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Better weather might have played some role, but it doesn't look that much better on the whole. January and especially February of 2013 were colder than of 2012 which closed the deficit. But on the other hand, the preceding period was warmer, but the deficit did not broaden. On the whole 12-13 was able to catch 11-12 despite its considerable initial deficit.
I guess my question here, is why would 2012/13 winter re-freeze SIA *not* catch up to 2011/12? We aren't yet at a place where the energy input during the summer/melt season combined with existing enthalpy is even close to preventing a complete refreeze of most of the basin by February. The only thing that might affect that would be serious circulation between the surface and deeper layers warming the surface vigorously at a rate high enough it would keep the surface about -2C. That's a pretty tall order, and unlikely except directly over where the relict North Atlantic flow enters the basin (interestingly enough, directly under the low-concentration band sweeping across the middle of the CAB...)
Further feed back question - once the refreeze is complete, we've put a insulating cap on the largest source of heat available, and directly limited the amount of heat that can be radiated out of the atmosphere. One line of logic here that we missed in spring might be that the February/March break up may have allowed enough heat out of the basin to slow the onset of melt. That's a bit tough to justify though, because of how quickly the leads refroze, and how rather small area they opened to radiation. So the question, reached circuitously is, how would a large expanse of generally thinner ice, of approximately the same area make any difference in the melt rate?
The open water and thin ice readily thickened, as theoretically expected. Given identical weather, you wouldn't even expect the deficit to be totally erased. You'd expect the deficit to be halved or something. But it was completely erased. Probably partially weather, and partially the greater radiation of open water and thin ice than thick ice.
Here I'm going to disagree - the physics isn't with you, I think. Given identical weather as you put it, I'd absolutely expect the refreeze to make up the SIA deficit, as it isn't really as dependent on air temperature, as it is on the lack of insolation. As I mentioned above, I don't think sufficient enthalpy or inputs exist yet outside of insolation that would significantly slow the refreeze. Raise the temperature of the entire water column a degree C or so, and I think then we'd see something very different, but that absolutely isn't going to happen year over year.
I think to understand this year, we need to go back to one of your other factors - albedo - and less directly, cloud cover. One of the notable aspects of late May and June was the storms and cloud cover that entered the arctic, and for the most part, stayed. That, much more than the end of winter SIA had the most to do with slowing melt. The lower air temperature isn't enough to explain it, as the ability of warm flow from the continents simply doesn't transport enough heat to make much of a difference other than to remove snow cover and a few tens of CM of surface ice.
I think we need to look more at the interaction between total heat content and salinity in the arctic basin, and what effect that has on circulation and the very narrow dynamic temperature range driving melt. Thinking in terms of scales of energy, that and total insolation are key, not so much weather.
If it were clear, even if a degree or so cooler, I think insolation would have overwhelmed that anomaly. This year, with as much persistent cloud cover as we have had, I think the albedo of the ice itself was far less material to what we saw happening, and as such means the refreeze is less important than other factors.
Regarding volume, I'm coming to think that is less meaningful a factor as practically affecting melt. As we saw last year, large volumes of thick ice shuttled into the Beaufort did not hinder it melting out. Rather, volume I think is more a measure of the coherent strength of the pack, and its ability to resist other forces being applied to it. I think we need to settle the question of just how much difference a "mesh" pack vs. "cottage cheese" pack makes in terms of net loss or capture of heat over time, and whether it is a symptom or contributor to reduction of the pack. That it *is* having a dramatic, negative effect on terrestrial animal life and sea mammals is almost a certainty.
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