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By KARL RITTER, Associated Press Writer Karl Ritter, Associated Press Writer
Fri Sep 11, 5:30 am ET
HELHEIM GLACIER, Greenland Suddenly and without warning, the gigantic river
of ice sped up, causing it to spit icebergs ever faster into the ocean off
southeastern Greenland.
The Helheim Glacier nearly doubled its speed in just a few years, flowing
through a rift in the barren coastal mountains at a stunning 100 feet (30
meters) per day.
Alarm bells rang as the pattern was repeated by glaciers across Greenland: Was
the island's vast ice sheet, a frozen water reservoir that could raise the sea
level 20 feet (6 meters) if disgorged, in danger of collapse?
Half a decade later, there's a little bit of good news and a lot of
uncertainty.
"It does seem that the very rapid speeds were only sustained for a short period
of time, although none of these glaciers have returned to the 'normal' flow
speeds yet," says Gordon Hamilton, a glaciologist from the University of Maine
who's clocked Helheim's rapid advance using GPS receivers on site since 2005.
Understanding why Greenland's glaciers accelerated so abruptly in the first
half of the decade and whether they are now slowing down is crucial to the
larger question of how fast sea levels will rise as the planet warms.
The issue has gained urgency as scientists rush to supply their latest findings
in time for negotiations on a new global climate pact, set for December in
Copenhagen.
Scientists say the Greenland ice sheet, which is up to 2 miles (3 kilometers)
thick and covers an area almost the size of Mexico, is losing about 7 billion
cubic feet (200 million cubic meters) of ice a year the equivalent of 80,000
Olympic-sized swimming pools.
That means snowfall on top of the ice sheet is not enough to replace what is
lost through surface melting and ice chucked out in the fjords by
faster-flowing glaciers. In the process, sea levels rise as towering icebergs
plunge into the Atlantic Ocean and displace water much like an ice cube
dropped into a drink.
The dynamics of the ice sheet on Greenland and the much larger ones on
Antarctica were not included in sea level rise projections by the U.N. expert
panel on climate change in 2007 because the phenomenon was poorly mapped at the
time.
The picture of what happened in Greenland is just starting to come together,
and scientists are still in the dark about how the underlying causes were set
in motion, how much was owed to natural variances and how much to man's
tinkering with the global climate system.
"This is like medical science in the 15th century," says David Holland,
director of the Center for Atmosphere Ocean Science at New York University.
"It's going to take a while to find out what's going on with the patient here."
The most popular explanation is that the patient Greenland's ice sheet
contracted its ailment not from warmer air, but a warmer ocean.
Scientists earlier believed that the biggest factor for the faster flow speeds
was meltwater seeping down to the base of the glaciers, lubricating the
bedrock. They're now shifting attention to ocean currents believed to have sent
pulses of warmer water from southern latitudes to Greenland's glacial fjords.
Holland found that such water was reaching the edge of western Greenland's
biggest glacier, the Sermeq Kujalleq. A team led by Fiamma Stranneo, of the
Woods Hole Oceanographic Institution in Massachusetts, made a similar discovery
last month with probes plunged into the chilly depths of Sermilik fjord, where
the Helheim Glacier ends.
"We've had a confirmation that the waters are really coming up to the glacier,"
Stranneo says, her voice nearly drowned by engine noise aboard the Arctic
Sunrise, a Greenpeace ship that offered her a chance to test her hypothesis.
"This is the first time that we've seen it in these southeast glacial fjords."
In July, the world's oceans were the warmest in almost 130 years of
record-keeping. Meteorologists say a combination of factors are at work,
including a natural El Nino system, man-made global warming and a dash of
random weather.
Coinciding with the shrinking of sea ice on the North Pole and the thawing of
the Arctic permafrost, the discovery of Greenland's runaway glaciers earlier
this decade raised a sense of urgency among scientists studying the impact of
climate change on the frozen north.
It has also been used by advocacy groups like Greenpeace to stress the
importance of reaching a deal in Copenhagen to limit global greenhouse
emissions.
The U.N.'s top climate official, Yvo de Boer, said Friday that negotiations on
fighting climate change are moving so slowly that it will be impossible to
reach a comprehensive deal by December. He said the Copenhagen meeting should
aim instead to agree on "key cornerstones" of emissions cuts and how to finance
them.
Even a partial melt of the ice sheet could have a big impact on sea levels,
with dire consequences for low-lying areas from Florida to Bangladesh.
The 2007 report by the Intergovernmental Panel on Climate Change projects a sea
level rise of 7 to 24 inches (20 to 60 centimeters) this century. Adding the
potential impact of ice sheets in Greenland and Antarctica, many scientists
have estimated the rise will be double.
"It doesn't sound like a lot, but it's an important difference by the way you
sort of deal with that issue," says Hamilton, taking a break from his GPS
measurements on a plateau overlooking Helheim's styrofoam-like bed of jagged
ice. "How you engineer for a sea level rise of 30 centimeters is quite
different as to how you would ... deal with a sea level rise of 1 meter."
His latest measurements indicate that Helheim is flowing at 6.5 miles (10.5
kilometers) per year, slightly down from its peak in 2005 but still 50 percent
faster than its normal pace.
Other researchers say some but not all of Greenland's glaciers have shown
similar slowdowns in recent years, suggesting that a sudden, dramatic increase
in flow speeds may not be such a cataclysmic and irregular phenomenon after
all.
Still, the flows remain fast enough to yield a net loss of mass from the ice
sheet. And if the world continues to warm, sudden spurts of glacial
acceleration may become more frequent, draining the inland ice until it,
eventually, collapses.
No one can say with certainty whether that will take 100 years, or 1,000.
"It's a little embarrassing to know so little," says Ian Howat, a glaciologist
based at Ohio State University. "We won't know it's going until it's gone. It
feels like that a little bit."