The news from the Arctic isn’t good, for polar bears or for humanity. Arctic sea ice has thinned dramatically since 2004, with older, thicker ice giving way to fragile young ice that can easily melt during the long, cool northern summer days. Researchers have long known that the overall area covered by arctic ice was decreasing, but these new satellite studies by NASA scientists at the Jet Propulsion Laboratory (JPL) demonstrate that the overall volume is decreasing dramatically — with unfortunate consequences for the planet.
Older, thicker arctic sea ice is more resistant to melting, and a persistent ice cover in the arctic helps cool the planet by reflecting a substantial amount of the sun’s rays back into space. On the other hand, open water absorbs the once-reflected heat, and this accelerates the warming of the planet.
Using NASA’s ICESat spacecraft, scientists have determined that the overall thickness Arctic sea ice has thinned by an average 2.2 feet over four winters. The total area covered by thicker, older ice that has survived at least one summer shrank has nosedived to 32% of the total — down from 62% in 2003. It’s the first time that older sea ice hasn’t been dominant. (Source: AFP, Nature, July 8, JPL, July 7, 2009).