Dr Jennifer Francis recently gave an excellent lecture at the Weather and Climate Summit about the wider impacts of the loss of Arctic sea-ice. I was lucky to see it via the internet last weekend and have waited until now to discuss because the presentation has only just been posted on YouTube. The video is 1:24 long, but is well worth viewing.
Dr Francis's powerpoint presentation can be downloaded here, probably easiest to right click and 'save as'. The presentation will be most legible run as full screen from powerpoint.
As usual I'll post link to the video as the Blogger video window is miniscule.
Dr Francis outlines the changes in the Arctic sea-ice as a background to the 'meat' of her lecture. I've already discussed the loss of multi-year sea-ice and the consequent thinning of the Arctic polar ice, you'll find more information here and here. And I've mused upon Maslanik's 2011 paper on recent trends in multi-year sea-ice and the 1990s period of positive Arctic Oscillation, here.
Surface temperature inversions have in the past capped the interaction between sea-ice and the atmosphere. However these have lessened in recent years and now the near-surface warming due to extensive open water is changing the atmosphere in the Arctic. Dr Francis states that the Arctic Dipole is a result of a high amplitude jet stream, that's not what I've gleaned from what I've read and it's something I'll have to mull over.
The reduced pole-equator temperature gradient is leading to weather patterns that are 'getting stuck'. As I've previously discussed, the jetstream has waves on it called Rossby waves, these waves move around the jetstream, the jetstream being formed by the boundary between cold Arctic air and warm subtropical air. However what Francis argues is that due to the reduced pole-equator temperature gradient (because the Arctic is warming, e.g. here) there is a reduced flow along the jetstream, the speed of the Rossby waves has reduced, and the wave amplitude has increased, with peaks moving further into the Arctic (which reminds me of the findings of increased mid latitude storm penetration into the Arctic).
Stu Ostro is mentioned in the questions, parts of the presentation are reminiscent of Stu Ostro's work on troughs and ridges around the Arctic. However Dr Francis is presenting images of troughs and ridges oriented longitudinally (across), whereas Ostro was concentrating on latitudinal ridging (up down), e.g. here, warning 20Mbyte pdf - right click and 'save as'.
The increase in wave amplitude is occurring around the northern hemisphere, however ridge peaks are located mainly just west of Greenland. This seems to explain the warm temperatures being experienced by that region e.g. Nunavut around Baffin Bay, CBC News. So whilst the findings of increased amplitude are hemispheric in nature, North America is the centre of action of the greatest ridging. If this is a persistent pattern into the future it could be important for melt from Greenland, because the atmospheric ridges are driving warm mid latitude air into that area.
Dr Francis also stated that early snow melt is allowing soils to dry earlier and additional warming as a result to feed Arctic Amplification. The early snow melt is correct, but I've not been able to look into soil drying as yet. However this issue immediately brings to mind Hansen's Climate Dice and the worrying connection I see between that and the danger of increasing drought, here. If we are seeing a drying around the Arctic this also has an impact on carbon emissions, as the Arctic warms if it mainly wet then emissions of methane may dominate, however if it is mainly dry carbon dioxide may dominate, and peat fires may add yet more carbon.
I've recently posted about a pre-print I've read by Cohen et al that (in my opinion) convincingly shows that the Arctic Oscillation is strongly connected with the rate of advance of Siberian snowfall, more here. Dr Francis didn't mention this or Cohen's preceding work, indeed she initially framed as a paradox that we've had recent cold winters despite global warming, then said she thought those cold winters were just weather and probably have no significance in terms of climate change.
My working theory remains that of Cohen - that Arctic sea-ice loss, mediated by Siberian snowfall, is responsible for the increasing tendency to cold winters in northern Eurasia, Europe, and the East coast of the US. However Cohen's findings and Francis's findings are not mutually exclusive. The results of the loss of Arctic sea-ice are not simple, nor do they affect each continent in the Northern Hemisphere in the same way.