Antarctic Sea Ice Reaches New
Maximum Extent
October 11, 2012
acquired September 26, 2012
Two weeks after a new record
was set in the Arctic Ocean for the least amount of sea ice coverage in the
satellite record, the ice surrounding Antarctica reached its annual winter
maximum—and set a record for a new high. Sea ice extended over 19.44 million
square kilometers (7.51 million square miles) in 2012, according to the
National Snow and Ice Data Center (NSIDC). The previous record of 19.39
million kilometers (7.49 million square miles) was set in 2006.
The map above shows sea ice
extent around Antarctica on September 26, 2012, when ice covered more of the
Southern Ocean than at any other time in the satellite record. The map is
based on an NSIDC analysis of data from the Special Sensor Microwave/Imagers
flown in the Defense Meteorological Satellite Program. Land is dark gray, and
ice shelves—which are attached to land-based glaciers but floating on the
ocean—are light gray. The yellow outline shows the median sea ice extent in
September from 1979 to 2000. Sea ice extent is defined as the total area in
which the ice concentration is at least 15 percent.
The graph of NSIDC data shows
the maximum extent for each September since 1979 in millions of square
kilometers. There is a lot of variability from year to year, though the
overall trend shows growth of about 0.9 percent per decade.
According to a recent study by
sea ice scientists Claire Parkinson and Donald Cavalieri of NASA’s Goddard
Space Flight Center, Antarctic sea ice increased by roughly 17,100 square
kilometers per year from 1979 to 2010. Much of the increase, they note,
occurred in the Ross Sea, with smaller increases in Weddell Sea and Indian
Ocean. At the same time, the Bellinghausen and Amundsen Seas have lost ice.
“The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen
Seas region and increasing ice coverage in the Ross Sea region is suggestive
of changes in atmospheric circulation,” they noted.
“The year 2012 continues a
long-term contrast between the two hemispheres, with decreasing sea ice
coverage in the Arctic and increasing sea ice coverage in the Antarctic,”
Parkinson added. “Both hemispheres have considerable inter-annual variability,
so that in either hemisphere, next year could have either more or less sea ice
than this year. Still, the long-term trends are clear, but not equal: the
magnitude of the ice losses in the Arctic considerably exceed the magnitude of
the ice gains in the Antarctic.”
On their Arctic Sea Ice News
and Analysis blog, scientists from the University of Colorado wrote:
“Comparing winter and summer sea ice trends for the two poles is problematic
since different processes are in effect. During summer, surface melt and
ice-albedo feedbacks are in effect; winter processes include snowfall on the
sea ice, and wind. Small changes in winter extent may be a more mixed signal
than the loss of summer sea ice extent. An expansion of winter Antarctic ice
could be due to cooling, winds, or snowfall, whereas Arctic summer sea ice
decline is more closely linked to decadal climate warming.”
NASA Earth Observatory images by Jesse Allen, using DMPS SSMIS ice
concentration data provided courtesy of the
National Snow and Ice Data Center (NSIDC). Caption by Michael Carlowicz
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