Terry,
I should point out that the pattern I'm talking about is a summer pattern. This winter's pattern is a Warm Arctic Cold Continents pattern due to low index AO. I'm not sure the two are in anyway related, WACC patterns have occurred long before Arctic sea ice loss. It's just that the sea ice loss is driving a pattern that is like the low index AO.
With regards the summer pattern, about which Wayne has proposed an idea about the cold pole shifting to over Greenland: I'm struggling to find a simple explanation, until I understand the mechanism I will not be able to give one.
I have some sympathy with Wayne's cold pole idea. However the geopotential height well still centres clearly on the Arctic ocean, and I still see this as an important problem with Wayne's view. I need to explain.
Take a pressure level in the atmosphere, say 500mb pressure. Pressure goes down as you go up in height, so at some height in the atmosphere there is a pressure of 500mb, that height is the geopotential height (GPH). Here's a plot of GPH for 2007 to 2012
http://farm9.staticflickr.com/8387/8669292944_5b1b4a4c25_o.pngThe scale is in metres, so over the UK GPH for 500mb was around 5600m, Over the northern states of the US it's around 5800m. You can see that the GPH drops towards the pole because the atmosphere is thinner over the polar regions.
Now the centre of action of the new summer circulation is over Greenland. From the GPH plot it can be seen that there is a ridge of GPH over Greenland. There always has been a ridge, but it is now about 50m higher than typical heights pre 2007. But it is clear that from the point of view of GPH the centre of action remains over the ice pack, not over Greenland. The Jetstream flows around the GPH well.
This GPH ridge is the cause of the new summer pattern, what causes the ridge is not known with certainty, it may be due to Eurasian snow retreat, but there may be a role for Arctic sea ice loss and formation of low pressure over the Siberian coast. I suspect that once the ridge is formed it creates connections with a region around it (3000km distant) via atmospheric waves which drive the formation of a belt of low pressure tendency in response to the Greenland GPH ridge.