NEWS NOTES ON SUSTAINABLE WATER RESOURCESGlacier Retreat“The volume of land ice on Earth is d...


Glacier Retreat

“The volume of land ice on Earth is decreasing. The glaciers in Montana’s Glacier National Park (GNP) have decreased in number, area, and volume since the park’s establishment in 1910. At the Last Glacial Maximum (approximately 20,000 years ago), Glacier National Park (GNP) was almost entirely encased in ice, with glaciers filling mountain valleys and extending onto the plains. All but the tallest peaks were covered by glaciers. Geologic evidence suggests that by approximately 11,500 years ago, the GNP landscape was nearly ice free. Lake sediment records suggest that, since approximately 6,500 years ago, small glaciers have been present and active.”

“Scientists, including U.S. Geological Survey (USGS) scientists, study glacier retreat using a variety of methods. Repeat photography provides an objective, qualitative account of historical glacier change. Remote sensing products and field measurements yield quantitative data that inform models and other analyses.”

“Comprehensive mapping of glacial moraines indicates that there were 146 small mountain glaciers in GNP at the Little Ice Age glacial maximum near the mid-19th century. Since then, every glacier has decreased in area. The rate of retreat, however, is not uniform across GNP glaciers, likely because of variations in glacier geometry, elevation, ice thickness, wind effects on snow, snow avalanches, and shading.”

“The amount of Earth’s land ice that will be lost in the future, and the timing of that loss, depends on the future trajectory of greenhouse gas emissions. Because the glaciers in GNP are small, however, their future is more certain and will include continued retreat and mass loss. Ongoing glaciological research will refine our ability to understand and forecast these physical changes and their downstream consequences.”

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