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99% of Alaska’s large glaciers are retreating

99% of Alaska’s large glaciers are retreating

99% of Alaska’s large glaciers are retreating
October 6, 2008

The bulk of glaciers in every mountain range and island group in Alaska are retreating, thinning, or stagnating, according to a new book by the U.S. Geological Survey (USGS).

The Glaciers of Alaska, a comprehensive overview of Alaska’s glaciers of Alaska authored by USGS research geologist Bruce Molnia, reports that more than 99 percent of Alaska’s large glaciers are retreating.

The book “uses a combination of satellite images, vertical aerial photographs (black-and-white and color-infrared photos taken from airplanes, looking straight down), oblique aerial photographs (color photos taken from the air at an angle, such as most regular photos), and maps, supported by the scientific literature, to document the distribution and behavior of glaciers throughout Alaska,” according to a statement from USGS.

This ship-deck-based August 1980 photograph of Muir Glacier and Muir Inlet, Glacier Bay National Park and Preserve, St. Elias Mountains, Alaska, shows the nearly 200-ft-high retreating tidewater end of Muir Glacier with part of its face capped by a few angular pinnacles of ice, called séracs. Note the icebergs in the ship’s wake in the lower right side of the photograph. The location of Muir’s terminus is less than a mile from the landward end of Muir Inlet. Photo courtesy of Bruce Molnia, USGS

This photo was taken in September 2003; in the 23 years between photographs, Muir Glacier has retreated more than a mile and ceased to have a tidewater terminus. Since 1980, Muir Glacier has thinned by more than 600 ft, permitting a view of a mountain with a summit elevation of greater than 4000 ft, located in the center of the photograph. A reexamination of the 1980 photograph shows that the summit of this mountain was visible but that it blended in with adjacent clouds. Photo courtesy of Bruce Molnia, USGS