Victims of global warming, glaciers are melting visibly.

But according to a new study funded by the Swiss National Science Foundation (SNSF), they melt even faster if they end up in a lake rather than on dry land.

Researchers have carefully studied the formation of new lakes resulting from the melting of eternal mountain ice.

The study focused on the 319 glaciers of more than 3 km² in area in the Himalayas, of which a fifth forms lakes.

They thus feed large rivers such as the Ganges and the Brahmaputra and contribute to the water supply of half a billion people.

Forecast water availability

The scientists used the European Sentinel-2 satellites which fly over the territory every five days.

Infrared images taken from 2017 to 2019 revealed that glaciers ending in a lake moved at an average speed of 20m per year – twice as fast as those ending on land.

The phenomenon can be explained "by the fact that the glacial tongue undergoes a lift effect which would reduce the resistance", according to the researchers.

"These results are very important for predicting water availability," added Tobias Bolch, the study's leader.

Indeed, when the glaciers flow faster, the water reserves accumulated in the ice are depleted more quickly and the rivers receive less.

Anticipating flood risks

"Until now, the acceleration caused by glacial lakes had not been integrated into the forecasts", specifies Tobias Bolch.

“In the affected regions of Asia, water shortages could therefore occur more quickly than expected.

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The results also make it possible to better calculate the rate of filling of the lakes and to establish from when the dam formed by the terminal moraine (lump of blocks and rock debris detached from a glacier) risks breaking and releasing a wave. giant in the lake.

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  • study

  • Planet

  • Global warming

  • Water

  • Climate change

  • Himalayas

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