|
|
ENVIRONMENT: Earth's Arctic Freezer Turning Into Hothouse
By Stephen Leahy
UXBRIDGE, Apr 10 (IPS) - The world is losing its northern freezer as Arctic winter ice is in sharp decline,
NASA scientists reported this week. Even with below average winter
temperatures, Arctic ice is thinner and covers less area than it did a decade ago.
Arctic sea ice is the cooling mechanism for the global climate system. As it
declines and the region warms - already three to five degrees Celsius warmer
- then inevitably there are local, regional and hemispheric climate impacts.
"We’ve already lost one third of the summer ice cover since the 1980s. There
are already impacts from this," says Ron Kwok of NASA's Jet Propulsion
Laboratory in Pasadena.
"A completely ice-free summer by 2013 is not impossible," Kwok said in a
telephone news conference. "You would have been laughed out the room if
you suggested this five years ago."
The new study shows that the maximum extent of the 2008-2009 winter sea
ice cover was the fifth-lowest since researchers began collecting such
information 30 years ago. The past six years have produced the six lowest
maximums in that record.
More stunning, and indicative of the rapid warming of the region, is the
decline in the thick, hard-to-melt multi-year ice, says Walter Meier, research
scientist at the National Snow and Ice Data Centre in Boulder, Colorado.
Multiyear ice is ice that is two or more years old and therefore doesn't melt in
the summer.
"Less than 10 percent is multiyear now. It used to be 30 percent in 1981,"
Meier said at the news conference.
Polar amplification is the reason why climate change is warming the Arctic far
faster than anywhere else. A combination of processes and feedbacks in the
region have resulted a three to five degree Celsius warming already. In 50 to
100 years time if average global temperature rises three degrees Celsius, the
Arctic freezer will be a hothouse - at least 10 degrees Celsius warmer.
"The polar cryosphere has long existed as a buffer against [global] climate
warming to an extent," Dick Peltier, Director of the Centre for Global Change
Science at the University of Toronto, told IPS.
The Earth’s great northern freezer is undergoing "great transformations of
energy" away from cooling and shifting to warming. More ice melt means
more open water resulting in more of the sun’s energy being trapped in the
Arctic Ocean and warming water temperatures. That means winter freeze-up
comes later, the ice is thinner, and more likely to melt when summer returns.
This positive feedback loop is already operating and the meltdown of the
Arctic sea ice looks to be irreversible he says.
"It's a bit like a flywheel now able to turn with reckless abandon."
The loss of Arctic sea ice won’t raise sea levels directly but as it acts to warm
the entire region that will affect the massive Greenland ice sheet. If the whole
ice sheet were to melt it would result in a six to seven-metre sea-level rise.
Recent studies report thinning at the margins of the Greenland ice sheet, an
increased fresh water discharge from outlet glaciers, and a significant
increase in surface melt, NASA reported in a release.
The current Arctic meltdown is already changing the local climate and having
impacts on northern peoples, Meier said.
"No Arctic ice in the summer will result in profound changes," says Peltier.
Meanwhile weather patterns in the Arctic have already changed with a
northward deepening of the North Atlantic Oscillation (NAO), says Peltier. The
NAO controls the strength and direction of westerly winds and storm tracks
across the Arctic and North Atlantic.
The jet stream has also shifted further north as the Arctic warms. The jet
stream is a fast-flowing westward current of air approx 10 kilometres above
the ground. It is the boundary zone between the warm tropical air mass of
the south and the cold polar Arctic air mass. Less ice in the Arctic weakens
the cold polar air and the jet, while continuing its ebb and flow as seen on
daily weather maps, is incrementally pushing northwards altering local
weather patterns.
"There has been a northward shift in precipitation, with more rain falling on
the northern boreal regions while the southern U.S. is becoming drier," says
Peltier. Although those observed changes are not directly attributable to the
Arctic ice loss, but to climate change overall. However there is no doubt that
the Arctic meltdown "will eventually affect our weather," he says.
The rapid warming of the Arctic has happened so quickly that scientists have
only begun to study what the potential implications may be. Chief among
their concerns is the vast region of permafrost that covers one quarter of the
land surface of the Northern hemisphere. The permanently frozen bog and
peatland contains enormous amounts of organic carbon - perhaps enough to
triple the amount currently in the atmosphere, as previously reported by IPS.
As the permafrost melts carbon dioxide and the more potent greenhouse gas
methane is released. And that seems to have been the case during the
extremely warm northern summer of 2007 when global atmospheric methane
levels shot up by several million tonnes after having been stable for more
than a decade. However there is no smoking gun pointing to permafrost.
"Our abilities to detect how much and where methane is being released is
really bad," says Peltier. And there is no "predictive capacity" to get some
insight into what might happen to permafrost and when. The International
Panel on Climate Change (IPCC) has made permafrost a priority for its next
major report in four or five years time, he said. "There is clear potential for
large methane releases."
(END/2009)
|
|
|
|
| |
|
|
What is RSS?
