Binntho, no there is no confusion.
I'm not so sure - I feel confused all the time ...
The summer minimum does not appear to be that closely tied to extent or thickness at maximum.
I'm sure there is no year-on-year predictive value in looking at winter extent + winter thickness. Last year showed that very decisively. But I did find it intriguing that in the longer run, the decrease in winter extent (10%) + winter thickness (35%) = 45% which is the decrease in summer extent over the same period. But these are percentages of values eyeballed off some graphs, so I won't make any claims to them being particularly correct, valid or significant.
Having said that, I do think that winter thickness (which to all purposes is strongly linked to winter volume) is the most important metric when looking at what might happen if things continue as they are - which they might not, of course!
In my last post I talked as if all the ice melted at the same rate irregardless of thickness (which I think is close enough for our purposes) and location (which is obviously wrong). Ice further south melts faster, ice closer to warm waters melts faster, ice closer to the periphery melts faster. And no doubt there are other factors to consider as well. This is a very complex 4 dimensional system, no single metric is going to tell us what the future might hold.
Only that ice which is very thin will experience large melt each year, the rest will not. This non-uniformity will extend the timeframe until an ice-free Arctic much longer than expressed by others here.
I'm not sure I follow your logic here. The "non-uniformity" you speak of has been there all the time, why should it change the projected outcome?
Thinner ice obviously has a higher chance of melting out than thicker. When has that not been true? But there is so much more thin ice than thick ice now, that is a change that has been ongoing for some time now. So shouldn't we conclude the time frame will be shortened rather than extended?
But all this talk of linearity and trends assumes a resilient system undergoing slow but steady change. And so far the Arctic has behaved like that, and the increasingly chaotic weather is, at least not yet, the decisive factor that it may become.
Personally I feel that the resilience is being chipped away, eventually to crumble into chaos. Using warlike metaphors fitting for this weekend, the ice is like a fortress that rebuilds its defenses each winter, only to suffer an increasing onslaught each summer. So far the ice has managed to retreat, and pulling its defenses along with it. But there is only so far it can go before the defenses crumble and the foes manage to destroy the rest. And this might happen quite suddenly.
The best defense of the sea ice is it's sheer size - even at minimum it's huge, maintaining a frigid atmosphere above and a cold-water lens below. Even as the ice becomes more fractured and mobile, the icepack maintains it's integrity, i.e. it is basically continuous at minimum, and landfast.
Going back to our original starting point of the landfast ice north of the Canadian Archipelago - this ice has so far mostly moved along the shore but can't very well move away from shore, mainly because of resistance from the ice further out. But as extent drops the whole area may break up and start drifting away from the shore. Two million km2 of ice that is drifting freely in the Arctic for a few weeks will really take a battering, the most serious consequence perhaps being that wave action and dispersion will break up the protecting underlying cold water lens.
We saw an example of how this might happen this winter, when a strong southerly wind managed to push the ice tens or even hundreds of kilometers away from the shore of Greenland, in an area of thick ice that does not melt out during summer (although it is pushed towards the Fram strait to eventual doom).
So my feeling is that irregardless of current linear trends, when we get closer to some threshold, all metrics may well plummet quite fast, as the normal resilience of the Arctic Sea Ice gives in to encroaching chaos. Logically one might then guess that the sea ice might vanish before the first of the linear trends reaches zero - but perhaps not. Perhaps we will see a period where e.g. volume flattens out while extent continues its linear decrease.
But then again, a minimum extent of 4 million km2, which is what we may expect at present, is already very fragile as the extreme melt of 2012 shows, when a combination of clear skies in early summer and very strong storms towards the end of summer caused extent to plummet by 2 million km2 in just over one month.
But I admit, that this is just my opinion also, and the Arctic will do whatever it does, regardless of what we say it will.
So true ...