Glacial Change in Montana’s Blackfoot-Jackson Basin

Glacial Change in Montana’s Blackfoot-Jackson Basin
Glacial Change in Montana’s Blackfoot-Jackson Basin

Search for information on Montana’s Glacier National Park, and you will likely come across the date 2030. That’s the year by which this park will purportedly be glacier-free.

Scientists arrived at the year 2030 through a simple geospatial model running on software from the 1990s. The model depicted the change expected to occur to glaciers in the Blackfoot-Jackson basin (shown above), an area that contains the largest concentration of glaciers in Glacier National Park. At the time of the study, glaciers in the basin were also among the park’s largest.

“It was conjectured that if the largest glaciers disappeared by 2030, most of the smaller ones would probably disappear too,” said Daniel Fagre, a research ecologist for the Northern Rocky Mountain Science Center of the U.S. Geological Survey.

The model took into account the basic parameters, such as warmer summer temperatures and meteorological snowfall. It did not account for more complicated factors such as “snow avalanching” and “snow scouring”—things that can keep a small glacier alive. But despite its simplicity, the model painted an accurate, if broad, picture of the situation: the shrinking of the ice in Glacier National Park is real and happening fast. “ People focus too much on the date, but the basic story is still true,” Fagre said. “These glaciers will be more or less gone in the next several decades.”

The images above show some of the more recent changes in the Blackfoot-Jackson basin. TheThematic Mapper (TM) on Landsat 5 acquired the top image on August 17, 1984. The Operational Land Imager (OLI) on Landsat 8 acquired the second image on August 23, 2015. Most of the blue color in these images is “permanent” snow and ice. Turn on the image comparison tool to see the footprint of the basin’s glaciers shrink.

Before these images were acquired, glaciers in the basin had already decreased from 21.6 square kilometers (8.3 square miles) in area in 1850 to just 7.4 square kilometers (2.9 square miles) in 1979. The Blackfoot and Jackson glaciers once ran together, as this photograph from 1914 shows; by 2009, they had retreated into separate valleys.

Other phenomena have left their mark on the landscape. In the 2015 image, a burn scar from the Thompson fire is visible southeast of Blackfoot glacier. As global and regional climate continues to warm, the frequency of fire in the park could increase.

For now, the clearest reflection of climate change is the ice. Year-to-year weather variations matter somewhat, but most of the loss is a response to decadal trends in warming. As we approach 2030, most of these glaciers will be “small insignificant lumps of ice on the landscape,” Fagre said. “These tiny remnants could last 10 to 15 years past that time if they are in sheltered places, but the park will no longer really have viable glaciers.”

View more images of shrinking glaciers across a larger area of the park by visiting World of Change: Glacier National Park.

NASA Earth Observatory images by Jesse Allen, using Landsat data from the U.S. Geological Survey. Caption by Kathryn Hansen.

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