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.
Fagre said the much more interesting thing about the satellite progression is the amount of information his team has to work with about the ice. The NASA animation starts with an image from Landsat 5’s thematic mapper camera shot of the Jackson-Blackfoot ice fields on Aug. 17, 1984. Three decades later, Landsat 8’s Operational Land Imager system rephotographed the spot on Aug. 23, 2015.
In the meantime, the image quality jumped from pixels that measured 30 meters square to pixels 50 centimeters square.
“That’s thousands of times better,” Fagre said. “It’s like having blurry vision and then putting on glasses.”
The newer images can tell the difference between permanent ice and seasonal snow, see ice hidden under rock debris, and measure the thickness of the deposits. Many glaciers appear to have deflated, as much of their vertical bulk has melted away.
That’s significant because the high-mountain ice deposits regulate water supplies and temperatures as the summer wears on. In 2015, the Logan Pass Visitor Center was down to less than a week’s worth of water supply just when the Reynolds fire erupted and cut off traffic across the Going to the Sun Road. Hikers along the Highline Trail found Granite Park didn’t have enough water to refill water bottles through much of August.
“That becomes more severe in the future, because there’s no backup system,” Fagre said. “This year, we’re in good shape right now. But unfortunately, in much of these mountain areas it only takes a few hot, dry, windy days to remove water from the landscape.”
The glaciers themselves also can change radically. Grinnell Glacier attracts the most visitors with its well-worn trail from Many Glacier Hotel. For years, it was also the park’s largest ice field. But steady melting has erased most of its presence.
“Last fall there was an event and 10 acres broke off – that’s 10 percent of its size,” Fagre said. “It occurred in September. A witness reported hearing a huge boom and saw water jetting up from a crack between the main glacier and that 10-acre piece, with water sloshing back and forth. By the time I got there, it had floated away and shattered into a million icebergs.”