Abstract

Net changes in thickness and volume of glacial ice and perennial snow at Mount Rainier, Washington State, have been mapped over the entire edifice by differencing between a high-resolution LiDAR (light detection and ranging) topographic survey of September–October 2007/2008 and the 10 m lateral resolution U.S. Geological Survey digital elevation model derived from September 1970 aerial photography. Excepting the large Emmons and Winthrop Glaciers, all of Mount Rainier's glaciers thinned and retreated in their terminal regions, with substantial thinning mainly at elevations <2000 m and the greatest thinning on south-facing glaciers. Mount Rainier's glaciers and snowfields also lost volume over the interval, excepting the east-flank Fryingpan and Emmons Glaciers and minor near-summit snowfields; maximum volume losses were centered from ∼1750 m (north flank) to ∼2250 m (south flank) elevation. The greatest single volume loss was from the Carbon Glacier, despite its northward aspect, due to its sizeable area at <2000 m elevation. Overall, Mount Rainier lost ∼14 vol% glacial ice and perennial snow over the 37 to 38 yr interval between surveys. Enhanced thinning of south-flank glaciers may be meltback from the high snowfall period of the mid-1940s to mid-1970s associated with the cool phase of the Pacific Decadal Oscillation.

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