By Adam Vaughan
Glacier in the Fitz Roy mountain range in Los Glaciares National Park, Argentina
Maciej Bledowski / Alamy
People living in the Andes in South America will reach “peak water” – defined as a declining availability of water – much sooner than expected because the glaciers they rely on have been found to be much thinner than thought.
The area’s glaciers have 27 per cent less ice than than previously estimated, according to a new global assessment of the thickness of the world’s glaciers. The work found stark regional differences in terms of fresh water supplies.
The study, which excludes Antarctica and Greenland, found that glaciers in the Himalayas have 37 per cent more ice than thought. That is good news for the 250 million people in the region who face pressure on water supplies as glaciers disappear under climate change.
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“This new data set of the world’s glaciers has a huge impact on water resources,” says Romain Millan at Grenoble Alpes University, France, who led the analysis. “In some regions, it’s positive, because in the Himalayas it reduces the pressure on the fresh water, but in other regions like the Andes, it’s increasing the pressure on fresh water availability.”
Millan and his colleagues arrived at their estimates by amassing 812,000 satellite photos of three glaciers, taken 400 days apart, to measure the velocity of the world’s rivers of ice. Previous studies estimating the ice thickness of glaciers have relied mostly on looking at the slope of the glaciers rather than the speed at which they move.
The research found that if all the glaciers melted globally, it would raise sea levels by about 26 centimetres, a fifth less than previous estimates. However, several glaciologists not involved in the study, including Regine Hock at the University of Oslo in Norway, say the result comes largely from excluding a number of glaciers in Antarctica, rather than the satellite data revealing there is significantly less ice globally.
Hock says the new data “is a major step forward”, but notes that ground observations of ice thickness are still sparse, limiting our ability to confirm estimates derived from space. “There are still large uncertainties regarding the exact ice volumes, especially in regions with few observations,” she says. Ground data on the Himalayan glaciers is particularly scarce.
That is why Daniel Farinotti at ETH Zurich, Switzerland, says: “The paper is a big step forward in quantifying Earth’s glacier reserves – and still it isn’t the truth.” However, he says the new research is at the forefront of narrowing the uncertainty on how thick glaciers are.
One of the satellites that the study relied on, the European Space Agency’s Sentinel-1B, has been offline since December due to a malfunction that still hasn’t been fixed. Millan says the outage is a reminder of how important such satellites are for monitoring the environment. “This new generation of satellites has completely changed the way we look at glaciers.”
Journal reference: Nature Geoscience, DOI: 10.1038/s41561-021-00885-z
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