Too early to tell if ice extent will reach new record low, but long-term downward trends are clear
By Bob Berwyn
SUMMIT COUNTY — Arctic sea ice extent, which hovered near average in May, has declined rapidly in the past few weeks to dip well below average and below the level it was this time of year in 2007, when it reached a record low in September.
“Basically, right now, we’re quite a ways below 2007, and neck and neck with 2010, which was the lowest for this time of year … we’re very near record low levels for this time of year,” said Dr. Walt Meier, a sea ice expert with the Boulder-based National Snow and Ice Data Center.
The steady decline of Arctic sea ice extent is considered to be one of the key symptoms of global warming, with serious implications for climate, weather, ocean currents and sea level rise. Several recent studies suggest that the warming in the Arctic is directly affecting seasonal weather patterns by changing air pressure gradients that drive the speed and shape of the jet stream. And just last month, atmospheric scientists reported monthly average carbon dioxide levels at remote Arctic sensing stations hovered above 400 parts per million for the first time on record.
“The setup looks a lot like it did in 2007 for the moment, but it’s still pretty early. It’s hard to tell if it’s going to follow 2007 but there’s certainly the potential to have a very low year,” Meier said.
“There’s already a lot of open water,” he said, explaining that the darker colored water (compared to the ice) more readily absorbs incoming solar radiation, which is at its maximum at the summer solstice. That, in turn, has the potential to magnify the melting even more during the latter part of the summer.
“One of the reasons we’ve seen that steep drop is that the Bering sea melted out pretty quickly once it got going,” Meier said, referring to the sector of the Arctic Ocean between Alaska and Russia, where sea ice extent stayed higher than average nearly all winter long.
“The Bering sea ice is always seasonal, it’s all pretty thin ice,” he said, adding that this past winter’s large ice extent in the Bering Sea may be factor in whether total overall sea ice extent drops to a new record low this year.
Meier discounted speculation that occasional seasonal increases in Antarctic sea ice somehow compensate for the steady and dramatic decrease of ice in the Arctic region.
Some well-known global warming deniers like Joe Bastardi often state publicly that the overall global sea ice balance is steady because of increases in Antarctic sea ice, but nearly all climatologists and cryologists discount that claim, pointing out that there is no such thing as a global sea ice balance.
Meier said the two systems are independent of each other, with different processes affecting the formation and melting of ice. Explained simply, the variations in Antarctic sea ice extent don’t suggest a long-term trend toward an increase, while the long-term trend in Arctic ice decline is clear.
“You can’t really say that one cancels the other out,” Meier said. The changes in Antarctica are a seasonal anomaly to some extent, but in the Arctic, a fundamental change is going on,” he said.
In addition to the decades-long trend of overall sea ice decline , the amount of thicker multi-year ice that persists for several seasons is diminishing quickly,” he explained.
“And we’re not seeing any kind of recovery toward normal,” he concluded.