The volume decreases at an increasingly accelerated rate due to global warming
Glaciers are melting all over the world. Each time faster. So far this century, scientists have recorded and investigated changes in its volume with great precision, but little is known about what happened during the 20th century. Swiss researchers have for the first time reconstructed the extent of ice loss from the Swiss country’s glaciers over the past century. The conclusion: the glaciers are dying, they lost half their volume between 1931 and 2016. And an additional 12% in the last six years.
Glacier monitoring in Switzerland has a long tradition, but the changes recorded during the 20th century are only known through few observations. Researchers from the ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) used historical images to reconstruct the topography of all Swiss glaciers in 1931 and analyze their evolution.
To reconstruct the ice masses, the glaciologists resorted to what is known as stereophotogrammetry, a technique used in Switzerland for more than a century that can be used to determine the nature, shape and position of any object from image pairs.
The researchers used images from the ‘TerrA’ archive, which covers around 86% of Switzerland’s glacier-covered area. They analyzed 21,703 photographs taken between 1916 and 1947. Based on these images, they determined the surface topography of the glaciers.
“If we know the surface topography of a glacier at two different points in time, we can calculate the difference in ice volume,” explains study lead author Erik Schytt Mannerfelt.
Significant glacial retreat
The study shows that not all glaciers are losing mass at the same rate. The extent to which they have decreased in volume depends mainly on three factors: first, the altitude to which the glacier is located; second, how flat is your nose; and third, the amount of debris existing in it.
“Our results indicate a strong spatial variability in glacier thinning, with glaciers in the north-east losing mass twice as fast as in south-west Switzerland. This variability is partly explained by the fact that losses of mass are pronounced for glaciers at a lower median elevation, with more gently sloping ends, and with a high current fraction of debris cover,” the authors explain.
But the glaciers did not recede every year. Although the climate in the 20th century was generally unfavorable for them, in the 1920s and 1980s there was sporadic growth in the mass of some glaciers. But in the long term the setback has been enormous.
“While there may have been growth in short-term periods, it’s important to look at the big picture. Our comparison between the years 1931 and 2016 clearly shows that there was a significant glacial retreat during this period“, highlights Daniel Farinotti, professor of Glaciology and co-author of the study.
Also, the total volume of glaciers is shrinking at an ever-faster rate due to global warming, as confirmed by the GLAMOS glacier monitoring network, managed by ETH Zurich. For comparison, while glaciers lost half their volume between 1931 and 2016, they lost 12% more in just six yearsbetween 2016 and 2021.
rivers of ice
“Glacial retreat is accelerating. Observing this phenomenon closely and quantifying its historical dimensions is important because it allows us to infer the responses of glaciers to a changing climate. This information is necessary to develop reliable scenarios for future changes in glaciers,” says Farinotti.
“In a period of rapidly rising air temperatures, regional mass balance data over a period of nearly 100 years is essential to accurately understand how glaciers respond to changes in climate,” the study says.
Among the fastest melting glaciers are those in Alaska, Iceland and the Alps. The situation is also having a profound effect on glaciers in the Pamir Mountains, the Hindu Kush and the Himalayas..
Glaciers are large masses of ice that form in the upper parts of mountains and slowly descend down the slope in the form of tongues. They’re like rivers of ice.
Glacial ice forms from the accumulation of snow. As the thickness increases, the compaction caused by the weight of the snow, the melting and refreezing of the crystals transform the snow, which loses porosity and gains density.
10% of the Earth is covered by glaciersbut that percentage reached 30% in recent geological times. Glaciers store approximately 75% of the fresh water on Earth.. About 91% of the planet’s glacial volume is found in Antarctica, and 8% in Greenland. Switzerland’s glaciers account for about half of those in the Alps.
Reference report: https://tc.copernicus.org/articles/16/3249/2022/
………
Environment section contact: [email protected]