The melting of the world’s glaciers is accelerating, in twenty years they have lost 4% of their volume

0



In the Alps, during the last two decades, the glaciers – here that of Argentière – have lost a third of their volume. – KONRAD K. / SIPA

  • A new study shows that the melting of the world’s 220,000 glaciers has accelerated over the past twenty years, losing a total of 4% of their mass.
  • They lost an average of 267 billion tonnes of ice per year.
  • The glaciers in the Alps, among the most affected, have lost a third of their mass in twenty years.

The melting of glaciers is one of the clearly identified symptoms of global warming, a visible consequence of the impact of greenhouse gas emissions. If, in places, specialists were able to observe the reduction of these layers of snow accumulated over the decades, it was more difficult to have a global vision of this melting at the level of the globe, some glaciers like those of Canada being the size of Corsica.

Thanks to satellite images, and to a new calculation method, an international team has just drawn up a complete mapping over the whole of the last two years. And it is far from encouraging. “It is as if there was a layer of ice of 60 cm which covered metropolitan France and which melted every year”, puts in perspective Etienne Berthier, glaciologist within the Toulouse laboratory for studies in spatial geophysics and oceanography, one of the co-authors of a
study recently published in Nature.

“The surprise is the speed of the acceleration”

In total, every year for the past twenty years, the 220,000 glaciers listed across the world have lost an average of 267 billion tonnes of ice. “The cumulative loss between 2000 and the end of 2019 corresponds to 4% of the total volume of glaciers, which is a lot. We expected this loss of mass but the surprise is the speed of the acceleration, we did not think it would be so strong, ”insists the researcher.

If between 2000 and 2004, this mass reached 227 billion tonnes, between 2015 and 2019, this rate has indeed increased to 298 billion tonnes.

A third of the glaciers in the Alps less

With areas more affected than others. In particular in Iceland, Alaska or even in the Alps. Between 2000 and the end of 2019, the glaciers of this latter massif thus lost 33% of their volume. Their average thickness is now 61 meters, 20 meters less than 20 years ago.

A decline which is not without consequence in certain areas such as Central Asia or the Andes where these water reservoirs play a crucial role in summer. The study also shows that in a region around the North Atlantic, which includes eastern Greenland, Iceland and Scandinavia, mass loss slowed slightly, but was significant. “It contrasts with the global acceleration landscape. This is explained by an increase in precipitation, in the form of snow accumulated at altitude, which somewhat offset the increase in temperature. We must not believe that these glaciers are filling up, they continue to lose mass, ”concludes Etienne Berthier.





Source link