About 14% of the ice and permanent snow atop Washington's Mount Rainier melted in the last 4 decades, a new study suggests. Researchers arrived at that figure by comparing the estimated thicknesses and extents of ice seen in a 1970 aerial survey with those measured by an airborne laser altimeter in 2007 and 2008. All but two of the 28 glaciers and snowfields have thinned and shortened at their lower edges, and the exceptions likely thickened only because large amounts of rock fell upon the ice in recent years and insulated it from warming temperatures. Overall, the volcanic peak lost about 0.65 cubic kilometers of ice —enough to cover the entire state of Rhode Island to a depth of 20 centimeters—during the 38-year interval between surveys, the researchers report online inGeology. Prior to the ongoing meltback, Mount Rainier's ice and snow coverage expanded from the late 1950s to around 1980 during a wetter-than-normal phase of a multi-decadal climate cycle called the Pacific Decadal Oscillation. These recent trends indicate that Mount Rainier's glaciers are very sensitive to warming and could grow again with modest changes in temperature or precipitation, the scientists say.
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