Arctic sea ice extent in January was 402,000 square miles below average — an area equivalent to about 60 percent of Alaska
In my previous article here at ImaGeo, I featured a Norwegian icebreaker with no winter sea ice to break in the high Arctic. Since then, the National Snow and Ice Data Center has published its monthly update on sea ice conditions — and the news is pretty dramatic.
Record warm Arctic air temperatures running an astonishing 11 degrees F above average at the surface helped drive sea ice to a record low in January.
A significant part of the 402,000-square-mile deficit came from unusually low ice coverage in the Barents Sea, including off the Arctic archipelago of Svalbard. Here, sailors aboard Norway’s KV Svalbard icebreaker were surprised by just how little ice they saw while on patrol recently.
“January was absurdly warm in the Arctic,” says NSIDC director Mark Serreze, quoted by Bob Henson in his excellent, detailed story about these developments at Weather Underground.
A phenomenon known as the Arctic Oscillation, or AO, helped push up air temperatures when it went into a strongly negative mode in January.
During the positive phase of the Arctic Oscillation, a high altitude low-pressure system associated with frigid polar air is bottled up tightly over the Arctic by strong jet stream winds. (See the righthand map in the graphic below.)
When the AO switches into a negative phase, higher pressure develops in places, weakening those winds and thereby causing them to deform. This, in turns, allows blobs of cold, polar air to spill southward — and abnormal warmth to build up in its place. (See the lefthand map below.)
The mid-latitudes also tend to get stormier when the Arctic Oscillation kicks into its negative phase. And goodness knows, we’ve had a fair bit of that recently!
While the Arctic Oscillation clearly played an important role in January’s record-high warmth and record-low sea ice extent, it also had co-conspirator: global warming — as this graphic illustrates:
Take a close look at that blue line. It shows how temperatures recorded at land stations in the Arctic have varied from the 1981-2010 mean. The warming trend since the 1970s is obvious — especially compared to the warming of the globe as a whole, shown by the red line. In fact, the Arctic has been warming at twice the rate as lower latitudes since the early 2000’s.
So while it is true that natural variations from winter to winter, driven by factors like the Arctic Oscillation, play a role in what happens up there, those are little squiggles on top of the longer term warming trend — which is driven by, well, us.