By Seth Borenstein - The Associated Press
Glaciers are melting at an accelerated rate, losing 31% more snow and ice each year than 15 years ago, according to 3D satellite measurements of all mountain glaciers in the world.
Scientists say this is due to climate change caused by human activity.
Using 20 years of satellite data, scientists calculated that the world's 220,000 mountain glaciers are losing more than 298 billion metric tons of ice and snow per year since 2015, according to a study published Wednesday in the journal. Nature.
The melt that flows into the world's oceans would be enough to sink Switzerland under 7.2 meters of water every year.
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The annual rate of thaw from 2015 to 2019 is 71,000 million metric tons more per year than from 2000 to 2004. Global rates of decline, different from the volume of water lost, have doubled in the last 20 years and “that it's huge, ”according to Romain Hugonnet, a glacier expert for ETH Zurich and the University of Toulouse in France, who led the study.
Half of the world's glacier loss occurs in the United States and Canada.
Melt rates in Alaska are "among the highest on the planet"
- the Columbia Glacier retreats about 115 meters (35 feet) a year, Hugonnet says.
Almost all the world's glaciers are melting, including those in Tibet that used to be stable, the study says.
Except for a few glaciers in Iceland and Scandinavia fueled by increased rainfall, melt rates are accelerating around the world.
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The almost uniform melting "reflects the global increase in temperatures" and is due to the use of coal, oil and gas, says Hugonnet.
Some minor glaciers are completely disappearing.
Two years ago, scientists, activists and government officials in Iceland held a funeral for a small glacier.
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"10 years ago, we were saying that glaciers were the indicators of climate change, but now they have become a memorial to the climate crisis," said Michael Zemp, director of the World Glacier Monitoring Service, who was not part of the study.
The study is the first to use 3D satellite imagery to examine all of Earth's glaciers not connected to ice sheets in Antarctica and Greenland.
Previous studies used only a fraction of glaciers or estimated the loss of glaciers on Earth using measurements of gravity from orbit.
Those measurements have large margins of error and are not useful, Zemp said.
Blocks of ice break off one side of the Perito Moreno glacier, near the city of El Calafate, in the Patagonian province of Santa Cruz, southern Argentina, on July 7, 2008.REUTERS
Glacier shrinkage poses a problem for millions of people who depend on seasonal melting for drinking water, and accelerated melting can cause fatal glacial lake spills in places like India, Hugonnet said.
But the biggest threat is rising sea levels.
The world's oceans are already rising due to warmer water expanding and due to the melting of ice sheets in Greenland and Antarctica.
But
glaciers are responsible for 21% of sea level rise
, more than ice sheets, according to the study.
Ice sheets are a longer-term threat.
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"It is becoming increasingly clear that sea level rise will be a growing problem as we move into the 21st century,"
recalled Mark Serreze, director of the National Ice and Snow Data Center.
