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Gas Glo

FrankD: the REAL curves are most likely S-shaped

Wipneus: I do not see reason for this. Especially for the September/August curves. The rate of ice shrinkage is significantly increasing, most likely from some self amplifying mechanism. That does not stop until the ice is gone.

I agree with FrankD.

The heat loss in winter through 50cm ice is going to be a lot more than through 100cm ice. The difference in heat loss between those two is a lot more than the difference between 100cm and 150cm. So this negative feedback may have barely begun to have an effect yet. I do not know how to quantify this but I figure that modelling does a better job of it than curve fitting.

For example
http://psc.apl.washington.edu/zhang/Pubs/Zhang_etal_2010GL044988.pdf

explains in the abstract "thinner ice cover increases winter ice growth"

The A2 scenario is the most aggressive scenario considered and that does not appear aggressive enough to me. I also do not like certain parts of the paper. Nevertheless there is a distinct leveling off at September extent of 2m km^2. Maybe that is sufficiently near ice free to be considered ice free but it doesn't fit your "That does not stop until the ice is gone."

I do not understand why anyone would ignore this and say they do not see any reason for S shape. It would be a completely different matter if people were saying thay had considered this and concluded that it wasn't going to have much of an effect until Sept and Oct were ice free. In that case I would like to see the logic / calculations of the argument. However, if it is just a matter of models versus people just saying they don't see any reason then it appears obvious that the models are the thing to look at and they do show S shapes.

Having said this, when I have tried to play about with the numbers, the heat budget gap does appear very large and I had difficulty believing that this negative feedback could act quickly enough to close a significant enough portion of the gap to make things appear as S shaped as the models. I do not believe in my ability to play about with the numbers like that so I prefer to believe the models despite the results of my attempts. I would be interested in seeing attempts by others to try to quantify the effects on the heat budget as the ice gets thinner.

FrankD

Wipneus,

I totally agree that the "tipping point" has already been passed. I thought from extent trends that was around 2002 (and have suggested that on a few blogs), but your new curve set looks pretty impressive for 1996. I note that late spring (May Jun Jul) curves show the fastest loss. I don't know what it signifies - just noting it - but its certainly what we saw last year.

GasGlo makes a good point about heat loss, but I was rather thinking of a few minor factors coming into play at lower volumes to prevent a complete zero.

Your curves are the net output of many factors. To some extent, everything that is in play has an impact on the curves so far, but over time, the relative impact of those factors changes, and brings in some uncertainty. I can't quantify any of these, so I'm just riffing on the process, but I think a few feedbacks will change:

1. Winter ice is declining more slowly than summer (this is obvious from volume and extent curves, and makes physical sense). In any given year, before "the core" of older thicker ice (a big part of that remaining 4000 cu km) can melt out, most of the first year ice needs to go. Each year, as the core gets smaller, there is more and more first year ice to work through, so the final demise should slow down a bit. Probably a bad anology, but think of it like stacking bricks. Each time you bend down, lift up a new brick and place it on top of the pile, it takes a little more energy just to lift the new brick to the top of the growing heap. If the winter volume was declining at the same rate as summer, this wouldn't make any difference, but because it's going slower, it might extend the final zero by a couple of years. However, I think that your curve fitting probably has this built in to a reasonable extent, and the difference between April volume and September volume has been remarkably consistent (~15,000 cu km), regardless of the absolute volumes involved, so it may not be a very important factor.

2. More cloud. 2010 saw record open water by the end of June, but then two months of cloudy weather. That may have just been a coincidence, but I think its part of "post-normal weather". More water vapour coming off the open water -> more cloud -> less surface insolation. As the core gets smaller, this may become a bigger factor, and act as a negative feedback. I think this would only have become a factor recently, and probably isn't really allowed for in your curves. However its hard to know how this compares to ice / open water albedo effects.

3. Geography. There are shallow ice-filled bays and channels in the Canadian archipelago which have weak currents, and are resistant to melting. I suspect that these will be the last to melt out completely. At the moment they are a small part of the volume total, so their resistance doesn't have a big impact on the trends, butas total volume declines, their contirubtion is greater and they may slow things down a bit before the last ice goes.

4. More cases like the Petermann Ice Island and increased flow of ice off land will all add to sea ice volume. Even with "zero ice" conditions, this is an additional, continuous source of ice that will last for quite a long time, and prevent a situation where there is literally no ice in the Arctic. Even if temps in the whole Arctic Ocean get to several degrees above zero, there will still be a continuous topping up of sea ice from land that will keep volumes above zero. Initally, this topping up might amount to a few hundred cubic kms (total guess), but will eventually decline to zero - once all Arctic glaciers have their termini on land, there will only be liquid run-off, not ice. But that will take a long time. It's also a big unknown. To date, land ice -> sea ice has been of little importance outside of Baffin Bay and Greenland Seas. But over the next few years, ice flowing off the Canadian and Siberian islands, and especially off the N Coast of Greenland will all help keep the central basin volume topped up (a little bit). I realise that this is not actually sea ice, but we count such ice in totals now.

Sorry if the above is a bit of a ramble. Partly I'm "thinking aloud" through the various factors. While I wanted to explain my reasoning, I also want to be clear that I don't think the tail will be very big. Probably less than 1000 cu kms, and only a few years long. As I said previously, we are already very close to bottoming out in September, so we will start to see it in the next couple of years if it is going to occur.

Gas Glo

2. More cloud.

I wonder if I am deluded in thinking that in several years time there will be a lot of sea fog in Oct, Nov & Dec. Heated from below by water and cooled by loss to space, there will be a fair bit of convection so presumably it won't be all that good an insulator to prevent heat loss to space.

Phil263

An interesting piece from the BBC website that talks about the effect of methane release following the 2010 BP oil spill in the Gulf.

The gist of the article is that a study found that virtually all the methane released by the spill was absorbed by bacteria before it reached the surface. Hence, the possibility that the same phenomenon could apply if the methane trapped at the bottom of the arctic floor was realeased because of warming waters.
However, scientists warn that there are big differences between the Gulf of Mexico and arctic waters. One is that the methane released in the Gulf came from very deep waters, while some part of the arctic are very shallow. The other obbvious difference is the water temperature.

The findings only concern methane gas released from the bottom of the ocean. It does not change alter the fact that methane may be released from thawing permafrost on land at at lake bottoms. I am not sure what would be the proportion of methane coming from ocean sources compared to land . Still an interesting study I think.

Phil263

Massive increases in SIE since the beginning of the new year according to JAXA::

1/1: +94k
1/2: + 74 k
1/3: +39k
1/4: + 122 k
1/5 :+ 126 k

The increase seems to be happening mostly in the HB and Bering areas and to a minor extent in the baffin Bay. The ice is just catching up I gather !

Neven

Indeed, Phil, 2010-2011 was 500K below all other years, but this has been reduced to approximately 150-200K. Mind you, PIPS is showing some moderately big arrows again:

If that trend keeps up, it might take another 10 days or so before the 2011 trend joins the fray again. Hopefully there will be a big refreezing spurt towards the end of the melting season.

Wipneus

Gas Glo:

Thank you for the critic. I admit that most of my experience with freezing over and thawing comes from observing my garden pond, which often de-freezes without any S curves. I will study the article in the coming days, it seems to draw far less alarming rates from basically the same data. Since it use physics rather than a mathematical abstraction, it will be interesting to compare.

explains in the abstract "thinner ice cover increases winter ice growth"

The abstract is talking here about the slow down in loss of mean annual average volume and I don't think I disagree. The negative feedback is already visible by the lower rate of ice volume loss in autumn when new ice is plenty and thin.

It is the late summer ice for which there is little hope: 1) at the current rate it will disappear within a couple of years 2) the rate of decline seems to be increasing instead of staying constant.

Once the late summer ice is gone, growth of the positive feedback is reduced. So I expect the loss of the ice cover during the other parts of the year will be delayed perhaps showing distinct S-curves.

FrankD:

I mostly agree with your points (although whether the cloud effect is both real and significant I wouldn't know). Let me add one more point:

5. The BPIOMAS model will have a "zero point" uncertainty in its scale. Zero in the graphs is only approximately zero ice cover (or the other way around).

Maybe we should define "ice free" as something below 1000 km3 or so.

Added the 2010 December data:
http://img411.imageshack.us/img411/2294/piomastrnd2.png
http://snipt.org/wkyg

idunno

Hi everybody,

It seems to me that the factor not being taken into account is the thickness of the ice and the effect that this will have on the final rate of disintegration.

First of all, this is because a thicker ice sheet is necessarily much stronger, and more able to resist the effects of wave action. As such, it will remain as a single solid object, and the increasing temperature of the surrounding sea and air have only two surfaces, top and bottom, on which to act.

A thinner ice sheet is much more likely to break into a slush puppy of unarticulated ice cubes, which is melting much more quickly, as the surrounding sea now has five surfaces to attack, instead of one. For example, if you look at the current map of Antarctica, the area of sea ice floating off the Ross ice shelf is clearly breaking into small blocks and is in the process of rapid disappearance; while the area to the East of the Antarctic peninsular is one solid block, which I would predict is much more likely to survive.

Thickness also matters because of the surface area of the resultant blocks floating about in the resultant "slush puppy"...

If you have an ice sheet 3 meters thick, or 3 units thick, let us assume that the result of physical break-up by wave action is to produce blocks of floating ice that are 3unitx3unitx3unit = 27 cubic units. This has exposed surfaces of 54 square units.

If the ice sheet is only 1 unit thick, and breaks into 1 unit cubes, then the same amount of ice volume is represented by 27 blocks of floating ice, with a combined exposed surface area of 162 square units.
i.e. three times as much ice is now being melted.

Given that the decline in volume in the Arctic is now running so far ahead of the decline in area, I think that this is due to become an increasingly important positive feedback...

which possibly helps to explain the latest Piomas values falling faster than any of the the mathematical models discussed above.

As volume divided by area/extent (=thickness) of the whole ice sheet has at least halved since 1979, the rate of ice loss due to this factor alone should have doubled.

Comparing the Sep 2010 and Sep 1979 figures from the Piomas table at the end of Wipneus's post above, volume has actually now fallen to less than a quarter of the 1979 figure at the height of the melt. So final melt-out should be 4 times as quick.

Sorry I noticed this. Depressing, innit?

Neven

A thinner ice sheet is much more likely to break into a slush puppy of unarticulated ice cubes,

Which is what we witnessed in last melting season's final weeks.

Depressing, innit?

It sure is. In fact, I do not agree with all these statistical projections, not because I think they are wrong, but because I don't want them to be true. If things really do keep accelerating like some people think they will, you can watch how I slowly evolve into a denialist.

Bfraser

idunno wrote:

It seems to me that the factor not being taken into account is the thickness of the ice and the effect that this will have on the final rate of disintegration.

Yes, this is an important factor (and is why volume is considered more important than area/extent).

And that reminds me of another important factor, which I haven't seen numbers for anywhere -- ice temperature. I'm sure that at one point, most of the ice (especially multi-year ice) was many degrees below freezing (perhaps -10C, which is roughly the average amount below freezing of the DMI 80N graph). However, since all ice forms much closer to 0C and not long has as much time to get colder before being melted/exported these days, I'm guessing that the total caloric input required to melt all the ice is falling even faster than the volume.

Peter Ellis

No, the specific heat capacity of ice is utterly irrelevant compared to the latent heat required to melt it. It takes 333.55 kJ to melt 1kg of ice, and only 2.11 kJ to raise the temperature of 1kg of ice by 1 degree.

FrankD

It's a small factor, but I wouldn't say utterly irrelevant. Since the ice typically gets to -30-ish, if I read the DMI graphs right, then ~15% of the heat required to melt it is taken up in warming it to zero. Some of the factors we've talked about above have probably been of a smaller magnitude. Back-of-the-envelope calcs say that every degree warmer the ice is before the thaw starts means an additional 30 cubic kilometres of ice volume is lost (maybe 30,000 km's in extent) at September minimum.

but because I don't want them to be true.
Neven, I earned some troll-abuse last summer (NH) for "wanting" the ice cap to melt. In fact I do, Now, I don't endorse cruelty to birds, but the sooner the canary dies, the sooner we can start doing something about the toxic gases in the mine. Or, to take another animal metaphor, to help prevent us frogs being boiled alive: en.wikipedia.org/wiki/Boiling_frog

We are on this arc of CO2 production that will have whatever effects it will over the next century, or two or three... Infinitessimal changes are not noticed, or are dismissed or trivialised. Only dramatic changes can jerk people (collectively) out of their complacency. Only clear signals will stop the folk on the other side of the mirror pretending that every thing is fine and dandy. And the sooner we get those clear signals, the sooner we can start treating the disease.

So bring it on I say - If we want good environmental policy in the future, we'll have to have a disaster". John Houghton was right. The sooner we get good policy, the easier the transition would be.

Finding a lump doesn't give you cancer. It means you've already got it, and now you know, you can start doing something about it. Those in denial unwittingly prefer massive doses of chemo to treat a body full metastised tumours. I'd rather an early lump-ectomy...

Bfraser

Thanks, Peter. That makes sense. I was off by an order of magnitude and remembered the latent heat as 33.55kJ.

Though just to avoid spreading errors, I checked on the internet and the specific heat is 4.186 kJ/kG, but that still makes the energy required to melt ice about the same as the energy required to raise ice by 80C.

Kevin McKinney

I agree with you, FrankD. Not that I really "want" the ice to melt, but that I do think we need some drama to wake people from their comfortable slumber of denial. Nothing for that like lots and lots of cold (but liquid) Arctic water.

But it's an emotionally conflicted position to be in, it must be said.

Jon Torrance

It's one advantage of Intrade so far offering only a contract on whether 2011 will set a new record minimum or not - since I've been betting against it at the, to me, surprising odds on offer (sure, I think it could set a new record next year but I also think whoever it was bought at a price implying they thought the odds of that were better then 75% is, in fact, overly alarmist) I'll either make money or we'll get a new record minimum - a silver lining for me whichever bad thing happens.

Artful Dodger

I guess it's this notion that "I'll be okay, regardless of what happens to the climate" that fuels denialism. By the time consequences actually impinge upon the few people that actually drive policy, no amount of money or power will be sufficient to purchase safety.

We are entering that period of consequences now because we failed to act at Kyoto. Cancun locks in our future, now only the timetable is in question, not the outcome.

Artful Dodger

Frank: Greenland lost about 500 Gigatons (GT) of ice in 2010. 1 GT is about 1 cubic kilometer of water equivalent, so Greenland calved about 400 to 450 km^3 of ice into the ocean (only about 10 - 20 % of Greenland ice melts, the rest calves from glaciers).

Even so, none (zero) of this ice will replenish sea ice in the Arctic. All of this ice will end up in the Atlantic and melt there in 1 to 2 years. All that matters for Sea Ice is the perennial ice pack in the Central Arctic Basin.

Andrew Xnn

Greenland has about 2.8Mkm^3 of ice. At 400 to 450km^3/year, it will take between 6000 to 7000 years for it to all melt.

Arctic Sea ice has between 4,000 to 21,000 km^3 and is melting somewhere between 350 to 800km^3/year. That works out to between 5 to 60 years.

The surface area of sea ice is between 1.3 to 7 times that of Greenland's ice cap. So, sea ice has potentially more of an impact on the climate. As it disappears, it will feed back thru both albedo and water vapor changes and will likely result in significantly altered weather patterns and something of a brave new world for the next generation.

FrankD

Lodger: I'm not suggesting that this is either a significant volume or that it is physically important in the great scheme of things but just to explain what I meant...
(The example below might be wrong on the detailed methodology because I have that forgetting disease I forget the name of, but follow me on the logic.)

Suppose Wipneus, you, me and Maslowski are all more or less correct and September sea ice is gone by 2015. September 1, AMSR-E extent hits zero. The next day, the Petermann Glacier calves a chunk of ice, say 260 sq km's in area. The people at IJIS then look at their 25 x 25 km grid and notice that one square of the grid in Nares Strait has more than 15% ice. They dutifully record ice extent of 625 sq kms (and area of 260 sq kms). Petermann Ice Island 2015-A moves down Nares Strait, through Baffin Bay and out into the Atlantic over a period of months. During that time it contributes its 260 sq kms to Sea Ice Area (and Extent, but the exact impact there is variable). Until this berg moves out of the zone in which area/extent is measured, it will add to the total. At least, it is counted like that now.

Again, I may have the detailed methodology wrong, but the point is that ice calving off into the sea will be counted in sea ice area, even if it does not represent actual "sea ice". Ice that is part of the Petermann Glacier does not count toward sea ice totals, but a berg calved off it does, until it leaves Baffin Bay. Glaciated areas around the Arctic are therefore a store of ice that is not physically relevant to the health of Arctic sea ice, but numerically serves to delay the point at which there is literally zero ice - part of the tail on the s-curve I referred to. Its a numerical issue only.

Andrew, while I agree it is dropping on a vastly longer timeframe, Greenland mass loss is not progressing in linear fashion either. That might be my next project. ;-)

Artful Dodger

Frank: Maslowski is not predicting Baffin/Labrador Sea Ice. His models are based solely on ice in the Central Basin.

Regarding Greenland, the appropriate number for 2010 ice mass balance is -500 GT, because loss is Melt + Calving. 2009 was -300 GT. It is the accelerating trend that is important for sea level rise, which will be catastrophic long before the supply of ice is exhausted in Greenland.

Artful Dodger

... and by Central Basin, I mean the contiguous permanent Sea Ice pack, which extends from the North Pole. Basins that melt out seasonally are not part of Maslowski's model.

Kevin McKinney

Funny you should mention that, FrankD. This just got posted on RC:

http://politiken.dk/newsinenglish/ECE1161570/greenland-close-to-unavoidable-meltdown/

It's a modeling study, and the authors estimated the "point of no return" for the GIS as no later than 2040.

Oy.

dorlomin

We are entering that period of consequences now because we failed to act at Kyoto.
= = = = == = = = = = = = = = = =
I would suggest that had Kyoto been fully enacted it will not have made much of a difference for some years. Much of the warming has been locked in by thermal inertia delaying the full impact (among other bits and bobs)

My personal belief is that climate mitigation is more about saving ourselves having to do it at much greater cost in a much quicker fashon ten years from now, than actually changing anything. I fear the signal is emerging from the noise and already takes considerable effort to deny, its no longer scepticism, no longer maybe if but but CLOUDS, its plain old denial and that has a short life time left as the numbers continue to come in.

We are merely delaying the inevitable in delaying action, in the end we will have to cut back rapidly, delay means that much more rapid when we sober up.

Artful Dodger

Here are Wieslaw Maslowski's Arctic Ocean heat inflows from a Conference presentation given in Hokkaido on 2008-06-24 (click the image below to open the original PDF):

When will Summer Arctic Sea Ice Disappear?

Since Maslowski attributes 60% of the loss of Arctic Sea Ice to increased heat inflow from the Ocean, understanding these inflows is key to understanding his model.

Let's fast forward in time to a newly Sea Ice free Arctic Ocean and calculate the change in the energy budget. First, summing all the inflows to the Central Basin, we get 23.613 TeraWatts (TW). Heat outflows total -5.18 TW, for a net heat inflow of 18.433 TW.

Let's further assume, with the mechanical barrier of sea ice removed, that heat inflow is evenly distributed in the new ice-free domain. Using 2010 min SIE of 4.8 M km^2 we can obtain a rough estimate of the change in the Central Basin heat budget, expressed in units of Watts per Square Meter.

So 18.433 TW = 1.8433 x 10^13 Watts, and 4.8 M km^2 is 4.8 x 10^12 m^2. Dividing, we get 3.84 Watts / m^2. This figure is a first approximation of the extra heat delivered to the surface layer in a sea ice free Central Basin.

This figure makes no attempt to estimate the change in heat due to the albedo flip associated with the replacement of highly reflective ice with dark liquid water. That energy budget will be discussed in my next post on this topic.

Clare

Kevin McK said:
"...Not that I really "want" the ice to melt, but that I do think we need some drama to wake people from their comfortable slumber of denial."

a Comment #4 on
http://climateprogress.org/2011/01/06/extreme-weather-events-helps-drive-food-prices-to-record-highs
"The wake up bell for the US population on global warming is likely to be food shortage and higher prices for food."
I apologise if this is somewhat off topic but do folk here -who always have sensible non-emotive comments to make - think this might be THE wakeup call people would listen to? Or will need to be some sort of extreme weather event in a major politcal centre like Washington DC or similar?
It seems to me food & water shortages can impact more widely at any one time while we have already had extreme weather events like the flooding in Pakistan but they seem to drop off the public 'radar' fairly quickly, so haven't happened in the 'right' place.

MikeAinOz

Claire, re: "this might be THE wakeup call". I think food prices are too difficult for people to to directly associate with climate change. The rising price of fuel may well have a greater effect. I read Neven's comments "you can watch how I slowly evolve into a denialist", and he is right. Melting ice will not do it either, it is too far away. The "wakeup call" will more likely come when it is too late, and the water rises over the seawalls of a changed environment, until then we are all in denial.

On the bright side, I'm looking forward to the coming melt season and the input from Cryosat-2. I'm even wondering whether Hudson bay will ice up completely or not. I'm also legally allowed to water my garden now, which is excellent and I shall do it while I can.

Artful Dodger

Hi Dorlomin.

You make excellent points. Our Kyoto commitments were far too weak, then largely ignored. However, it's that 1997 time frame for the start of action that I'm referring to, and what has happened to Arctic Sea Ice during 13+ years of inaction.

Figure 2(3) from the SI Appendix to Eisenmana & Wettlauferb (2009) shows the response over time of Arctic sea ice mean thickness to a fixed change in climate forcings:

Eisenmana & Wettlauferb (2009) Appendix Figure S2(3)

In the diagram above, two examples are studied, each with a different initial state for mean ice thickness. In Year Zero of the Experiment, climate forcings are instantaneously changed to a level which will cause average sea ice thickness to reach equilibrium at 3 m depth (steady state for the annual cycle). The time response demonstrates the delay in the sea ice system. Note that after 5 years, 50% of the change in thickness has occurred. After 10 years, 75% has occurred, and after 15 years, sea ice thickness is in equilibrium with climate forcings.

Laxon et.al (2003) in letters to nature found that average winter sea ice thickness has a standard deviation of 24.5 cm, or 9% of the average. So in the real world, a new equilibrium should be reached within 15 years, +/- a few years to allow for natural variability.

What does this mean for our failure to act after Kyoto? Over 13 years, fully 88% of the 1997 heat imbalance is now represented in Arctic sea ice thickness.

But in 1997, CO2 was 363.5 ppm, but now is 389.8 as of 2010. So the above graph is a simplification of our predicament. We are in an era of steadily increasing forcings, which don't become fully revealed in Arctic sea ice for about 15 years. The effect of CO2 released in 2010 will not be felt fully until 2025.

The limited scope of Cancun means Nations will not start meaningful C02 reduction before 2020. That CO2 commits the Arctic to imbalanced climate forcings until at least 2035, plus lead time to convert Industry.

I expect the Arctic Ocean will be perennially ice-free by that time, and will show why in my next comment on this topic.

Daniel Bailey

Re: Claire

Katrina was not enough. The Tennessee flooding was not enough. Sorry to be so blunt, but neither location was "important enough" for the American Public to wake up and take notice. At this point I'm not sure if even open water at the North Pole will be enough.

It will probably take a Russian-style heatwave in New York City that kills a few hundred thousand people for the US to wake up enough to try and act. That would be "the right place".

But then I'm not always sensible.

The Yooper

Artful Dodger

Kevin, thanks for the heads up on the Greenland Ice Sheet paper. A PDF is freely available from here, and here's a citation to the Journal article.

Mernild, Sebastian H., Glen E. Liston, Christopher A. Hiemstra, Jens H. Christensen, 2010: Greenland Ice Sheet Surface Mass-Balance Modeling in a 131-Yr Perspective, 1950–2080. J. Hydrometeor, 11, 3–25.
FrankD

One other aspect I've been looking at over the colder months (and thanks to La Nina, that even applies here in Australia!) is duration of the thaw.

While its only a short dataset, I took IJIS extent data and checked the date on which extent fell below or rose above the various million sq km increments. I took the average for 2002 - 2009, and compared to the data for 2010. For thaw, 6 of 8 points were earlier. For freeze, 7 of 8 points were later (I had to project the 8th point - 13 M sq kms - since we're not there yet.) Nothing too unexpected there.

I also looked at the duration of the period between which the extent dropped below a given mark, and when it passed it on the way up again. Again, I compared the 2002-2009 average to the 2010 data - so we find that ice extent was below 6 M sq kms for 51 days last year, compared to an average of 43.4 days, below 7 M sq kms for 77 days, compared to an average of 72.1, etc...

The average of these durations (8 points from 6 M to 13 M sq kms) was 8.5 days longer than the average for 2002-2009 (which period was, of course, longer than the durations prior to 2002).

I tried to post the data in this thread, but the formatting shunted it to the spam filter (I guess) so I've posted the data here: http://snipt.org/wklG

I've graphed the results and looked at trends, which I might post some time. Ultimately, that was fairly pointless - as with all such exercises trending extent, they offer hope of it being several decades before we see an ice-free September. I wish.....

FrankD

Thanks for clarification on Maslowski, Lodger. It doesn't make much difference to what I was saying though.

While I mentioned Maslowski in passing, I was referring to IJIS extent, which does cover the other basins. However, if you prefer, replace references to "Petermann Glacier calving into Nares Strait" with "One of the glaciers in Peary Land calving into the Arctic Basin".

Again the point was that - numerically - ice calved from glaciers surrounding the Arctic is and will continue to be added to sea ice totals, defering the point at which we get to literally zero sea ice.

Your (Maslowksi's) power budget figures are very interesting. I suspect they might also yield some useful numbers on the lifespan of the remaining pack. I'm off to crunch some numbers.... :-)

Neven

Clare, high food prices will be blamed on ethanol and speculators (which both have to do with it, as does AGW). But as long as the root cause behind the symptoms that cause higher food prices and food riots elsewhere, ie the need for the economy to grow exponentially, isn't exposed, we're still not getting anywhere.

As for the Arctic: IJIS down again, big arrows looking Arctish Dipoley (a bit like an Arctic Dipole setting up):

Andrew Xnn

Big arrows pointing towards Severnaya Zemlya.
Ice must be piling up and getting pretty thick near that coast.

Had to look that place up too... Interestingly, it wasn't "noticed" until 1913.
That makes it one of the last large land mass discovered.
Not surprising current population is 0.

Artful Dodger

Let's return to the topic of albedo flip, which is what happens when lost sea ice is replaced by dark liquid water in the Arctic Ocean. Sea ice reflects about 70% of incoming shortwave radiation, but open ocean reflects only about 7% of the Sun's energy. This albedo flip makes a 10-fold difference in Solar heat input to the Arctic Ocean, and is critical for estimating when the perennial ice pack will collapse.

Let's get started. If we know the ratio of open water to sea ice, and the amount of incoming solar energy, we can calculate solar heat input to the Ocean. This will be used in the heat budget, later.

Solar insolation from 70N to the Pole averages about 100 W / m^2. Allowing for clouds and atmosphere, ~70 W / m^2 reaches the ocean surface (useful as a 1st approximation).

If 70 incoming Watts hits sea ice, only about 21 Watts / m^2 is absorbed, due to the 0.7 albedo. However, if it hits open ocean, about 65 Watts is absorbed. Now here's the inspired bit which we will use later: when the Ocean is partially covered with sea ice, then total solar heat absorbed can be calculated if we know the proportion of sea ice to open water.

We have a measure of this 'compactness' of the sea ice pack. At the ASI blog, we call it CAPIE (the ratio of Cryosphere today Area Per IJIS Extent). For example, on July 15, 2010 CAPIE was about 69.5% so we can estimate the heat absorbed by the Arctic Ocean above 70N at about 34 W / m^2.

Using this technique, we can create summary statistics for Summer 2010, which are an estimate of the total solar heat input for the season. I have a tad more spherical trigonometry to do, then I'll be back with another comment continuing this topic.

Peter Ellis

Eh, compactness isn't the right figure to use.

Let's say you have a given amount of ice at a given compactness. Now, pretend the left half of it vanishes instantaneously. Area and extent are both halved, but the compactness is unchanged.

What you want is the ratio of the ice area to the total sea area. Moreover, since the denominator of that is fixed by Earth's geography, you can cancel it out and just use ice area as a measure of how much extra sunlight is being absorbed.

If you want to do better than that, you'll need to adjust for latitude on a pixel-by pixel basis over time.

Neven

I've opened a new Open Thread. Please continue there. I'll copy the last comments.

Artful Dodger

No, Peter. I am estimating the heat budget within the perennial ice pack. The mechanical properties of sea ice make the pack ice a separate domain from the Ocean. Here's an example:

By Aug 31, 2010 the SST gradient in the East Beaufort sea was up to 22 C over 150 km. Warm water did melt the ice edge, but Sea Ice physically separated the interior of the pack, preserving the perennial ice pack.

As long as temperature gradients persist, your approach will not work. Heat is stored separately in the Ocean, then released to the atmosphere in the Fall, without ever adding a calorie or KJ to the central pack ice. This is not the knock-out punch that will cause the sudden loss of the perennial ice pack.

Talking to the BBC about Arctic Sea ice in 2007, Maslowski said: "In the end, it will just melt away quite suddenly". What I am after is a description of the mechanism for that complete collapse. Think of popping a balloon, verses deflating one.

www.google.com/accounts/o8/id?id=AItOawkpUaD_uYjZAIrhpA6AA5KyEs-CSoL4zlM

NSIDC has just released its August analysis ->

http://nsidc.org/arcticseaicenews/

Chris K

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