A couple of things were missing from the 2015/2016 winter analysis posted a few days ago, and so I've decided to present them in this separate blog post. Most of these images come from the website of NSIDC research scientist Andrew Slater.
The relationship between thermodynamics and sea ice thickness can be thought of most simply in terms of freezing degree days (FDD), which is essentially a measure of how cold it has been for how long. The cumulative FDD is simply daily degrees below freezing summed over the total number of days the temperature was below freezing.
That means that this year has a bit of a head start, and these maps provided by Dr. Andrew Slater display the differences in concentration between this year and the four years with the lowest minimums on record (2007, 2011, 2012 and 2015). Red means there's less ice now, blue means more: