× Thanks for reading! Log in to continue. Enjoy more articles by logging in or creating a free account. No credit card required. Log in Sign up {{featured_button_text}}

To be a glacier, a field of ice must move. Seen from space, they also appear to breathe.

A pair of new animations from NASA’s Earth Observatory compile three decades of satellite images that show Glacier National Park’s landmarks shrinking as climate conditions change. But seen in sequence, the alpine glaciers seem to inhale and exhale as occasional big-snow years occur.

“The overall trend is to become smaller and retreat,” said Dan Fagre, research ecologist for the Northern Rocky Mountain Science Center of the U.S. Geological Survey in West Glacier. “But this isn’t a simple linear trend, the way humans are pre-wired to think. It’s hard to look at a particular year and say climate change is happening or not happening. That’s why scientists are often reluctant to talk about trends until they have enough data.”

A computer model in the 1990s looked at Glacier Park’s shrinking ice and forecast a complete loss of moving glaciers by 2030. While that model wasn’t complex enough to include some factors that can help a glacier extend its status, it remains reasonably accurate. From 150 glaciers tallied when geologists first surveyed the area in 1850, the park’s total dropped to 83 by 1968. Today, there are 25 still-moving ice fields that qualify as glaciers.