From the Union of Concerned Scientists (Erika Spanger-Siegfried):
It is polar night in the Arctic—a darkness that lasts from early October to early March. Temperatures rarely escape freezing in that darkness, averaging -30° F until the light begins to return in spring. Right now, however, temperatures across much of the Arctic are 36 degrees F above normal. Large areas are well above freezing. And instead of rapidly expanding, sea ice extent is in decline.
Taken together, this is not unusual. It’s unheard of.
The degree to which current Arctic conditions are straying from the norm may prove to be the greatest change yet measured there—the latest signal from the Arctic that all is not well.
And while the frozen top of the world may seem remote and unimportant at the moment, what happens there matters greatly to both our immediate and long-term future.
Breaking down the Arctic breakdown
The Arctic plays an important role in moderating global climate. When heat from the tropics is delivered north to the Arctic by winds and ocean currents, the region exerts a cooling effect on both. Without this distribution of energy, the lower latitudes would overheat. Sea ice and snow- and ice-covered land (known as the “cryosphere”) help the Arctic to stay cool by reflecting most of the incoming solar energy back to space.
But the Arctic, like the rest of the planet, is warming, and unlike the rest of the planet, warming in the Arctic can feed rapidly on itself.
To describe one of the feedbacks: Warmer temperatures drive greater melt of sea ice, which exposes open ocean, and exposed water absorbs heat from sun that was previously reflected. Ocean temperatures rise as a result, and when winter comes, the sea ice has a harder time rebounding amidst warmer air and water temperatures. The following year, the melt season begins with sea ice cover that is thinner and smaller in extent.
There are other feedbacks, and all are complex. For a closer look at these reinforcing cycles, see my colleague’s blog on Why the Arctic Matters. As the National Snow and Ice Data Center puts it:
A small temperature increase at the poles leads to still greater warming over time, making the poles the most sensitive regions to climate change on Earth. According to scientific measurements, both the thickness and extent of summer sea ice in the Arctic have shown a dramatic decline over the past thirty years. […] The loss of sea ice also has the potential to accelerate global warming trends and to change climate patterns.
Okay. With this in mind, let’s look at the state of the Arctic at this time.
Sea ice extent
In the polar night, Arctic sea ice historically rebounds from summer melt as both the water and air cool. In recent decades, the ice has been declining in both extent and volume.
This year, with warm ocean temperatures and continued delivery of warm air from the lower latitudes, the ice is struggling to rebound. October saw new record lows for Arctic sea ice extent.
In November, Arctic sea ice extent remains well below average for this time of year. In each of the last three days, a time of year when sea ice is normally growing, it has shrunk instead (see figure below). Arctic sea ice is melting up there in the polar darkness.
According to experts following this closely, as of Sunday, November 20, Arctic sea ice is now ~1.1 million square kilometers below the previous record low.
Sea surface temperatures
With larger areas of the Arctic ice-free each year, and for longer periods of time, the Arctic Ocean is absorbing more heat.
This fall, sea surface temperatures are well above average, with anomalous warmth persisting into November as seen in the figure below. Scientists have reported ocean temperatures 25° F above average in some locations.
The chart below looks at this warmth by a different measure: “freezing degree days.” By many available measures, the oncoming Arctic winter is in a nose dive unprecedented in recent record keeping.
A weakened polar vortex and wobbly jet stream have been identified as factors in recent anomalous winters, both colder and warmer, and indeed, meandering winds are currently delivering warm air far northward to the Arctic, and a deep, snowy freeze in Eurasia.
The combination of factors driving Arctic air temperatures today has resulted in a stunning temperature anomaly—persistent, vast areas of 36° F above normal, shown in the map below.
Wild cards, like the unusual cyclone that struck the Arctic last winter, driving temperatures 50 degrees above normal, may compound and accelerate ice loss, according to a recent NASA study.
It’s as if the Arctic is trying to be heard. It’s hard to imagine stronger signals to send.