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The park's glaciers have been slowly melting since about 1850, when the centuries-long Little Ice Age ended. They once numbered as many as 150. ((Canadian Press))

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, a government researcher said Wednesday.

Warmer temperatures have reduced the number of named glaciers in the northwestern Montana park to 25, said Dan Fagre, an ecologist with the U.S. Geological Survey. He warned that the remaining glaciers might 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.

From the Himalayas to Alaska, glacier melting has accelerated in recent decades as global temperatures have increased. The melt shows the climate is changing but does not show exactly what is causing temperatures to go up, Fagre said.

The park's glaciers have been slowly melting since about 1850, when the centuries-long Little Ice Age ended. They once numbered as many as 150, and 37 of those glaciers eventually were named.

A glacier needs to be about 10 hectares to qualify for the title. If it shrinks any smaller, it does not always stop moving right away. A smaller mass of ice on a steep slope would still continue to grind its way through the mountains but eventually would disappear.

The latest two glaciers to fall below the 10-hectare threshold were Miche Wabun and Shepard. Each had shrunk by roughly 55 per cent since the mid-1960s. The largest remaining glacier in the park is Harrison Glacier, at about 188 hectares.

Melt threatens tourism

Smaller glaciers and warmer temperatures could lower stream flows, which in turn could prompt fishing restrictions and hobble whitewater rafting businesses, said Denny Gignoux, who runs an outfitting business in West Glacier. Tourism is a $1 billion a year industry in the area.

"What happens when all these threats increase?" Gignoux asked.

Two environmental groups released a report Wednesday highlighting the threat to tourism of fewer glaciers. The report by the Rocky Mountain Climate Organization and Natural Resources Defence Council included an analysis of weather records that showed Glacier was two degrees hotter on average from 2000 to 2009, compared with 1950 to 1979.