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Washington’s Mount Rainier is either the snowiest place on the planet or a close second. According to records collected over the past century, the average annual snowfall in the Rainier’s Paradise area is nearly 640 inches, or over 53 feet.
But this summer’s record heat triggered rapid snowmelt that left the scenic peak a bit dull and gray. The conditions prompted the National Park Service to warn visitors to keep their eyes and ears open to avoid mudslides and rock-laden debris fed by melting snow that can suddenly sweep into the valleys.
Dr Samuel Browd, 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.
“Hitting shrinking snowpack and glaciers, ”Browd wrote. “#Climate Emergency is right. Will be in the top of the 90s again in #Seattle this week. Be concerned about the future we are leaving for our children.
He has a point. The more than two dozen glaciers that keep Rainier snow-capped year-round have shrunk dramatically in recent decades. International scientists recently issued dire warnings that warmer temperatures will spread for the foreseeable future and will require bold action to reduce carbon emissions if we are to curb the trend. Members of the US Congress are negotiating a key spending plan that includes key climate provisions.
The Rainier Glaciers are just one visible sign of warming. Each year, the glaciers are covered with winter snowfall. In spring and summer some of this snow melts, but at higher elevations it survives more and is covered with fresh snow. As the cycle repeats itself, glaciers form. But these are not fixed features. Scientists describe glaciers moving like a conveyor belt, slowly sliding down the mountain, shedding snow at lower elevations, and building the glacier higher.
With increasingly warmer temperatures, the process of adding and removing snow from glaciers around the world has turned too far into the red.
On Rainier, glaciers cover a third of the area less and their thickness has decreased by 45% since 1900, said Scott Beason, geologist at Mount Rainier National Park, in a recent report.
Yet this winter was so promising. The volcanic peak received above average snowfall from January through early summer. Then, in late June, the record-breaking heat dome struck, roasting the Pacific Northwest.
“What was unusual about this heat wave was that it was very hot and very hot at different altitudes or altitudes,” said David Shean, assistant professor of civil and environmental engineering at the ‘UW.
For several days, if not weeks, the freezing level hovered at 18,000 feet – well above the summit of Rainier at 14,411 feet, Shean said. The snow began to melt quickly, rolling 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 glaciers retreat, they expose loose rocks and boulders at their base.
“This stuff is ripe to be part of a debris flow,” said Weston Thelen, a geophysicist and seismologist at the Cascades Volcano Observatory. “The added ingredient is water.”
The water sometimes comes from what is called a “glacial flood”, where a sudden large stream of water is released from a glacier, possibly triggering a debris flow.
These events are not very frequent. The drainage of Tahoma Creek on the southwest side of Rainier is the most frequent site for debris flows on the mountain, accumulating at least 32 events since 1967. Two years ago, a debris flow in the drainage took place. resulted in flooding of rocks and sediment and led to a road closure in the area.
Signs that a flow is coming include a rapid change in the water levels of streams and rivers, ground shaking, and a loud roar. 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 visitors to monitor flows during the last period of high temperatures.
“Are [debris flows] more frequent due to climate change? I can’t say for sure, ”Thelen said. “I can say that the materials, the loose rock at the bottom of the glacier, are more exposed than 30 years ago, 100 years ago. That part of the equation is there.
Researchers recently began installing an update to the Mount Rainier Lahar Detection System, a suite of monitors that can detect more massive, dangerous and rare volcanic mudslides called lahars. Since lahars only occur every few hundred years, more frequent debris flows will be helpful in fine-tuning and calibrating the system. Thelen, in fact, is hoping to catch a flow before early September, when he has to remove some of his seismometers and microphones before the snow returns.
And the snow will be back. As climate change warms the world, it is also altering precipitation patterns, creating more heavy rains and snowfall in places. It’s possible that changes in weather conditions will increase Rainier’s snowfall, but it could also lead to heavier rainstorms that wash away snow and ice.
Even as the planet warms, Mount Rainier, which rises skyward, should be able to retain many of its glaciers for some time despite the shrinkage. The outlook for low elevation glaciers in the Cascade and Olympic Mountains is less promising.
“Of the glaciers we have in the lower 48, Mount Rainier is in pretty good shape,” Shean said. “Glaciers will retreat, but they’re not going away anytime soon. “
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