The author of today's post, Sheryl Canter, is an Online Writer and Editorial Manager at Environmental Defense.
Researchers have been expecting Arctic ice to melt and shrink, but not this fast! The National Snow and Ice Data Center, part of the University of Colorado at Boulder, reports that Arctic sea ice has shrunk to a 29-year low, significantly below the previous record low set in 2005.
In September 2007, the Northwest Passage, a direct shipping route from Europe to Asia that explorers sought for centuries, was ice-free for the first time since satellite records began.
As of September 16, sea ice extent was 1,590,000 square miles, surpassing the previous one-day record of September 20–21, 2005, by more than 461,000 square miles – roughly the size of California and Texas combined.
Arctic ice extent from satellite photos. The picture on the left was taken in September 1979; the picture on the right was taken on September 9, 2007. Source: National Snow and Ice Data Center.
NASA scientists are struggling to explain the sudden drop. Arctic ice cover can vary quite a bit from year to year, and this year's weather did encourage melting. There were unusually clear skies, warm winds from the south, and winds and currents moved ice out of the Arctic Ocean next to Greenland. But natural variations don't account for the huge magnitude of the drop. Global warming is the primary cause of this year’s record low sea ice, as well as the significant decreases over the past few decades – that much is clear. But scientists still aren't sure why the ice cover is shrinking so much faster than predicted.