), le plus grand glacier des Alpes. vignette|Le glacier Briksdal, en Norvège. vignette|Front du glacier Hubbard, en Alaska. Un glacier est une masse de glace plus

right|thumb|upright=1.3|Glacier de Grinnell dans le Parc national de Glacier (États-Unis) montrant le recul depuis 1850 de USGS. Le recul des glaciers depuis 1850, ou plutôt le « recul du front des

L' est un phénomène observable au niveau mondial depuis le début du , qui résulte du réchauffement climatique. Le niveau moyen des océans augmente de entre 1901 et 2018, la moitié de cette hausse

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The remoteness and extreme conditions of the Arctic make it a very difficult environment to investigate. In these regions, the wind has a substantial effect and redistributes a large part of the snow which complicates precipitation estimates. Moreover, the snow mass balance on sea ice is still poorly understood notably due to the complex structure of its surface. Quantitatively assessing the snow distribution on sea ice and its connection to the sea ice surface features is an important step to remove these uncertainties. In this thesis, we implemented a physics-based snow saltation model in the open source fluid dynamics software OpenFOAM. After validation against real and numerical data, we used the model to simulate snow deposition on a small piece of MOSAiC sea ice with a complicated structure of pressure ridges. The results demonstrate that a large fraction of snow accumulates in their vicinity, which compares favorably against terrestrial laser scans. The accurate modelling of snow distribution on sea ice should help to better constrain precipitation estimates and more generally the projections of future sea ice mass balance changes.

2020

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Assessing the impact of ground ice degradation on high mountain lake environments (Lago Nero catchment, Swiss Alps)

Monica Bulgheroni, Nicola Deluigi

In high mountain hydrosystems, glacial meltwater composition is potentially affected by the degradation of alpine permafrost terrains and ground ice bodies releasing atmospheric pollutants that have been stored in permafrost terrains for several decades. In this study we investigate the potential local permafrost distribution as well as the physical and chemical ground water characteristics of the periglacial environments of the Lago Nero ("Black Lake") catchment, a high alpine basin located in the Southern Swiss Alps. Our approach combines in situ geological and geomorphological mapping, potential permafrost distribution modelling, a thermal monitoring of ground surface temperatures and the study of the meltwater chemistry of an intact rock glacier (active or inactive rock glacier, i.e. containing ice) and several perennial ice patches. The comparison of elemental concentrations between the periglacial terrains and the Lago Nero outflow unveiled the presence of atmospheric chemicals in the meltwater. Considering the temporal concordance between the recorded peak of sulphur deposition between 1965 and 1980 and the last identified period of positive glacier mass balance occurred in the region (1961-1985), we argue that the enhanced melting of ground ice related to the recent severe warming is nowadays releasing "legacy" pollutants that have been stored in the cryosphere for several decades.

SPRINGER BASEL AG2020

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, , , ,

The remoteness and extreme conditions of the Arctic make it a very difficult environment to investigate. In these polar regions covered by sea ice, the wind is relatively strong due to the absence of obstructions and redistributes a large part of the deposited snow mass, which complicates estimates for precipitation hardly distinguishable from blowing or drifting snow. Moreover, the snow mass balance in the sea ice system is still poorly understood, notably due to the complex structure of its surface. Quantitatively assessing the snow distribution on sea ice and its connection to the sea ice surface features is an important step to remove the snow mass balance uncertainties (i.e., snow transport contribution) in the Arctic environment. In this work we introduce snowBedFoam 1.0., a physics-based snow transport model implemented in the open-source fluid dynamics software OpenFOAM. We combine the numerical simulations with terrestrial laser scan observations of surface dynamics to simulate snow deposition in a MOSAiC (Multidisciplinary Drifting Observatory for the Study of Arctic Climate) sea ice domain with a complicated structure typical for pressure ridges. The results demonstrate that a large fraction of snow accumulates in their vicinity, which compares favorably against scanner measurements. However, the approximations imposed by the numerical framework, together with potential measurement errors (precipitation), give rise to quantitative inaccuracies, which should be addressed in future work. The modeling of snow distribution on sea ice should help to better constrain precipitation estimates and more generally assess and predict snow and ice dynamics in the Arctic.

COPERNICUS GESELLSCHAFT MBH2022

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