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The world’s glaciers contain less ice than previously thought

A new worldwide survey of over 250,000 mountain glaciers has revised earlier estimates of glacial ice volume. The results suggest that there is 20 percent less ice available in the world’s glaciers than previously thought. These findings have important implications for estimates of freshwater availability, as well as for climate models taking into account the relation between glacier melting and sea level rise

A research team led by the Institute of Environmental Geosciences (IGE) in France and Dartmouth College in the United States has studied more than 800,000 pairs of satellite images of glaciers acquired in 2017 and 2018 by NASA’s Landsat-8 and the European Space Agency’s Sentinel-1 and Sentinel-2 satellites. The data, which was processed using over one million hours of computation at IGE, comprises information about 98 percent of the world’s glaciers, including large ice caps, narrow alpine glaciers, slow valley glaciers, and fast tidewater glaciers.

“We generally think about glaciers as solid ice that may melt in the summer, but ice actually flows like thick syrup under its own weight,” said study senior author Mathieu Morlighem, a professor of Earth Sciences at Dartmouth. “The ice flows from high altitude to lower elevations where it eventually turns to water. Using satellite imagery, we are able to track the motion of these glaciers from space at the global scale and, from there, deduce the amount of ice all around the world.”

According to the scientists, the world’s glaciers contain about 20 percent less ice than initially thought. These findings fundamentally change projections for climate-driven sea level rises. The new estimate reduces the potential for glacial contribution to sea level rise by approximately three inches, revising downwards the projected number from 13 to 10 inches. 

While this may seem good news to many, the researchers stress the fact that comparing global differences with previous estimates is only one side of the picture. “If you start looking locally, then the changes are even larger. To correctly project the future evolution of glaciers, capturing fine details is much more important than just the total volume,” Professor Morlighem explained.

 The research findings suggest that many of the world’s glaciers are shallower than previously estimated. In South America’s tropical Andes Mountains, for example, there is nearly a quarter less ice than previously thought. This means that there is up to 23 percent less freshwater stored in an area on which millions of people depend to get their water supplies.

“Many regions around the world have less ice than we thought, and it will have implications for millions of people,” Professor Molighem said. “Drinking water, power generation, and agriculture are among the essential services that will be impacted by these findings.”

Further research is needed to clarify the evolution of glaciers in various parts of the world, and assess the potential impact their potential melting due to global warming might have on sea level rises and freshwater availability.

The study is published in the journal Nature Geosciences

By Andrei Ionescu, Staff Writer

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