songster

not reallyWhat can one say to this? How are we supposed to form beliefs except based on evidence? This is a science forum.

Are you looking specifically at Greenland on those charts? Nobody disputes that the US and Canada have had an unusually snowy winter - largely because of the same blocking patterns that have reduced snow in Greenland.

http://www.independent.co.uk/environment/snowfalls-are-now-just-a-thing-of-the-past-724017.html

Well yes, the question is then whether Crackopalypse will accelerate the melt (because the ice is thinner in the refrozen leads) or retard it (because the leads allowed more ice to form, so there is more ice there to melt). As I said on the other thread, when the cracking happened, the ice that was in the Arctic before the event didn't just go away. It's all still there, presumably as thickened ridges elsewhere in the basin. We are currently at almost exactly the same (measured) area and (modelled) volume as last year, so the average thickness must be the same, it's just distributed differently. The ice in the refrozen leads is thinner, the ice between them must therefore be thicker if you believe the PIOMAS model.You could perhaps argue that a less homogeneous ice thickness is more prone to melting out, because the thin bits will melt out faster and expose open water, leading to albedo flip. However you don't get to pick and choose where and how to apply that argument - that's cheating. All across the Russian side of the Arctic, the ice thickness is more homogeneous this year than last (because of improved thickness in Kara / Laptev), while along the Canadian coast it is less homogeneous this yeat than last (because of Crackopalypse). PIOMAS is not data, it is a (good) model. If, as is very likely, it is significantly lower than last year, it does not mean that there genuinely is less volume, it means that the model predicts that there is less volume. This is an important distinction.

No, because we have no observations to use to check it, until Cryosat reports some months later. PIOMAS is a good model, but it is not data. If you want to to pontificate and prognosticate on what PIOMAS may or may not be modelling in mid-May, I'm happy to guess that it will be a new record low. What degree of low, I have no idea. I will note however that PIOMAS seems to disagree with you about the impact of Crackopalypse, since that was the point at which this year's modelled volume took a sharp upward turn relative to the last few years.

Yeah, if we get below 11 million before the last week of May I'll concede the omens are on for a new record (edit: context for that is that it would be 1.5 weeks ahead of the record to date, set in 2006). Below 10.5 million and we might be looking at a complete melt out. Otherwise, my general prediction is for a reversion to the mean downward trend and an extent somewhere between 2007 and 2012 - which is still catastrophic in the wider scheme of things. Overall, I'm expecting a series of whimpers rather than a bang over the next couple of decades.

Stop reading tealeaves. If I could have one wish granted this season it would be for people to only talk about melt rates if they're averaged over at least 5 days, preferably a week or so. Yes, today was a sharp drop on IJIS. A few days before that was a sharp rise, and a few days before that, a drop...[Edit: just checked the date of gagerg's post - after the first downward blip, which bounced up again two days later. I rest my case.] Right now we can say nothing at all about the melt rate except that since mid-late Feb we have been bobbling along more or less dead on the "2000's average" line, plus or minus noise. Nothing much interesting happens with Arctic ice extent until the start of June, because everything before that is happening in seasonal seas. Look how the lines cluster in late May. http://www.ijis.iarc.uaf.edu/en/home/seaice_extent_prev.htm

*sigh* Well, I asked for punctuation and Jesus tapdancing Christ did I get it.

Well, if you're interested in betting real money I'll happily put 50 quid on it. You say 5.8, I say 3.6-3.7, so split the difference and say that if it's above 4.7 I'll give £50 to your charity of choice, and vice versa? Or would you prefer a "nobody wins" buffer zone in the middle?

It's not a model, it's real data - the thing is it's difficult to see Arctic ice through clouds, and all the different sites use slightly different algorithms to remove the clouds. If you look at the pictures, you'll see that most of the change at the moment is in the sea of Okhotsk (lower left, scroll back/forwards a few days to see the changes). http://www.ijis.iarc.uaf.edu/cgi-bin/seaice-monitor.cgi?lang=e Right now there's a huge Lettuceoff cyclone sitting right on top of that area (look at the MODIS RGB channel to see what it looks like in optical wavelengths), so it's a miracle they're getting any data at all.

... you're expecting the ice to increase by 2.43 million (72%) in a single year? On what grounds?

In need of something all right. Grammar, punctuation and coherence would be at the top of my list.

I think he may be saying that if you take the last 30 years and average them, you find the average is slap bang in the middle :-)

The only quote from him I can find says nothing about the shards being related to the wavelength. If true, it's worth bearing in mind that he'll have been talking about swell waves, not surface ripples (the latter won't have enough energy to fracture ice). Swell waves have a wavelength from 150-500+m depending on the size of the ocean basin. Think, GW, think. Barber says a 100-mile floe collapsed in a matter of minutes. If it spread out the way you describe, then the outer edges of the fractured ice would have to have moved apart by 100 miles or so in that time frame. Short of a freaking nuclear bomb, you can't fling tonnes of ice that far that fast. I know that's what you envision. It's wrong. But that's not what Barber saw! What he saw was "a surface of heavily decayed ice composed of some small MY floes (1 tenth) interspersed in a cover dominated by heavily decayed FY floes (1 tenths) and overlain by new sea ice in areas of negative freeboard and in open water between floes." i.e. small chunks embedded in first-year ice, fragmented but not "spread" in the manner you envision. Here's the PDF: http://www.arcus.org/files/search/sea-ice-outlook/2009/10/pdf/regional/barber-etal-2009-regional-summary.pdf Yes. Yes it did. It thinned in situ and then got broken into smaller chunks that were glued back together with first-year-ice in between the remnants. Barber wasn't saying that the multi-year ice was collapsing and spreading out, he was reporting that it had already gone!

To be even-handed, I'll say that anyone going for over about 4.5 is similarly out of touch with reality. In the entire record, the largest year-on-year gain is slightly over 1 million, so 4.5 represents an absolute ceiling for sane prediction. I have no idea who the three going for over 4.8 are, but if they want to contact me by email I'll happily bet real money against any of them.

Effectively none. I've pointed this out to you a few times and you've never once given an indication of trying to think through the basic geometry of the situation. Your model is essentially one whereby a 3+ metre thick chunk of multi-year ice somehow spreads out and becomes a much wider area of 1-2 metre ice. The problem is that it's blatantly unphysical. Ice floes have a vast area in comparison to their thickness, they're tens, hundreds or even thousands of metres across. If you take a small multi-year ice floe, say 100x100m at 3m thick and then fracture it even further into a hundred individual pieces, each remaining fragment is still 3m thick and 10x10m in area. Collapse, yes, but there is no spread. "Spread" can't occur unless your floe breaks into shards that are less than 3m across. You're modelling it like a glacier calving, but an ice floe is not a glacier. The multi-year ice (call it "palaeocrystic" if you like, but please check the spelling!) is thinning in situ and becoming less concentrated. It is not increasing in area. Barber's "rotten ice" was not multi-year ice that had magically spread out and taken up more area. Rather, it was low concentration chunks of multi-year ice embedded in first-year ice. The point of his observations on the ground was to show that the remote observations were overestimating the remaining multi-year ice area, because (for various physical reasons) a 10:90 mix of multi-year:first-year ice was giving the same radar signature as 100% multi-year ice. That is very different from the process you outline as "collapse and spread".

Well yes, but they said that after 2007, and over the following two years the losses bounced back to the long term trendline. Tietsche et al showed the same for a very wide range of different ice levels. Arctic sea ice summer minimum seems to be governed by overall climatology, and not by hysteresis effects (pre-conditioning, "tipping points", or what have you). I don't see any reason for this season to differ. However, as and when it does bounce back to trend, it's important not to be misled into a belief that the trend itself is recovering.

3.6-3.7 million, i.e. reversion to the mean (but accelerating) trend and therefore a similar size "recovery" to what we saw from 2007-2008. Main difference is that 2012 is less of an excursion below the long term trend, and so the apparent recovery won't be sustained for a second year, unlike 2009.

Yay, time for a new thread! (Or we could just replay last year's since I don't anyone's opinions have shifted :-p )

I saw the same picture, on the same forum, and it was nothing to do with a break in the ice, it was a cap cloud forming as air rose up and over the New Siberian Islands (and several downstream ripples from the same process).

Well no, that's the whole point of how sea ice forms. Because saline water just keeps getting denser as it cools, the ice doesn't form until the entire water column below it (for many tens of metres at least) is chilled to the freezing point. You have to stir very deeply to bring up water warm enough to melt the ice.

Exercise: Do the same for the last few years looking for stories on the MMR/autism nonsense, or HIV/AIDS denial. You'd have orders of magnitude more.

... in the Beaufort, yes - but the ice has to go somewhere. Look at it this way: the ice is trying to move in a roughly circular pattern (the Beaufort gyre). The multi-year ice up in the Lincoln sea ain't budging much, so the stuff in the Beaufort gets put under tension and ripped apart. The flip side of that is that there will be compression around the rest of the circle, from the East Siberian sea, through the Laptev sea and across the pole itself. Looking at Hycom, the thinnest part of that is probably the Laptev sea, so I would guess that'll be the part to buckle first and ridge or over-ride.

A simple question. There is a reasonable area of leads opened up in the Beaufort, as we've all been discussing. Where has that ice gone? Given the temperatures, there are only three options. 1) Increased ice concentration elsewhere in the Arctic - i.e. there was a gap somewhere else which has now filled in. 2a) Export via Bering or Fram straits 2b) Expansion of the ice edge around Svalbard (i.e.the whole pack "moved over" a bit) 3) Ridging and thickening.

Eh, no. Yes, mechanical energy can lead to melt, but it does so by raising the temperature. All energy ultimately ends up randomised as heat - that's simple entropy. But if the heat isn't there, if the temperature is -50 degrees, then there's no melting going on. I think you're getting confused by the nature of the water phase space. Because water expands as it freezes, then yes, very high pressure can induce melting without changing the temperature. However, it's a vanishingly small effect, you need hundreds of atmospheres of pressure to affect the melting point by even a single degree, and it never gets down below about -20C (which occurs at about 2 thousand atmospheres). At pressures above that, the melting point goes up again. All of this is several orders of magnitude away from what you'd see in the Arctic! http://www.lsbu.ac.uk/water/phase.html