The revised estimate reduces global sea level rise by 3 inches if all glaciers were to melt. But it raises concern for some communities that rely on seasonal melt from glaciers to feed rivers and irrigate crops. If glaciers contain less ice, water will run out sooner than expected.
Countries are already struggling with disappearing glaciers. Peru is investing in desalination to make up for declining freshwater. And Chile hopes to create artificial glaciers in its mountains. The Nature Geoscience study assessed how quickly glaciers were moving across the landscape, or their velocity. Such measurements allow scientists to more accurately measure volume, as the way glaciers flow indicates where ice is thick or thin. But collecting this information has been limited by technology.
The work analyzed more than 800,000 pairs of images of glaciers taken between 2017 and 2018, and found that many were shallower than previously assessed. Scientists now estimate there is 20 percent less glacial ice present with the potential to melt into the ocean and raise sea levels. Currently, glaciers are responsible for 1 mm of annual sea level rise, or 30% of the yearly increase.