More than a thousand new lakes created: in less than two centuries, global warming has profoundly reshaped the landscape of the Swiss Alps, causing massive glaciers to melt.

A new comprehensive inventory of Swiss glacial lakes has revealed that “since the end of the Little Ice Age around 1850, nearly 1,200 new lakes have appeared in the former glacial regions of the Swiss Alps.

1,000 of them still exist today, ”reveals this study carried out by the Swiss Federal Institute for Water Science and Technology (EAWAG), the University of Zurich and the Federal Office for the Environment.

An "impressive number" and "much faster" training

When the ice fields retreat, they often leave behind depressions and natural dams;

basins which, by filling with meltwater, form new lakes.

"We were surprised, on the one hand by their impressive number and, on the other hand, by their much faster training", explains Daniel Odermatt, head of the remote sensing group at Eawag, quoted in a press release presenting his work. .

“At the start of the project, we had counted on a few hundred glacial lakes”, underlines the researcher, adding that “180 have been added in the last decade alone”.

"Observe and analyze the influence of climate change on glacial lakes"

Daniel Odermatt underlines that this inventory constitutes "an excellent starting point for observing and analyzing the influence of climate change on glacial lakes".

As in the rest of the Alps, glaciers in Switzerland are melting.

Last year alone they lost 2% of their volume, according to the annual study published by the Swiss Academy of Sciences.

And even if the Paris Agreement to limit global warming below 2 degrees centigrade were to be successful, a 2019 study by the prestigious Swiss Federal Institute of Technology in Zurich estimated that two-thirds of alpine glaciers will have evaporated.

"Visible proof"

"Visible proof of climate change in the Alps", according to the researchers: between 2006 and 2016, the rate of formation of new glacial lakes increased significantly.

On average, 18 new lakes have formed each year and the aquatic area has increased annually by more than 400 square meters.

In 2016, the largest lake measured 40 hectares although for the most part the water bodies were less than one hectare.

The complete inventory was made possible thanks to data accumulated since the middle of the 19th century.

“When the ice began to melt at the end of the Little Ice Age, it aroused the curiosity of naturalists of the time,” explains Nico Mölg, a postdoctoral fellow who worked with Daniel Odermatt.

The researchers were able to rely on the Dufour maps produced between 1840 and 1870, then on aerial photographs taken in 1946 and on data from Swisstopo, the Federal Office of Topography.

"Individually estimate the potential dangers of each lake"

Beyond climate change, the inventory is useful for Civil Security.

For each of the 1,200 lakes, the scientists recorded the location, the altitude, the dimensions of the lake at the various times given, but they also determined the type and material of the dam as well as the runoff and documented the development of the lake.

"In a next step, these bases will make it possible to estimate individually the potential dangers of each lake, for example the risk of sudden emptying of the lake in the event of rupture of the dam", underlines the press release.

All is not negative and the researchers note "natural phenomena constitute spectacular tourist attractions and the artificial extension of lakes offers new opportunities for hydraulic energy".

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