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Sea ice minimum forecasts

Filed under: — gavin @ 17 July 2009

One of the interesting things about being a scientist is seeing how unexpected observations can galvanize the community into looking at a problem in a different way than before. A good example of this is the unexpectedly low Arctic sea ice minimum in 2007 and the near-repeat in 2008. What was unexpected was not the long term decline of summer ice (this has long been a robust prediction), but the size of 2007 and 2008 decreases which were much larger than any model had hinted at. This model-data mismatch raises a number of obvious questions – were the data reliable? are the models missing some key physics? is the comparison being done appropriately? – and some less obvious ones – to what extent is the summer sea ice minimum even predictable? what is the role of pre-conditioning from the previous year vs. the stochastic nature of the weather patterns in any particular summer?

The concentration of polar expertise on the last couple of questions has increased enormously in the last couple of years, and the summer minimum of 2009 will be a good test of some of the ideas that are being discussed. The point is that whether 2009 is or is not a record-setting or near-record setting minimum, the science behind what happens is going to be a lot more interesting than the September headline.

In the wake of the 2007 minimum, a lot of energy went in to discussing what this meant for 2008. Had the Arctic moved into a different regime where such minima would become normal or was this an outlier caused by exceptional weather patterns? Actually this is a bit of false dichotomy since they aren’t exclusive. Exceptional patterns of winds are always going to be the proximate cause of any extreme ice extent, but the regime provides a background upon which those patterns act. For instance, in the paper by Nghiem et al, they showed the influence of wind patterns in moving a lot of thick ice out of the Arctic in early 2007, but also showed that similar patterns had not had the same impact in other years with higher background amounts of ice.

This ‘background’ influence implies that there might indeed be the possibility of forecasting the sea ice minimum a few months ahead of time. And anytime there is the potential to make and test predictions in seasonal forecasting, scientists usually jump at the chance. So it proved for 2008.

Some forecasting efforts were organised through the SEARCH group of polar researchers, and I am aware of at least two informal betting pools that were set up. Another group of forecasts can be found from the Arctic ice forecasting center at the University of Colorado. I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).

What was particularly interesting about last years forecasts was the vast range of forecasting strategies. Some were just expert guestimates, some people used linear regression on past data, some were simply based on persistence, or persistence of the trend. In more mature forecasting endeavours, the methods tend to be more clustered around one or two proven strategies, but in this case the background work is still underway.

Estimates made in June 2008 for the September minimum extent showed a wide range – from around 2.9 to 5.6 M km2. One of the lowest estimates assumed that the key criteria was the survivability of first year ice. If one took that to be a fixed percentage based on past behaviour, then because there was so much first year ice around in early 2008, the minimum would be very low (see also Drobot et al, 2008). This turned out not to be a great approach – much more first year ice survived than was predicted by this method. The key difference was the much greater amount of first year ice there was near the pole. Some of the higher values assumed a simple reversion to trend (i.e. extrapolation forward from the long-term trend to 2008).

Only a couple of the forecasts used physics-based models to make the prediction (for instance, Zhang et al, 2008). This is somewhat surprising until one realises how much work is needed to do this properly. You need real time data to initialise the models, you need to do multiple realisations to average over any sensitivity to the weather, and even then you might not get a range of values that was tight enough to provide useful information.

So how did people do? The actual 2008 September minimum was 4.7 M km2, which was close to the median of the June forecasts (4.4 M km2) – and remember that the 2007 minimum was 4.3 M km2. However, the spread was quite wide. The best estimates used both numerical models and statistical predictors (for instance the amount of ice thicker than 1m). But have these approaches matured this time around?

In this year’s June outlook, there is significantly more clustering around the median, and a smaller spread (3.2 to 5.0 M km2) than last year. As with last year, the lowest forecast is based on a low survivability criteria for first year ice and I expect that this (as with last year) will not pan out – things have changed too much for previous decades’ statistical fits on this metric to be applicable. However, the group with the low forecast have put in a ‘less aggressive’ forecast (4.7 M km2) which is right at the median. That would be equal to last year’s minimum, but not a new record. It would still be well below the sea ice trend expected by the IPCC AR4 models (Stroeve et al, 2008).

There is an obvious excitement related to how this will pan out, but it’s important that the thrill of getting a prediction right doesn’t translate into actually wanting the situation to get worse. Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.

858 Responses to “Sea ice minimum forecasts”

  1. 501
    BobFJ says:

    Phil. Felton 490 you wrote:

    [1] It doesn’t really matter why you got the science wrong it gets corrected.
    [2] Your original question appears to be how to find K&T, your problem might be that it was actually published in ‘97.
    http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    If your item [1] is in response to my 485, as I understand it, you do at least know of the second law of thermodynamics; broadly that HEAT can only flow towards a colder sink. Now consider this:
    No one has disagreed that sunlight penetrates water down to a depth of around 100 metres, (blue…. red less) where it is converted from EMR to HEAT. Furthermore, that a substantial portion of that HEAT then reaches the surface, where it escapes as HEAT and via conversion to EMR. How does it do this unless there is a reducing temperature gradient towards the surface, which enables convection and conduction? Is there enough turbulence or whatnot to negate the influence of law2. I doubt it except maybe close to the surface in average conditions. What is your view, and what/how/why can you assert that I am wrong?

    When it comes to the skin itself, do you disagree that the majority of the terrestrial surface cooling is from evaporation, and that this must drastically cool the skin?
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Your item [2] must relate to my 488.
    Thanks for the link to K & T’s “Earth’s Annual Global Mean Energy Budget”, but the source for the claim I was asking Kevin to clarify in his 300 was:
    “Albedo is not only an issue at optical wavelengths, but at infrared wavelengths. Back radiation in the infrared will not be reflected by the water due to angle of incidence–and, according to Kiehl & Trenberth ‘98…”

  2. 502
    Hank Roberts says:

    > impact

    And don’t forget the biology. From the older topic
    http://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/comment-page-1/#comment-23508
    Cecilia Bitz says:
    13 January 2007 at 14:24
    … Have I heard from researchers with interest in the ice retreat? I am in contact with several biologists in my universtity and others that I have met in various meetings.

  3. 503
    BobFJ says:

    Doug Bostrom Reur hilarious 486 and 487:
    No amount of your classic word-smithing can conceal the fact that you have not a clue about the elementary mechanics, let alone the quantum mechanics of the topic. For instance, the end heating of your iron ingot (a highly conductive SOLID) is totally unrelated to the specifics as originally raised in my 367/p8 for top of water. (a FLUID). Perhaps you could try reading 367, but it is fairly advanced, touching on QM. Among other things, this gives that the absorption coefficient of infrared in water is about a billion times greater than the blue part of the visible spectrum. Oh, BTW, others here have no objection to this meaning that infrared is fully absorbed in the “skin” of the water. Might I suggest that you should not attempt ridicule as a defence/attack in debate, especially when you only have a simplistic understanding of the topic. Oh, and BTW, the skin is predictably colder than below, primarily because of evaporation. (It has been claimed that up to 50% of the HEAT loss from the terrestrial surface is from Evapo-transpiration, the greatest of the three basic HEAT loss processes.)

  4. 504
    Larry N says:

    re:497

    I would seriously doubt that sea ice is actually increasing (refreezing) in any area, not for another month.

    One must remember that sea ice area does not take in account the ice volume. What is happening is that the peanut butter is being spread around thinner on the bread, so to speak. When weather favors ice compaction, the sea ice area will show an increased melt rate.

    It would be nice if we had daily estimates of volume calculations, however I do not know of such graphs.

  5. 505

    #500 That is East of the rockies…

    Phil F. Please confirm it aint so:

    http://www.arctic.noaa.gov/gallery_np_weatherdata.html

    No IR down welling? and a truly remarkable shift in the drift, explaining in part the current ice picture.

  6. 506
    Doug Bostrom says:

    BobFJ 3 August 2009 at 9:59 PM

    Sure, Wingman Bob, whatever. Infrared heating of a liquid is impossible in your world. Molecules of liquid are mysteriously frozen, unable to convey energy in any direction except (mysteriously) in the direction of greater warmth. Energy is pushed uphill by mysterious demons.

    Sorry, I just can’t look at your world without laughing.

  7. 507

    Walt Meier (NSIDC)

    On the ice thickness, there’s a nice recent paper:

    http://www.agu.org/pubs/crossref/2009/2009JC005312.shtml
    Kwok R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, D. Yi (2009), Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008, J. Geophys. Res., 114, C07005, doi:10.1029/2009JC005312.

    Here’s a NASA press release with info if you can’t get to the paper:

    http://www.nasa.gov/home/hqnews/2009/jul/HQ_09-155_Thin_Sea_Ice.html

    The European Space Agency will launch an altimeter, Cryosat-2, later this year that will be able to get routine thickness estimates and NASA will continue collecting aircraft and satellite measurements in the future. For older data, there are submarine data dating from the 1950s through the 1990s. Those are more sporadic and not as complete, but it is quite clear that the recent measurements are markedly lower than during the submarine period.

    On the slowing of the area and extent, there is indeed a temporary slowdown in the extent due to a shift in the winds, dispersing the sea ice and slowing down the extent. This is expected to be temporary, though by mid-August, it is not unusual for the rate of decline begin to gradually slow. However, this didn’t happen until much later last year because there was so much thin ice. It will be interesting to see what develops this year.

  8. 508
    Phil. Felton says:

    Re #505

    I’m afraid it is so Wayne, why I know not.

    “Weather plot: This plot presents air temperature, air pressure, and winds measured by the meteorological station. No radiometer was deployed this year.”

  9. 509
    BobFJ says:

    Referring to the Jakobshavn glacier in Greenland per the NSIDC image tendered by Gavin, this shows more rapid melt in recent years, but it is relevant to note that it is erratic and is a short-term 5-year observation, from 2001-2006. In other words, it has occurred during the current warming pause, that was discussed earlier on this site @ http://www.realclimate.org/index.php/archives/2009/07/warminginterrupted-much-ado-about-natural-variability/#more-686

    However, the average rate of retreat between 1964-2001, was of an order of magnitude lower. Yet, in extreme paradox, this was the greatest prolonged period of warming, prior to the current warming pause. On the other hand, the earlier contradictory period of 37 years would usually be considered long enough to be adequate for trend determination.

    Here is a composite image visually demonstrating the scale of the retreat events, compared with the Hadley Northern Hemisphere temperatures. A broader study shows that counter-intuitively, there is very poor correlation over the 150 years of retreat data, compared with HADCRUT NH temperatures.
    http://farm3.static.flickr.com/2573/3775490997_b6e8c91f72_o.jpg

    Comments anyone?
    If anyone is interested that a recent short term retreat event may not be a crisis after all, there is more comforting detail @ 436/p9 & 458/p10

  10. 510
    Doug Bostrom says:

    BobFJ 3 August 2009 at 9:59 PM

    Whoops, my apologies, I was all hung up on:

    “However, since infrared is (you agree) only absorbed in the skin of the water, and re-emission is an instantaneous process, there is virtually no opportunity for the slower downward process of conduction to take place. Thus, although it IS a very different process, it is somewhat similar IN EFFECT to reflection.”

    I missed where you morphed your earlier radiation-proof ocean idea into:

    “When it comes to the skin itself, do you disagree that the majority of the terrestrial surface cooling is from evaporation, and that this must drastically cool the skin?”

    Further to your spluttering outrage, this latest hypothesis of yours shares the same basic fault your earlier musings about the self-healing properties of ice exhibited. No real data, no numbers, no equations, no development of the mechanism you imagine dominates the picture. All I hear is repetition of the same assertion using various verbal permutations, in this case with a strangely shifting shape.

    Here’s an idea. You’re an engineer, I’m sure you’re good with numbers. Why not produce some models of your concept? You could research and then plug in real-world subsurface temperature gradients, convection, conduction, pelagic mixing, real-world dewpoints, real-world wind velocities, effective illumination temperatures as are actually found on this planet. Perhaps you could demonstrate that evaporative cooling can effectively isolate the sea from IR heating even where the conditions for so doing seem very wrong, such as the Arctic.

    Or, alternatively you could dig in the literature and find out if somebody else has already done this work for you.

    Unless you do that you’re not going to sound very persuasive to anybody who knows as much about this topic as do I, which is very little indeed. Without devoting any effort to developing your idea you’re simply indulging in idle speculation, again. That being the case, you surely can’t justify being angry when somebody fails to deliver you a snappy salute.

  11. 511
    BobFJ says:

    Dave, Reur 476/p10, you wrote:

    How do you respond to recent papers that sea ice losses are due to wind shifts, not warming in the north Atlantic?

    I have not seen the papers you refer to, but the following article from NASA is relevant:

    http://www.nasa.gov/vision/earth/lookingatearth/quikscat-20071001.html

    Extract:
    Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic,” he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.

    “The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century,” Nghiem said.

  12. 512
    BobFJ says:

    To the moderator,
    I notice that the new blog software now accepts a post for moderation without allocating a new post number, and that means that it can no longer disrupt the numbering sequence if it is rejected?

    Some commenters here tend to cherry-pick and ridicule a selective line or two from an earlier post, without referring to the original post ID to enable readers to check in full the real context, and whether the relevant stuff has been properly addressed or simply evaded.

    It may be that post numbers tended earlier to be unreliable, but that is no longer the case?

    Do you agree that when commenters respond to earlier stuff, that they should clearly state what it is that they are responding too?

  13. 513
    Mark says:

    “For instance, the end heating of your iron ingot (a highly conductive SOLID) is totally unrelated to the specifics as originally raised in my 367/p8 for top of water. (a FLUID).”

    In what way?

    Inter-atomic/molecular distances are very comparable. In fact, given that temperature is the ***kinetic energy content of a molecule*** and that liquid molecules are known for their freedom to move (unlike solids, where phonons are the mode of temperature transport: and they don’t even EXIST as a real thing!), this would seem more likely to be a problem for keeping a solid cold despite incident IR more than for a liquid.

    Truly you live in bizzarro world.

  14. 514
    Mark says:

    “Everyone has seen the graphs, however, I find it a useful exercise to examine the numerical values”

    I did:

    1980 Northern Hemisphere = 10.4 million sq km
    2008 Northern Hemisphere = 9.0 million sq km (1.4 million lower in 28 years = 0.05 million per year)
    2009 Northern Hemisphere = 8.8 million sq km (0.2 million lower in 1 year)

    Did you not read past the name??

  15. 515
    Mark says:

    Karst, now look at some different numbers:

    The ice LOSS over a year min-max dec YY-1 to jul YY.

    Check also the numbers as to how they vary.

    You seem to be demanding that for ice to be melting it has to be monotonically melting year-on-year.

    Why would you expect that to happen in the face of weather???

    For the straw?

  16. 516

    BobFJ writes:

    It has been claimed that up to 50% of the HEAT loss from the terrestrial surface is from Evapo-transpiration, the greatest of the three basic HEAT loss processes.

    Whoever claimed this was wrong. The surface is at, let’s say, 288.15 K with an emissivity of 0.95, which means it radiates about 371 watts per square meter. It absorbs 161.4 x 0.85 + 348 x 0.95 = 137 + 331 = 468 watts per square meter from sun and atmosphere, respectively, which means there’s another 97 watts per square meter it has to lose. That’s from 17 W/m^2 due to conduction and convection (“sensible heat”) and 80 W/m^2 due to evapotranspiration (“latent heat”). So of the Earth’s 468 W/m^2 of cooling, 80 or 17% is from evapotranspiration. This is not “up to 50%” except in the loosest sense.

  17. 517
    Nick Barnes says:

    BobFJ @ 509, on Jakobshaven. Check MODIS: the glacier has retreated by an additional 2 or 3 km since the 2006 line, especially along the front of the southern ice stream. Now that the glacier front is above the neck and head of the fjord and into the body of the ice sheet, I would expect the retreat to slow and broaden.

  18. 518

    Re #511

    BobFJ,

    You have cherry picked your excerpt. The previous paragraph says:

    “The scientists observed less perennial ice cover in March 2007 than ever before, with the thick ice confined to the Arctic Ocean north of Canada. Consequently, the Arctic Ocean was dominated by thinner seasonal ice that melts faster. This ice is more easily compressed and responds more quickly to being pushed out of the Arctic by winds. Those thinner seasonal ice conditions facilitated the ice loss, leading to this year’s record low amount of total Arctic sea ice.”

    I already explained that in my post #477

    Re #476 where Dave asks “How do you respond to recent papers that sea ice losses are due to wind shifts, not warming in the north Atlantic?”

    Which papers?

    In any case, the reason more ice is lost from the Arctic due to wind is that the ice is now thinner and so has broken into smaller pieces which are more likely to be blown about. In other words, it is not a matter of winds OR warming. It is a matter of winds AND warmer oceans AND warmer air due to greenhouse warming.

    HTH,

    Cheers, Alastair.

  19. 519
    dave p says:

    regarding #482 one effect is that in England it seems to be causing a lot of summer rain. In 2007, the first big melt year we had out wettest ever June, causing floods in places. In 2008 we had our wettest ever July. Summer rainfall this year is running at twice it’s normal rate. A downstream effect?

  20. 520
    Mark says:

    “regarding #482 one effect is that in England it seems to be causing a lot of summer rain.”

    I believe that has more to do with the Jet Stream staying where it is rather longer than normal.

  21. 521
    Hank Roberts says:

    BobFJ writes:
    It has been claimed ….

    Do you think people should cite their sources? Otherwise it’s a bit harder to figure out whether someone’s making stuff up or quoting an unreliable source.

  22. 522
    Rod B says:

    Barton Paul Levenson (516), with much hesitation, I have a quibble with your calculation — though it might be a matter of definition. The total cooling of the surface has to equal the absorbed solar heating: about 138 – 161 W/m^2, depending on emissivity factor. The cooling from IR emission is the difference between outgoing and “back” radiation, about 63 W/m^2 (from T&K, 2008 and using a=1.0) . That leaves 98 W/m^2 — 17 from thermals and 80 from evaporation (latent). From this direction, evaporation at 80 is 50% of the total cooling of 161.

  23. 523
    Hank Roberts says:

    Yep, BobFJ cherrypicks.
    BobFJ, you’ve ignored previous answers.
    Don’t just repost talking points from the PR here.
    People notice.

    Quoting a bit from my reply posted earlier to Dave (you know how to find this):

    GLACIOLOGY: Winds, Not Just Global Warming, Eating Away at the Ice Sheets RA Kerr – Science, 2008 – sciencemag.org
    … Dave …“wind shifts, not warming in the north Atlantic”
    Science: “Winds, not just global warming”

    Not hard to understand.

  24. 524

    #509 BobFJ

    The answer is thermal inertia.

    Remember context is key. Any data you look at out of context might look funny. That is why cherry picking is so silly.

    It only ‘looks’ counter intuitive, but it is not. The human mind is limited by perspective until knowledge and understanding meet closer to truth to relieve the prematurely apparent contradiction.

    Natural variability is short term. Climate is long term. Oceanic thermal inertia keeps the warming at bay in relation to the additional forcing imposed.

    Regional variation and natural variation are pieces of the puzzle, but not the whole puzzle.

    Remember, we are on a new path, that of warming, natural variation does not go away, it just weaves like a drunk driver on a different road.

    http://www.ossfoundation.us/projects/environment/global-warming/natural-variability

    Also, global change is not just about Jakobshavn, it’s about what is happening to the entire cryoshpere of the planet.

    In other words we know the large signal, and it is warming. We don’t know all the details that are below the large signal in various time scales. The decadal processes are being looked into and science will just keep getting better.

    That fact that we don’t know everything does not negate the fact that we (science) know a lot.

    http://www.ossfoundation.us/projects/environment/global-warming/what-we-dont-know

    http://www.ossfoundation.us/projects/environment/global-warming/what-we-know

  25. 525
    G. Karst says:

    Mark — #514,#515 -4 August 2009 @ 2:54 AM

    “You seem to be demanding that for ice to be melting it has to be monotonically melting year-on-year.”

    Read my post. I simply posted NSIDC data, without any comment or demands for anything. I implied no relevance or importance to NSIDC monthly averages. You are the only one who is drawing conclusions to this observational data (poor scientific skills). July total ice extent indicates July 2009 was a rapid ice decrease month. June was not. Beyond this simple statement, I don’t know what you want me to say. You seem to want an argument even when my data agrees with you. Maybe next months data will give us something to disagree about. You should wait until I actually make a statement before disagreeing with it.

    You may not be interested in observations, but there are others who may. Please refrain from dictating what observations are valid for this blog. It is not all about you! If the moderator feels that ice observations are supercilious, then he/she should say so and I will gladly stop posting the report. Otherwise, it is what it is!

  26. 526
    Doug Bostrom says:

    BobFJ 4 August 2009 at 2:43 AM

    “Some commenters here tend to cherry-pick and ridicule a selective line or two from an earlier post, without referring to the original post ID to enable readers to check in full the real context, and whether the relevant stuff has been properly addressed or simply evaded.”

    Perhaps you should be more specific. Which of your ideas make you squeamish when you’re asked to explain and demonstrate them in detail?

    How about this? When you make a controversial assertion why not -first- address your concept properly, show how it functions numerically, rather than simply evading that work and expecting readers to accept that you’ve overturned generations of publications with a stroke of your pen. By so doing I think you’ll save a lot of useless back-and-forth and perhaps arouse the genuine interest of some the quant mavens who frequent RC.

    It smacks of evasion when, asked to develop a quantitative model of your hypothesis about evaporative cooling losses, you instead swerve into a meta-discussion about moderation minutiae.

    You could do the work at some rough level of granularity, right? Perhaps a first pass would be promising enough to dig in, but in any case it’s -your- idea to let starve or thrive as -you- choose.

  27. 527
    Susan Anderson says:

    Thanks to all who took the trouble to flesh out responses to my and Tenney’s emphasis on Willi’s question and our and others’ comments, as well as my observations as a Boston resident. That’s lot to digest and good stuff!

    Despite the possibility of an association between colder early summer weather here and around Minnesota and the melt in the north (not just north Atlantic but midwest), this “weather” is exploited as evidence of cooling. We have just had the most peculiar June and July in living memory, very cold and wet. I am well aware that there is a danger in oversimplifying this and climate is much too complicated to draw a straight line. There has already been good and sufficient response to this and I understand those points inasmuch as I am able to do so. I’m not suggesting making trouble by supporting the insupportable. But it is interesting that this point is quite obvious from a commonsensical point of view by thinking and observing nonscientists such as a city worker I met down the block a couple of days ago(!).

    Despite my considerable interest and understanding of what science is and does, I am not a scientist myself (I couldn’t digest differential equations and took to art instead).

  28. 528
    Mark says:

    “Read my post. I simply posted NSIDC data, without any comment or demands for anything.”

    You ***started*** with that.

    You didn’t continue with it:
    #498:

    “He is entirely right for this July. I shouldn’t have to remind either one of you, that this is a monthly average report. Last month indicated the reverse”

    You demand that the figure is the reverse for this year from the same time last year as if this is important, begging the question “if it’s warming, why is this year ice extent higher?” thereby indicating a demand that for it to be warming, it must be a monotonically (that is for each year the month has to have less ice than the same month last year) decreasing.

    So you did demand it.

    Or are you withdrawing that statement in post 498 because it doesn’t mean anything?

  29. 529
    Mark says:

    “The total cooling of the surface has to equal the absorbed solar heating”

    RodB you’re wrong.

    This only has to be the case when the system is in thermal equilibrium.

    If your point was extant without that requirement, it would be impossible to boil water, since the water would lose heat as fast as it gained it from the hob.

  30. 530
    Doug Bostrom says:

    Arctic sea ice news updated today:

    http://nsidc.org/arcticseaicenews/

    Remarkable how this year’s graph seems to mirror 2008.

  31. 531
    G. Karst says:

    Mark, #528:

    I repeat “It is what it is”!

  32. 532
    Doug Bostrom says:

    Susan Anderson 4 August 2009 at 2:10 PM

    I’m sorry I’ve not got time to wade back and see if this was covered, but a note in today’s update of Arctic ice news may help with your picture of the weather in your area:

    “The strong Beaufort Sea high-pressure cell that occurred both this summer and in 2007 is part of a larger scale atmospheric pattern known as the Pacific North American (PNA) “teleconnection.” The airflow in the western hemisphere is usually characterized by a low pressure trough over the North Pacific, a ridge over western North America, and a trough over eastern North America. The PNA describes the strength of this pattern. When the PNA is positive, the normal pattern is amplified and the airflow becomes more “wavy” than usual. While the expressions of the PNA vary by season, the strong western North American ridge during the positive PNA favors a strong Beaufort Sea high pressure system. The stronger than usual trough over eastern North America also helps to explain the cool and rainy weather that has gripped this area much of the summer.”

  33. 533
    Walter Manny says:

    530:

    Interesting, recent concavity in 2009:

    http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

  34. 534
    Rod B says:

    Mark (529), of course you’re correct but it’s an insignificant nit on the question at hand. It changes the percent of cooling from evaporation probably less than one, while I was using ballpark (albeit accurate, but not exact) figures.

  35. 535
    BobFJ says:

    Northwest passage and NSIDC aficionados should be interested in this CANADIAN article (1/Aug/ 09) which has this opening paragraph:

    Despite predictions from a top U.S. polar institute that the Arctic Ocean’s overall ice cover is headed for another “extreme” meltdown by mid-September, the Environment Canada agency monitoring our northern waters says an unusual combination of factors is making navigation more difficult in the Northwest Passage this year after two straight summers of virtually clear sailing.

    Read more @:
    http://www.montrealgazette.com/technology/pockets+choking+Northern+Passage+officials/1853191/story.html

    Oh, and you might find this CANADIAN surface observation history histogram of the past 38 years interesting?
    http://ice-glaces.ec.gc.ca/prods/CVCHACTWA/20090727180000_CVCHACTWA_0004492483.gif

    Comments anyone?

  36. 536
    BobFJ says:

    Rod B Reur 522, you wrote:

    Barton Paul Levenson (516), with much hesitation, I have a quibble with your calculation — though it might be a matter of definition. The total cooling of the surface has to equal the absorbed solar heating: about 138 – 161 W/m^2, depending on emissivity factor. The cooling from IR emission is the difference between outgoing and “back” radiation, about 63 W/m^2 (from T&K, 2008 and using a=1.0) . That leaves 98 W/m^2 — 17 from thermals and 80 from evaporation (latent). From this direction, evaporation at 80 is 50% of the total cooling of 161.

    Thanks for that Rod; you are correct in recognising that EMR is a different form of energy than HEAT. HEAT is transported by EMR only when there is a potential difference between two opposing sources.
    Confirming that, here are some less confusing depictions than K & T 1998:

    http://education.gsfc.nasa.gov/ess/Units/Unit2/u2L5aimage.jpg
    http://en.wikipedia.org/wiki/Earth's_energy_budget (containing two graphics)

    BTW, there is an update of K & T 1998 here:
    http://chriscolose.wordpress.com/2008/12/10/an-update-to-kiehl-and-trenberth-1997/#comment-981

  37. 537

    NSIDC latest:

    “This year, cloud fields provided by Jennifer Kay at the National Center for Atmospheric Research show fewer clouds over the Beaufort Sea than in 2007, leading to strong melt in that region. However, over the Chukchi and East Siberian Seas, the Arctic sky has been cloudier than 2007.”

    I don’t know if this is what I saw, at least in The Canadian Arctic, although it cleared up a bit of late. Baffin Bay was mostly clear, MODIS didn’t show that. But over all, it was much cloud free in 2007. Particularly during the Solstice period over the Beaufort area, causing an amazing sequence of melting. I’d like to see Modis results month by month. Don’t know why they were bunched up.

    Thanks Phil,, darn… Why they do a thing like that? No radiometer??? The ultimate instrument for warming , not over a particularly important area of sea ice…

    Many thanks John Reisman for your links above, still they are not Arctic specific, its hard to get good data from that location.

  38. 538
    Doug Bostrom says:

    BobFJ 4 August 2009 at 5:27 PM

    “Comments anyone?”

    1) WHY IS Canadian IN ALL CAPITALS?

    2) Why did you choose to highlight that particular tiny fraction of the Arctic?

    3) What about this http://ice-glaces.ec.gc.ca/prods/CVCHDCTEA/20090727180000_CVCHDCTEA_0004492565.gif particular tiny fraction of the Arctic?

    4) What about this

  39. 539
    Doug Bostrom says:

    Oops, cut my self off while commenting on BobFJ’s smoking CANADIAN gun.

    More cherries from the fraction of the Arctic covered by Canada’s truly excellent analyses of their bit:

    This year’s departures from “normal” for:

    Eastern Arctic
    http://ice-glaces.ec.gc.ca/prods/WIS55DPTCT/20090727180000_WIS55DPTCT_0004492567.gif

    Western Arctic
    http://ice-glaces.ec.gc.ca/prods/WIS56DPTCT/20090727180000_WIS56DPTCT_0004492488.gif

    Weekly historical and recent ice cover for:

    Eastern Arctic
    http://ice-glaces.ec.gc.ca/prods/CVCSWCTEA/20090727180000_CVCSWCTEA_0004492568.gif

    Western Arctic
    http://ice-glaces.ec.gc.ca/prods/CVCSWCTWA/20090727180000_CVCSWCTWA_0004492486.gif

  40. 540
    Doug Bostrom says:

    Ooh, this is fun! Interactive ice coverage graphing tool, producing trend lines (mostly depressing regardless of your point of view).

    Canadian Ice Service – Ice Graph Version 1.0,

    http://ice-glaces.ec.gc.ca/IceGraph/IceGraph-GraphdesGlaces.jsf

  41. 541
    BobFJ says:

    Nick Barnes, you wrote in 517:

    BobFJ @ 509, on Jakobshaven. Check MODIS: the glacier has retreated by an additional 2 or 3 km since the 2006 line, especially along the front of the southern ice stream. Now that the glacier front is above the neck and head of the fjord and into the body of the ice sheet, I would expect the retreat to slow and broaden.

    Thankyou Nick.
    Here is a comparison of the image extracted from the MODIS site, and that of the NSIDC image discussed earlier. It shows some conflicts and issues, See notes thereon:
    http://farm3.static.flickr.com/2488/3790963832_1dd0405660_o.png

    Further to those notes: According to NSIDC, there has been a progressive retreat since 1851, but comparison with HADCRUT shows no correlation with NH air temperature. I agree that if the glacier has retreated to a significant plateau, then it should slow, but bearing in mind that this is said to be the fastest flowing glacier in the world, there would seem to be something rather powerful driving it, such as a long gravitational gradient. As you point-out, there appears to be a strong north and south stream in the ice sheet, and of course, ice creeps. (or maybe some of the possibilities I raised in 436/p9 & 458/p10 apply)
    If the NSIDC data for 1964-2001, (37 years) are correct, showing slow retreat during that greatest period of warming, it is paradoxical that it was followed by, for one year only, an annual linear retreat rate of the order of 150 times faster. (before slowing down again)

    Re MODIS: http://bprc.osu.edu/MODIS/?p=24

  42. 542
    Rod B says:

    BobFJ (536),, I agree the NOAA/NASA diagram is easier to comprehend, but I think a little is lost in the translation by showing the net IR EMR and not showing the gross IR emissions from the Earth’s surface with the back (downwelling) radiation from the total atmosphere. Those radiation mechanisms are partially different and are necessary for understanding the processes

  43. 543
    BobFJ says:

    Alastair McDonald Reur 518;
    Yes, I agree that sea ice melts from a combination of factors, (who wouldn’t?), but you may have misunderstood my 511.
    My meaning was that Dave referred to “recent papers”, attributing wind shifts as the primary cause, without any links to back it up. I brought-up the NASA article as the only relevant thing I’ve seen on this. (And, BTW, as you also asked, what papers?)
    Here is part of my 511 again, but I‘ve added bold emphasis to an interesting line in the extract that perhaps you did not notice. Might I dare to say that if true, this could have wider regional implications, even prior to 2007?:
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    I have not seen the papers you [Dave] refer to, but the following article from NASA is relevant:
    http://www.nasa.gov/vision/earth/lookingatearth/quikscat-20071001.html
    Extract:
    Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic,” he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.
    “The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century,” Nghiem said.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Yes, I cherry picked this extract, because I thought it would provoke interest in reading the article, for which the link was given for anyone so interested to do.

    It seems as I write, that you are the only one interested in that NASA article, and thankyou.

  44. 544
    Mark says:

    “EMR is a different form of energy than HEAT. HEAT is transported by EMR only when there is a potential difference between two opposing sources.”

    IR = EMR.

    IR=HEAT.

    Sheesh.

  45. 545

    Rod, the total cooling is 468 W/m^2, not 161. IR heats the surface, not just sunlight.

  46. 546

    BobFJ, again radically revising modern physics, writes:

    Thanks for that Rod; you are correct in recognising that EMR is a different form of energy than HEAT. HEAT is transported by EMR only when there is a potential difference between two opposing sources.

    EMR transports ENERGY, and losing energy causes a material substance to lose HEAT, which makes it DECREASE IN TEMPERATURE. That’s why a hot object, even left in a vacuum, will cool down. It radiates away the heat. Earth’s surface is primarily cooled by infrared radiation, secondarily by evapotranspiration, and tertiarily by conduction and convection, to the tune of 371, 80, and 17 W/m^2, respectively.

  47. 547
    Sekerob says:

    Yesterday somewhere someone inserted comment about this sudden concave shape of the JAXA curve. Why I really don’t know other than another one who goes like ‘finally finally again the world is cooling’. Well NANSEN Arctic ROOS does both AREA and Extent, and the copmparison tells me the melt is still very much on and the break up index is still on the rise and that is not a good sign.

    http://arctic-roos.org/observations/satellite-data/sea-ice/observation_images/ssmi1_ice_ext.png

    http://arctic-roos.org/observations/satellite-data/sea-ice/observation_images/ssmi1_ice_area.png

    Wait Wait, it was here, walter manny #533 showing insight. Nothing personal Walter, but it does pay to look a little bit further before calling it interesting.

  48. 548

    Sea ice melt curve is now “concave?” Short-term changes. No big deal–though I will confess I was/am hoping for a low minimum this year, heading into the Copenhagen conference. Political? Sure, but politics is how society gets stuff done. Or not. . . I’m worried about the prospect of “not.” The evidence convinces me that “not” dealing with AGW will be a very bad thing for the future.

    The curve? I’m pretty sure we’ll see it turn down again before we hit true bottom.

  49. 549

    By the way, we had been discussing crevasses and melt ponds earlier on this thread.

    Coincidentally, I found this information, showing that crevasses filled with meltwater can propagate the crack downward even if initially as shallow as 6-15 meters:

    http://web.pdx.edu/~chulbe/science/Larsen/larsen2002.html

    (Note references at bottom of report.)

  50. 550
    Walter Manny says:

    548

    Kevin, what I found interesting about the concavity is that it is the only one in the eight curves shown that exhibits that shape in late July. Already it appears to be reverting to its previous slope. I doubt it is significant, but to me it was interesting. Seems to be at a sort of graphical crossroads at the moment. In any event, we’ll see.

    Walter