My current understanding/prejudice is that the most reliable thickness data for the current Arctic sea ice is the Cryosat NRT data from CPOM:http://www.cpom.ucl.ac.uk/csopr/seaice.html
As I understand it, that data set is from actual measurements rather than models. Also, I haven't heard so far of any reason not to trust its accuracy.
Is that fair? I have no reason for bias but am simply an amateur.
So I wanted to compare this year's status to previous years, using that site. Only certain data sets are readily available that I can see, and so the gif below shows some sort of apples-to-oranges comparison.
The frames are, in order
1) Latest 5km Grid of 28-day Thickness : 2/1/17 - 29/1/17 (shows for 200 ms)
2) Thickness over March+April 2011 (shows for 50 ms) = "Spring 2011"
3) Spring 2012
4) Spring 2013
5) Spring 2014
(Those are the only years I can see readily available.)
So basically its comparing the ice thickness around mid-January 2017 with that around the end of March for 2011 to 2014.
So we have to imagine how much ice will be added over the next month-and-a-half if we want to see if we are worse off, or better off, than in those previous years.
The worst ice situation from those previous years was in 2013.
As can be seen from the gif, the ice pack in the vertical middle of the plot - i.e. excluding the Beaufort, Chukchi and Bering Sea on the Pacific Side and the Barents, Kara etc on the Atlantic side - was not really worse than currently. Add another month-and-a-half of ice growth and that part might generally be thicker in Spring 2017 than it was in 2013.
(Say add about a half-metre of ice then, roughly:
dark blue -> light blue
light blue -> green
green -> yellow
yellow -> red
So the vertical-centre part as described above will probably not be the weakness this Spring.
Instead, the worry is the Pacific and, particularly, Atlantic peripheral seas. These are seen to have much less ice than in previous years, albeit shown 1.5 months later.
The worst sea in the comparison is probably the Barents Sea. Unless the ice is added there, quickly and dramatically, the Barents Sea is likely to melt out early in the upcoming melt season. That, in turn, might make the whole Atlantic side into a 'kill zone' for any ice drifting over there during the melt season.
On the Pacific side, the Beaufort, Bering and Chukchi Seas might also melt out earlier in the 2017 melt season than they did in 2011-14, forming another 'kill zone', on the Pacific side. We already saw that feature in 2015 and, even more, last year.
In summary, a quick comparison was made of the available CPOM CryoSat NRT Arctic sea ice thickness data for this January vs. Spring in 2011-14. The main conclusion is that the sea ice this melt season looks likely to be vulnerable on the Atlantic (mainly) and also Pacific sides. Now it's all up to the weather and currents over the next six months.
The gif needs a click to start.