I've been paying close attention to the Arctic sea ice level recently and the forecast for this year has not been looking very good. All winter, the sea ice extent has tracked close to the two standard deviation line. But, in recent weeks it has been going well below that level and may even be approaching three standard deviations. Here is a plot of the 2016 sea ice extent (red), along with the 2015 (blue) and average (grey) extents. The shaded area is plus or minus two standard deviations.
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| Source: NSIDC |
For the point of clarity, one standard deviation (sigma) means about 65% of the measurements will fall within that plus-or-minus range. Two sigmas means about 95% of the measurements will fall in the plus-or-minus range. Three sigmas takes us all the way to 99.7% of the data. That means the likelihood of the current sea ice extent happening within the long-term average is between 3 and 50 chances out of a thousand. And yet, the winter sea ice extent has been near the two sigma line for most of the past decade.
There is quite a bit of winter remaining, but we can begin to reach some conclusions. First, the level is so low it is highly unlikely to recover. Last year (2015) was not only the lowest maximum, but also the earliest. In comparison, the ice extent for February 18th was 275,000 square kilometers lower than last year and 1,095,000 square kilometers below the long-term average. Based on the data, I think it is safe to predict at this time that 2016 will rank as the lowest maximum sea ice extent ever recorded.
But, that's not all. Looking at the ice extent I am beginning to wonder - have we already seen the maximum ice extent for the year? Ten years from now, this level might be viewed as a good thing. But, if it happens this year it will be viewed as a collapse of the sea ice.
Stay tuned.
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