Washington’s Mount Rainier is either the snowiest place on Earth, or a close runner up. From records collected over the past century, the average annual snowfall at Rainier’s Paradise area is nearly 640 inches, or more than 53 feet.
But this summer’s record-setting heat triggered a rapid snow melt that has left the picturesque peak looking a bit dingy and gray. The conditions have prompted the National Park Service to issue a warning to visitors to keep their eyes and ears peeled for mud and boulder-laden debris flows fueled by melting snow that can suddenly surge into valleys.
Dr. Samuel Browd, a pediatric neurosurgeon in Seattle who works for Seattle Children’s Hospital and the University of Washington, tweeted a photo of a scruffy Rainier taken from an airplane window during a recent flight.
“Striking the reduction in snowpack and glaciers,” wrote Browd. “#ClimateEmergency is real. Will again be in the high 90s in #Seattle this week. Worry about the future we leave to our kids.”
He has a point. The more than two-dozen glaciers that keep Rainier snowcapped year-round have shrunk dramatically over past decades. International scientists recently issued dire warnings that hotter temperatures will stretch into the foreseeable future and require bold actions to cut carbon emissions if we want to curb the trend. Members of the U.S. Congress are currently negotiating a key spending plan that includes critical climate provisions.
Rainier’s glaciers are just one of the visible signs of the warming. Each year, the glaciers are covered by winter snowfall. In the spring and summer, some of that snow melts, but at higher elevations more survives and is covered by new snow. As the cycle repeats, glaciers are formed. But they’re not fixed features. Scientists describe glaciers moving like a conveyor belt, sliding slowly down the mountain, losing snow at the lower elevations and building the glacier higher up.
With ever warmer temperatures, the process that adds and subtracts snow from glaciers worldwide has tilted too far into the red.
On Rainier, the glaciers cover one-third less area and their thickness has dropped by 45% since 1900, said Mount Rainier National Park geologist Scott Beason in a recent news story.
Yet this winter held so much promise. The volcanic peak received above-average snowfall starting in January and lasting into early summer. Then in late June, the record-breaking heat dome hit, roasting the Pacific Northwest.
“What was unusual about that heat wave is it was really hot and it was really hot across a range of altitudes or elevations,” said David Shean, a UW assistant professor of civil and environmental engineering.
For several days, or perhaps even weeks, the freezing level hovered at 18,000 feet — well above the top of Rainier at 14,411 feet, Shean said. The snow began to rapidly melt, pouring down the mountain.
“The glacier has no choice but to retreat to higher elevations where it’s colder,” Shean said.
And that creates other potential problems. As the glaciers recede, they expose loose rocks and boulders at their base.
“That stuff is ripe for being part of a debris flow,” said Weston Thelen, a geophysicist and seismologist with the Cascades Volcano Observatory. “The added ingredient is water.”
The water sometimes comes from what’s called a “glacial outburst flood,” which is a sudden, large gush of water is released from a glacier, possibly triggering a debris flow.
These events aren’t super common. The Tahoma Creek drainage on the southwest side of Rainier is the most frequent site for debris flows on the mountain, racking up at least 32 events since 1967. Two years ago, a debris flow in the drainage carried a flood of rocks and sediment and led to a road closure in the area.
Signs that a flow is coming include a rapid change in water levels of streams and rivers, shaking ground and a loud roaring sound. People are advised to flee to higher ground at least 200 feet above the bottom of a valley. The National Park last week tweeted a reminder to visitors to watch out for flows during the most recent stretch of high temperatures.
“Are [debris flows] more common because of climate change? I can’t say that for sure,” Thelen said. “I can say the materials, the loose rock at the bottom of the glacier, is more exposed than it was 30 years ago, 100 years ago. That part of the equation is there.”
Researchers recently began installing an update of the Mount Rainier Lahar Detection System, a suite of monitors for detecting more massive, dangerous and rare volcanic mudflows called lahars. Because lahars occur only every few hundred years, the more frequent debris flows will be useful for fine-tuning and calibrating the system. Thelen, in fact, is hoping to catch a flow before early September when he’ll need to remove some of his seismometers and microphones before the snow returns.
And the snow will be back. While climate change is warming the world, it’s also altering precipitation patterns, creating heavier rain and snowfall in places. It’s possible that shifting weather patterns could increase Rainier’s snow, but it could also result in heavier rainstorms that wash away snow and ice.
Even as the planet heats up, skyward-reaching Mount Rainier should be able to hold on to many of its glaciers for some time, despite the shrinkage. The outlook for lower elevation glaciers in the Cascade and Olympic mountains is less hopeful.
“Of the glaciers we have in the lower 48, Mount Rainier is in pretty good shape,” Shean said. “The glaciers will retreat, but they won’t disappear any time soon.”