Switzerland’s 1,400 glaciers lost half of their total volume in less than a century and the retreat of ice is accelerating, a study has found.
Ice volumes shrunk by half over the 85 years from 1931 to 2016, according to researchers from ETH Zurich and the Swiss Federal Institute of Forest, Snow and Landscape Research.
Since 2016 they have lost an additional 12%.
“Glacier retreat is accelerating,” said Daniel Farinotti, a co-author of the study, which was published in The Cryosphere, a scientific journal.
“Closely observing this phenomenon and quantifying its historical dimensions is important because it allows us to infer the glaciers’ responses to a changing climate.”
By area, Switzerland’s glaciers amount to around half the total in the Alps.
In the first reconstruction of ice loss in Switzerland in the 20th century, based in part on an analysis of changes to the topography of glaciers since 1931, the teams combined long-term observations of glaciers, measurements in the field and aerial and mountaintop photographs.
Those photographs included 22,000 taken from the peaks between the two world wars.
By using multiple sources, the researchers could fill in the gaps, as only a few of Switzerland’s glaciers have been studied regularly over the years.
Their research involved using decades-old techniques to allow for comparisons of the shape and position of images of terrain and the use of cameras and instruments to measure angles of land areas.
The teams compared surface topography of glaciers at different moments, allowing for calculations about the evolution in ice volumes.
They found not all glaciers have been losing ice at the same rates.
Altitude, amounts of debris on the glaciers and the flatness of the glacier’s “snout” – its lowest part, which is most vulnerable to melting – were all found to affect the speeds of retreat.
They also found two periods, the 1920s and 1980s, experienced sporadic growth in glacier mass – though that was overshadowed by the broader trend of decline.