[Mb-civic] Arctic Ice Cap Shrank Sharply

[Mha Atma Khalsa]

Arctic Ice Cap Shrank Sharply This Summer, Experts Say

 

By ANDREW C. REVKIN
Published: September 28, 2005
 
http://www.nytimes.com/2005/09/28/science/earth/28cnd-
ice.html?ex=1285560000&en=fa8ce530c19444e4&ei=5090&partner=rssuserland&emc=rss

The floating cap of sea ice on the Arctic Ocean shrank
this summer to what is probably its smallest size in a
century, continuing a trend toward less summer ice
that is hard to explain without attributing it in part
to human-caused global warming, various experts on the
region said today.

The findings are consistent with recent computer
simulations showing that a buildup of smokestack and
tailpipe emissions of greenhouse gases could lead to a
profoundly transformed Arctic later this century in
which much of the once ice-locked ocean is routinely
open water in summers.

It also appears that the change is becoming self
sustaining, with the increased open water absorbing
solar energy that would be reflected back into space
by bright white ice, said Ted A. Scambos, a scientist
at the National Snow and Ice Data Center in Boulder,
Colo., which compiled the data along with NASA.

"Feedbacks in the system are starting to take hold,"
Dr. Scambos said. "The consecutive record-low extents
make it pretty certain a long-term decline is
underway."

The North Pole ice cap always grows in winter and
shrinks in the summer, but the new summer low,
measured on Sept. 19th, was 20 percent below the
average minimum ice extent measured from 2000 back to
1978, when precise satellite mapping of the ice began,
the snow and ice center reported.

The difference between the average ice area and the
area that persisted this summer was about 500,000
square miles, or twice the size of Texas , the
scientists said.

This summer was the fourth in a row with ice extents
sharply below the long-term average, said Mark
Serreze, a senior scientist at the snow and ice center
and a professor at the University of Colorado in
Boulder.

A natural cycle in the polar atmosphere, the Arctic
Oscillation, that contributed to the reduction in
Arctic ice in the past was not a significant factor
right now, he said, adding that rising temperatures
driven by accumulating greenhouse-gas emissions had to
be playing a role.

He and other scientists said that there could be more
variability ahead, including some years in which the
sea ice will grow. But they have found few hints that
other factors, like more Arctic cloudiness in a
warming world, might reverse the trend.

"With all that dark open water, you start to see an
increase in Arctic Ocean heat storage," Dr. Serreze
said. "Come autumn and winter that makes it a lot
harder to grow ice, and the next spring you're left
with less and thinner ice. And it's easier to lose
even more the next year."

The result, he said, is that the Arctic is "becoming a
profoundly different place than we grew up thinking
about."

Other experts on Arctic ice and climate disagreed on
details. For example, Ignatius G. Rigor at the
University of Washington said that the change was
likely due to a mix of factors, including residual
influences from the atmospheric cycle.

But he agreed with Dr. Serreze that the influence from
greenhouse gases had to be involved.

"The global warming idea has to be a good part of the
story," Dr. Rigor said. "I think we have a different
climate state in the Arctic now."
 



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