Remember the scale of the Arctic. If you shrank the Arctic down to a lake 3 or 4 km across that 5m ice would be 5 mm thick. What looks like a tiny floe on MODIS will be 100s of metres or kilometres across. We've seen semi-permanent ice shelves 10s to 100s of metres thick in both Arctic and Antarctic crumble within days, so no suprise that 5m thick ice may crumble into 'small' pieces given the right conditions.
I guess my point was just that if that's the thickest, supposedly strongest ice in the basin, why is it crumbling so easily when the strain could (presumably) be accommodated by thinner, weaker ice to the north? But I guess if the ice is anchored to the CAA on one side, and the CAB is being rotated, a weak zone has to appear somewhere. But this development really puts to lie the idea that all of that thick multi-year ice is a stronghold against the melting. It's not. By the end of the summer it could all have migrated to the Beaufort and Chukchi, and melted. Or shot out the Fram, if the rotation shifts direction. Or both, as will probably be the case.
The whole ice cap is mobile. It doesn't have to move by internal deformation, it can just float wherever the wind and currents push it. I expect that this year or next we'll see the whole cap pull away from Greenland and the CAA leaving open water in between.
We're basically at the point where there will be first and second year ice, and nothing else.