Glaciers may be melting faster than scientists thought, causing 25 to 30 percent of global sea level rise, according to comprehensive research published in Nature on Monday.
While previous studies had only assessed 500 glaciers, the new study looked at more than 19,000 glaciers using both satellite data and field visits, lead study author and University of Zurich glaciologist Michael Zemp told CNN. The researchers found that, between 1961 and 2016, the world's non-polar glaciers had lost around 9,000 billion tons of ice and contributed 27 millimeters to rising ocean levels. That's enough ice to turn the U.S. into an ice-rink four feet thick.
The new report put the shrinkage rate for glaciers at 18 percent faster than that calculated by another international study in 2013. It found that glaciers are contributing as much ice melt to sea level rise as the Greenland ice sheet and more than the Antarctic ice sheet, National Geographic reported. In the 1960s, when the study period began, glaciers would melt in summer and regain mass in winter. But beginning around the 1980s, they began to lose more in the summer than they regained in winter, and by the 1990s, almost every glacier they studied was losing more than it could recuperate. Only glaciers in southwest Asia are not losing mass because of regional climate factors, the Associated Press reported.
"The drama is that it's increasingly negative," study co-author and University of Zurich geographer Frank Paul told National Geographic.
Today, glaciers lose about 335 billion tons of ice a year, the equivalent of one millimeter per year of sea level rise, according to a University of Zurich release.
"Globally, we lose about three times the ice volume stored in the entirety of the European Alps – every single year!" Zemp said.
Glaciers in Alaska contributed the most to sea level rise, while glaciers in Patagonia and the rest of the Arctic were also major contributors. Glaciers in the Alps, the Caucasus mountains and New Zealand were also shrinking fast, but were too small to contribute to sea level rise.
Glacier loss isn't just a problem for coastal areas, however. It could also be destructive for the communities that depend on them for drinking water.
"In Peru, they really are like water towers," Paul told National Geographic.
The study found that glaciers in Canada, the U.S., New Zealand and Europe could melt completely by 2100.
"Under current loss rates we are going to lose glaciers — basically all glaciers — in several mountain ranges," Zemp told CNN.