Scientists have discovered that the winter ice levels are at record lows.
Instead of easing toward its typical March maximum in coverage, the Arctic’s sea ice appears to be more inclined toward getting a head start on its yearly summer melt-out.
As of Sunday, March 8, Arctic sea ice as calculated by Japan’s National Institute of Polar Research extended across 13.65 million square kilometers. This value is more than 450,000 sq km below the record extent for the date.
Even more striking is the consistency of the ice loss over the last couple of weeks. March is often a time of rapid gains and losses in ice cover, as seasonal warming and melting battle it out with quick refreezing when shots of cold air return.
This year, the ice extent peaked on February 15 at 13.94 million sq km, and it looks increasingly unlikely that the ice will manage to return to that very early peak over the next couple of weeks. No season in the Japanese database has fallen short of the 14-million mark, so if the February peak stands, it will mark the lowest maximum in the Arctic since satellite monitoring began in 1979.
Using a slightly different formula for calculating extent, the National Snow and Ice Data Center comes up with a similar record low for the date. In an update on March 4, NSIDC stated:
“The Arctic maximum is expected to occur in the next two or three weeks. Previous years have seen a surge in Arctic ice extent during March (e.g., in 2012, 2014). However, if the current pattern of below-average extent continues, Arctic sea ice extent may set a new lowest winter maximum.”
Not only is Arctic sea ice essential to many ecosystems: it serves as a powerful tracer of recent warming, and its absence in summer allows open water to absorb much more heat from sunlight. While the ice has seen some modest recovery in recent years, it has failed to fully mend the fabric torn by the record-setting drop of 2007.
The overall thickness of the ice, and the fraction that’s survived for multiple years (multiyear ice), have both suffered major losses. A comprehensive survey just published in The Cryosphere found that ice thickness in the central Arctic dropped by 65 percent from 1975 to 2012.
Experts differ strongly on when we might see a summer that melts nearly all of the Arctic’s ice (typically defined as less than a million sq km of extent by the normal September minimum).
Computer models suggest this point might not be reached till the 2040s or later, while simple extrapolation from recent years would produce an effectively ice-free September by the 2020s, perhaps even sooner.
Source | http://www.wunderground.com