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Under and over the ice

Filed under: — gavin @ 10 March 2011

I really like the fact that there is still so much to discover about important parts of the climate system. The Bell et al paper in Science Express this week (final version in Science) reporting on the surprising results from airborne ground-penetrating radar studies of the Antarctic Ice Sheet is a great example. The ice sheets themselves are the biggest challenge for climate modelling since we don’t have direct evidence of the many of the key processes that occur at the ice sheet base (for obvious reasons), nor even of what the topography or conditions are at the base itself. And of course, the future fate of the ice sheets and how they will dynamically respond to climate warming is hugely important for projections of sea level rise and polar hydrology. The fact that ice sheets will respond to warming is not in doubt (note the 4-6 m sea level rise during the last interglacial), but the speed at which that might happen is highly uncertain, though the other story this week shows it is ongoing.

The radar results (shown on the right) picked up on some really weird looking features that look to be related to pressure-related freezing of basal meltwater as it is pushed uphill by the weight of the ice sheet above. If that sounds odd, it is because it is.

How can water flow uphill in the first place? This is a function of the pressure gradients. If there is a lot of ice above a valley, but it tapers off towards a mountain range, the pressure on any liquid water at the bottom of the valley will be greater than the pressure up the side of the mountain. This will force water uphill. Incidentally, there are many sub-glacial geomorphological features that show this effect in places affected by the LGM ice sheets.

The freezing point of water is also pressure dependent. With 3km of ice pressure above it, water freezes at about -2ºC (the change is -7.5*10-8 ºC/Pa). Water below 0ºC can therefore exist at the base of the ice sheet (and can also be seen emerging from under ice shelves). When the pressure forces this water upwards to lower pressure areas, this can promote instant freezing, and this seems to be the explanation for the structures seen in the radar.

The surprise is how large these structures are, one shown in the paper is 10′s of km long and 100s of meters thick – certainly large enough to be important in ice flow locally, though probably not at the continental scale.

However, at the continental scale, there is a new assessment of the net mass balance of Antarctica and Greenland. Rignot et al have updated results, including those from the GRACE gravity measurement satellite, to the end of 2010 and show that the downward trend in ice mass is continuing (stronger in Greenland than in Antarctica). The net rise in sea level associated with this decline is about 1.3 mm/yr, which will likely accelerate with further warming. Complementary analyses of the surface mass balance of Greenland (Tedesco et al, 2011) also show that 2010 was a record year for melt area extent.

This rate of melting is more than was figured into the tabulated IPCC AR4 estimates of sea level rise, and any further acceleration will obviously make the discrepancy worse. Indeed, even in the highest forcing A1F1 scenario, the IPCC calculated only a 0.3 mm/year contribution from the ice sheets averaged over the whole 21st Century! This was clearly a gross underestimate.

Extrapolating these melt rates forward to 2050, “the cumulative loss could raise sea level by 15 cm by 2050″ for a total of 32 cm (adding in 8 cm from glacial ice caps and 9 cm from thermal expansion) – a number very close to the best estimate of Vermeer & Rahmstorf (2009), derived by linking the observed rate of sea level rise to the observed warming.

There is certainly more to learn about ice sheets, and more of a reason than ever to do that as fast as possible.


119 Responses to “Under and over the ice”

  1. 51
    John Pollack says:

    Of course there is a positive correlation between recent global warming and large earthquakes – but there is also a correlation between earthquakes and the number of reservoirs, the number of obese people, and the number of iPhones. Correlation does not mean causality! All it means is that two things share the same trend, such as a recent rise, whether there is any relationship between them or not.

    In this case, if you look closely, McGuire and others are talking about geological events that have some proximity to recent changes in ice loading. That’s not the case for the recent large earthquakes.

    Most scientists won’t pursue a putative relationship between global warming and recent large earthquakes because of a lack of a plausible causal mechanism. This means there would be an excellent chance that they’d be wasting valuable time on a wild goose chase.

    Scientists have been through this drill many times before, e.g. solar cycles and various posited correlations with weather. This has led to the development of a large body of statistical tests aimed at distinguishing random events from actual relationships.

    [Response: Exactly. --eric]

  2. 52
    Greg Simpson says:

    “Four of the top ten strongest…”
    Sorry, should have been four of the top thirteen strongest.

  3. 53
    jyyh says:

    someone could make a statistical analysis on the clusters of larger earthquakes keeping in mind that quakes under 6.5 may have gone unnoticed as late as 19th century on areas with less population. assuming the processes within the mantle are constant, there should be some clustering present, shouldn’t there?

    Captcha Politics, sublect

  4. 54
    Everett Rowdy says:

    Agreed: mere correlation does not equal causation.
    Considering that:

    1) Glacial retreat is attributed with a corresponding isostatic rebound; and
    2) The rate of isostatic rebound is accelerating along with the accelerating rate of deglaciation (http://www.skepticalscience.com/Greenland-rising-faster-as-ice-loss-accelerates.html)

    It seems to me that the more rapid decompression of the crust could be a mechanism that would influence other plate activity. It might not be, or it may be impossible to determine, or the spreading epidemic of obesity may be offsetting the lost glacial ice weight – I don’t know.

    I appreciate the skeptical approach that there is no relation until a viable theory is borne out by multiple experiments. Another skeptical approach would be to question the position that two of the largest mechanisms adjusting the earth’s crust have no bearing on each other.

    My calculator isn’t big enough, but I’d be curious (and I accept that this may be no more than a party trick factoid) to compare how much earth is moved by isostatic rebound compared to a major earthquake.

    [Response: That's easy: earthquakes can move the crust vertically by cm to m in a few tens of seconds (let's call that mm/s); isostatic rebound occurs at rates of mm/year (or less). So the difference in magnitude is about a factor of around the number of seconds in a year, or about 30 million.--eric]

  5. 55
    Didactylos says:

    Greg Simpson: And 3 of the top 13 happened in the 1950s, and another 3 happened in the 1960s (including the 2 most severe recorded earthquakes).

    So what’s your point?

    The Richter scale wasn’t developed until 1935. Early magnitudes are all estimates.

  6. 56
    SteveEl says:

    Re 36:

    Interesting idea Aaron. I’ve ranged all over the mountains in the area of Lake Missoula. How do you explain the visible shorelines, if the valley had been full of ice until the moment of melting? I’m assuming the ice you hypothesize was still in glacial motion at the time of the hypothetical sudden melting, so wouldn’t that have erased the humps on little shoreline humps on numerous mountain slopes? Or maybe what I saw as humps were somehow formed some other way and i’m just confused? (I’m not a geologist)

  7. 57
    SteveEl says:

    MOD, my post to arron should have been re #36 not 32

    Daedalus2u, (re 32), that’s an interesting idea. I hope someone comes up with some sexy video showing this hypothetical concept in motion.

  8. 58
    Everett Rowdy says:

    Thanks for the calculation Eric. Along with upgrading my calculator, I should probably upgrade my cerebellum.

    Originally I was pondering a comparison of earthquakes and isostatic rebound over time – curious to know if there was a hare – tortoise relationship where the tortoise might eventually catch up. But considering the magnitude and frequency of earthquakes, especially if we take into account the lower end of the Richter scale from .1- 3.0 magnitude, the tortoise has no chance. That is: plates are always in motion, constantly surpassing isostatic rebound rates.

    Thus any relation between isostatic rebound and tectonic activity would be of fantastically miniscule proportions.

    All right – I think I have caught up with the rest of the class.

  9. 59
    Aaron Lewis says:

    re # 56 Steve,
    I think that in cold years, Clark River froze in place and did not move. There would have been shallow pools of water (from the Clark River in the summer) that formed the wave benches. In warm years, moulins would form, and falling melt water from above, would rapidly warm the ice until it suffered a progressive collapse.

    We think that lowlands will be warmer than higher altitudes. However, sometimes basins catch draining cold air and are colder than the slopes above them.

  10. 60
    Greg Simpson says:

    “So what’s your point?”

    Point? The point is only that we’ve had a lot of big quakes recently.

  11. 61
    Dave Werth says:

    Aaron, #59,

    Glacial Lake Missoula formed when a tongue of the Cordilleran Ice Sheet blocked the outlet of the Clark River in Idaho. Eventually the water level behind the glacial tongue built up to the point where it washed out the ice releasing the lake waters. This happened at least 25 times over a 2000 year period from 15,000 to 13,000 years ago.. Geologists estimate after each flood it took an average of 55 years before the tongue washed out again.

    It was not a result of the Clark River simply freezing solid or ice melting quickly (on a human scale, ice was melting relatively quickly on a geologic scale at the time).

    http://en.wikipedia.org/wiki/Missoula_floods

  12. 62
    Tokodave says:

    59 and 56. Glacial Lake Missoula was formed by the damming of the Clark Fork River by a lobe of the continental ice sheet in the general vicinity of Sandpoint, Idaho. It was a lake and the shorelines reflect the depth of water in the lake and the wave action on the shorelines at that specific surface water elevation. Like any large lake in the northern tier of states or the Canadian provinces, it may well have been covered with ice during cold winters but neither the lake nor the Clark Fork River ever froze in place.

  13. 63
    One Anonymous Bloke says:

    What I’m hearing (from reading here and elsewhere) is that while the re-arrangement of Earth’s water may have a seismic effect, the effect will be indistinguishable from general low-level seismic activity at the scale we are currently able to measure. It’s background noise.

  14. 64
    Elli Davis says:

    I don´t think the sea level will rise on some places in one time; it may have a different forms. Have you consider also the seabed abnormalities caused by earthquakes? As we know from the latest one there was a huge whirlpool that certainly changed the seabed. And by my opinion it may have an influence on the sea level after the water drops down back again.

  15. 65
    wili says:

    Meanwhile, a newly active volcano, Shinmoe dake, in the southern island, Kyushu, may end up cooling off the planet for a couple years if it blows big–but that will not be of much comfort to the already triply besieged citizens of Japan.

    http://www.pamil-visions.net/southern-japan-volcano/224213/

  16. 66
    Jiri Moudry says:

    With “still so much to discover”, how good are our models?

  17. 67
    don gisselbeck says:

    To further explain Lake Missoula, it catastrophically emptied about 50 times when the water floated the ice dam. The multiple shorelines were caused by thinner ice producing successively lower lakes. It doesn’t seem to involve pressure melting.

  18. 68
    Abel says:

    Hi as a person with no formal expertise and am just an interested plebe, in item of info I read years ago in response to Lawrence (43) . A hypothesis that was raised and supposedly presented to Einstein who considered it a possibility but had other interests. Namely that warming of the oceans increases atmospheric H2O increasing atmospheric energy, this as with ENSO deposits more snow at the poles and northern winters, but more importantly extreme monsoonal and cyclonic rainfall in the tropical areas on fixed land masses as in Aust recently close to the rotational circumference provides a rotational imbalance due to mass transfer from the fluid oceans to the fixed land mass and slight wobble, being seasonal the Earth does not compensate and it results in a seasonal flexing of the plates . I too would be interested if anything further has been researched in this area. Re insurance connection. Believe me I would trust their research scientists more than many others, the ultimate bookies are only interested in the odds and the facts.
    Thanks Abel

  19. 69
    Ray Ladbury says:

    Jiri Moudri,
    The goodness of a model depends on how well it predicts future behavior of the system. Our models of ice flow are still pretty crude, but most of the uncertainty is on the high side.

    As to climate models, they are adequate to have predicted a more than 30 year warming trend, as well as the spatial and temporal characteristics of the warming. Again, though, there is a fair probability that the models underpredict the severity of the problems we will face. Uncertainty is NOT your friend.

  20. 70
    Phil Mattheis says:

    This comment follows the embedded thread here related to Glacial Lake Missoula “wave benches” (#56, 59, 62, etc), but also does dance at the edges of this larger discussion about liquid water at the edge of ice, deep valley freezing, etc.

    1. There are good reasons to think that the “wave benches” of Glacial Lake Missoula, along the mountain sides in north western Montana-Idaho border country, may not all be due to old shorelines (and maybe none of them are…).

    “Cryoturbation steps” are well described in the physics literature about effects of freeze-thaw cycles. My favorite resource is a wonderfully written book by Neil Davis at University of Alaska Fairbanks (UAF) called “Permafrost – A Guide to Frozen Ground in Transition” (still in first edition from 2001 – things change slowly in this field?). He discusses the phenomenon at length, with thermodynamics as his base to the science.

    Meanwhile, if you wander around the hillsides in the historic Lake Missoula region, those benches are persistent and very regularly continuous, including areas that just could not have been old lake shore. They are predominantly seen on north facing slopes, which is where cryoturbation effects are most likely seen at lower latitudes. The cryoturbation effects are independent of any body of water, frozen or not…

    2. Davis’s book is built around his “Universal System Happiness Rule” that restates the 2nd law of thermodynamics as: “Every system is happiest when it contains the least possible amount of free energy.” He uses that concept to explain all matter of the odd things that happen in regions where permafrost is common, including the presence of super-cooled liquid water molecular skins on surfaces of ice at bottoms of frozen mountain valleys. The ice formations described at the start of this thread are well in range of those explanations.

    Spoiler alert: you do need to (re)capture grasp of thermodynamics to follow the arguments, which can be a gatekeeper for many of us whose areas of science don’t require much physics. The book served as nightly sleep aid for me for weeks until I managed to keep awake long enough to put it together…

    This thread serves as another example of that problem common to translating science for real world consumption – not so complicated once you grasp the basics, but most of those basics are much more complicated than the common world view… Faith is easier.

  21. 71
    Tokodave says:

    Post 70: It seems like this is once again wandering off topic, but this discussion illustrates the classic: It is not necessary to understand something in order to argue about it…

    “Meanwhile, if you wander around the hillsides in the historic Lake Missoula region, those benches are persistent and very regularly continuous, including areas that just could not have been old lake shore. They are predominantly seen on north facing slopes, which is where cryoturbation effects are most likely seen at lower latitudes. The cryoturbation effects are independent of any body of water, frozen or not…”

    In fact, in western Montana, north slopes, or aspects, are typically timbered and are the least likely place to see any evidence of Glacial Lake Missoula. The shorelines visible on Mt Sentinel immediately east of Missoula are a west facing slope and similar evidence of Glacial Lake Missoula are found on south facing slopes north of Missoula, among other places. Have a look at this photo: http://formontana.net/shores.html and draw your own conclusions.
    Since the water depth where Missoula now sits was estimated to be 950 feet deep, why could these areas have not been a lake shore?

  22. 72
    Alan Bryant says:

    So your counter point is a “new assessment of the net mass balance of Antarctica and Greenland.”
    What validity would this assessment be if it was at all modeled before this new information was introduced?
    Is that your story?
    Oh, there is some guys out there that show a whole new hydro-dynamic process regarding ice sheets, but lets not forget this other assessment that may or may not even be relevant.
    Way to go Gavin.

    [Response: :) - so gravity measurements stop working if ice is formed differently. Curious. - gavin]

  23. 73
    Rob says:

    I know this thread is about ice sheets and not particularly about sea ice, but still, the developments in the Arctic over the past few years, and especially the sharply declining ice volume numbers as estimated by models like PIOMAS made me realize something very interesting and also very obvious:

    I think it was Trenberth who asserted that currently our GHG emissions cause a radiative forcing across the top of atmosphere, essentially reducing our planet’s cooling, by some 1 W/m^2. On most of the planet, that heat flux goes into warming the oceans, causing the planet to warm up, as witnessed by multiple observations.

    However, in the Arctic, that heat cannot go anywhere. It’s the coldest spot around, so it cannot offload heat to another place, and it’s ocean is covered with ice so it perpetually at close to 0 C. So the heat can only go into melting sea ice.

    The Arctic covered by sea ice is some 1.5 E 13 m^2 in size. With 1 W/m^2 forcing, this means that the Arctic accumulates some 4.7 E 20 Joule of heat per year that has no place to go. That is enough heat to melt some 1400 Gton (km^3) of sea ice, every year.

    Incidentally, if we look at the PIOMAS ice volume numbers, we see a reduction of volume of indeed some 1500 km^3 per year. Look at volume numbers per month, as they reduce year after year :
    http://snipt.org/wnoP
    (courtecy of FrankD posted at Neven’s Arctic blog)

    So it seems that Arctic sea ice volume reduction is very easily explained by our GHG emissions, and the reduction in radiation from the Arctic that this has caused.

    Please tell me where I made a mistake, because if this is correct, then we have less than 3 years to see an ice-free Arctic ocean in summer.
    Even worse, it is a-priori unclear when the equilibrium will be restored, since every year the Arctic still accumulates 5E20 Joule more heat.

    Sorry if I posted something in the wrong thread. But the importance of the prospect of an ice free Arctic in the very near future, and the attribution of our GHG emissions as a cause of that scenario, made me realize that it’s better to post a simple attribution calculation in the wrong thread than to let this go by unnoticed.

    Please prove me wrong.

  24. 74

    #72–”What validity would this assessment be if it was at all modeled before this new information was introduced?”

    If “this assessment” is the Rignot et al paper, then what is “this new information?” Presumably “assessment be” should have been “assessment have,” but “modeled” is utterly unclear.

    “Is that your story?”

    Boy, that one must be tough to answer. Whatever “Gavin’s story” may be, it has to be clearer than this comment.

  25. 75
    Don Gisselbeck says:

    @ #70 I suppose this is again a bit off topic, but I have lived, hiked and ridden in and around Missoula for decades. I contemplate Mt Sentinel on my morning commute. I have never seen the north facing “wave benches” and the formations on the west and south faces make sense only as shore lines. Today the snow outlines a prominent line 600 ft or so up that can be traced across 2 mountains and several miles. http://www.flickr.com/photos/23839726@N00/5533697330/ and http://www.flickr.com/photos/23839726@N00/5533696914/
    (Sorry I haven’t figured out the link business yet.) This is another example of settled science being challenged by strange outlying opinion.

  26. 76
    Hank Roberts says:

    > in the Arctic, that heat cannot go anywhere. It’s the coldest
    > spot around, so it cannot offload heat to another place …
    > Please prove me wrong.

    You can do that for yourself; it’s what scientists do all the time.
    How could you prove yourself wrong? Well, first ask yourself if you could be wrong. Can a colder object lose heat to a warmer object?
    http://www.drroyspencer.com/2010/07/yes-virginia-cooler-objects-can-make-warmer-objects-even-warmer-still/

    But then ask yourself if you could be wrong a second way, even if you’d been right in your first mistaken assumption.

    Is there any place near Antarctica that’s colder?
    How could you check? Find an instrument:

    http://mynasadata.larc.nasa.gov/P18.html
    “The difference between the extreme cold of outer space and what you measure when you point an infrared thermometer at the sky is caused mainly by the water vapor in the atmosphere, which is warmed as it absorbs infrared emitted by the Earth. Water vapor strongly absorbs the infrared radiation emitted by the Earth.”

    Check the relevant conditions:
    http://www.google.com/search?q=antarctica+humidity
    “0.03% average humidity … The Antarctic Climate …”
    http://www.antarcticconnection.com/antarctic/weather/index.shtml

    Consider the result (Google wants to help):
    http://www.google.com/search?q=antarctica+heat+loss+to+space
    “Jun 9, 2010 … The Antarctic continent has two main roles with global climate: it’s the area of the Earth with the most important heat loss towards space ….” http://www.gdargaud.net/Antarctica/MeteoDdU.html

    See? You can do this for yourself.

  27. 77
    Hank Roberts says:

    Oh, and just to tie that one up, compare the Arctic (an ocean surrounded by land) with the Antarctic (a high-elevation, very low-humidity icecap, surrounded by ocean). What difference does it make if the Arctic ice melts? What do you think? Will the Arctic lose less heat to space when the sea is covered with frozen ice, and the air over that is colder and dryer? or when the sea is open water, and the humidity is higher there?

    “Humidity in the Arctic
    In the Arctic, the prevalent air mass is characterized by low temperatures and low moisture content. The continental air of the subarctic in winter is significantly colder and dryer than arctic marine air. Steam fog which occurs when cold air moves out over a warm water surface, causing moisture to evaporate into the air near the surface, is common in arctic regions. A typical value of relative humidity at the surface is 50 to 60 percent.”
    http://nsidc.org/arcticmet/factors/humidity.html

  28. 78
    Thomas says:

    53,54:
    I think statistical analysis of earthquake clusters has to overcome some difficuluties. It is well know that any large event changes the stress distribution over a substantial area. This increases the probablity of other earthquakes in the area -and perhaps on adjacent sections of the same fault system for a number of years. So one has to be able to disambiguate this effect from the signal you are looking for.

    54:
    There are modern (although much smaler) analogs for the lak Missoula emptying. I think Lake George in Alaska undergoes an annual event. Doubtlessly there are other locations in the world with longer breakout periods.

  29. 79
    Rob says:

    Hank,
    I think you failed to understand my point.
    You point out yourself that the Arctic can cool only to space.

    So if GHGs indeed cause a 1 W/m^2 forcing (reduction in cooling) then heat should build-up in the Arctic, to the account of 5E20 Joule per year.

    Now since IR emissions from ice/snow and water are fairly similar, the only way to get rid of that heat by increased radiation would be to increase the temperature.

    My point is that because ice cannot be warmer than 0 C, that heat has to go to melting, and it does, as witnessed in the reduction of ice thickness in the ice volume graph here :

    http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png

    Note that this graph is heading for an abyss (ice free September) no later than 2016.

    After we have an ice free September, radiation can increase again, due to water warming up (just like what happened in all other oceans). However, until then it seems that GHG forcing in the Arctic caused a 70% reduction in (September) ice volume and is heading for total elimination before 2016, at least if PIOMAS and Navy ice-thickness measurements is to be trusted.

  30. 80
    Thomas says:

    Rob there is nothing special about the arctic. The forcing of 1 watt/ meter squared is a change to the radiation balance globally averaged. There is no reason a priori that at any particular location the radiative balance must change by the average. Only that globally averaged that is what you would get for a quasi equilibrium state. Just because the arctic is a net sink, doesn’t imply it is a net sink for the change. Only detailed simulations can answer that question.

  31. 81
    Rob says:

    Thanks Thomas,
    I appreciate your comments, but the “detailed simulations” have been done over and over again in many different peer-reviewed publications. Most of these simulations are faced with variability of some 10 W/m^2 in the various heat in- and out-flux numbers. Also, many of these simulations are not even valid for ice-free conditions (they assume ice cover).

    The changes that we see reflected in PIOMAS ice volume indicate a long-term loss of some 700 km^3 ice loss per year (recently accellerating to 1000 km^3 loss per year), which is equivalent to a 1 W/m^2 ‘forcing’. So long-term observations of PIOMAS easily fall withing the noise of these “detailed simulations”.

    Still, if PIOMAS (and the Arctic ice volume numbers in the link I provided) are correct, then we will hit ground-zero (ice free conditions) before 2016, at a rate of 1000 km^3/year deficit. That translates to a forcing deficit of 1 W/m^2 which would only become in equilibrium (after some ocean warming calculations) if we experience 3 C average temperature anomalies over a 2-3 month period during summer. That means ice free conditions for 2-3 months, and sea surface temperature anomalies of 0-6 C over the entire Arctic region.

    That is a vastly different Arctic than we currently experience, folks !

  32. 82
    Hank Roberts says:

    > You point out yourself that the Arctic can cool only to space.

    No, I pointed out that the Arctic _can_ cool to space, after you missed that part.

    Next, I pointed to Spencer’s explanation that a cooler object can lose heat to a warmer object.

    Others point out this isn’t just radiation and melting; air and water movement transfer a lot of heat.

    You’re claiming authoritative sources for data:

    > at least if PIOMAS and Navy ice-thickness measurements is to be trusted.

    You’re fitting a simple curve to recent years. The people fitting “natural cycles” curves do the same, picking the chunk of time they want.

    Look at the previous century; where do your simple curves fall?

  33. 83
    Hank Roberts says:

    > if this is correct, then we have less than 3 years to see an
    > ice-free Arctic ocean in summer.

    Perhaps you’d be interested in a wager on this? I can suggest some people who might like to make a bet with you on your prediction.

  34. 84
    Rob says:

    > > You point out yourself that the Arctic can cool only to space.

    > No, I pointed out that the Arctic _can_ cool to space, after you missed > that part.

    Sure, but the Arctic can ONLY cool to space. And when you realize that in summer ice cannot get above 0 C, all heat due to GHG forcing will go to melting sea ice. Which was my point.

    > Next, I pointed to Spencer’s explanation that a cooler object can lose
    > heat to a warmer object.

    I think you misunderstood Spencer. A cooler object can lose IR radiation to a warmer object, but it will not loose heat, since it will always receive more IR radiation from the warmer object than it loses to it.

    > Others point out this isn’t just radiation and melting; air and water
    > movement transfer a lot of heat.

    For sure, air an water move a lot of heat into the Arctic. But my point is that even if you consider that heat flow to remain constant over long periods (decades), the GHG forcing in the Arctic would explain the reduction in ice volume.

    > You’re claiming authoritative sources for data:
    > > at least if PIOMAS and Navy ice-thickness measurements is to be trusted.
    >
    > You’re fitting a simple curve to recent years. The people
    > fitting “natural cycles” curves do the same, picking the chunk of time
    > they want.
    >
    > Look at the previous century; where do your simple curves fall?

    I hear you, but PIOMAS is not an appeal to authority. There is a physical explanation for the trend (GHG forcing), and even for the accelleration of the loss of volume (albedo amplification).

    > Perhaps you’d be interested in a wager on this? I can suggest some
    > people who might like to make a bet with you on your prediction.

    Well, that’s a good one.
    I normally engage in bets only when I know the probablities of the outcome.
    In this case, there is one issue that prevents me from engaging in a bet.
    That is the difference in model projections of ice volume in PIOMAS (collapse by 2016) versus projections in IPCC models (summer ice until at least 2050). That difference I do not understand because I do not know the differences between the models. One key paper is Tietsche et al, which uses IPCC models to project recovery when ice gets too thin (or even ice free conditions).
    Give me some time to study that paper in detail, and I’ll be back.

    Also, it sure will be interesting to see what will happen this summer in the Arctic.

    P.S. Are these “people” that you refer to (that would engage in a wager) scientists ? If so, I’m more interested to hear their argument than to bet with them.

  35. 85
    Hank Roberts says:

    > only cool to space
    Nope. Look at the ocean circulation; where does the cold bottom water go? What flows in to replace it? Look at the air circulation — same. You know those bursts of cold air in the American midwest in the winter? What replaces that cold air further north?

    > bet
    http://scienceblogs.com/stoat/2011/03/sea_ice_-_and_now_for_somethin.php

  36. 86
    Rob says:

    Hank,
    > > only cool to space
    > Nope.

    I think you are mistaken. Why do you think that cold ocean bottom water got so cold ? And where do you think those bursts of cold air in the American midwest came from ?

    The Arctic is a heat sink, with only space to keep it cool.
    And our GHG emissions reduce that cooling, which causes rapid sea ice melt.

    I just put $10,000 on that statement, by accepting William’s bet.

    (Thanks for the pointer to William’s post)

  37. 87
    Dan H. says:

    Rob,
    Are you accepting Neven’s bet where he believes that Arctic sea ice will set a new low within the next 3 years? If so, then I would tend to side with you as we witnessed higher minimums over the past 4 years making 2007 appear unusualy low. I would not take that bet over the longer term though.

  38. 88
    Rob says:

    Dan,
    Both Neven’s poll and the market’s opinion on intrade seem to favor a record minimum THIS year already (not even waiting 3 years).

    http://www.intrade.com/aav2/trading/contractInfo.jsp?conDetailID=744206&z=1300944608087

    So if you are convinced that ice extent will expand over the next three years, then there are plenty of opportunities to make money.

    Seems that the market is loosing faith in the conservative “the ice will recover” sort of opinions.

  39. 89

    Bell has extrapolated his observations forwards to 2050, as have Vermeer & Rahmstorf (2009). These give an ice sheet contribution of about 150mm by then; a mere 39 years away.

    Hansen recently commented that an extrapolation from 1mm/yr this decade plus a guestimated doubling time for the rate of 10 years would give 5 metres SLR by about 2095. But he didn’t give a particularly solid basis for his assumption of continued doubling of the rate.

    Are any of these authors prepared to put their necks out and give us a prediction for 2100 AD on the same seemingly robust basis as they used for their 2050 prediction?

  40. 90
    Dan H. says:

    Rob,

    It is not that I think the minimum extent of sea ice will expand over the next three years, but that we will not break the low of 2007. The minimum extent has already increased 25% since the low in 2007. It appears that 2007 was anomalously low, just like global temperatures were anomalously high in 1998. The trend is lower, but the extrapolated trend lines do not approach 2007 levels in the next three years. I would not be surprised if this year’s minimum was higher than 2009 considering the rather strong La Nina.

  41. 91
    Rob says:

    Dan wrote :

    “I would not be surprised if this year’s minimum was higher than 2009 considering the rather strong La Nina.”

    With all due respect, but are you serious about your statements, or are you just repeating rethoric you heard on climate change deniers blogs ?

    2011 ice extent is currently more than half a million km^2 below 2009 and 600k km^2 below 2010. What’s worse, ice volume is on a crash course to hit rock-bottom within a few years.

    http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png

    Maybe you will get a willing ear at sites like WUWT or CA or from Goddard, but let me assure you that physics and reality are not particularly graceful towards denial, scapegoating and preconceived belief systems.

    Besides that, I’ve given you 3 pointers that show that opinions like yours are no longer believed by the market place. So if you are serious about this, then offer a bet, or anonymously make your money on Intrade.

    But for all time sake, stop bothering scientists and the rest of us rational thinking people with your fairy tales that all is nice and dandy with the Arctic and that 2011 ice extent may actually top the 2009 minimum.

    The time of denial and blaming scientists and empty rethoric is over.
    It’s time we face reality as it has been staring us in the face all along.

  42. 92

    90, Dan H.

    My question to you, what really matters more than predictions, is what will your own reaction be if this year does present a new minimum? Will you start to doubt your obstinate refusal to consider global warming as a threat? Or will you just shrug your shoulders, say it’s an anomaly, and bet that the ice will recover 150% next year?

    Personally, I’m of the opinion that this year’s ice may well shape up to be frighteningly, earth shatteringly low. I won’t make that a prediction because one can never tell. Last year, looking purely at extent, the ice first stayed high late into Spring, then dropped precipitously, and then just when it looked certain to be headed for another record melt it put on the brakes.

    The difference that I see this year is that when looking at the actual ice distribution at The Cryosphere Today, and comparing it to previous years, one can see that while the area of 15% (or 30%) ice coverage is roughly the same as in previous years, if a bit low, the extent of ice breakup in the 15% to 80% range this year is substantially more advanced than in all previous years, including 2007. It’s all counted the same when compiling those simple extent graphs, but it’s not actually the same. Really, if one were to look at the image right now without a date on it, being asked to guess what time of year it is in the Arctic, one might say that it looks like mid to late May or even early June.

    Of course, things can change rapidly, but my own understanding is that the ice is and has been rotten for some time, that it has been melting from underneath, but that no matter what happens, the results can always be easily disguised by nature, due to the fact that the sun goes south for the winter and the whole thing refreezes, however thinly and superficially, to mask what is really going on.

    Will this be the year that this all becomes apparent? It’s much too soon to say, and I’m never in the prediction business. It’s a fun game, but it’s only a game. Right now, however, the data (the graphs, and the images of the ice concentrations) are all pointing to a precipitous melt this year.

    But what are you going to say if it does happen? Will it finally be time to wake up and become responsible about things? Will it be time to use your energies and posts into making people more aware of the issue, rather than heaping praise on people like Watts and Nova and Lindzen for the complicity in damaging the future of the human race?

  43. 93
    Dan H. says:

    Rob,
    Yes, the current ice extent is below the 2009 values, but it is also above the 2006 values, and 2006 witnessed the 2nd highest minimum in the past decade. On the flip side, 2010 had the 2nd highest maximum, and look what happened in the summer. Only 2003 showed a continuation from winter into summer. Based on the data, I see no reason that this year should exceed the 2007 minimum.
    If you refuse to talk rationally with scientists, that is fine with me. But if you continue your whining and insults, maybe you should go elsewhere, as scientists will take you less seriously.

    Bob,
    What is your basis for suggesting that this year’s ice will be “frightening, earth-shattering low.” I made my statement that cold northern waters will keep the ice from reaching a new minimum low. Further, low ice maximum was likely a result of the warmer Greenland temperatures. What do Watts and Nova and Lindzen have to do with my posting energy?

  44. 94

    93, Dan H.

    I already provided my basis for suggesting this year’s ice could be (not will be, don’t put words into my mouth) very, very low… the ice appears to be breaking up early (as evidenced at Cryosphere Today), even though the area of concentrations above 15% is still reasonably normal and so the pretty graphs all look not-too-bad.

    I can’t find your statement in this thread about cold northern waters, and I don’t think your Greenland logic applies (albedo that far north during winter months is going to be a bare minimal factor — although you do get points for the recognition of a positive feedback potentially in action in the system). I also doubt that La Nina has anything to do at all with ice extent (just because cold water is exposed in certain oceans or parts of the oceans doesn’t mean the whole planet suddenly got instantly colder everywhere — that’s not what La Nina does or is).

    I honestly don’t think any of that matters. There are far too many unmeasured factors which we don’t understand right now to predict ice extent in any particular year. All that we can accurately do is to measure the trend (seriously down), evaluate qualitative differences (i.e. rotten ice), and wait and see. Although if I were to jump from a skyscraper, I may not do a very good job at all of predicting exactly where I’ll land, but it’s not too hard to predict the eventual end result.

    As far as the Watts/Nova/Lindzen comment… it wasn’t actually directed at you specifically, but rather denial-lurkers in general… although I notice you did completely skip and fail to answer my main question, which I placed at both the beginning and end of my post…

    Predicting ice extent is a game for the likes of S. Goddard. But if the extent reaches a new minimum in the next three years, will you begin to take global warming seriously, or just blame it on a “bad year” and keep expecting things to just average out, or to blame things on some other convenient phantasmical mechanism like the end of the latest La Nina or any other convenient excuse?

    Sorry, I don’t mean to attack you personally, but I’ve grown tired of the repeat offenders showing, over the course of literally years (not necessarily you, again), absolutely no sign of ever opening their “skeptical” minds to the idea that maybe they are wrong, and it’s time to reconsider.

    How many years of decline (ice) and increase (temperatures) will it take for you (and others like you, who are reading but not commenting) to reconsider your rather staunch position?

  45. 95

    #93–Dan, two comments:

    1) Not in volume. . .

    See:

    http://psc.apl.washington.edu/wordpress/wp-content/uploads/axel/ice_volume/BPIOMASIceVolumeAnomalyCurrent.png

    2) What ‘cold northern waters?’

    See:

    http://ocean.dmi.dk/arctic/satellite/index.uk.php

    (Looks like they are rather warmer than climatology to me.)

  46. 96
    Dan H. says:

    Bob,
    I disagree that the ice is breaking up early. This year does not look all that different from others, 2005 showed a much earlier break up, and 2010 was much later. My La Nina point, combined with a largely negative NAO, indicates that colder waters are being measured in the northern oceans. 2007 reached its record low in the presence of a large amount of Atlantic water entering the Arctic. I do not see that happening this year, but se ice extent is relatively unpredictable on a yearly basis.
    I am not sure what your last two paragraphs are all about, nor what you would expect me to say if the sea ice does reach a new minimum.

  47. 97
    adelady says:

    Kevin – you should point out that folks need to select ‘Anomalies’ to get the full flavour of the problems exhibited on that DMI map. ‘Warmer than climatology’ is putting it mildly.

    The anomaly hotspot off Newfoundland / west of Greenland has been in that area for weeks, and it’s very ‘hot’. I have no idea what the effect will be once the ice gets moving, but it gives no cause for optimism. The other ‘feature’ – for want of a better word – of the anomaly maps has been the fleeting and very small guest appearances of any blue areas. There just don’t seem to be any balancing features of other areas being colder than climatology to offset the really large and persistent ‘hot’ areas.

    (Coming from a place that has never recorded a temperature below 0C, I find these conversations about ‘warmth’ in the Arctic a bit disconcerting.)

  48. 98

    That’s a good tip, Adelady–I forgot the thing defaults to absolute temperatures. As you say, the anomaly scale is more useful (at least for this purpose.

    I know what you mean about the relative scales of ‘warmth’–as a kid in Sault Ste. Marie, Ontario, 80 F was very ‘warm’ indeed. So when I first arrived in Athens, Georgia, to find 95 F (September 5th at 7 PM, no less!) it was rather a shock. But one does adjust.

  49. 99
    Rob says:

    Dan,

    Sphaerica (Bob) stated the question that really comes to mind when reading your responses :

    “what will your own reaction be if this year does present a new minimum? Will you start to doubt your obstinate refusal to consider global warming as a threat? Or will you just shrug your shoulders, say it’s an anomaly, and bet that the ice will recover 150% next year?”

    You did not answer this question, which seems to indicate that you are in denial about the ice loss trend in the Arctic.
    Would you care to correct your silence ?

    You also state :
    “This year does not look all that different from others”
    You mention a few cherry-picked maxima/minuma which supposedly would give some merit to your statement, while completely ignoring that the 95% of other points that you could have picked would have falsified your statement.

    You also ignored any of the ice-volume trend that was presented which shows that ice volume at Sept minimum is currently is only 25% of what it was in the 80′s, and is on track to hit rock-bottom (disappear) by 2016.
    http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png

    And neither did not give any scientific argument that indicate would show any form of slowdown from the accellerating downward trend of sea ice.

    So overall, I conclude that you fail to see what most other people realized a long time ago, or you don’t believe what you are saying yourself.

    There is always one test to see if somebody is sincere in their opinion :

    Put your money where your mouth is.

    I currently have a bet offer outstanding at Stoat, for $ 10,000, that ice extent will dip below 3 million km^2 in 2011, 2012 or 2013. This is about 2 to 3 standard-deviations below the average trend (which is already steeply downward), so if you are serious when you say that “This year does not look all that different from others” then you would jump on it in a heartbeat.

    If you don’t want to bet, then you should ask yourself why not.
    Why, if you don’t want to put your money on it, are you venting opinions that you don’t even believe yourself ?
    And remember that nobody but you yourself can make you realize that you may be in denial about what’s really happening out here in the real world.

    Try to answer Bob’s question at least…

  50. 100
    adelady says:

    Dan, if you want to see whether and how much the Arctic ice is changing, Cryosphere Today has one handy feature, apart from the animation and a whole heap of other goodies. When you scroll down you get the option of comparing one day with another.

    Last melt season I made a habit of comparing the most recent picture available – usually a day earlier than the latest day in the animation – with the same date 30 years ago, sometimes with 2007. Very sobering.

    Just now I’m comparing this year’s date just with last year’s. Downright nasty most of the time. Doing the same thing for 2007 or for 1980 I reserve for days when I’m pretty cheerful or determined. These comparisons do not make for happy viewing.

    But there’s no point in covering our eyes or looking away. This is not a film, it’s reality. Look right at it, straighten the shoulders and get on with what’s needed.


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