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Muldrow Glacier in Denali National Park and Preserve stops surging

Muldrow Glacier near the beginning of the surge.
Muldrow Glacier near the beginning of the surge.
Published: Sep. 3, 2021 at 5:32 PM AKDT
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ANCHORAGE, Alaska (KTUU) - The Muldrow Glacier in Denali National Park began surging in December 2020 and it stopped surging on July 21, 2021.

“Typically surges stop really fast and it corresponds with an outburst flood,” Chad Hults, regional geologist for Alaska National Park Service said. “What we think is, the water that’s under the glacier that’s basically lubricating the base and decoupling it from the ground, allows it to move really fast and surge, and once that water releases, then it grounds out, basically.”

Because the Muldrow Glacier has surged before, researchers were expecting it to surge again. They placed equipment on and around the glacier to monitor and observe the surging glacier’s movements.

“Surges aren’t well understood,” Hults said. “What their mechanisms are, why glaciers surge. They know there’s water associated and decoupling of the base and build-up of ice in the upper reaches that builds potential energy. At some point, the water retained in the ice becomes too much for it to hold that back and it releases all that energy in a surge. We were talking to the glaciologists at USGS and UAF, they were saying one of the key things they wanted to understand is how surges ended.”

The equipment, including two GPS units placed on the toe of the glacier and in the middle of the glacier, will help that understanding.

“The toe of the glacier had stopped around July 21, but the upper glacier especially up in the Traleika, a tributary of the Muldrow, was still surging at about 10 to 15 meters per day and then the main stem was moving about two and a half meters per day,” Hults said.

Data and time-lapses of the glacier are still being analyzed. One camera took a picture of the toe of the glacier every day. The movement of the glacier is clearly visible as the pictures move from one to the next. The camera changes angle dramatically at one point.

Hults says that’s because a bear knocked it over shortly after the surge stopped so they didn’t capture the full glacial outburst.

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