NASA Examines Arctic Sea Ice Changes Leading to Record Low In 2007
- From: baalke@xxxxxxxxxxxxx
- Date: Mon, 01 Oct 2007 14:33:32 -0700
Oct. 1, 2007
Tabatha Thompson
Headquarters, Washington
202-358-3895
tabatha.thompson-1@xxxxxxxx
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
alan.buis@xxxxxxxxxxxx
RELEASE: 07-216
NASA EXAMINES ARCTIC SEA ICE CHANGES LEADING TO RECORD LOW IN 2007
WASHINGTON - A new NASA-led study found a 23-percent loss in the
extent of the Arctic's thick, year-round sea ice cover during the
past two winters. This drastic reduction of perennial winter sea ice
is the primary cause of this summer's fastest-ever sea ice retreat on
record and subsequent smallest-ever extent of total Arctic coverage.
A team led by Son Nghiem of NASA's Jet Propulsion Laboratory,
Pasadena, Calif., studied trends in Arctic perennial ice cover by
combining data from NASA's Quick Scatterometer (QuikScat) satellite
with a computing model based on observations of sea ice drift from
the International Arctic Buoy Programme. QuikScat can identify and
map different classes of sea ice, including older, thicker perennial
ice and younger, thinner seasonal ice. Between winter 2005 and winter
2007, the perennial ice shrunk by an area the size of Texas and
California combined. This severe loss continues a trend of rapid
decreases in perennial ice extent in this decade. Study results will
be published Oct. 4 in the journal Geophysical Research Letters.
The scientists observed less perennial ice cover in March 2007 than
ever before, with the thick ice confined to the Arctic Ocean north of
Canada. Consequently, the Arctic Ocean was dominated by thinner
seasonal ice that melts faster. This ice is more easily compressed
and responds more quickly to being pushed out of the Arctic by winds.
Those conditions facilitated the ice loss, leading to this year's
record low amount of total Arctic sea ice.
Nghiem said the rapid decline in winter perennial ice the past two
years was caused by unusual winds. "Unusual atmospheric conditions
set up wind patterns that compressed the sea ice, loaded it into the
Transpolar Drift Stream and then sped its flow out of the Arctic," he
said. When that sea ice reached lower latitudes, it rapidly melted in
the warmer waters.
"The winds causing this trend in ice reduction were set up by an
unusual pattern of atmospheric pressure that began at the beginning
of this century," Nghiem said.
The Arctic Ocean's shift from perennial to seasonal ice is
preconditioning the sea ice cover there for more efficient melting
and further ice reductions each summer. The shift to seasonal ice
decreases the reflectivity of Earth's surface and allows more solar
energy to be absorbed in the ice-ocean system.
The perennial sea ice pattern change was deduced by using the buoy
computing model infused with 50 years of data from drifting buoys and
measurement camps to track sea ice movement around the Arctic Ocean.
193,000 square miles each decade. Since 2000, that rate of declineFrom the 1970s through the 1990s, perennial ice declined by about
has nearly tripled.
Results from the buoy model were verified against the past eight
years
of QuikScat observations, which have much better resolution and
coverage. The QuikScat data were verified with field experiments
conducted aboard the U.S. Coast Guard icebreaker Healy as well as by
sea ice charts derived from multiple satellite data sources by
analysts at the National Oceanic and Atmospheric Administration's
National Ice Center in Suitland, Md.
The new study differs significantly from other recent studies that
only looked at the Arctic's total sea ice extent. "Our study applies
QuikScat's unique capabilities to examine how the composition of
Arctic sea ice is changing, which is crucial to understanding Arctic
sea ice mass balance and overall Arctic climate stability," Nghiem
said.
Pablo Clemente-Col?n of the National Ice Center said the rapid
reduction of Arctic perennial sea ice requires an urgent reassessment
of sea ice forecast model predictions and of potential impacts to
local weather and climate, as well as shipping and other maritime
operations in the region. "Improving ice forecast models will require
new physical insights and understanding of complex Arctic processes
and interactions."
Other organizations participating in the study include the University
of Washington's Polar Science Center, Seattle, and the U.S. Army Cold
Regions Research and Engineering Laboratory, Hanover, N.H.
Media also may contact: Sandra Hines, University of Washington,
206-543-2580; Marie Darling, U.S. Army Cold Regions Research and
Engineering Laboratory, 603-646-4292; Lt. James Brinkley, National
Ice Center, 301-394-3018; and Peter Weiss, American Geophysical
Union, Washington, 202-777-7507.
For more information about QuikScat, visit:
http://winds.jpl.nasa.gov/missions/quikscat/index.cfm
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