An already relentless melting of the Arctic greatly accelerated
this summer, a warning sign that some scientists worry could mean
global warming has passed an ominous tipping point. One even
speculated that summer sea ice would be gone in five years.
A picture taken 23 August
2007 shows a glacier seen from the Ice Fjord on the Norwegian
Arctic archipelago of Svalbard. Arctic archipelago of Svalbard
recently experienced its highest temperatures since the end of the
Viking Age around 800 years ago, the Norwegian Polar Institute said
Tuesday.
Greenland's ice sheet melted nearly 19 billion tons more than
the previous high mark, and the volume of Arctic sea ice at
summer's end was half what it was just four years earlier,
according to new NASA satellite data obtained by The Associated
Press.
"The Arctic is screaming," said Mark Serreze, senior scientist
at the government's
snow and ice data center in Boulder, Colo.
Just last year, two top scientists surprised their colleagues by
projecting that the Arctic sea ice was melting so rapidly that it
could disappear entirely by the summer of 2040.
This week, after reviewing his own new data, NASA climate
scientist Jay Zwally said: "At this rate, the Arctic Ocean could be
nearly ice-free at the end of summer by 2012, much faster than
previous predictions."
So scientists in recent days have been asking themselves these
questions: Was the record melt seen all over the Arctic in 2007 a
blip amid relentless and steady warming? Or has everything sped up
to a new climate cycle that goes beyond the worst case scenarios
presented by computer models?
"The Arctic is often cited as the canary in the coal mine for
climate warming," said Zwally, who as a teenager hauled coal. "Now
as a sign of climate warming, the canary has died. It is time to
start getting out of the coal mines."
It is the burning of coal, oil and other fossil fuels that
produces carbon dioxide and other greenhouse gases, responsible for
man-made global warming. For the past several days, government
diplomats have been debating in Bali, Indonesia, the outlines of a
new climate treaty calling for tougher limits on these gases.
What happens in the Arctic has implications for the rest of the
world. Faster melting there means eventual sea level rise and more
immediate changes in winter weather because of less sea ice.
In the United States, a weakened Arctic blast moving south to
collide with moist air from the Gulf of Mexico can mean less rain
and snow in some areas, including the drought-stricken Southeast,
said Michael MacCracken, a former federal climate scientist who now
heads the nonprofit Climate Institute. Some regions, like Colorado,
would likely get extra rain or snow.
More than 18 scientists told the AP that they were surprised by
the level of ice melt this year.
"I don't pay much attention to one year ... but this year the
change is so big, particularly in the Arctic sea ice, that you've
got to stop and say, 'What is going on here?' You can't look away
from what's happening here," said Waleed Abdalati, NASA's chief of
cyrospheric sciences. "This is going to be a watershed year."
2007 shattered records for Arctic melt in the following
ways:
? 552 billion tons of ice melted this summer from the Greenland
ice sheet, according to preliminary satellite data to be released
by NASA Wednesday. That's 15 percent more than the annual average
summer melt, beating 2005's record.
? A record amount of surface ice was lost over Greenland this
year, 12 percent more than the previous worst year, 2005, according
to data the University of Colorado released Monday. That's nearly
quadruple the amount that melted just 15 years ago. It's an amount
of water that could cover Washington, D.C., a half-mile deep,
researchers calculated.
? The surface area of summer sea ice floating in the Arctic
Ocean this summer was nearly 23 percent below the previous record.
The dwindling sea ice already has affected wildlife, with 6,000
walruses coming ashore in northwest Alaska in October for the first
time in recorded history. Another first: the Northwest Passage was
open to navigation.
? Still to be released is NASA data showing the remaining Arctic
sea ice to be unusually thin, another record. That makes it more
likely to melt in future summers. Combining the shrinking area
covered by sea ice with the new thinness of the remaining ice,
scientists calculate that the overall volume of ice is half of
2004's total.
? Alaska's frozen permafrost is warming, not quite thawing yet.
But temperature measurements 66 feet deep in the frozen soil rose
nearly four-tenths of a degree from 2006 to 2007, according to
measurements from the University of Alaska. While that may not
sound like much, "it's very significant," said University of Alaska
professor Vladimir Romanovsky.
? Surface temperatures in the Arctic Ocean this summer were the
highest in 77 years of record-keeping, with some places 8 degrees
Fahrenheit above normal, according to research to be released
Wednesday by University of Washington's Michael Steele.
Greenland, in particular, is a significant bellwether. Most of
its surface is covered by ice. If it completely melted -- something
key scientists think would likely take centuries, not decades -- it
could add more than 22 feet to the world's sea level.
However, for nearly the past 30 years, the data pattern of its
ice sheet melt has zigzagged. A bad year, like 2005, would be
followed by a couple of lesser years.
According to that pattern, 2007 shouldn't have been a major melt
year, but it was, said Konrad Steffen, of the University of
Colorado, which gathered the latest data.
"I'm quite concerned," he said. "Now I look at 2008. Will it be
even warmer than the past year?"
Other new data, from a NASA satellite, measures ice volume. NASA
geophysicist Scott Luthcke, reviewing it and other Greenland
numbers, concluded: "We are quite likely entering a new
regime."
Melting of sea ice and Greenland's ice sheets also alarms
scientists because they become part of a troubling spiral.
White sea ice reflects about 80 percent of the sun's heat off
Earth, NASA's Zwally said. When there is no sea ice, about 90
percent of the heat goes into the ocean which then warms everything
else up. Warmer oceans then lead to more melting.
"That feedback is the key to why the models predict that the
Arctic warming is going to be faster," Zwally said. "It's getting
even worse than the models predicted."
NASA scientist James Hansen, the lone-wolf researcher often
called the godfather of global warming, on Thursday was to tell
scientists and others at the American Geophysical Union scientific
in San Francisco that in some ways Earth has hit one of his
so-called tipping points, based on Greenland melt data.
"We have passed that and some other tipping points in the way
that I will define them," Hansen said in an e-mail. "We have not
passed a point of no return. We can still roll things back in time
-- but it is going to require a quick turn in direction."
Last year, Cecilia Bitz at the University of Washington and
Marika Holland at the National Center for Atmospheric Research in
Colorado startled their colleagues when they predicted an Arctic
free of sea ice in just a few decades. Both say they are surprised
by the dramatic melt of 2007.
Bitz, unlike others at NASA, believes that "next year we'll be
back to normal, but we'll be seeing big anomalies again, occurring
more frequently in the future." And that normal, she said, is still
a "relentless decline" in ice.
(China Daily December 12, 2007)
