People living in the Andes in South America will reach âpeak waterâ â defined as a declining availability of water â much sooner than expected because the glaciers they rely on have been found to be much thinner than thought.
The areaâs glaciers have 27 per cent less ice than than previously estimated, according to a new global assessment of the thickness of the worldâs 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 as glaciers disappear under climate change.
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âThis new data set of the worldâs glaciers has a huge impact on water resources,â says at Grenoble Alpes University, France, who led the analysis. âIn some regions, itâs positive, because in the Himalayas it reduces the pressure on the fresh water, but in other regions like the Andes, itâs increasing the pressure on fresh water availability.â
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 worldâs 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 . However, several glaciologists not involved in the study, including 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 âis a major step forwardâ, but notes that ground observations of ice thickness are still sparse, limiting our ability to confirm estimates derived from space. âThere are still large uncertainties regarding the exact ice volumes, especially in regions with few observations,â she says. Ground data on the Himalayan glaciers is particularly scarce.
That is why at ETH Zurich, Switzerland, says: âThe paper is a big step forward in quantifying Earthâs glacier reserves â and still it isnât the truth.â 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 Agencyâs Sentinel-1B, due to a malfunction that still hasnât been fixed. Millan says the outage is a reminder of how important such satellites are for monitoring the environment. âThis new generation of satellites has completely changed the way we look at glaciers.â
Nature Geoscience
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