Melting glaciers deliver further evidence of climate crisis

There are growing fears of the impact of climate change in the Swiss Alps after a new study reported the rate of thawing is rapidly accelerating.

A team of researchers from ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) have reconstructed the topography of all Swiss glaciers in 1931. Based on these reconstructions and comparisons with data from the 2000s, the researchers conclude that the glacier volume halved between 1931 and 2016.

The study cautioned Swiss glaciers are rapidly melting and the pace is increasing.

“While there may have been growth over short-​term periods, it’s important to keep the big picture in mind. Our comparison between the years 1931 and 2016 clearly shows that there was significant glacial retreat during this period,” said Daniel Farinotti, professor of glaciology at ETH Zurich and WSL, and co-​author of the study. What’s more, the total glacier volume is decreasing at an ever faster rate, as confirmed by the glacier monitoring network GLAMOS, which is managed by ETH Zurich. By way of comparison, while glaciers lost half their volume between 1931 and 2016, they lost a further 12 percent between 2016 and 2021 – i.e. in just six years.”

He added: “Glacier retreat is accelerating. Closely observing this phenomenon and quantifying its historical dimensions is important because it allows us to infer the glaciers’ responses to a changing climate. This information is needed to develop reliable scenarios for future glacier changes.”

For their reconstruction, the glaciologists turned to what is known as stereophotogrammetry, a technique that can be used to determine the nature, shape and position of any object on the basis of image pairs. This technique has long been in use in Switzerland: from the First World War until the end of the 1940s, engineers from the Swiss National Survey – today swisstopo – surveyed large swathes of the Swiss Alps from some 7,000 locations using phototheodolites (a combination of a camera and an angle measuring device).

The researchers used the material from this image archive, which covers about 86 percent of the glacierised area of Switzerland. They analysed around 21,700 photographs taken between 1916 and 1947.

“Based on these photos, we determined the glacier surface topography. If we know the surface topography of a glacier at two different points in time, we can calculate the difference in ice volume,” explained lead author Erik Schytt Mannerfelt of ETH Zurich and WSL. Since the images were taken in different years, the researchers decided to use the mean year 1931 as a reference and reconstructed the surface topography of all glaciers for that year.

The study concluded that not all glaciers are losing mass at the same rate. The extent to which they have decreased in volume depends primarily on three factors: first, the altitude at which a glacier is located; second, how flat the glacier snout is; and third, the amount of debris on the glacier.

The researchers used the material from this image archive, which covers about 86 percent of the glacierised area of Switzerland. They analysed around 21,700 photographs taken between 1916 and 1947.

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