Ice floes float in Baffin Bay above the Arctic Circle in 2008. (Jonathan Hayward/Canadian Press via AP)
Two weeks ago, I wrote about how the warmth of the Arctic this year — featuring temperature departures many degrees Celsius above normal — had scientists floored...
In my post, they used words such as “absurdly” or “ridiculously” to describe how the temperature has increased in the region this year.
That warmth has major consequences for key Arctic systems, including vulnerable sea ice, which when it melts leaves many darker patches of ocean exposed — patches that then absorb the sun’s radiation rather than reflecting it away as sea ice does. Thus, loss of sea ice further warms the whole system, in a process known as “Arctic amplification.”
In the figure below from the National Snow and Ice Data Center (NSIDC), you can see that right now, Arctic sea-ice extent is running not only well below average but also below levels seen during 2012, which went on to set the record for lowest Arctic ice extent (which occurs in the late summer or early fall).
Arctic sea ice was at a record low level for its average extent in January, according to the center — over a million square kilometers smaller than the average ice extent seen from 1981 to 2010. And now, February has set another record monthly low, the center announced Wednesday. “Arctic sea ice was at a satellite-record low for the second month in a row,” it noted.
“It’s not a good start to the year,” said Julienne Stroeve, a senior research scientist with the center.
The average extent in February was just 14.22 million square kilometers (5.48 million square miles), or 200,000 square miles lower than in the previous record-low February, which occurred in 2005, the group said. That was 1.16 million square miles below average for the month.
Monthly February sea ice extent for 1979 to 2016 shows a decline of 3.0 percent per decade. (National Snow and Ice Data Center.)
This is happening amid a dramatically warm start to the year — recent satellite data, for instance, suggests that February was the warmest month ever in this particular record of the planet’s atmosphere.
[February was Earth’s warmest month in the satellite record]
“Air temperatures at the 925 hPa level were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean near the pole,” the NSIDC noted. (A measurement of air pressure, 925 hPa corresponds to about 3,000 feet above Earth’s surface.)
Stroeve cautions, however, that just because sea ice levels are at record lows at the start of this year — a phenomenon that may be influenced by the strong El Niño event that we’ve been witnessing — that doesn’t mean that in the summer, when sea ice reaches its annual low, there will also be a record.
“Those regions of the ice cover that are low right now, they’re going to melt out anyways in summer,” Stroeve explained. What remains in September is therefore something of a separate issue. The all-time record low point for Arctic sea ice occurred in September 2012.
“The trends are negative everywhere,” Stroeve said. “Of course they’re stronger in the summer time, but they’re in the winter as well.”
Meanwhile, there’s another possible record in the offing — though this one is a tad more complicated to explain, as well as less certain to occur. It’s called a new “low maximum” for winter sea ice — which may sound like a contradiction in terms, although it isn’t.
In general, ice extent grows throughout the winter toward an annual peak and then declines toward a low in late summer or early fall. Thus, the moment when it peaks is the “maximum” and when it reaches its lowest extent is the “minimum.” And in general, as Arctic sea ice has declined, its maximum extent has also declined — last year set a record low, at just 14.54 million square kilometers.
This year, in contrast, ice has not even reached that extent, though it was extremely close Tuesday, at 14.472 million square kilometers, and appeared to be leveling off.
Thus, the coming week or more will tell whether the stunning warmth of the Arctic will continue to set records.
And of course, declining sea ice won’t be the only consequence of the extremely warm Arctic this winter. For instance, the outbreak of a second early-season wildfire this year in Alaska — in February — hints at how this early-season warmth could set the stage for other major problems in the Arctic as the year advances.
The bottom line is that the Arctic is clearly warming up much faster than the planet as a whole — just as climate scientists have long predicted. The consequences for from our atmosphere — thawing permafrost is expected to emit additional greenhouse gases — to our coastlines (the melting of Greenland and Arctic glaciers will raise seas) will be profound.
Chris Mooney reports on science and the environment.
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