Melting mountain glaciers may not survive the century

If you don’t have it already hiked a glacier you might want to start soon. The world’s high mountain glaciers are melting faster than scientists previously thought; since 2015, they have lost nearly 300 billion tonnes of ice per year. If this rate of melting continues, many could disappear entirely by mid-century, according to a comprehensive new study released today.

Researchers in Canada, France, Switzerland and Norway have collected 20 years of satellite images taken from a special camera on a NASA satellite called Terra. The device, called ASTER, for Advanced Spaceborne Thermal Emission and Reflection Radiometer, has taken images of more than 210,000 glaciers around the world, each photographing with two separate objectives to create three-dimensional views of their surface features. The study excluded the massive ice caps that cover Greenland and Antarctica, which are being studied by other teams of scientists.

The new analysis, published today in the newspaper Nature, found that between the years 2000 and 2004, glaciers lost 227 billion metric tons of ice per year. But between 2015 and 2019, that rate jumped to 298 billion tonnes per year, a change the study authors attribute to warmer temperatures and increased precipitation. Taken together, this meltwater flowing along rivers and into the oceans accounts for about one-fifth of the observed sea-level rise over the past 20 years.

And the problem is not just the rise in sea level, although it is a significant problem, threatening the well-being of the residents of coastal nations like Indonesia, Bangladesh, Panama, the Netherlands, and some parts of United States. In some inland areas, millions of people depend on melting snow for clean water; in years when there is not much snow, glaciers provide a backup water source. This is especially true in parts of the Andes, Himalayas, and Alaska. “They provide fresh, plentiful water to many systems across the planet,” says Brian Menounos, professor of earth sciences at the University of Northern British Columbia and author of the new study. “Once those glaciers are gone, you don’t have that buffering ability.”

Menounos says that previous studies of glacier melt took fewer measurements in both space and time, which gave a bit of a blur on the actual shrinkage of glaciers. By using detailed satellite imagery, he says, “we were able to show that with our estimates, we significantly reduced the uncertainty.” To calculate the numbers for 211,000 glaciers, it took a supercomputer at the University of Northern British Columbia that ran almost full time for a year.

The new analysis provides a grim warning about the future, says Jonathan bamber, professor of geographic sciences at the University of Bristol who was not involved in the study. “This is the most comprehensive, detailed and in-depth assessment of global glacier mass loss in the 21st century ever undertaken,” he wrote in an email to WIRED. “The level of detail of the results allows us to see for the first time changes on individual glaciers around the world.”

Bamber says the analysis shows that if the trend continues, some low-lying mountain regions will lose their glaciers entirely by 2050. “While the results and the work are impressive, the main message is rather grim,” he said. Bamber continued. “Glaciers are disappearing, with profound impacts on water resources, natural hazards, sea level rise, tourism and local livelihoods.”

The study’s authors agree with that assessment, and Menounos said some areas, like the Cascades and Montana Glacier National Park, will likely be ice-free by mid-century. “See them while you can,” he insists.

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