Muldrow Glacier in Denali National Park is surging:
In early March, pilot Chris Palm, who took the photo above, noticed something very different about Denali Park’s famed Muldrow Glacier. The normally smooth surface of the glacier was broken up by crevasses stretching across the width of Muldrow.
The long awaited surge had begun.
The 39 mile long, Muldrow Glacier last surged in 1957, so scientists were thrilled to study a natural phenomenon that has not occurred here in 64 years.
Surge-type glaciers are relatively rare, with approximately 1% of the glaciers world-wide being surge glaciers. Denali National Park has several, most of which get their start from the face of North America’s tallest peak.
As snow and ice builds up at the higher elevations of a glacier, meltwater is also building up underneath the glacier. This meltwater acts as a lubricant when the weight from above passes equilibrium. The glacier then surges downward at a rate of up to 100 times faster than normal. At some point, the meltwater trapped under the glacier will be released in an outburst flood. Once the water is reduced significantly, the glacier’s surge will slow and it will go back to a state of quiescent (non-surge) once again. Over time, the process repeats itself. Muldrow Glacier has a history of surging roughly every 50 years.
There are two GPS stations on the glacier to monitor its movement. There are also four time-lapse cameras facing different areas of the glacier, including one at the terminus to monitor the glacier’s “bulldozing action”. Another is looking over the McKinley River in order to capture images of the outburst flood. The Alaska Earthquake Center also has a seismic monitoring station, and a sound station has also been installed in an attempt to capture the grinding sound of the surging glacier.
In 1957, most accounts have the surge starting in May, 1956 on Traleika Glacier, which is the main tributary of Muldrow. Muldrow Glacier would advance over 4 miles before the surge ended in September of 1957. Approximately 3.3 cubic kilometers of ice was redistributed from the upper reaches of the glacier to its toe. At the upper levels, the ice thickness had dropped as much as 170 meters, but the toe rose to a 200 foot tall ice wall.
Currently, the Muldrow Glacier is moving between 10 to 20 meters per day, and is only 800 meters short of the 1957 terminus. At the current rate of surge, Muldrow will reach the 1957 distance in June.
All images, photos and maps are courtesy of the NPS; Sources include: NPS – Denali NP&P, Alaska Department of Natural Resources, University of Alaska – Fairbanks