Just as much of the Northeast is beginning to emerge from one of the longest deep freezes in recent memory, in the Arctic, sea ice has finally reached its maximum extent for the year.
The National Snow and Ice Data Center in Boulder, Colorado announced that on March 21, the total amount of ice cover for the Arctic peaked at 5.7 million square miles, or 282,000 square miles below the 1981-to-2010 average. This is the fifth-lowest winter ice cover extent since satellite records began in 1978. The lowest maximum extent recorded was in 2011 at 5.65 million square miles of ice cover.
In September 2012 after the summer melt season, less ice covered the Arctic than had ever been recorded before — a shocking 18 percent less, prompting observers to predict that the Arctic might see an ice-free summer long before the end of the century.
Ice cover in the Arctic varies considerably on a seasonal basis — growing in thickness and extent during the winter and shrinking in volume over the summer — as well as on a year-to-year basis. But Arctic sea ice extent has been trending downwards dramatically over the past four decades and the scientific consensus points squarely at human-caused climate change as the culprit.
In the latest IPCC report, the world’s leading climate scientists confirmed that Arctic summer sea ice was declining at rates much faster than predicted by most models.
CREDIT: National Snow and Ice Center
This year’s relatively low maximum sea ice cover may have been affected by the overall milder winter experienced throughout the Arctic, as most of the coldest air moved south to Canada and the United States. In February, temperatures were 7.2° to 14.4°F above normal for much of the Arctic.
A recent study by the National Snow and Ice Data Center and NASA, researchers found that the length of the Arctic ice summer melt season has lengthened by an average of five days per decade from 1979-2010. While the melt season is being extended on both ends — earlier start of melting in the spring and later start of freezing in the fall — the researchers found that the slower start of freezing in the fall was adding the most days to the season. The fall freeze is occurring later because there is now a smaller temperature gradient between the air and warming surface ocean waters. That smaller gradient means heat loss to the atmosphere is slowing down, and freezing is delayed.
The steady decline of sea ice has repercussions that extend far beyond the Arctic and the polar bears and Inuit who depend on the dwindling frozen habitat. While the melting of floating ice does not affect sea levels when it melts, sunlight that once would have bounced back into space from the bright, reflective surface is absorbed by the now much darker ocean water. This accelerates localized warming, melting permafrost which further exacerbates the cycle by releasing carbon dioxide and methane into the atmosphere. Localized warming also quickens the pace of melting for land-based ice sheets in Greenland. This causes sea levels to rise, threatening low-lying coastal communities around the world.
There is also evidence that suggests that warmer air in the Arctic can disrupt the jet stream leading to bizarre weather in North America and Europe.