especially vulnerable coastline may
already be feeling the shrink.
That coast, a stretch of the Alaskan
Beaufort Sea west of Kaktovik, has never
been calm. Features such as islands and
points that dotted these shores when
early explorers first mapped the coast
have since disappeared. But shoreline fissures and crags may be growing increasingly more vulnerable. Recently, a team
of U.S. researchers, including Jorgenson,
collected a series of historic aerial photographs from a 60-kilometer span of the
coast dating back to the 1950s and compared the photos with modern images.
When scientists started taking pictures
here, land loss was proceeding at a fast
clip, about seven meters per year. By 2002
to 2007, those rates had doubled to nearly
14 meters per year along these beaches,
Jorgenson, Benjamin Jones of the U.S.
Geological Survey’s Alaska Science Center in Anchorage and colleagues reported
in Geophysical Research Letters in 2009.
“If we see like 15 meters a year …
that’s a very dramatic number,” says
Irina Overeem, a geomorphologist at
the University of Colorado at Boulder
who wasn’t involved in the 2009 study.
“I don’t think there’s many sites around
the world that match that.”
Overeem, who also monitors erosion
in northern Alaska, has lost a lot of
recording equipment to the encroaching
sea. She is attempting to track the culprits
behind the erosion that steals her gear,
and the reasons for that erosion’s accel-
eration. Again, Overeem and other scien-
tists have turned to ice for an explanation.
In this case, though, the responsible ice
doesn’t cover the land. During much
of the year, it’s only accessible by boat.
Fetching storms Melting ice
exposes more water surface. This
extra “fetch” gives waves extra
room to build up — meaning more
storm damage and erosion.
Tracking loss A recent
study along one 60-kilometer
stretch of Alaska’s Beaufort
Sea coast found that mean
annual erosion rates increased
from 6. 8 meters per year from
1955 to 1979 to 13. 6 meters
per year from 2002 to 2007
(detailed erosion rates are
shown at right).
San Francisco last year at a meeting of the
American Geophysical Union.
Less ice also means worse damage
from storms, like the one that inundated
To make a big wave,
Atkinson explains,
winds need a lot of
room to blow. Extensive
sea ice leaves little open
water — or fetch — to
be had, and as a result,
the surf has little
room to gain momentum. “You might
have a 100-mile wind, but if you only
have a mile of open water fetch, you
might only get 3-foot waves,” says
Atkinson. But if the ice drops away tens of
miles, “now the same storm can produce a
much more damaging marine response.”
Because of these ice-erosion connections, how much land the Arctic stands
to lose probably depends on future ice
melting there. And the future looks grim,
says James Overland, an oceanographer
with the National Oceanic and Atmospheric Administration’s Pacific Marine
Environmental Laboratory in Seattle.
2007 was not a good year for ice forecasters such as Overland. A freak weather
pattern sent warm winds blowing north,
melting swaths of sea ice already weakened from years of steady temperature
increases. As a result, summer ice extent
shrank to a record low level, nearly
40 percent below the historic average.
Regions that were once dependably
capped with ice all year turned slushy.
“Essentially, we were really unlucky in
2007,” Overland says.
The coast’s protective blanket may
never recover, Overland says. He suspects
FROM TOP: T. DUBÉ; B.M. JONES ET AL/GEOPH YSICAL RESEARCH LETTERS 2009, © 2009 AMERICAN GEOPHYSICAL UNION,
REPRODUCED/MODIFIED BY PERMISSION OF AMERICAN GEOPHYSICAL UNION
