As if record-breaking losses of sea ice and thawing permafrost weren't enough, climate change is also sweeping parts of the Arctic out to sea. New research in Geophysical Research Letters reports that the rate of erosion along a stretch of Alaska's northeastern coastline has doubled over the past 52 years. Such deterioration of arctic coastlines is likely to have significant impacts on local ecosystems, communities living in the Arctic, and oil and gas development.
Arctic shorelines are especially susceptible to erosion because their sediments are often held together by nothing more than ice. Scientists have been concerned about these fragile coasts, because they will be pounded harder by waves as the sea ice disappears and storms intensify. Warmer water and rising sea levels make matters even worse.
Ground zero might well be the coastline along the Beaufort Sea in northeastern Alaska, where the sediments are particularly ice-rich and the shore unprotected. To find out just how much land was being lost from this area, geographer Benjamin Jones of the U.S. Geological Survey (USGS) Alaska Science Center in Anchorage, Alaska, and his colleagues used old aerial photographs of a 60-kilometer stretch of coastline.
Between 1955 and 1979, the coastline retreated an average of 6.8 meters per year. That annual rate increased 28% over the next 23 years. And from 2002 to 2007, erosion chopped off a whopping 13.6 meters of land per year. During a period of record sea ice loss from 2007 to 2008, 25 meters were eroded from a segment of the coastline. Jones attributes the shift to various effects of climate change: stronger storms, a loss of sea ice, a warmer ocean, and a rise in sea level.
The effects of erosion are already evident: A 1970s petroleum test well was washed out to sea between 2004 and 2005, and an abandoned Inupiaq village is threatened. There are also risks to nesting migratory birds and 45,000 caribou that calve in the area each year, say researchers.
Jerry Brown, a retired geocryologist who studies permafrost and former president of the International Permafrost Association, says that this study quantifies what scientists have been observing for years in coastal erosion. "This particular area might be extreme, but we learn a lot from extremes," he says. Geologist John Mars of USGS in Reston, Virginia, who has previously analyzed this coastline with satellite data but didn't participate in this study, says that Jones's research does a better job than his previous work of identifying more accurate rates of retreat and the increased rate of coastal erosion over the past 5 years.