Yosemite's largest ice mass is melting fast

Los Angeles Times

Lyell Glacier has shrunk 62% over the past century and hasn't moved in years. It's a key source of water in the park, and scientists say it will be gone in 20 years.

The photo on the left of Lyell Glacier in Yosemite National Park was taken by the U.S. Geological Survey in 1883; the one on the right was taken by park geologist Greg Stock in late September. (U.S. Geological Survey; Greg Stock)

By Louis Sahagun

October 1, 2013, 9:12 p.m.

Climate change is taking a visible toll on Yosemite National Park, where the largest ice mass in the park is in a death spiral, geologists say.
During an annual trek to the glacier deep in Yosemite's backcountry last month, Greg Stock, the park's first full-time geologist, found that Lyell Glacier had shrunk visibly since his visit last year, continuing a trend that began more than a century ago.
Lyell has dropped 62% of its mass and lost 120 vertical feet of ice over the last 100 years. "We give it 20 years or so of existence — then it'll vanish, leaving behind rocky debris," Stock said.
The Sierra Nevada Mountains have roughly 100 remaining glaciers, two of them in Yosemite. The shrinkage of glaciers across the Sierra is also occurring around the world. Great ice sheets are dwindling, prompting concerns about what happens next to surrounding ecological systems after perennial rivulets of melted ice disappear.
"We've looked at glaciers in California, Colorado, Wyoming, Washington and elsewhere, and they're all thinning because of warming temperatures and less precipitation," said Andrew Fountain, professor of geology and geography at Portland State University in Oregon. "This is the beginning of the end of these things."


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