Glacier National Park

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Glaciers

Glacier National Park is dominated by mountains carved into their present shapes by the huge glaciers of the last ice age. These glaciers have largely disappeared over the last 15,000 years. Evidence of widespread glacial action can be seen throughout the park in the form of U-shaped valleys, glacial cirques, arêtes and large outflow lakes that radiate like fingers from the base of the highest peaks. Various warming and cooling trends have occurred since the end of the ice ages. The last recent cooling trend was during the Little Ice Age that took place approximately between 1550 and 1850.[17], The glaciers in the park expanded and advanced during the Little Ice Age although not nearly as great an extent as they had during the Ice Age. Coincidentally, the park region was first explored in detail near the end of the Little Ice Age and a systematized survey began in which the number and size of glaciers was documented on maps and by photographic evidence. Much of this late 19th century work, was not done out of a particular desire to document glaciers but was undertaken to lure tourism into the region or to search for mineral wealth.

During the middle of the 20th century, examination of the maps and photographs from the previous century provided clear evidence that the 150 glaciers known to have existed in the park a hundred years earlier had greatly retreated, and in many cases disappeared altogether.[18] Repeat photography of the glaciers, such as the pictures taken of Grinnell Glacier between 1938 and 2005 as shown, help to provide visual confirmation of the extent of glacier retreat.



The U.S. Geological Survey began a more systematic study of the remaining glaciers, in the 1980s, which continues to the present day. Only 27 glaciers remained by 2005, and scientists generally agree that if the current global warming continues, all the glaciers in the park will be gone by 2030.[18] This glacier retreat follows a worldwide pattern that has accelerated even more since 1980. The extensive glacier retreat that has been observed in Glacier National Park is a key indicator of climatic changes on a worldwide scale. Without a major climatic change in which cooler and moister weather returns and persists, the mass balance (accumulation rate versus melting rate) of glaciers will continue to be negative and the glaciers will eventually disappear, leaving behind only barren rock.[18]

After the end of the Little Ice Age in 1850, the glaciers in the park retreated moderately until the 1910s. The retreat rate rose rapidly and continued to accelerate from1917 through the 1930s. A slight cooling trend from the 1940s until 1979, helped slow the rate of retreat and in a few cases some glaciers even advanced a few tens of meters. However, during the 1980s, the glaciers in the park began a steady period of loss of glacial ice, which continues into the 2000s. In 1850, the glaciers in the region near Blackfoot and Jackson Glaciers covered 5,337 acres (21.6 km2), but by 1979, the same region of the park had glacier ice covering only 1,828 acres (7.4 km2). 73 percent of the glacial ice had melted away between 1850 and 1979.[19] At the time the park was created, Jackson Glacier was part of Blackfoot Glacier, but the two separated into different glaciers by 1939.

The impact of glacier retreat on the park's ecosystems is not fully known. Some scientist believe that cold water dependent plant and animal species could suffer due to a loss of habitat. Reduced seasonal melting of glacial ice may also affect stream flow during the dry summer and fall seasons, reducing water table levels and increasing the risk of forest fires. The aesthetic visual appeal that glaciers provide to visitors will also be lost as the glaciers retreat. [20]