Glaciers are melting all over the world. Faster every time. Until this century, scientists have recorded and studied changes in volume with great precision, but little is known about what happened in the 20th century. Swiss researchers have for the first time reconstructed the extent of ice loss from the Swiss country’s glaciers in the past century. The result: the glaciers are dying, Between 1931 and 2016 they lost half of their volume. And an additional 12% in the last six years.
Glacier monitoring has a long tradition in Switzerland, but changes recorded in the 20th century were only a few observations. Researchers from 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 glacial masses, glaciologists have turned to what’s known as stereophotogrammetry, a technique that has been used in Switzerland for over a century and can be used to determine the nature, shape, and position of any object from pairs of images.
The researchers used images from the ‘TerrA’ archive, which covers about 86% of Switzerland’s glacial 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 Erik Schytt Mannerfelt, lead author of the study.
Significant glacial retreat
The study shows that not all glaciers lose mass at the same rate. The degree of reduction in volume depends mainly on three factors: first, height where the glacier is located; second, how straight are you nose; and third, the amount debris present in it.
“Our results point to a strong spatial variability in glacier thinning, with glaciers in the northeast losing mass twice as fast as those in southwest Switzerland. This variability is partly explained by the fact that mass losses are evident for glaciers at lower median height, with lighter sloping tips.” and with high current debris cover,” the authors explain.
But the glaciers did not retreat every year. Although the climate of the 20th century was generally unfavorable for them, During the 1920s and 1980s there was occasional growth in the mass of some glaciers.. But in the long run, the setback was huge.
“Even though there has been growth in the short-term, it is important to look at the big picture. Our comparison between 1931 and 2016 clearly shows that there was significant glacial retreat during this period.“, underlines Daniel Farinotti, professor of glaciology and co-author of the study.
Moreover, 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, glaciers lost half their volume between 1931 and 2016. they lost 12% more in just six yearsBetween 2016 and 2021.
ice rivers
“Glacial retreat is accelerating. Observing this phenomenon closely and measuring its historical dimensions is important because it allows us to understand the responses of glaciers to changing climate. This information is essential to develop reliable scenarios for future changes in glaciers,” says Farinotti.
“During a period of rapid temperature rise, regional mass balance data over a period of almost 100 years are crucial to fully understanding how glaciers respond to changes in climate,” the study says.
The fastest melting glaciers include those in Alaska, Iceland and the Alps. The situation also has a profound impact on glaciers in the Pamir Mountains, Hindu Kush and Himalayas..
Glaciers are large masses of ice that form on the tops of mountains and slowly descend in tongues. as they are ice rivers.
Glacial ice forms from snow accumulation. As the thickness increases, the compression caused by the weight of the snow, melting and re-freezing of the crystals transforms the snow that gains density by losing its porosity.
10% of the world is covered by glaciershowever, this rate has reached 30% in recent geological times. Glaciers store about 75% of the fresh water on Earth.. About 91% of the planet’s glacial volume is located in Antarctica and 8% in Greenland. Switzerland’s glaciers make up about half of those in the Alps.
Reference report: https://tc.copernicus.org/articles/16/3249/2022/
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