I am as surprised as everyone else by the quick deterioration of the ice. ...
We've had hints. Thinking back to the refreeze, the regions now disintegrating were late to freeze, and suffered heavily from persistent imports of heat through the Bering. This was reflected in some of the thickness maps, but others consistently reported that the ice was probably a meter or more thicker than it actually was.
Roll forward to today. Speaking in approximations, in recent years (2015 to present) volume at peak is running around 21,000 KM3 at max. If you take the most recent maximum extent - about 14,000,000 KM2, we end up with an average ice thickness of about 1.5 meters.
Looking earlier - here I'm thinking of the old regime - 1980-89, the extent isn't particularly greater - only about 16,000,000 KM2, but typical average volume is much higher - on the order of 31,000 KM3, which gives us at that time a typical average thickness of around 1.93 - call it almost 2 meters.
The difference between the two - 50 centimeters - is very key, because the drop in thickness and volume means that we've passed a key threshold: the typical energy taken up during the melt season in the Arctic is almost enough to melt out all volume. The number here, approximating from Jim Pettit's graphs examining typical volume lost during the melt season, divided by max area works out to be about 1.3 meters of melt.
Obviously that melt isn't distributed evenly, nor is ice thickness. However, it does mean that regions which do not pass that 1.3 meter thickness during the refreeze are now at serious risk. It will take extraordinarily favorable conditions for ice retention to prevent an *average* melt from melting out the areas where this is true.
I think that's what we are seeing here, and elsewhere, such as the interior of the CAB where we've been having surprising losses in area. Interstitial ice formed in leads during the season which did not have time to thicken sufficiently past that 1.3 meter threshold is disappearing.
We are definitely in a new regime.