Andrea Thompson livescience.com Yahoo News 15 Dec 09;
SAN FRANCISCO - Time-lapse photography of crumbling Alaskan coastlines is helping scientists understand the "triple whammy" of forces eroding the local landscape: declining sea ice, warming ocean waters and more poundings by waves.
The erosion rates from these forces are greater than anything seen along the world's coastlines, with the coast midway between Alaska's Point Barrow and Prudhoe Bay falling into the ocean in the inland direction by up to one-third the length of a football field annually, scientists have found.
"This is pretty eye-popping," Robert Anderson of the University of Colorado at Boulder said here today at the annual meeting of the American Geophysical Union.
Time-lapse imagery and videos taken by Anderson and his team show how frozen blocks of silt and peat - that contain about 50 percent to 80 percent water ice - are toppled into the Beaufort Sea within a matter of days during the summer months as large waves and warm waters combine to attack the coast.
The dramatic erosion is created by the combination of three main factors: longer ice-free conditions in the summer months (which are lengthening by about two weeks per decade); warmer ocean waters that can melt more of the ice trapped in the coastal soils; and the widening of the gap between the coastline and the sea ice that occurs in the summer months, giving waves more room to batter 12-foot-high (3.5 meters) coastal bluffs.
"What we are seeing now is a triple whammy effect," Anderson said. "Since the summer Arctic sea ice cover continues to decline and Arctic air and sea temperatures continue to rise, we really don't see any prospect for this process ending."
"The landscape is beginning to respond to the acceleration of warming," he said.
The rates of erosion in these areas are several tens of meters per year, compared to other rocky coasts, where erosion rates would be closer to several millimeters or centimeters a year, Anderson said.
"These rates are way out of whack," he said.
This erosion is concerning to scientists not just for the indications it gives of the rate of global warming in the Arctic, but because the area is an important habitat for birds and other wildlife.
While there are no towns in the specific area studied, coastal erosion threatens some abandoned military and petroleum structures. And areas that now aren't as close to the coast could find themselves threatened.
"Even something 1 kilometer [3 miles] away could be dumped into the sea in a matter of years," Anderson said.
You can watch the video at the university's web site: http://www.colorado.edu/news/r/fff17f8947aba3f5e502f0ed30adb9ee.html
Alaska coast erosion threat to oil, wildlife
Yereth Rosen, Reuters 21 Dec 09;
ANCHORAGE, Alaska (Reuters) - A portion of Alaska's North Slope coastline is eroding at a rate of up to 45 feet a year, posing a threat to oil operations and wildlife in the area, according to a new report issued by scientists at the University of Colorado.
Warmer ocean water has thawed the base of frozen bluffs and destroyed natural ice barriers protecting the coast, causing large earth chunks to fall each summer, the scientists said.
"What we are seeing now is a triple whammy effect," study co-author Robert Anderson, an associate professor at the University of Colorado's Department of Geological Sciences, said. "Since the summer Arctic sea ice cover continues to decline and Arctic air and sea temperatures continue to rise, we really don't see any prospect for this process ending."
The scientists studied coastline midway between Point Barrow, the nation's northernmost spot, and Prudhoe Bay, site of the nation's biggest oil fields. The erosion, if it continues, could ultimately be a problem for energy companies such as Exxon Mobil Corp and BP Plc.
Findings were presented last week at the annual meeting of the American Geophysical Union in San Francisco. They backed up other studies of erosion along Alaska's Beaufort Sea coastline.
A study by U.S. Geological Survey scientists published in February found that erosion along a stretch of Alaska coastline during 2002 to 2007 was twice as fast as in the period from 1955 to 1979. That USGS study also found erosion occurring at a rate of 13.6 meters (44.6 feet) annually from 2002 to 2007.
The three-year University of Colorado study aimed to examine how erosion is occurring, said co-author Irina Overeem, a scientist at the University's Institute of Arctic and Alpine Research.
The scientists employed time-lapse photography, global positioning systems, meteorological monitoring, and analysis of sediment and sea-ice distribution.
Photographic images snapped every six hours during the around-the-clock sunlight of summer were particularly dramatic, Overeem told Reuters.
"There's a notching effect that just notches, notches, notches and then topples over," she said. "The cliffs are more than half ice -- they're basically dirty icebergs -- so warm water, stronger waves and higher wave action quickly carves them away," she said.
Although the study area holds no communities, there is infrastructure at risk, mostly abandoned military and oil-field sites and their associated waste dumps, the scientists said. Also at risk are ponds and lakes that support migratory shorebirds.
The threat of collapsing military and oil-field infrastructure, including toxics-laden waste, has prompted several government agencies to launch emergency cleanup programs.
The U.S. Bureau of Land Management since 2005 has cleaned up three old, erosion-threatened wells and plans to start in on a fourth well later this winter, said Wayne Svejnoha, branch chief for energy and minerals. Each well cleanup takes about two months and costs $12 million to $14 million, Svejnoha said.
Erosion threats to shorebirds were confirmed by another federal manager.
"The erosion is very obvious," said Rick Lanctot, Alaska shorebird coordinator for the U.S. Fish and Wildlife Service. In some spots, saltwater has inundated lakes and ponds, killing off plants that birds eat, while heavy wave action has displaced driftwood used as nest sites, said Lanctot, who has worked there since 1991.
(Reporting by Yereth Rosen; editing by Bill Rigby, Gary Hill)
