Three views of sea ice

The troops are getting restive. What wil happen to this year’s sea ice? Rumours abound. Let’s look at some pictures.


Probably the least interesting is this one from NSIDC. But it looks exciting, doesn’t it. Woo-hoo, look, the sea ice now is lower than it was in 2007, that means it will be at minimum, too, doesn’t it? Well no, of course not. Look at this one from AWI:


2006 was well below 2007 at this point, and turned out to be uninteresting. As far as I know, no-one believes in predicting the minimum (which, of course, is the only number anyone gives a toss about) based on previous months. And when I say no-one cares about anything else that isn’t really true; various people have started caring about the ice volume instead, but I’m a bit dubious about how exciting that is.

But for no reason that I can strongly justify, I happen to prefer the IJIS AMSR pix, reproduced below:


Which is similar too, but clearly not identical too, the AWI pic. Which shows the obvious: that retrieval from space isn’t exact.

Anyway, so what? So, it is not too late to join in the great predict-sea-ice-this-year party. My entry this year is “the same as” last year: linear trend since 1979, this time *not* omitting 2007 or 2008. As I recall, last year RMG was kind enough to work out what that came to in real numbers; perhaps he will again. As before, the possibility of a bet only really makes sense if people actually think very differently from me: which would be, either they think that there will be substantial ice growth this year, or some sudden collapse.

So, there you go: usual money on offer, which is to say “unlimited”, in the sense that so far no-one has wanted to take me close to my limit. If you manage to get there I’ll let you know.

I’d also be interested in the other betting pools that are presumably around this year.

* Me declaring victory in 2008
* The 2009 results
* Me wondering, in January, what we might bet on this year and various people making impractical suggestions 🙂

[A couple of updates: firstly, I should mention that Gareth has been pushing the ice volume stuff and I admit that picture does look interesting.

and second, NB says “The ice is looking uncommonly mushy on MODIS” which I think I’d pay attention to, and look at myself, if I had the time. Maybe during tomorrows’s batch of compilations.

And third, the default bet is:

That the september mean ice *extent* be below 4.835; but with a “buffer” where we call it a draw: between 4.735 and 4.935, no one wins. I’m taking the “high” side of this; anyone interested in the “low” side let me know. For my part, 4.835 is arrived at as the 1979-2009 trend extrapolated, minus 0.5 which is the SD. It seems to have become tradiational for people to bet small amounts, which is fair enough if we’re just playing. But this was intended to flush out the “the sea ice is in catastrophic decline” people. OTOH, if there are any “the sea ice will certainly recover this year” people then you can get odds on trend-plus-SD, i.e. ice being above 5.835 if you like (note that those are all spuriously precise but never mind) -W]


55 thoughts on “Three views of sea ice”

  1. What odds are you offering on:
    1) Less than last year? [no odds]
    2) A new minimum? [I regard that as unlikely]
    3) Less than 4 M km^2 [very unlikely]
    3) Less than 3 M km^2 [not a chance]
    4) Less than 2 M Km^2 [ye cannae break the laws of physics]
    5) Less than 1 M km^2 (in othr words ice free?) [definitely not]



    [I regard 3 onwards as very unlikely; in an ideal world I’d give you odds of at least 10-1 in your favour; but in this world, I can’t see the point, as I wouldn’t make enough for it to be worth my while. 2 you can have 2-1 in your favour – is that good enough? -W]


  2. FWIW: If we get a warm summer, I think 2007 is in the sights — could be more, could be less, but less than last year in any event. Reason? My new favourite graph.

    This melt season is starting with a lower volume of ice than 2007/8/9 – the lowest in the record – and thin ice can disappear quickly.

    But no bets, unless they’re in quatloos… 😉


  3. Do the sums and I’ll take £10 on the low side. I’m not particularly expecting to win, but if I do then some cash in hand would be compensation for the sense of impending doom.

    The ice is looking uncommonly mushy on MODIS. I’ve been watching it for years and I don’t remember it being quite like this in May.


  4. I think the most important point in all those graphs is the difference between the long average and the recent years in #2. Variability within even a decade is low, but recent years compared to the multi-decadal average stand out quite clearly.


  5. Bets are on. I’m doubling down on the beer from last time.

    Prediction: the 2010 minimum will be a record low, by a wide margin. There is a hint of method in the madness: we’re starting from low ice volume and are experiencing slow development of the first year ice, plus we’re in the rising phase of a sunspot cycle to give things a little boost.

    But really I’m taking a flyer.

    [“A record low, by a wide margin” – hmm, that sounds takeable. How about defining “a wide margin” as “by as much as 2007 exceeded the previous record”? Sets you a high bar, though -W]


  6. Another hint things are heading downhill?

    NSIDC notes that “changing wind patterns have caused older, thicker ice to move south along Greenland’s east coast, where it will likely melt during the summer.”

    But in the “he said, he said” spirit of modern journalism, for balance we turn to Anthony Watts’ prediction:

    “What can be said about the short term trend in Arctic sea ice is that for the past two years, it has recovered from the historic low of 2007. It recovered in 2008, and more in 2009. If today’s Earth Day gift is any indication, it appears that it is on track now for a third year of recovery in 2010 as we’ve been saying at WUWT since fall of 2009.”


  7. >”As I recall, last year RMG was kind enough to work out what that came to in real numbers; perhaps he will again.”

    Tut tut. You should have read the comments to posts you linked and found in post 14 of

    that the numbers had already been run for you:

    [Ahem. Ah yes. Thank you 🙂 -W]

    “Williams default position of “will fit the 1979-2009 slope extrapolated to 2010” on extent column of
    gives a line of 163.4-0.078625*year which gives 5.37, 5.29 and 5.22 for 2010, 2011, and 2012.”

    or were you wanting 5 day average minimums rather than September average?

    [Good question. My personal preference would be for September average, but the excitement tends to be over the absolute minimum; and since we’re not really doing this for Science, perhaps we should go for the Headlines -W]

    Anyway you going for 5.37 and others going for ~4.3 = sept 2007 extent figure suggests betting on September extent being above or below 4.835 million km^2.


  8. I’m not sure about the detail so no bets on this season’s minimum from me, but the ice volume figures do suggest bad news for the long term. Ice extent often holds up quite well and this gives the summer ice reasonably stable albedo, but the loss of volume is more significant, and visual reports from recent scientific expeditions tends to support the view that the ice is likely to continue melting, and at an accelerating rate over the long term.

    At this point, anybody making optimistic predictions of Arctic recovery is just whistling to keep his courage up.

    [Agreed; I don’t think anyone credible is predicting *recovery* -W]


  9. Incidentally, I don’t find it at all surprising that you’re leading your announcement of the betting pool for Summer, 2010 with an unfashionably disparaging reference to the pessimistic data point that’s making the rounds of the blogs at the moment–the recent tantalizing dip in an NSIDC Arctic sea ice graph below the equivalent level for the infamous Summer, 2007 season.

    These factoids based on a single data point show up with distressing regularity as talking points on blogs by people who should know better. We should leave the selective use of statistics to those who have nothing else to sustain them.

    (And of course, my “whistling” reference was as I think you guessed a richly deserved swipe at Watts)



    Not sure if that graph will display but is an intrade graph of prices that can be roughly interpreted as probabilites of 2010 minimum per IARC-JAXA being higher than 2009. I have sold 5 ($10 contracts) at 50, sold 5 at 45, bought 2 at 35 bought 5 at 37 and sold 3 at 43. So I have been involved with 20 of a total volume of 30. The best buy and offers at 22 and 48 are also mine.

    Anyway, you might prefer to be aware of that contract rather than just seeing a few odd bets here that only provide a snapshot. Instead you will be able to see the estimated probabilities change over time.

    Of course, if you don’t think intrade probabilites are doing a good job, then join intrade and make some money 😉

    [Well, thanks for that. I can’t see it from work, but will when I get home. But you are right: if there is money to be made in the real world, no need to limit myself to a little pool -W]


  11. The explanation page for that chart Gareth recommends on sea ice volume — update rate and the model they’re using with links:

    “… The blue line represents the trend calculated from January 1 1979 to the most recent date indicated on the figure. Total Arctic Ice Volume for March 2010 is 20,300 km^3, the lowest over the 1979-2009 period and 38% below the 1979 maximum. September Ice Volume was lowest in 2009 at 5,800 km^3 or 67% below its 1979 maximum. Shaded areas represent one and two standard deviations of the anomaly from the trend. Updates will be generated at 3-5 day intervals….

    Model Validation
    PIOMAS has been extensively validated through comparisons with observations from US-Navy submarines, moorings, and satellites. The example on the left shows a comparison of PIOMAS-derived ice volume anomalies with anomalies measured by the NASA ICEsat Satellite. More details on the model, assimilation procedures and validation results …”


  12. #11

    Anyway you going for 5.37 and others going for ~4.3 = sept 2007 extent figure suggests betting on September extent being above or below 4.835 million km^2.

    I would definitely take below on that bet. I’m not sure W. has expressed a willingness to take the high end on that one though.

    Suggestion: why not offer both bets (i.e. September average *and* minimum)?


  13. You reckon William will lose big on his bet on the linear trend, bigcitylib? How low do you think it will go, and why?


  14. How about it, then?

    [You’re on, in principle. Sorry I’m slightly out of touch (how ironic). I presume 4.835 is last year, minus additional trend, minus 0.5, but that doesn’t look quite right.

    Sorry for the delay – I sort-of wanted to look at the Intrade stuff, and still do -W]


  15. I got 4.835 from crandles above; I haven’t checked the sums. I’ll leave it with you; drop me email.


  16. #11, 18
    4.835 is halfway between the Sept. linear trend to 2009 extrapolated to 2010, and Sept. 2007 minimum. I’ll take below that for 10 pounds even as well. But I’d also suggest a “buffer” where we call it a draw (e.g. between 4.735 and 4.935, no one wins).

    [OK, another small spender :-). Buffer is fine too -W]


  17. Yes, that sounds good to me. Alternatively, a linear bet, a penny or two per thousand km^2, with the zero-point at 4.835. Exactly how and when will the bet be decided?

    [The blog-owners decision is final. Unless anyone is prepared to put up over £100, in which case I’ll admit an external arbiter -W]


  18. I didn’t see a pointer to the second graph’s source. So here is one.

    [Thanks. It wasa missing “>” on my part, now corrected -W]


  19. Your description of the calculation producing the 4.835 figure is different from crandles above (he split the difference between the trend prediction and the 2007 number). For the complete avoidance of doubt, here is my offer:

    If the september mean arctic sea ice *extent*, as reported by NSIDC in their monthly update, is below 4.735 million square km, you pay me £10; between 4.735 and 4.935, no one wins; above 4.935, I pay you £10.

    Accept by edit to this comment.

    [Accepted -W]


  20. Well, William, I probably don’t have any interesting bet for you this year. At least not now that you’re allowing the last 3 years of low sea ice into your predictor. I get 5.37 million km^2 for the linear prediction of this year based on all of 1979-2009.

    I’m still working on the details for my contributions to the sea ice outlook. The model-based prediction is about 5.15 million km^2, which leaves awfully little room for an over-under between us. The statistical one will be something like 4.7, which gives a bit of room, but not a lot. It’s less when you consider that I don’t disbelieve our model more than the statistical.

    Still, averaging the two, I get 4.93 million km^2 (almost the same as my statistical prediction for last year!?). That’d suggest an over/under line of 5.15. Given how close last year was, if NSIDC reports exactly 5.15, no bet. Anything over that is your win, and anything under it is mine.

    Per my usual, it’s 50 quatloos, not cash.

    I’ll take this up at a little more descriptive length at my place next week. The statistical method is better fleshed out this year, and leads to some interesting (to me at least) comments about when we’re liable to be seeing 0 extent years.

    [At the moment, I don’t feel confident enough to risk anythink no over/under 5.15. I’ll look for your post next week, though, and see if that convinces me -W]


  21. What does one years number tell us anyway? Shouldn’t we be predicting the trend for 2009-2014 or something like that?

    Trend for Sept extent 1979-2009 is -.079 m km^2.
    Trend for Sept extent 1995-2009 is -.152 m km^2.

    WC, your 0.5 SD margin is really rather large compared to the differences in trend which gives the impression that perhaps you are the same as the rest of us in expecting some acceleration in the rate of extent reduction but simply at the low end of the rate of acceleration compared to some/most people. Not being prepared to bet even a few quatloos on over 5.15 would seem to back up this view.

    So what to do to flush out your views more fully?
    Can I invite people to post their expected rates of decline?


  22. A sea ice question:

    The Arctic tends to spin, and this spin would tend to fling the heavier water to the outside and push the lighter sea ice into the middle, shrinking the ice extent. Is this effect strong enough to matter in the real world? Would years in which the AO reinforces this spin tend to compact the ice more than normal and years in which AO opposes this spin have less of a compacting effect?


  23. “… the acceleration in the sea ice decline since the mid 1990s may have been partly triggered by the strongly positive AO mode during the preceding years (Rigor et al. 2002 and Rigor and Wallace 2004) that flushed older, thicker ice out of the Arctic…. However, the longevity of ice in the gyre began to change as a result of warming along the Alaskan and Siberian coasts. In the past, sea ice in this gyre could remain in the Arctic for many years, thickening over time. Beginning in the late 1990s, sea ice began melting in the southern arm of the gyre ….”


  24. 3) Less than 4 M km^2 {I regard 3 onwards as very unlikely; in an ideal world I’d give you odds of at least 10-1 in your favour}

    You have stated you will not take this bet in cash, fair enough, would you give 10-1 on less than 4×10^6 km2 on IJIS in quatloos?

    Or perhaps even odds on less than 4×10^6 km2 on IJIS over the next decade? Or some other level?


  25. Today’s pictures are clearer:less cloud over land, very thin cloud over the sea.

    Interestingly, running blink comparisons on this tile over the last few days, all these big floes seem to be moving west, at about 1 km/hour. I would expect them to flow east, towards Fram Strait, but they are heading for the Beaufort Sea (apart from a small area in the Lincoln Sea, which is flushing down the Nares Strait). Someone who is technically competent could put together a little movie. In any case, it all seems to be much more broken-up and mobile than I would like.


  26. Just got back from a marvellous week Off The Net. Do you have any comment on the current state of those various graphs, or of the ice north and east of Cape Morris Jesup?


  27. Are you still taking bets on the 4.735 or below vs 4.935 or above? I’ll bet £50 on below if you are.

    [Yes, still going. Taken -W]


  28. Regarding the ice to which I refer, it is breaking up, but doesn’t appear to be moving anywhere. Here’s yesterday:
    Compare to a week previously:
    And two weeks:

    For those who like to watch the North-West Passage, here’s a great tile from Sunday:
    and from a week earlier:


  29. That earlier NWP shot looks (to me) to have quite a bit more thin cloud over parts of it. The difference *may* not be as marked as it first looks – though I’ll admit I’ve not looked at these sort of shots that much.


  30. Adam@40: yes, there is more cloud in the earlier shot. You can get a clearer view in some other shots from the same week, and the Aqua shots. In short, the eastern end of the ice bridge has retreated some distance (while the western end has not), and a large area to the south of the deep-water channel (in the McClintock Channel?) has broken up.

    I’m just advocating watching these MODIS mosaic shots, generally, to add excitement to the horse race. Also some of them are very beautiful. I might get around to writing a bit of Python to suck tiles down and make animations out of them.


  31. Thanks Nick (@41) – think I see what you were getting at. I was distracted two broken areas that didn’t look broken up in the first one until you looked carefully though the cloud.

    Quick & dirty bash script:
    for (( i=150; i <= 170; i++ )); do
    feh -dF *

    Left & right arrow keys in feh will step through, otherwise I believe you can set-up an automatic transition time in slideshow mode, too. Or create a contact sheet, etc.


  32. Sorry missed the less than symbol – I had changed it but it reverted when I edited the previous post in preview mode.

    Thanks Nick (@41) – think I see what you were getting at. I was distracted two broken areas that didn’t look broken up in the first one until you looked carefully though the cloud.

    Quick & dirty bash script:
    for (( i=150; i <= 170; i++ )); do
    feh -dF *

    Left & right arrow keys in feh will step through, otherwise I believe you can set-up an automatic transition time in slideshow mode, too. Or create a contact sheet, etc.


  33. I’m one of those “the sea ice is in catastrophic decline” people and I’m willing to put my money where my mouth is, i.e. bet that the September mean ice *extent* will be below 4.835 M km^2. I don’t earn much teaching here in Thailand, but I am willing to bet about an eighth of my monthly salary (which at the current exchange rate from Thai Baht to British Pounds is about 100 pounds stirling). BTW, I am a regular reader of and I don’t usually gamble, but I regard this as as close to a sure thing as I am going to find, and certainly better than betting on the outcome of the World Cup. So, who’s going to hold the money? PS found your website through The Economist June 15, 2010 online edition.


  34. After a month or so of thinking my money on this bet was surely lost (July weather having been very bad for melting), some melting and compaction in early September puts us exactly in the ballpark, and right now I think it’s a toss-up between WMC winning and this ‘buffer’ area. Depends on how long the current melt goes on before we bottom out, and on how rapid the extent recovery is.

    [Mmmm, it is all coming down to the wire 🙂 -W]


  35. In fact, coupled with David Barber finding how rotten multiyear sea ice has become and choppier conditions, I’d hazard a guess that extent will continue to decline next week, even nosedive.


  36. Some time before, I needed to buy a building for my corporation but I didn’t have enough cash and couldn’t order something. Thank God my dude proposed to take the personal loans at reliable creditors. Thus, I acted that and was satisfied with my short term loan.


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