page_title: Shoshone National Forest
section_title: Glaciology
hierarchical_section_title: Shoshone National Forest / Geography and geology / Glaciology
caption_attribution_description: English: Gannet Peak and Gannett Glacier in the Wind River Range of Wyoming
context_page_description: Shoshone National Forest is the first federally protected National Forest in the United States and covers nearly 2,500,000 acres in the state of Wyoming. Originally a part of the Yellowstone Timberland Reserve, the forest is managed by the United States Forest Service and was created by an act of Congress and signed into law by U.S. President Benjamin Harrison in 1891. Shoshone National Forest is one of the first nationally protected land areas anywhere. Native Americans have lived in the region for at least 10,000 years, and when the region was first explored by European adventurers, forestlands were occupied by several different tribes. Never heavily settled or exploited, the forest has retained most of its wildness. Shoshone National Forest is a part of the Greater Yellowstone Ecosystem, a nearly unbroken expanse of federally protected lands encompassing an estimated 20,000,000 acres.
  The Absaroka and Beartooth Mountains are partly in the northern section of the forest. The Wind River Range is in the southern portion and contains Gannett Peak, the tallest mountain in Wyoming.
context_section_description: According to the U.S. Forest Service, Shoshone National Forest has the greatest number of  glaciers of any National Forest in the Rocky Mountains. The forest recreation guide lists 16 named and 140 unnamed glaciers within the forest, all in the Wind River Range. Forty-four of these glaciers are in the Fitzpatrick Wilderness, centered around the highest mountain peaks. However, the state water board for Wyoming lists only 63 glaciers for the entire Wind River Range, which includes glaciers in adjacent Bridger-Teton National Forest. Researchers claim that for most of the period that glaciers have been known to exist in the forest, that they have been in a state of general retreat, with glacial mass losses of as much as 25 percent between the years 1985 and 2009.
  Reversing the growth of mid-latitude glaciers that occurred during the Little Ice Age (1350–1850), there has been a worldwide reduction of mountain glacial ice since, with some regions losing as much as 50 percent of their peak ice cover. This can be correlated by examining photographic evidence of glaciers taken over time even with an absence of other means of documentation. The behavior of the glaciers of Shoshone National Forest is consistent with this pattern. In one study of Dinwoody and Gannett Glaciers, during the period from 1958 to 1983, the thickness of these glaciers was reduced 77 and 61 ft (23 and 19 m), respectively. 
  Gannett Glacier, on the northeast slope of Gannett Peak, is the largest single glacier in the U.S. Rocky Mountains. It has reportedly lost over 50 percent of its volume since 1920 with 25 percent of that occurring between the years 1980–1999. Upper Fremont Glacier has been studied more than any other glacier in the Wind River Range. Scientist have obtained ice cores from the Upper Fremont Glacier and found that there have been measurable changes in the atmosphere over the past several hundred years. The Upper Fremont Glacier and the Quelccaya Ice Cap in the Andes of South America both show nearly identical atmospheric records, which indicate a global linkage of atmospheric conditions over time.
  The small glaciers in the forest are less able to resist melting than the great ice sheets of Greenland and Antarctica. Once a glacier begins retreating, it may fall into disequilibrium and be unable to find mass balance (accumulation versus melting rate) at any size. Without a favorable climate change, it will continue to retreat until it disappears. Loss of glacial ice already reduces the summer glacial runoff that supplies water to streams and lakes and provides a cold-water source vital to certain fish and plant species. This, in turn, may have a significant impact on the forest ecosystem over time.
caption: Gannett Glacier on the slopes of Gannett Peak
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