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Glacier researcher: Montana has lost 75 glaciers since mid-20th century

Named glaciers that have been lost
Posted at 12:58 PM, Nov 29, 2023
and last updated 2023-11-30 08:06:15-05

Montana's glaciers have been around for ages, but these ancient giants are melting.

Ice covered much of northwestern Montana roughly 21,000 years ago and some remaining glaciers are estimated to be at least 7,000 years old.

These slow-moving features of the landscape have been retreating for some time, and according to new research coming out of Portland State University, 52 named glaciers and even more without formal names have disappeared in the western U.S.

“The reason why we did the project was that glacier maps really haven't been updated since mid-century, mid 20th-century. And for Montana, what that means is the 1960s," Professor Andrew Fountain said.

Fountain is a geology professor emeritus at PSU and the lead researcher on the Earth System Science Data study. He first began researching glaciers in 1980, but his most recent work refreshes an outdated inventory as the ice giants shrink in size.

“Overall, the trend is not a change in precipitation as much as it is changing air temperatures, warming air temperatures. And that's what we're seeing reflected in the glacier shrinkage and there's the tangible evidence of this climate change," he continued.

This latest glacial study reveals six named glaciers in Montana have retreated to the extent that they can no longer be classified as such.

Boulder, Blackwell, Gray Wolf Glaciers have been reduced to rock glaciers (rocky debris with ice) or snow fields (ice that does not move). Fissure Glacier has left the threshold for minimum size. Two glaciers called "Grasshopper" have also been delineated.

Here's a map and chart outlining where they're located.

Named glaciers that have been lost
Montana's lost glaciers
Here are the mountain range locations of Montana's "lost" glaciers. To see the additional glaciers that have been lost in the western U.S. click here.

According to Fountain, even more glaciers without formal names have lost their presence in the Treasure State. He told MTN News more research coming out early next year will delve into these lost no-name glaciers.

"Overall, 75 glaciers in Montana have gone and what I mean by disappeared is either they've entirely vanished, or they've turned into a snow patch," Fountain explained; "or else it dropped below our area threshold."

Glaciers change shape year-to-year, but with warming trends, they are melting faster than they’re being replenished by annual snowfall.

“As winter temperatures warm, even though we might have the same amount of precipitation, more of it falls as rain than snow than it did 40 years ago. So the glaciers get less replenished in the winter, and then they get melted more in the summer and it's kind of a double whammy," Fountain explained.

Glaciers are imperative for high alpine ecosystems. They feed streams during the late summer and early autumn seasons, keep water temperatures cool, and act as a reserve for water supply.

“They're not there to do that anymore. So those alpine regions are increasingly susceptible to drought," Fountain said.

Temperatures are anticipated to continue warming in the decades to come and that will put even more pressure on Montana’s remaining glaciers.