* NASA says 97 percent of icy island's surface thawed in
* Sea route from Europe toward Pacific is largely ice free
* No prediction on possible opening of Northwest Passage
By Deborah Zabarenko
WASHINGTON, July 25 For a few days this month,
NASA's images of the Greenland ice sheet turned red, indicating
that for a while, almost the entire surface of the vast frozen
island was melting.
The big melt in Greenland is part of an overall picture of
an unusually warm season across the Arctic, with much of the sea
route from Western Europe to the Pacific as free of ice in July
as it normally would be by summer's end, the chief of the U.S.
National Snow and Ice Data Center said on Wednesday.
On an average summer, about half of Greenland's surface ice
melts, according to NASA. This summer, satellites showed about
97 percent of the ice sheet thawed at some point in mid-July.
The change was swift, as seen in images posted here
On July 8, there was a big white area in the middle of the
image, indicating that 40 percent of Greenland's surface had
thawed; by July 12, virtually the whole island was pictured as
red, showing widespread defrosting.
For Mark Serreze, director and senior research scientist at
the Colorado-based National Snow and Ice Data Center, one
interesting aspect of the Greenland event is its relative
This kind of comprehensive surface melting might happen
about every 150 years or so in Greenland, which would make this
year unusual but not unprecedented, Serreze said by telephone.
However, he said, most of the previous events were clustered
around a period 7,000 years ago known as the Holocene Thermal
Maximum, when variations in the sun's tilt on its axis sent more
sunshine to extreme northern latitudes, warming them up.
There is no such solar tilt going on now, but the melt is
occurring just the same. The NASA report, released Tuesday,
followed a report last week that showed Greenland's Petermann
Glacier breaking off an iceberg almost twice the size of
Manhattan, or 70 square miles (181 square km).
HOLES IN THE ICE
"What we're seeing over Greenland now is really just part of
this much bigger picture of a very warm melting summer in the
Arctic," Serreze said.
He said the sea ice across much of the Arctic is in a "sorry
state" - thinning, with Swiss-cheese-like holes that can be seen
in high-resolution satellite images.
When Greenland's land-based ice sheet melts, it can have an
effect on sea levels. When the sea ice across the Arctic melts,
it has little impact on sea levels but a powerful impact on
weather in the Northern Hemisphere, leading some climatologists
to call the Arctic Earth's air conditioner.
Right now, Serreze said, Arctic sea ice is at the extreme
low end of the satellite record for this time of year, and on
track to be similar to 2007, when Arctic ice shrank to its
smallest size in the satellite record and probably the smallest
size in hundreds of years.
Satellites started monitoring the Arctic in 1979; ship and
aerial observation before that provides an accurate record for
the last 60 years or so. To check on ice cover before that,
scientists examine ice cores and other evidence.
The so-called Northwest Passage, a water route from the
Atlantic to the Pacific that winds through the Arctic, first
opened up in 2007. Serreze would not speculate about whether
this route will be open this year, saying it would depend on
wind and currents in the region. He said ice cover in the
Chukchi Sea off the Alaskan coast is near normal.
However, the passage eastward from the North Atlantic to the
Pacific shows open water as far north as it would normally be
during September, typically the month when Arctic sea ice hits
its low ebb.
More information on Arctic sea ice is available online at nsidc.org/arcticseaicenews/
(Reporting By Deborah Zabarenko, Environment Correspondent;
Editing by Fred Barbash and Bill Trott)