I say this because I'm pretty sure that the Francis/Vavrus paper
The key paper is "Revisiting the evidence linking Arctic Amplification to extreme weather in midlatitudes", Dr Elizabeth Barnes, 2013 GRL. A PDF copy is here, but I've quoted the abstract in it's entirety.
Previous studies have suggested that Arctic Amplification has caused planetary-scale
waves to elongate meridionally and slow-down, resulting in more frequent blocking patterns and extreme weather. Here, trends in the meridional extent of atmospheric waves over North America and the North Atlantic are investigated in three reanalyses, and it is demonstrated that previously reported positive trends are an artifact of the methodology. No significant decrease in planetary-scale wave phase speeds are found except in OND, but this trend is sensitive to the analysis parameters. Moreover, the frequency of blocking occurrence exhibits no significant increase in any season in any of the three reanalyses, further supporting the lack of trends in wave speed and meridional extent. This work highlights that observed trends in midlatitude weather patterns are complex and likely not simply understood in terms of Arctic Amplification alone.
Additionally there is Screen & Simmonds, 2013, "Exploring links between Arctic amplification and mid-latitude weather.", Abstract. A paper that finds "that possible connections between Arctic amplification and planetary waves, and implications of these, are sensitive to how waves are conceptualized."
The Francis/Vavrus paper linking Arctic Amplification to increased amplitude of waves in the Jetstream and 'stuck' weather patterns is now looking like it is wrong. In the Barnes paper it is noted that "metrics that focus on a narrow range of isopleths to track the ridges and troughs of a passing wave will incorrectly interpret a shift of the geopotential height field as a change in wave extent. When this shift is accounted for, no significant trend is found."
In other words, with the warming of the northern hemisphere the atmosphere has been expanding, shifting geopotential heights upwards (geopotential height being the height at which a certain pressure level is found). And causing a northward shift of geopotential height. Barnes attacks the problem in a very intelligent way, she defines two indices, SeaMaxMin is the seasonal excursion of peaks and troughs in the 500mb GPH field, where GPH is 5700m up in the atmosphere, DayMaxMin is the same index but on a daily basis. In line with Francis and Vavrus SeaMaxMin has an upward trend, but crucially DayMaxMin doesn't. This is fatal problem for the Francis/Vavrus paper, because if their hypothesis is correct both indices should show an upwards trend.
One problem I have with the Barnes paper is that while I can't fault the reasoning behind the following finding:
The lack of increasing trends in the atmospheric blocking patterns further supports the lack of trends in the wave meridional extents and wave phase speeds, and suggests that Arctic Amplification over the past 30 years has not had a quantifiable impact on slow-moving weather patterns over North America or the North Atlantic.In my examination of the blocking data kindly made public by Dr Anthony Lupo, the increase in blocking in that data was particularly over Europe, image, but that's another issue.
None of this seems to me to affect Dr Judah Cohen's work on winter links to reduced sea ice mediated by snow line advance in October. But it may help to throw some light on the Greenland blocking and the summer pattern. I'm still considering that. The pattern is real, I don't see how it affects Overland et al's finding of an atmospheric shift in the Arctic post 2007, and I don't see that it invalidates my related obsession with the post 2007 summer pattern. If anyone thinks I'm being blinkered in this, that's what the comments are for.