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SELAWIK: Alaska’s Largest River Thaw Slump Still Eroding
Alaska Region, August 2, 2010
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The headwall of the Selawik slump towers 70 feet high, constantly dropping thawing sediment to the slump floor. July 2010. Photo by Susan Georgette.
The headwall of the Selawik slump towers 70 feet high, constantly dropping thawing sediment to the slump floor. July 2010. Photo by Susan Georgette. - Photo Credit: n/a
Dr. Joel Rowland prepares to take permafrost depth measurements along the thaw slump's headwall. July 2010. Photo by Susan Georgette.
Dr. Joel Rowland prepares to take permafrost depth measurements along the thaw slump's headwall. July 2010. Photo by Susan Georgette. - Photo Credit: n/a

A large “thaw slump” created by permafrost failure occurred on the upper Selawik River in northwest Alaska in 2004. Since that time the slump has seasonally transformed the once clear river into a turbid (muddy) one for many miles downstream. The largest of its kind in Alaska, the slump has attracted the attention of geologists, hydrologists, fisheries biologists, and other scientists interested in understanding the dynamics and impacts of this event.

In July, Selawik Refuge staff accompanied two geologists on field investigations of the slump. For a third year, Dr. Benjamin Crosby from Idaho State University continued to document the rates and mechanisms of slump growth, the character of sediment released into the river and its impact on river function, and the potential for similar features in the drainage. Dr. Joel Rowland of Los Alamos National Lab initiated studies on Arctic river bank erosion and river mobility and on landsurface failures modeling. The slump, especially its headwall, continues to actively thaw and expand.

Access to the thaw slump is not easy. A floatplane dropped off the research crew on a tundra lake, where they portaged their gear to the river’s edge, assembled “folding” canoes, and paddled 25 miles over two days to the slump. After 2-3 days of on-site research, the crew canoed another 25 miles, stopping along the way at additional research sites, then disassembled the boats and portaged the gear to another tundra lake for a floatplane pick-up.

In the past 50 years, Alaska has warmed at more than twice the rate of the rest of the United States’ average. These higher temperatures contribute to permafrost warming, which can create dramatic changes in both hillslope stability and river dynamics. The Selawik River thaw slump presents an unusual opportunity to study this harbinger of climate change. Research on the slump is expected to continue for many years into the future.

 


Contact Info: Susan Georgette, 907-442-3799 ext 16, susan_georgette@fws.gov



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