Last week, temperatures in the Arctic once again went above freezing, following a split in the Polar Vortex that allowed warm air currents to flow into the region, with some stations recording temperatures 25ºC (45ºF) above normal. This event accompanies an abrupt retreat of sea ice in the Bering Sea, having lost almost one-third of its coverage in just over a week.

Greenland’s Cape Morris Jesup weather station, the northernmost station on the planet, recorded more than 24 hours of above-freezing temperatures over the course of February 19-20. This accompanied a mass of above-freezing air that continues to flow northward over the Norwegian Sea, reaching further north than the Norwegian archipelago of Svalbard. The North Pole itself rose above -6ºC (21ºF) on February 21–roughly the same temperature that it was in parts of the US southwest at that time.

"How weird is that?" exclaimed University of California at Berkeley physicist Robert Rohde. "Well it’s Arctic winter. The sun set in October and won’t be seen again until March. Perpetual night, but still above freezing."

In the preceding week, the Bering Sea lost nearly one third of its sea ice, putting the ice extent at 60 percent below the 1981-2010 average, further pushing a record low for the ice sheet this season. And all of this during a period when the ice sheet is supposed to be growing.

"[Bering sea ice] is in a league by itself at this point, and looking at the weather over the next week, this value isn’t going to go up significantly. It’s going to go down," explains Richard Thoman, climate science and services manager for the National Weather Service Alaska region, referring to the weather patterns that would take effect on the week of February 19.