Report: Global warming has hastened glacial melt

WASHINGTON -- Global warming has melted glaciers in the United States at a rapid and accelerating rate over the past half-century, increasing drought risks and contributing to rising sea levels, the federal government reported Thursday based on data from a 50-year study of glaciers in Alaska and the Pacific Northwest.

Federal officials say the study includes the longest records of glacial melt recorded in North America.

The U.S. Geological Survey study focuses on three glaciers: the Wolverine and Gulkana in Alaska and the South Cascade Glacier in Washington, which are known as "benchmark glaciers" because their varying climates and elevations are representative of thousands of other glaciers across the continent.

The Gulkana and Wolverine glaciers have both lost about 15 percent of their mass since the mid-1950s, the data show. The South Cascade Glacier has lost nearly a quarter of its mass.

The shrinking glaciers clearly result from global warming, federal researchers say.

"There is no doubt that most mountain glaciers are shrinking worldwide in response to a warming climate," USGS scientist Edward Josberger said in a written statement. "Measuring changes in glacier mass provides direct insight to the link between glaciers and climate."

For decades, USGS researchers have periodically measured the three glaciers' size, with tools including measurement stakes and photographic surveys. Their data include tallies of winter snow accumulation and summer melt.

In each case, the data show summer melting accelerated in the past 20 years, a driving force in the overall shrinking of the glaciers.

When glaciers shrink, scientists say, water runoff declines -- setting the stage for drier conditions, particularly at the end of summer, when other supplies often dwindle.

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