Swiss glaciers have lost half their volume since 1931, Swiss researchers said Monday after the first reconstruction of the country’s ice loss in the 20th century.
The rapid melting of glaciers in the Alps and elsewhere, which scientists say is being caused by climate change, has been monitored more closely since the early 2000s. Until now, however, there has been little insight into how glaciers changed before that in the 20th century, as only a handful of individual glaciers have been tracked over time and with different models to estimate their volume.
But Swiss researchers from ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research WSL say they have now been able to reconstruct the topography of all Swiss glaciers in 1931 and thus show their development.
“Based on these reconstructions and comparisons with data from the 2000s, researchers conclude that glacier volume halved between 1931 and 2016,” they said in a statement.
Their study, published in the journal The Cryosphere, used material from the TerrA image archive, which covers around 86 percent of Switzerland’s glaciated area, and analyzed around 21,700 photographs taken between 1916 and 1947.
– Dramatic twist –
For their reconstruction, the glaciologists used what is known as stereophotogrammetry – a method with which the type, shape and position of any object can be determined from pairs of images.
“If we know the surface topography of a glacier at two different points in time, we can calculate the difference in ice volume,” study lead author Erik Schytt Mannerfelt said in the statement.
The researchers presented side-by-side pairs of images showing the same location almost a century apart, indicating the dramatic change that has taken place.
Fieschergletscher, for example, resembled a vast sea of ice in 1928, but by 2021 only a few tiny splotches of white remained on the lush green mountainside.
Because the images used for the reconstruction were taken in different years, the study used the mean year 1931 as a reference and reconstructed the surface topography of all glaciers for that year, the statement said.
In their statement, the researchers stressed that glaciers had not steadily receded over the past century, pointing out that there had even been sporadic mass glacier growth in the 1920s and 1980s.
But while there may have been growth in the short term, Daniel Farinotti, professor of glaciology at ETH Zurich and WSL and co-author of the study, said it was “important to keep the big picture in mind”.
“Our comparison between the years 1931 and 2016 clearly shows that there was a significant glacial retreat during this period,” he said in the statement.
And the total glacier volume is decreasing faster and faster.
While the Swiss glaciers lost half their volume in the 85 years up to 2016, according to the Swiss glacier measurement network GLAMOS, they lost a further 12 percent in the following six years alone.
Farinotti said the evidence was clear: “Glacier retreat is accelerating.”
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