http://www.cnn.com/2003/TECH/science/10/24/arctic.warming.ap/index.html
Arctic
being 'transformed' by warming
Friday, October 24, 2003 Posted: 1:01 PM EDT (1701 GMT)
WASHINGTON (AP) --
NASA scientists released new evidence this week
that the Arctic region is warming up and its sea ice cover is
diminishing, with implications for further climate change throughout
the globe.
Satellite data compiled
by Josefino Comiso, a senior research
scientist at the National Aeronautics and Space Administration's
Goddard Space Flight Center, show that compared with the 1980s,
surface temperatures across most of the Arctic warmed significantly
in the last decade, with the biggest temperature increases occurring
over North America.
"Previously, similar
studies used data from very few points scattered
in various parts of the Arctic region," Comiso said. "These
results
show the large spatial variability that only satellite data can
provide."
When compared with
ground-based surface temperatures, the rate of
warming in the Arctic between 1981 and 2001 was eight times the
rate of warming over the last 100 years, said Comiso, whose work
will be published November 1 in the American Meteorological Society's
Journal of Climate. "The Arctic is in the process of being
transformed,"
he said.
The data came from
thermal infrared images taken by polar-orbiting
satellites run by the National Oceanic and Atmospheric Administration.
Researchers found that
warming is prevalent over most of the Arctic
-- some areas bucked the trend, including Greenland, where temperatures
appear to be cooling by about 0.2 degrees per year.
Springtime arrived
earlier and was warmer, while warmer autumns
lasted longer. Most important, temperatures increased by an average
of just more than 2 degrees Fahrenheit per decade over sea ice
during Arctic summers.
This summer, a lengthened
melt season appears to be affecting
the volume and extent of permanent sea ice.
Another NASA-funded
researcher, Mark Serreze of the University
of Colorado-Boulder, reported Thursday that the extent of Arctic
summer sea ice in 2002 reached the lowest level ever recorded
by satellites.
"It appears that
the summer of 2003, if it does not set a new
record, will be very close to the levels of last year," Serreze
said.
"How much of this
warming is due to natural fluctuations and
how much is caused by human activity, we don't really know,"
he added. "But the fact is, the climate is changing, and
in the Arctic it is changing rapidly."
Last month, U.S-Canadian
researchers reported that the Arctic's
largest ice shelf, the 270-square mile Ward Hunt Ice Shelf along
the north shore of Ellesmere Island, had fractured for the first
time in several thousand years, draining a freshwater lake that
it had contained and raising the prospect that it could break
into large icebergs like those seen from disintegrating Antarctic
ice shelves.
And a team of Chinese
scientists who completed a 74-day Arctic
expedition in September found that the thickness of the sea
ice now averages 8.8 feet, down from an average of more than
15 feet in the 1980s.
Beyond having more
open water and accelerating local changes,
such as erosion, in the Arctic, warming trends and changes
in ice cover could greatly affect ocean climate processes,
said Michael Steele, an oceanographer at the University of
Washington, Seattle.
Liquid water absorbs
more of the sun's energy rather than
reflecting it away from the surface as ice does. That means
the Arctic could get even warmer, and even more ice could melt.
Steele said such dynamics could change the temperature of ocean
layers; impact ocean circulation and salinity; change marine
habitats; and affect shipping.
Ocean circulation changes,
particularly in the Arctic and
North Atlantic, can affect weather patterns over much of
the globe.
For instance, Chinese
scientists have already found a link
between sea ice cover and temperature and rainfall in the
Yangtze River basin during the rainy season.
And circulation around
the Arctic for the past 20 years or
so has been in a general pattern that allows more frequent
bursts of cold air to move into the heart of North America
during the winter, noted David Rind, a senior researcher
at NASA's Goddard Institute of Space Studies in New York.
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