23 May 2006 - Scientists
at the U.S. National Snow and Ice Data Center
(NSIDC) recently announced that March 2006 showed
the lowest Arctic winter sea ice extent since
satellite measurements began.
March is the month in which
Arctic sea ice usually reaches its maximum extent,
but because of warming global temperatures, due
largely to fossil fuel burning, sea ice extent
has been on a downward trend.
Acoording to NSIDC, March 2006
mean sea ice extent, indicated by the red dot,
is 300,000 square kilometers (about the size of
Italy) less than the 2005 record.
What is sea ice extent?
Sea ice extent is the area of
the ocean that is covered by at least 15 percent
ice. In 1979, when satellites took the first measurement,
it covered about 16.4 million square kilometers.
However, this year the sea ice extent only covered
14.5 million square kilometers – nearly a 12 percent
drop.
Sea ice is melting because the
earth’s temperature is rising fast. In fact, according
to NASA, the hottest five years worldwide on record
have been 2005, 1998, 2002, 2003 and 2004. In
other words, last year was the warmest year on
record.
Why does it matter?
Sea ice reflects much of the
sun's radiation back into space, but when sea
ice melts it is replaced by dark, ice-free ocean
water that absorbs more of the sun's energy and
accelerates global warming. This is referred to
as a ‘positive feedback’ in the climate system,
leading to faster global warming.
According to an interview with
the English newspaper The Guardian, Walt Meier
of the NSIDC, said there was a “good chance” that
the Arctic tipping point—the point at which warming
begins a self-reinforcing acceleration—has been
reached.
