Neven, your various measures of ice concentration are interesting, but I'm not sure if I understand the reasoning. For example :
I figured that if I used SIA at a low resolution, grid cells will be big and thus melt ponds and leads will have a larger impact on the numbers.
That is not necessarily the case. In fact, SIA numbers should be rather insensitive to resolution.
After all, if ice concentration is, say 30% over some area A of the Arctic, then regardless of the grid cell size, SIA will be calculated as 0.3*A.
'Extent' on the other hand DOES depend on the grid cell size. Especially on the ice edge.
So your NAPAE graph (NSIDC SIA / UH SIE) will be similar to (UH SIA / UH SIE) which is the 'blue' lines in Wipneus' ice concentration / compactness graph :
And indeed these 'blue' lines (with the black line being 2017) show concentration that is not as high as NSIDC's compactness graph.
The only thing I think you can conclude from that is that currently, there are fewer 'wide' (3km-25km) polynia than there were in prior years.