BILLINGS, Mont. —Glacier National Park has lost two more of its namesake moving icefields to climate change, which is shrinking the rivers of ice until they grind to a halt, the U.S. Geological Survey said Wednesday.
Higher temperatures have reduced the number of named glaciers in the northwestern Montana park to 25, said Dan Fagre, an ecologist with the agency.
He warned the rest of the glaciers may be gone by the end of the decade.
"When we're measuring glacier margins, by the time we go home the glacier is already smaller than what we've measured," Fagre said.
The latest two to fall below the 25-acre threshold were Miche Wabun and Shepard. Each had shrunk by roughly 55 percent since the mid-1960s. The largest remaining glacier in the park is Harrison Glacier, at about 465 acres.
On a local scale, fewer glaciers mean less water in streams for fish and a higher risk for forest fires. More broadly, Fagre said, the fate of the glaciers offers a climate barometer, indicating dramatic changes to some ecosystems already under way.
While the meltoff shows the climate is changing, it does not show exactly what is causing temperatures to rise.
In alpine regions around the world, glacier melting has accelerated in recent decades as temperatures increased. Most scientists tie that warming directly to higher atmospheric concentrations of greenhouse gases such as carbon dioxide.
Some glaciers, such as in the Himalayas, could hold out for centuries in a warmer world. But more than 90 percent of glaciers worldwide are in retreat, with major losses already seen across much of Alaska, the Alps, the Andes and numerous other ranges, according to researchers in the United States and Europe.
In some areas of the Alps, ski resorts set atop glaciers have taken drastic measures to stave off the decline, such as draping glaciers in plastic sheeting to keep them cooler.
It could prove a losing battle: Scientists working for the United Nations say the last period of widespread glacial growth was more than three decades ago, lasting only for a few years.
Since about 1850, when the Little Ice Age ended, the trend has been steadily downward.
The area of the Rocky Mountains now within Glacier National Park once had about 150 glaciers, of which 37 were eventually named.
Fagre said a handful of the park's largest glaciers could survive past 2020 or even 2030, but by that point the ecosystem would already be irreversibly altered.
Fagre said geological evidence points to the continual presence of glaciers in the area since at least 5000 B.C.
"They've been on this landscape continually for 7,000 years, and we're looking at them to disappear in a couple of decades," he said.