What [NSIDC] maps show is that the ice got younger, not melted. How does ice get younger?
I suggest that Ekman transport is sending surface water under the ice where it promotes bottom melting. This would be yet another feedback mechanism. It would accelerate ice loss through thinning, showing up as faster than expected thinning - i.e. volume loss - in the central pack.
July 21st 2010
And Ocean Mixing
Many hottest weather records are broken in northern hemisphere.
Summer arctic ice at record low in extent.
By September the Arctic Ocean is freely navigable by both the northern sea route and the north west passage.
Reduced ice cover affects sea temperatures, in turn affecting Arctic current flows and air movements. Thinner ice, instead of piling up as pressure ridges due to compression effects, cracks into sections due to tension and agitation effects.
The Arctic is virtually ice-free by late summer: there is open water at the North Pole.