F.Tnioli,
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However all of that relies on continually increasing melt season losses. This is not guaranteed, nor is it likely in my opinion. A large element of the increased losses is not due to a long term increase in volume loss during the melt season, but is due to step jumps after 2007 and 2010, both years of large volume loss.
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Critical is understanding what is leading to the increased loss of volume during melt seasons. It is increased amounts of ice in thinner categories leading to greater open water formation and greater ice albedo feedback. If thickness merely tends to a nominal 2m in April then further gains through April thinning will not happen. The process will instead be more gradual.
Therefore I doubt that seasonal losses will continue to increase as they have done in recent years.
I doubt it too, but not in a way you do. My doubt is related to the lack of complete knowledge of all possible major factors which influence Arctic melt mode. There is, if small, possibility that anthropogenic (man-made) change may be a major factor - few years ago, i've seen a part of a very serious discussion of a few very serious scientists which i (nor any member of general public) was not supposed to be able to see, and it mentioned that "we have to start it in 2013, otherwise it'd be too late" - they were talking about cooling the Arctic artificially. I do not exclude the possibility that they actually started to do it, exactly in 2013 indeed.
But other than that, i think you are missing some important factors which accelerate summer melt even when practically all ice is FYI:
- the change of average chemical composition of FYI in recent years. Generally, afaik, average salt content of the ice is increasing, and i believe this leads to easier melt (ice melts at lower temperature);
- naturally fluctuating SSTs for most of world ocean, and influence of this fluctuation upon Arctic. Most simplifying, one can relate to El-Nino / La-Nina events,
http://ggweather.com/enso/oni.htm . As you see, 2007 and 2010 volume drops relate very nicely to distinct peaks of SSTs worldwide. There is some time lag and variability - the fraction of warmer near-surface water energy which ends up in Arctic is different every time, and paths are not the same - sometimes it takes longer for much El-Nino heat to arrive to Arctic than other times. Yet, general correlation is definitely present. Well, last ~1,5 years were rather calm, and luckily, possibility for a strong El-nino starting early this summer did not materialize, but current reports (
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf , etc) indicate some 80% probability of El-nino this fall. If it happens, - even moderate-strength El-nino may result in yet another massive drop of minimum annual volume some time in 2015 or 2016. You shouldn't exclude such drops - these are a very part of average trend; if you exclude such years, then also at least exclude same number of years which had most freeze up - and then calculate;
- vast areas of shallow Arctic continental shelf are now open to sunlight for a large part of high insolation months. Those will release methane in rapidly increasing amounts. Some already do, since ~2010. We talk ~hundred million of tons of the gas - annually. For now. In some 10...20 years, it may get to Gt-scale. I hope you do know GHG properties of methane. If you do not, you should. What's not usually mentioned, though, is the local effect. See, methane GHG potential is multiplied by high insolation during Arctic June/July, - i mean that the more energy comes in per day, the more energy (in absolute numbers) end up being trapped by the same amount of GHGs. Plus, local concentrations are, of course, much higher than worldwide averaged methane content, - this is also sometimes forgotten. Last but not least, local warming above/at Arctic shallow continental shelves which contain much methane clathrate not far from seabed, - will of course create self-reinforcing feedback: the more methane ends up in the air in the region (for a substantial time) -> the more energy is trapped by this methane's GHG effect -> the faster warming goes -> the faster methane gets released. In a sense, now-nearly-complete loss of MYI was one big thing shaping the mode of Arctic melt, yes, - but methane release in Arctic is likely to become the "next big thing", you see. If you are not familiar with dr. Shakhova and dr. Semiletov papers and interviews - perhaps you'd like to seek them: those are scientists who are working there, in the field, in Arctic, and their work is much about methane clathrates (among other things). Findings are not exactly... encouraging.
- Thermal inertia and recent massive warming of Arctic. See, Arctic surface temperatures rised up much higher than world average during late 20th century and 2000s (
http://appinsys.com/globalwarming/RS_Arctic_files/image026.gif ). Estimates vary, somewhat; personally, i estimate Arctic is now some ~3,5C above pre-industrial, if not more. And most of this change happened after 1990. Thing is, thermal inertia is a huge thing in all large things oceanic. Arctic is not an exception. Again, estimates vary, but general agreement is some 30...40 years - is the time which is required for any deep ocean to get saturated with heat enough to approach the new equilibrium. During this time frame, ocean absorbs much of the energy which otherwise would go towards increasing surface temperatures. But obviously, as it does so, - it loses its potential to do so (granted that forcing would become stabilized - which is, of course, not the case; i am just trying to illustrate physics of it). End result is: what melt we've seen so far - is mostly the result of things done some 25+ years ago; things done since then - in 1990s, in 2000s, and last few years, - are mostly not yet reflected by the state of Arctic ocean (and thus, its ice). Yet, we know what were the things done during last ~25 years - namely, mankind emitted about as much carbon dioxide as it did during all of its previous industrial history (yep, just in 25 years or so!); massive increase in forest fires average strength and amount, resulting in more CO2 into the air; methane content has rised, too; industrial and transport activities in Arctic more than doubled.
How exactly you can expect any sort of stability in such conditions - is beyond me. Sure, it's possible theoretically - if humans would indeed geoengineer in the Arctic powerfully enough, and/or if the Sun suddenly would get cool enough, or, say, if good aliens would arrive to Earth and lend us a hand of knowledge and galactic friendship, for a funny example. Because if things go "on their own" - Arctic already has more than needed to see it ice-free in about some 5...10 years, the only thing preventing it from being ice free right now (by the end of the summer, of course, - not year-round) - is thermal inertia mentioned above...