livescience.com Yahoo News 18 Feb 09;
Most of California isn't falling into the sea yet, but big parts of Alaska are.
In a possible sign of things to come, erosion of a stretch of Alaska's coast surged in recent years to more than double the average historical rate, threatening some towns, a new study finds. The loss of land is documented in photos that show newly collapsed sections of permafrost coastline as well as decades-old artifacts that have slipped into the sea.
Scientists caution that the study does not include the entire coastline, but they said the shift might be due to declining Arctic sea ice extent, increasing summertime sea-surface temperatures, the rising sea level, and increases in storm power and corresponding wave action.
"These factors may be leading to a new era in ocean-land interactions that seem to be repositioning and reshaping the Arctic coastline," the scientists write in the Feb. 14 issue of the journal Geophysical Research Letters.
The details
The study involved a 64-kilometer (40-mile) stretch of the Beaufort Sea. Researchers compared the period 2002 through 2007 to average erosion rates during two previous periods.
The details:
Average annual erosion rates along the area studied had already climbed from about 20 feet (6.1 m) per year during the 1950, 60s and 70s to 28 feet (8.5m) per year in the period from the late-1970s to the early 2000s. The most recent erosion rates reached an average of 45 feet (14 meters) per year during the 2002 to 2007 period, said Benjamin Jones, a geologist with the U.S. Geological Survey in Anchorage.
They also documented sections of coastline that eroded more than 80 feet (24 meters) during 2007 alone.
The researchers caution that the pattern may not be representative of the overall Arctic. However, it may well forecast the future pattern of coastline erosion in the region, they said.
"This segment of coastline has historically eroded at some of the highest rates in the circum-Arctic, so the changes occurring on this open-ocean coast might not be occurring in other Arctic coastal settings," Jones said. But Arctic climate change is leading to rapid and complex environmental responses in both terrestrial and marine ecosystems in ways that will almost certainly affect the rate and pattern of coastline erosion in the Arctic, the authors write.
Interestingly, there were no westerly storm events during the summer of 2007, traditionally thought to be the drivers of coastal erosion in this region the Arctic. However, 2007 did boast the minimum arctic sea-ice extent and the warmest ocean temperatures on record.
Slipping into the sea
Jones and his coauthors verified in another recent study the disappearance of cultural and historical sites along the same stretch of the Beaufort Sea. Those sites include Esook, a turn-of-the-century trading post now buried in the sea and Kolovik (Qalluvik), an abandoned Inupiaq village site that may soon be lost.
At another site, near Lonely, Alaska, Jones snapped a picture of a wooden whaling boat that had rested on a bluff overhanging the ocean for nearly a century. A few months later the boat had washed away to sea. That study was published in the journal Arctic.
"The recent trends toward warming sea-surface temperatures and rising sea-level may act to weaken the permafrost-dominated coastline by helping more quickly thaw ice-rich coastal bluffs and may potentially explain the disproportionate increase in erosion along ice-rich coastal bluffs relative to ice-poor coastal bluffs that we documented in our study," Jones said.
"Any increases in already rapid rates of coastal retreat will have further ramifications on Arctic landscapes - including losses in freshwater and terrestrial wildlife habitats, in subsistence grounds for local communities, and in disappearing cultural sites," he said, "as well as adversely impacting coastal villages and towns. In addition, oil test wells are threatened."
Alaska Coasts Melting -- And Not Just the Ice
Rebecca Carroll, National Geographic News 20 Feb 09;
Part of Alaska's coast is drifting into the sea at twice the rate it has in the past, reshaping the Arctic shoreline, a new study says.
The trend could seriously threaten the area's caribou and other wildlife, as well as local landmarks that document human settlements.
Some stretches of the state's northern shore along the Beaufort Sea receded by more than 80 feet (25 meters) in summer 2007 alone, when Arctic sea ice was at a record low.
In the past, spurts of erosion had often been linked to storms, but there were no major storms in 2007. That suggests "a shift in the forces driving erosion," said lead author Benjamin Jones, a research geographer at the U.S. Geological Survey.
One major force now is global warming, according to the research.
The study of the 40-mile (64-kilometer) stretch of coast was published this week in the journal Geophysical Research Letters.
Out to Sea
Warming air and sea temperatures are melting the ice in the region's permafrost, or perpetually frozen earth. The meltwater then streams over the land and melts more permafrost, carrying sediment into the sea as it goes.
From 2002 to 2007, the melting ice caused the coast to disappear at a rate of about 45 feet (14 meters) a year. That's up from an annual average of 30 feet (9 meters) between 1979 and 2002 and 20 feet (6 meters) between 1955 and 1979.
Remains of the ghost town of Esook, a hundred-year-old trading post, have been buried underwater as a result of the erosion, Jones said.
And near the town of Lonely, Jones took a picture of a whaling boat that a few months later was swallowed by the sea after nearly a century on shore.
The erosion also threatens oil wells. At least one has already been lost since 2002, and another will soon be gone, if the melting continues at these rates.
Especially Vulnerable
Larry Hinzman, director of the International Arctic Research Center in Fairbanks, Alaska, said the permafrost in this region has a considerable amount of ice, which is one reason it is melting so fast.
"If it were a different soil type, it would have less ice and would not erode so quickly," said Hinzman, who was not involved with the research.
Hinzman said the findings "would not be representative of the whole Arctic, but there are many places in the Arctic where the permafrost does contain similarly massive amounts of ice.
"This is not an unusual landscape feature in Alaska, Canada, or Siberia, but it would be unusual in Greenland, Iceland, and [the Swedish archipelago] Svalbard," he said.
The researchers call for more study of the erosion patterns so that preservation plans can be devised and new development can avoid early demise.
"Erosion is a natural process, and it is likely that this coastline has experienced erosion for quite some time," Jones said. It's the speed at which it is now occurring that worries researchers.
