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.”
References
- Parkinson, C.L., and D.J. Cavalieri (2012, August 15) Antarctic sea ice variability and trends, 1979-2010. The Cryosphere, Volume 6, pages 871-880.
- NASA Earth Observatory (2009, April 20) Sea Ice.
- NASA Earth Observatory (n.d.) World of Change: Antarctic Sea Ice.
- NASA (2009, September 1) What's Holding Back Antarctic Sea Ice from Melting. Accessed October 10, 2012.
- National Snow and Ice Data Center (2012, October 2) Poles Apart: A record-breaking summer and winter. Accessed October 10, 2012.
- The New York Times (2012, October 3) Running the Numbers on Antarctic Sea Ice.
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
- Instrument:
- DMSP - SSMIS