Glaciers contain less water than exempted before

An international study shows the decline in ice volumes contained in the glaciers, with the main consequence, a lower elevation of the sea level and a decrease in freshwater reserves.

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Not only are glaciers undergo the effects of global warming, melting, but ice volumes they contain would be less important compared to previous estimates. According to an international study, published in Nature Geoscience , Monday, February 7, which measured the flow rate and thickness of more than 250,000 mountain glaciers in the world, 98% of the number of these glaciers, the drop in volume of ice which contributes directly to the elevation of the sea level would be 20%. “An important discovery that will have implications for millions of people around the world”, which would reduce the water masses available, according to Mathieu Morlighem, Professor of Earth Sciences in Dartmouth (United States) and co-author of the study.

Knowledge of flow speeds makes it possible to estimate the thickness and spatial distribution of the ice, which, explains the study, “conditions both the total volume of these water tanks and their contribution future on the rise of the seas “.

The realization of this “Atlas” glaciers, with the measurements of their volumes, was made possible by the analysis of 800,000 pairs of satellite images – two views at a month of difference are indeed necessary for Knowing the speed, by studying, for example, the displacement of crevasses -, “including large glacial caps, narrow alpine glaciers, slow valley glaciers and fast marine glaciers”, during the years 2017 and 2018.

Consequences for millions of humans

The glacial masses are poorly known, with depth measurements for only 1% of the glaciers, indicate the authors. The actual volume of ice was uncertain, and therefore the quantification of the water resources present in glaciers. “Thanks to satellite imagery, we are able to follow the movement of these glaciers since the space on a global scale and, from there, to deduce the amount of ice around the world”, still explains Mathieu Morlighem.

This ice flows from the high altitudes to the low altitudes turning into fresh water, available for local populations. “The study of flow speeds allows us to be more precise. The glacier flowing under the effect of its own weight, we can know the distribution of the mass of the ice. Until then, the methods were Limiting, based on the slope of the glaciers. In addition, the studies estimated the thickness only at the center of the glaciers, and we then extrapolated “, details the world Roman Millan, researcher at the CNRS, co-author of the study. The uncertainty of previous publications was due, in part, to the absence of measures of the glacial flow that reveals, underlines the study, “the location of the thick and thin ice”.

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/Media reports.