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"It means that the decrease could be regressing to the linear trend, instead of deviating from it and becoming more of an exponential downward trend." It'd be nice if this were the case, but honestly I doubt it. Given the feedbacks inherent in the system, nonlinearity of some sort (negative or positive; it could follow a Gompertz-esque curve, after all, as the models would have it) seems likely. I can't see much physical justification for an assumption of linearity. ...But then, I've been wrong before. I thought 2013 was going to be a year of dramatic melt, for example...
Toggle Commented Jan 10, 2014 on PIOMAS January 2014 at Arctic Sea Ice
Reprieved, reprieved! This is a lot better than it could have been. Not good in any sense of the word, and the Arctic being the unpredictable beast it is things could always change at the eleventh hour, but this could have been a heck of a lot worse.
Toggle Commented Aug 3, 2013 on PIOMAS August 2013 at Arctic Sea Ice
Many thanks for the update, Neven! The continuing high pressure systems you mention are rather foreboding, particularly considering that it was at about this time that 2012 ceased its spectacular June freefall; I'll be interested to see if the high pressure persistence allows 2013 to catch up. if I'm very much looking forward to the average June NSIDC concentration graphs; I notice that the final shape of the ice following both the 2012 and 2007 melts VERY roughly matches the configuration of consolidated vs. fragmented ice in the June average concentration maps, and although that suffers the triple flaws of minute sample size, subjective judgment, and retrospective comparisons, and thus probably isn't worth a hill of beans*, I'm under immense suspense this melt season and I'm liable to grasp at any potentially-predictive straw I can find. *Which, I imagine, would actually be worth a fairly large sum of money. Let us suppose that this is a very small hill of beans. Or just one bean, maybe.
I can't fathom how we could possibly get a monthly average extent of zero for September (particularly since by that point both melt and freezing are going on at different points in the Arctic, and if everything's melted in the hot bits...well, there's nowhere to go but up), but that's your business, Paul, not mine, I guess. Anyway. I'm kind of flummoxed, frankly. On one hand, so far there's little of the massive fragmenting on the perimeter that led to the spectacular Pacific-side collapse we saw in 2012, and I'm just not really ready to believe that ALL of that ice could melt out again so perfectly this year. On the other hand, that recent cyclone has bashed a huge swath of ice in the central Arctic to bits. Melt will proceed more slowly there than it would have if the fragmentation had occurred perimeter, but it will happen. I'm just not sure whether the slow speed of melt there will be overwhelmed by the combination of melt from both the inside and the outside, or vice versa. There's also the matter of whether the March fragmentation will have a significant effect, leading to a repeat of 2012's Pacific collapse. Goodness knows I've no answers to that. I suppose my guess is for an average extent below 2007's (thanks to the greatly-reduced volume and central cavity) and possibly below 2012, but if so not too far below. Probably a wee bit above. Shall we say...3.8 million km^2? I don't recall what my previous prediction was, but it was definitely lower than that, as I was expecting a faster start to the melt season and a May drop in volume that never happened. Mind, I would also expect an absolutely bizarre distribution of ice in the final reckoning, with a huge bite taken out of the Atlantic side, battered but intact ice above Greenland and the Canadian archipelago, and fragmented, thin, but still unmelted ice over towards the Pacific side.
Lodger: That did occur to me as a possibility, but if that was so, wouldn't the data be limited to spring and mid to late summer, with empty patches during the minimum and maximum? Instead, we only get data during the refreeze, with none during the melt, when I'd think... Oh. Hm. Not sure if this is correct, but it occurs to me that the problem might be melt pools on the surface of the ice. After the minimum and on up to the maximum, the pole is shrouded in darkness, and there shouldn't be any melt pools on the surface of the ice--so if the satellite detects open water, it's definitely a crack in the ice itself, and not water pooling on the surface. During the melt season, though, you would get multiple pools forming, which would (depending on the ice thickness and its surface geometry) give multiple different values for the level of the water, thus preventing an accurate calculation of the ice freeboard. I suppose one might get around that by devising an algorithm that only looked at fissure-shaped patches of water, although I don't know enough about how the ice behaves to know if that would really work.
Finally, a graph of Cryosat-2 data! I was beginning to think they'd never release it. I'm puzzled by the lack of spring and summer data, though; does anyone know the reason for that? Is there something about sunlight reflecting off of the ice that makes taking readings difficult (more microwave light emitted by the ice and water themselves, perhaps)?
Thanks very much for the info, Wayne! That's very interesting; I wonder if that ~-11 ˚C temperature would change with different ice thicknesses? That is, would warmer air temperatures be needed above thicker multiyear ice vs. first year ice before the fragility you mention started to become apparent? On another note, that video is breathtaking; I'm particularly interested by all the beautiful, silvery air bubbles (I presume?) visible on the underside of the ice. I highly doubt that they have any real importance in terms of the behavior of the ice, but I do wonder where they come from; surely, no gases released from further down in the water column would make it that high without being dissolved. Air trapped under the ice by wave motion, maybe, or perhaps a much gentler version of the famous diet Coke + Mentos "reaction," with the underside of the ice providing a highly textured substrate that makes it easier for gases to emerge from solution.
Wayne, would you mind giving me a link for that "-11 ˚C air temperature required for freezing" bit that you mention? I've done some (admittedly, cursory) scrounging around, and I can't seem to find a reference that mentions that value.
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Sep 24, 2012