By Sid Perkins
Aerial photographs taken over the past 50 years show that Alaska’s coastlines of permafrost aren’t that permanent after all.
The constant pounding of surf sculpts shorelines in the lower 48 United States year-round, but along Alaska’s northern coast, erosive wave action is limited to the 3-to-4-month period when the waters are icefree.
Using aerial and satellite photographs, researchers calculated erosion rates along a 10-kilometer section of the shore of Elson Lagoon, near Barrow.
Between 1979 and 2000, the surf chewed away about 1.3 meters of shore each year, says Jerry Brown, an analyst with the International Permafrost Association in Woods Hole, Mass. This annual rate of erosion in northern Alaska is comparable to those experienced elsewhere in the United States (SN: 7/8/00, p. 20).
On the northernmost section of coast that the researchers analyzed, about 0.6 m of beach on average was lost to the surf each year between 1948 and 1997. Then, between 1997 and July 2000, the average annual rate jumped to 1.5 m, Brown notes.
Although erosion seems to have accelerated recently, Brown and his colleagues say the recent losses fall within the normal variation seen along this coastline in the past. More analysis would be needed before anyone could pin the apparent surge in erosion on factors associated with global warming.
