Still... The behavior of these two recent years indicates that the trend towards the first virtually ice-free Arctic summer is perhaps, mercifully, drawing out a bit longer than was suspected during the apparently nightmarish eve of the melting season in early 2013. As it was for amateurs as myself. The 2012 melt season, as with 2007, did horrendous damage to the ice that won't simply bounce back in the same manner as it could decades ago. At least with the serious dive in multiyear ice, it seemed that a year with such a high percentage of first year ice as in early 2013 would be the set up to disaster. On the long-term scale, 2013 could be objectively seen as a bad year for ice, but was not to be the black swan year. Nor will 2014. And maybe not 2015 either. This is a gradual process. In any given year, the energy will shift towards melting the high latitudes. In another, it will go into the oceans; or warm the continents, and then whereas ice may appear to be doing "better" in a given year, the rest of the world swelters and observes extreme weather events. It's probably not too likely, yet, that every facet of climate change will manifest in every corner of the globe in a single year. I think 2012 was about as close to that point as I've ever observed in my lifetime, quite honestly. Hottest year on record for the United States, highest record melt of the GIS, and lowest ice extent in the Arctic. The year was nuts inside and out. But the longer picture is coming together, bit by bit...
As to whether the first ice-free summer even constitutes an irreversible tipping point from the physics standpoint isn't so obvious. A prolonged period of conditions unfavorable for ice retention will make a difference when the sun goes down. This seems to be when we approach a tipping point that is irreversible. (Non-surprisingly, but personally, I believe this will depend on human behavior in the years leading up to an ice-free summer, and how that trajectory works out will determine the permanence of our damage. But I'm not optimistic there will be change fast enough...)
A paper by Tim Lenton in 2012, "Arctic Climate Tipping Points", says as much.
The year that the North Pole becomes seasonally ice-free will likely be seen as a ‘tipping point’ by non-experts. Whilst politically important, several authors argue it is unlikely that such a transition involves an irreversible bifurcation (Eisenman and Wettlaufer 2009; Tietsche et al. 2011).
Summer sea-ice cover can recover quickly in models when the climate cools into the following winter, because thin ice grows more rapidly (Notz 2009), and with diminished icecover, excess heat is more rapidly transferred to the atmosphere and radiated to space (Tietsche et al. 2011)
(both are negative feedbacks). However, if cloud cover increases after summer sea-ice loss, then this could act as an insulating blanket in autumn–winter restricting sea-ice recovery (positive feedback) and potentially creating multiple stable states (Abbot et al. 2011).
Though some form of a tipping point is already possibly in play, the likes of which we've seen in serious melt years. It harkens to the loss of multiyear ice very dramatically altering the character of the sea ice going into the next year.
More fundamentally, a ‘tipping point’ need not involve an irreversible bifurcation (Lenton
et al. 2008). Some models show that as the ice cap gets thinner, it becomes prone to larger fluctuations in area, which can be triggered by relatively small changes in forcing (Holland et al. 2006). This could represent ‘tipping point’ behaviour, even if the changes are readily reversible. Certainly such large ice loss events can have significant impacts, as was seen in 2007.
I expect 2014 to be a "bad year" for ice, in that it will sit in a ranking consistent with the long-term trends of man-made global warming. It's entirely conceivable it will finish with more ice preserved than 2013. Or a suddenly fast-melting August, as it happened in 2008, could suddenly align 2014 very close to 2007. Don't know yet. I am not looking forward to a moment of bifurcation, and I do think it will happen in my lifetime.
As for this year, Nares looks to be opening up. That will be interesting to watch as we enter the last half of July.