The most heavily glaciated mountains in the lower 48 are in Washington, which is home to more than 70 percent of the American West’s ice. Most dramatic are the massive glaciated flanks of Mount Rainier and the icy vertiginous peaks of the North Cascades. But apart from their scenic attraction, these glaciers are becoming something of a giant laboratory for scientists who are studying worldwide glacier retreats.

According to a good article in the Tacoma News Tribune:

Since the 1970s, virtually all of the glaciers outside the world’s polar regions have shrunk, said Andrew Fountain, a Portland State University glaciologist who has studied glaciers throughout the western United States. “You don’t find an advancing glacier anymore,” Fountain said.

The most obvious culprit may be climate change, but like many natural systems glaciers are enormously complex. Retreats happen for a variety of reasons, many of which are unconnected to rising concentrations of atmospheric carbon and other greenhouse gases. Still, even if widespread glacial retreats are not happening solely—or even primarily—because of global warming, melting mountains are certainly an ominous sign.

In the Pacific Northwest, for instance, scientists are predicting less and less wintertime snowpack in the Cascade Mountains as a direct consequence of warmer temperatures. And snowpack, of course, is necessary to sustain the glaciers that beckon tourists and help supply water to the region’s streams during summer months.