This Arctic winter has startled even the most even-keeled scientists, with records set for low sea ice extent, high temperatures and other indicators of a climate gone awry.
Sea ice has plummeted to record lows and stayed there as pulses of unusually warm air have swept across the region, with the latest one set to reach the North Pole on Thursday. According to the National Snow and Ice Data Center (NSIDC), sea ice extent hit record lows for the months of November, December and January.
This comes on the heels of a year in which sea ice extent hit its second-lowest level on record at the end of the summer melt season in September.
The new figures for January sea ice extent, released on Tuesday, showed sea ice extent averaged 5.17 million square miles for the month, which was the lowest January extent in the 38-year satellite record.
This is 100,000 square miles, or slightly larger than the state of Oregon, below the previous lowest January extent in January 2016.
To put it in a longer-term perspective, sea ice extent during January was 487,000 square miles below the January 1981 to 2010 long-term average. This means the Arctic was missing an area of sea ice about the size of South Africa. Keep in mind that this is the middle of winter, when much of the high Arctic is still shrouded in darkness.
Sea ice throughout the past three months has been especially low in the Kara, Barents and Bering Seas. Remarkably, during January the sea ice edge remained north of the Svalbard Archipelago in far northern Norway, which typically is surrounded by sea ice during the winter. This retreat, the NSIDC stated, was "largely due to the inflow of warm Atlantic water along the western part of the archipelago."
The NSIDC cited the analysis of a NASA researcher, Richard Cullather, who found that the winter of 2015-2016 was the warmest on record in the Arctic during the satellite era, which began there in 1979. It's unclear if 2017 will rank higher, given the whims of natural weather variability and the long-term influence of human-caused global warming.
In addition, sea ice extent is at record low levels in the Antarctic, where a relatively small area of sea ice cover surrounds a land-based ice sheet. This means that global sea ice is at a record low, but this metric does not reveal the true impacts of global warming, since Southern Hemisphere sea ice variability has been linked to other factors.
Meanwhile, Arctic sea ice loss has been conclusively tied to human-caused global warming, which has accelerated in the past few years. The Arctic is warming at twice the rate of the rest of the globe, causing changes to cascade throughout the eight Arctic nations and beyond.
Some studies have shown that sea ice loss is causing changes to weather patterns in the northern mid-latitudes, including across North America and Europe. While this is still a contested area of climate science, the saying that "what happens in the Arctic doesn't stay in the Arctic" is now part of the climate change lexicon.