This animation compares the 2005 annual Arctic minimum sea ice from 09/21/2005 (shown in orange) with the 2007 minimum sea ice from 09/14/2007. The average minimum sea ice from 1979 through 2007 is shown in green. Source: NASA Goddard Space Flight Center Posted by: http://www.desmogblog.com
Sea ice is frozen seawater floating on the surface of the ocean. Some sea ice is semi-permanent, persisting from year to year, and some is seasonal, melting and refreezing from season to season. The sea ice cover reaches its minimum extent at the end of each summer and the remaining ice is called the perennial ice cover. The 2007 Arctic summer sea ice has reached the lowest extent of perennial ice cover on record – nearly 25% less than the previous low set in 2005. Check out http://www.desmogblog.com for more.