Over the last few days, 30% concentration Arctic ice extent has increased by about 10% – a very early and rapid freeze for mid-September.
Extent has almost returned to 2009/2005 levels.
So what has caused this rapid rise?
It is mainly due to cold water. Note that the ice (black line) was tracking just below 2005 (red line) until mid-August. Then southerly winds started blowing, pushing the ice edge back and melting some it. Ace the ice melted, it cooled the water.
This left a large region of water just above the freezing point. As soon as temperatures dropped below freezing, the ice refroze very quickly. This is what is known as a negative feedback. The melting ice created conditions which allowed new ice to easily form.
Now that the ice is back to where it “should be” I expect that growth will slow down some – because the region of cold water has been consumed.
There is another factor though. Temperatures this autumn in the high Arctic have been the coldest since 2004, and are just above the 50 year mean.
Because this is the hottest year ever and the Arctic is the fastest warming place on the planet.