Better imaging helps scientists map glaciers

New technology can give scientists a closer look at glaciers – but there aren’t many left.

Early last century, there were an estimated 150 glaciers – ice bodies larger than 25 acres – in Glacier National Park. Now, only 26 glaciers remain.

Montana’s glaciers are shrinking.

New data released by the U.S. Geological Survey and Portland State University indicate that since 1966, the warming climate has reduced the size of 39 glaciers, some by as much as 85 percent.

Scientists collected data for the 37 named glaciers in Glacier National Park and two glaciers on U.S. Forest Service land. On average, the 39 glaciers have been reduced by 39 percent since 1966, which was the first year that all the glaciers were aerially photographed.

To collect the data, scientists compared 50 years of aerial photographs and satellite images to measure the perimeters of the glaciers. All photos were taken in late summer, after seasonal snow had melted and the glacial ice extent was most evident.

They also conducted GPS ground surveys and did repeat photography.

With new satellite technology, the scientists can get higher-resolution color images of glaciers.

This is a big deal for USGS scientist Daniel Fagre, of the Northern Rocky Mountain Science Center, who heads up the study of glaciers in Glacier National Park.

“We can see great detail,” Fagre noted. “We’re able to make a better determination of glacier state.”

With the grainy black and white images of the past, it was difficult to distinguish bedrock under the ice from rock that had fallen on top of glaciers.

The better imaging is helping.

For example, now the team has discovered that part of Siyeh Glacier’s extent was actually buried under rock. After a site visit, they confirmed that Siyeh was actually large enough to still be considered a glacier. Before, unable to see the rock covering the ice, they had deemed it too small and taken away its glacier status — a glacier has to be 25 acres or larger to still be considered a glacier.

But “no glaciers are increasing,” Fagre added.

Fagre has studied Glacier Park’s ice bodies since 1991.

“Since I’ve been going to various glaciers, there’s real distinct differences every time I visit,” he noted.

It’s easier to access some glaciers than ever before, he explained, because the ice and snow is only up to his knees – the glaciers are losing thickness, too.

As a result, the new data is a very conservative estimate of ice loss, Fagre said, because it only takes aerial extent into account. The loss is actually much greater due to thinning of the glaciers.

Fagre’s team visits Sperry Glacier yearly to measure ice thickness loss, and they’re starting to use LIDAR to get 3-D pictures of the glaciers.

LIDAR is an imaging technique in which laser beams are sent – usually from planes – down to the glaciers. Scientists use the measured time it takes for the light to bounce back to the plane to get an estimated height of the ice.

“We’re adapting our research to use even more tools as we move forward,” Fagre said.

Shrinking glaciers provide a visual indicator of holistic ecosystem change in the northern Rocky Mountains.

“What we try to emphasize is that glaciers are just one component of a mountain ecosystem,” Fagre noted. “Glaciers are easier to see, but trees and animals are responding as well. Glaciers are barometers of change in the whole ecosystem.”

Ice loss can also affect aquatic species by altering stream water volume, water temperature, and runoff timing at higher elevations.

Glaciers are a good marker of climate change because they aren’t particularly sensitive to yearly temperature or precipitation variation, Fagre said. If they’re shrinking, it necessarily indicates a marked shift in climate over decades.

“Glaciers are telling you about a long term change, and that’s why we monitor them,” he noted.

Most cold parts of the planet are responding more quickly to warming, Fagre added.

“Our glaciers were small to start with,” he said.

Huge Himalayan glaciers are “self-refrigerated,” he explained, and it takes longer for them to lose ice.

Generally, the smallest glaciers in the Park are the ones that have melted and disappeared most quickly, Fagre noted. Larger glaciers tend to be more resilient, and so do glaciers that are shaded by a rock face and facing north, as opposed to south or west.

Shrinking glaciers also mean that the seasonal snowpack is shrinking, which could have implications on water supply for recreation and irrigation, he said.

Additionally, the retreat of glaciers could decrease tourism in Montana.

The historic photographs of glaciers and the recreations are available at https://www.usgs.gov/atom/13896, and the live dataset can be seen at https://www.sciencebase.gov/catalog/item/58af7022e4b01ccd54f9f542.

A table of changing glacial extent is available at https://www.usgs.gov/data-tools/area-named-glaciers-glacier-national-park-gnp-and-flathead-national-forest-fnf-derived.

This information is part of an ongoing USGS glacier study in Montana, Alaska, and Washington to understand the impact of large-scale climate patterns on glaciers in distinctly different mountain environments across North America.