Posted on May, 23 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.

The figure below best illustrates this trend and shows that this year we’ve hit an all time low.
 


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.