DENALI NATIONAL PARK — The Muldrow Glacier is surging for the first time in 64 years, moving 10 to 20 meters — 30 to 60 feet — every day.
The Muldrow Glacier flows from Denali, the tallest peak in North America, and parts of the glacier can be seen with the naked eye from Eielson Visitor Center. From that vantage point, the summit of Denali is 33 miles away.
The Muldrow Glacier is one of four confirmed surging glaciers in Denali, among hundreds of glaciers in Denali National Park & Preserve. The upper 27 miles usually flow slowly but constantly downhill, as most glaciers do, according to the National Park Service. The lower seven miles remain stagnant, having been deposited during glacial surges 1,800 years ago. Younger moraines were deposited about 900 years ago during surges in 1905 and 1956-57.
The Muldrow Glacier is on the move again and surging in 2021. A surge is usually a short-lived event when a glacier advances substantially, far faster than normal.
One geologist described it this way: “Think of a surge more as a wave going through the water,” he said. “It’s a wave that propagates down through the glacier.”
The last notable surge took place in 1956-57 when the glacier advanced about four miles in a matter of months.
“There is evidence of a smaller surge in the 1970s,” said Paul Ollig, the park’s acting public information officer. “But we’re still tracking down data on that.”
This most recent surge was noticed in early March by a K2 Aviation pilot but likely began sometime in January.
“He saw some significant new crevassing, especially up near the top of the glacier where it comes down off the face of Denali,” Ollig said. “He started taking a bunch of pictures.”
The photographs show crevassing along the entire length of the glacier. A crevasse is a deep crack or fissure in the glacier.
“It dramatically changes the look of this glacier from its previous quite stagnant appearance,” he said.
Once the National Park Service learned of the surge, researchers there and statewide began collecting data and conducting overflights for a closer look.
According to glaciologists, the surge is not caused by climate change. Instead, it is the result of “the glacier’s unique geographic morphology.” The glacier has about a 50-year surge cycle, Ollig said.
“Ice builds up and then everything just kind of gives and flows dramatically downslope,” he said. “What we think is that this surge is likely hydrological, caused by the interplay of ice building and the supply of water to the base. Water will lubricate it, reduce friction, and that increases the flow of the ice.”
As water melts at the base of the glacier, the glacier flows faster.
“More flowing can increase the pressure of melting, which increases the rate of flow,” he said. “It’s a cool phenomenon.”
Only 1% of glaciers throughout the planet are classified as surge-type glaciers, Ollig added.
The moving ice makes it dangerous for mountaineers traveling on the glacier, due to new crevasses and continual upheaval of the glacier surface.
Two groups that applied for permits to climb the north route of Denali, via the Muldrow Glacier, were notified of the danger and are re-evaluating their plans, Ollig said.
In addition, the surge poses the real possibility of an outburst flood, a rush of water from the terminus of the glacier at the McKinley River.
“That can occur with no warning,” Ollig said. “For obvious safety reasons, backpacking in this area of the park might be restricted.”
Park researchers are setting up cameras focusing on that area, to capture any possible outburst flood on film.
Researchers want the public to know they are not likely to see the glacier move from the park road or from Eielson Visitor Center.
“It’s less than dramatic from that vantage point,” Ollig said. “You might see more ice than you normally would at that section of the terminus, there might be jumbled ice chunks, but it won’t look different from so far away. “
It is likely that the surge will be over by the time the visitor season opens at Denali.
“It usually lasts for a few months, tops,” he said.
Reach columnist/community editor Kris Capps at kcapps@newsminer.com. Follow her at twitter.com/FDNMKris.
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March 21, 2021 at 08:00PM
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Denali's Muldrow Glacier is on the move: Glacier's surges occur naturally but could pose some dangers - Fairbanks Daily News-Miner
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