Some years like 2005 (red) had essentially no growth during the same period. What happened this year is that the late ice “loss” starting in mid-August (which made our friends on the other side so happy) left a lot of cold water behind that refroze easily – once the wind stopped and the temperatures dropped below freezing.

Note the the heat released from the freezing ice is now showing up as a spike in the DMI temperature graph.

http://ocean.dmi.dk/arctic/meant80n.uk.php