Swiss glaciers have lost half their volume since 1931, according to a study published by scientists on Monday August 22, who have for the first time reconstructed the retreat of glaciers since the 20th century.
The melting of glaciers in the Alps – which experts attribute to global warming – has been closely monitored since the early 2000s. But researchers did not know much about their evolution in the previous decades, because only a few glaciers were then closely followed.
Volume halved between 1931 and 2016
To better understand their evolution, researchers from the Swiss Federal Institute of Technology Zurich (ETH Zurich) and the Federal Institute for Forest, Snow and Landscape Research (WSL) have reconstructed the topography of the set of Swiss glaciers that existed in 1931.
“Based on these reconstructions and comparing with data from the 2000s, the researchers conclude that the volume of glaciers was halved between 1931 and 2016”ETHZ and WSL said in a statement.
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The study, published in the scientific journal “Cryosphere”, indicates that glaciologists used archive images (21,700 photographs taken between 1916 and 1947) covering 86% of the Swiss glacial surface and stereophotogrammetry, a technique that makes it possible to determine the nature, shape and position of an object using images.
“If we know the surface topography of a glacier at two different times, we can calculate the difference in ice volume”said the study’s lead author, Erik Schytt Mannerfelt, in the release.
“The retreat of glaciers is accelerating”
The result is striking. Thus, the Fiescher glacier, of which only a few tiny white spots remained in 2021, looked like a huge sea of ice in 1928. According to scientists, glaciers have not retreated continuously over the past century. They even experienced episodes of mass growth in the 1920s and 1980s.
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Despite this growth over short-term periods, “our comparison between the years 1931 and 2016 clearly shows that there was a significant glacial retreat during this period”said one of the authors of the study, Daniel Farinotti, professor of glaciology at ETHZ and WSL.
And the glaciers are now melting at an increasingly rapid rate. While they lost 50% of their volume between 1931 and 2016, it only took them six years – between 2016 and 2022 – to lose 12%, according to the Swiss glacier survey network GLAMOS. For Daniel Farinotti, the evidence is irrefutable: “The retreat of glaciers is accelerating. »
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