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Kevin McKinney

Did anybody mention that the La Nina has officially dissipated?


We are now ENSO neutral, and could see an El Nino by late summer... or not. (Models differ.)


Hi all,

Interesting that PIOMAS has actually increased year on year - just.

Still, there has been a long period of continuous decline.

Some time ago somebody posted on here some information on the fall off of the Atlantic Multidecadal Oscillation. Is there any fresh information on this?

As far as I understand it, the AMO is one of the most important factors in the recent spectacular decline of Arctic Sea Ice. If it has peaked, and is about to start running cold, I think this would be a game-changer.

If anybody has any relevent info, please share...

William Crump


If the "statistical error bars are quite large" then how meaningful is the 2012 projection line? Instead of a single line, the chart should show the whole band of possibilities represented by the error bars.

In looking at "actual" amounts from the PIOMAS model, 2012 appears to be closely following 2011 as noted by idunno.

What physical processes in terms of winds and temperature and ice transport would have to be different in 2012 from 2011 in order for the September 2012 minimum to be 75% (based on a drop from 4,000 km3 to 3,000 km3)of the volume at the minimum in 2011?

Any one year drop of the magnitude suggested by the 2012 projection line in the September minimum volume will have more to do with natural variability than long term CO2 forcing.

Axel Schweiger, Ron Lindsay, and Cecilia Bitz have posted a comment letter on Real Climate "Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation" that sets forth why such line drawing is suspect when dealing with a complex non-linear system like arctic ice.

Two excerpts from the comment letter follow:

"So does it make sense to extrapolate sea ice volume for prediction? In order to do a successful extrapolation several conditions need to be met. First, an appropriate function for the extrapolation should be chosen. This function needs to either be based on the underlying physics of the system or needs to be justified as appropriate for future projections beyond just fitting the historical data.

But what function should one choose? Since we don’t really have data on how the trajectory of the Arctic sea ice evolves under increased greenhouse forcing, model projections may provide a guide about the shape of appropriate function. Clearly, linear, quadratic or exponential functions do not properly reflect the flattening of the trajectory in the next few decades seen for example in the CCSM4 (Fig 3). The characteristic flattening of this trajectory, at first order, arises from the fact that there is an increasingly negative (damping) feedback as the sea ice thins described by Bitz and Roe (2004) and Armour et al. (2011). The thick ice along the northern coast of Greenland is unusually persistent because there are on-shore winds that cause the ice to drift and pile-up there. So extrapolations by fitting a function that resembles a sigmoid-shaped trajectory may make more sense, but even that, as shown in the figure, yields a much earlier prediction of an ice-free Arctic than can be expected from the CCSM4 ensemble."

On the discussion of when the arctic will be "ice free" they caution:

"But when will the Arctic be ice free then? The answer will have to come from fully coupled climate models. Only they can account for the non-linear behavior of the trajectory of the sea ice evolution and put longer term changes in the context of expected natural variability. The sea ice simulations in the CMIP5 models are currently being analyzed. This analysis will reveal new insights about model biases, their causes, and about the role of natural variability in long-term change.It is possible that this analysis will change the predicted timing of the “ice free summers” but large uncertainties will likely remain. Until then, we believe, we need to let science run
its course and let previous model-based predictions of somewhere between “2040 and 2100″ stand”

See the full comment at:



"Interesting that PIOMAS has actually increased year on year"

I think it might be more accurate to say that the peak volume occurred a couple of weeks later. having been lower than last year during the previous month. besides the difference either way is trivial and observations suggest that that volume was only achieved due to late extent increase of tissue thin ice in low latitude areas where it is almost irrelevant it will melt so fast.


William: You can get an idea of the error bands in September in this graph:

I haven't calculated them for other times in the year, but I fully expect them to be "large", like in September.

About the realclimate discussion: read L. Hamiltons comment #45. I would probably word it similarly.


Hi Philiponfire,

Yes that's possibly the case. However...

I am previously on record somewhere as saying that I think that Maslowski's prediction of an ice-free Arctic in 2016 +/- 3 years is IMO too conservative.

This was based on the fact that Maslowski was using 2006 numbers, and that the solar cycle 24 was due to peak over the next couple of years, coincident with the peak of the AMO.

Given that solar cycle 24 is fairly feeble last time I looked, then if the AMO has already peaked, I might well change my mind.

Because its not just PIOMAS; DMI average Arctic temperatures are below average for the first sustained period since whenever ago; there has been a late surge in extent and/or area...

Fluctuation/natural variation/noise, perhaps; alternatively it could be the first signs of a change of the tide...

If AGW has to melt the Arctic ice against the background of a decline in the AMO, I think it will take much, much longer.

In theory, and I won't claim to be able to do the maths, or even to know what the right maths is to do, then a decline in the AMO could lead to a recovery of the Arctic Ice for 40 years or so, even with continuing anthropogenic forcings.

Chris Reynolds

Is anyone else having problems downloading?

I've tried repeatedly today and what I've been downloading only runs to day 91!. Tried again just now - same result.


Same here, Chris. I downloaded the data when I saw I still had CT SIA data up to the 15th (to generate the PICT average thickness map), but they're still running up to April 1st.


Idunno, since Chris Reynolds’ critics on 13 april on the suggestion that the AMO was related to last winter’s exceptional low Atlantic side ice extent, I’ve been reading more into this. While Chris is right that the actual AMO index is pointing at neutral state last months, NOAA graphics indicate the oscillation is still in its positive mode, which started in the 90’s and will probably last into the 2030’s. As with MEI/ENSO or AO/NAO on LTP, AMO is a calculated mean expression of measured SST’s between the equator and Greenland/Florida and Liberia. It is an expression of a coupled troposphere-ocean system, with time-lagged effects in different regions. The whole lot is under constant forcing through AGW. The time lag is important here. My assumption is, that a peak through 2010-2011 coincided with particular circumstances around Greenland/Baffin Bay, promoting the high SST’s then. While south of 60 dN the actual index became neutral, the flux continued right into the Barentsz Sea last winter. So what’s been going on cannot strictly be defined through the term AMO, but is related. Is the flux in decline? As far as it’s a peak, yes. But in my opinion it shall have a lagged effect in the Atlantic side of the Arctic Basin up to the New Siberian Islands. Most heat will be stored in the AW layer, 100-600 m under the ice. But this protective stratification isn’t as stabile as it used to be and the properties of these waters have changed…
On your suggestion that negative AMO could block 40 years of forcing... that seems hard to imagine while CO2 is creeping up to the 400's.


15th?? Isn't SIA upto about 26th still online? Wipneus, as you have the data could you post the April 2012 numbers here?

William Crump


Thanks for the error band graph and the Hamilton quote. Both are quite informative.

The published scientific literature on arctic ice does not appear to support an "ice free" Arctic within the time frame of the chart you referenced in your comment.

Published projections, though with varying definitions of what constitutes "ice-free", all project an ice-free Arctic ocean somewhere between 2037 (Wang and Overland, 2009) and the end of the century.

Given the amount of natural variability, an accurate prediction of the minimum volume level in September of 2012 is more a matter of luck than science. I do not see why a prediction based on an extrapolation using an exponential curve fit and historical volume information from the PIOMAS model is a valid method of predicting 2012 volume levels or when "ice free" conditions will occur.

To the best of my knowledge, there is no scientific study based on the physical forces and processes that are expected to affect future Arctic ice conditions which supports the use of an exponential line as the best fit for predicting future changes in Arctic ice volume.

The models appear to show a future rate of ice decline that is many orders of magnitude slower than the exponential line used in the chart referenced in your comment. This slower rate of decline is due to the increasing influence of negative feedback factors, such as loss of ocean heat due to loss of the insulating impact of Arctic ice.

Even if the exponential fit in the error band chart is appropriate for predicting the 2012 minimum volume, it is not certain that 2012 will have a lower volume amount than 2011. The error band chart appears to support the a possibility of higher volume in 2012 than 2011.

The line drawn on the chart above makes it appear that a 25% decline in ice volume is almost certain to occur in 2012. While this is one possible outcome, it is not the only outcome that lies within the 95% probability range.

The error band chart appears to say that there is a 95% confidence level that the 2012 minimum volume will be between 5,000 km3 - which is an increase of 1,000 km3 from 2011 - and 500 km3 - a virtually "ice-free" state, a range of 4,500 km3. The wide band of possible outcomes makes the use of the exponential line for projecting the 2012 minimum volume nearly worthless.

Rather than draw a single line, the 2012 prediction line should start from current ice conditions at a particular date and show an expanding cone of possible outcomes for 2012 volume that would be within the 95% probability range.

If this is a correct analysis of the error band chart, then to draw only a single line as a statistical projection of the possible level for 2012 is very misleading. If I am misreading the error band chart, please let me know.

Darren Wood

Hi a layman's question for you is there a point where the thickness of the ice will allow for;
wind and wave movement to break it up and stop it acting as a pack?

If so will that reduce the albedo? Just thinking of how a pond melts.(albeit a big pond!)

Kevin McKinney

Will, for a review discussing these very issues of extrapolation from observed trends vs. models, see:


(Maslowski et al., 2012)

Daniel Bailey

Thanks, Kevin, for that new overview & assessment from Maslowski. Note that Figure 9 (p. 15), incorporating data through 2009, still shows the original 2006 extrapolation of 2016 ± 3 years is still on-target.



The models appear to show a future rate of ice decline that is many orders of magnitude slower than the exponential line used in the chart referenced in your comment.

Not just the future rate, I think. A model that would give realizations that are closely following an exponential decline upto 2011, yet followed by an orders of magnitude slow down, invisible until now, would be needed.

William Crump


Do you believe the extrapolation in Figure 9 that the Arctic will be ice free in October-November of 2016? That is what it shows as the "ON" at the top of the graph means October-November.


Thanks for providing this article.

Maslowski does a good job of showing that the existing models have understated observed ice loss, and describes the difficulties of modeling a system as complex as Arctic ice.

How he makes the leap of faith that figure 9 is a better method for prognostication of future Arctic ice conditions rather than use improved models, I do not know.

His "prediction" is a simple linear extrapolation based on a limited data set (one might say cherry picked) of October-November mean volume for 1996 through 2007 which he states shows a decline of 1,120 per year. Maslowski excludes data for 1979 to 1996 which showed an increase in volume - the dashed red line in figure 9. Starting with a 2007 October-November mean of under 9,000 km3 he derives that the Arctic will be ice free in 9 years from 2007. The standard deviation amount for this claim is plus or minus 2,353 km3 per year.

I think Wipneus has a better idea than Maslowski, but I doubt we will get a model that can duplicate the chaotic system of natural variability entailed in the steep decline up to 2011.

The volume declines of 2007 and 2010 were steep, but we also saw in 2008 and 2009 that volume increases are possible over the short term. Current ice conditions may not matter in making a long term prediction as this cautionary statement from the Real Climate article illuminates.

"The seasonal prediction issue and the prediction of the long-term trajectory are fundamentally different problems. Seasonal prediction, say predicting September ice extent in March, is what is called an initial value problem and the September ice extent depends both on the weather, which is mostly unpredictable beyond 10 days or so, and the state of the ocean and sea ice in March. Improving observations to better characterize that state, and improving models to carry this information forward in time is our best hope to improve seasonal predictability. The prediction of the long-term trajectory, depends on the climate forcing (greenhouse gases, aerosols, solar variability) and how the model responds to those forcings via feedbacks. A recent model study showed that the crossover between initial-value and climate-forced predictability for sea ice occurs at about 3 years (Blanchard-Wrigglesworth et al. 2011). In other words, a model forgets the initial sea ice state after a few years at which point the main driver of any predictable signal is the climate forcing. In fact, coupled model simulations have shown that even removing all the sea ice in a particular July has little lasting impact on the trajectory of the ice after a few years (Tietsche et al. 2011)."

For now I will stick with a later date for an ice free Arctic at the minimum than 2016 and look for a better data set upon which to make an armchair prediction. Until then, I will continue to defer to the likes of Wang and Overland who forecast an ice free Arctic by 2037 in a 2009 research paper.

William Crump


The PIOMAS graph is showing that 2012 has been at the same level as 2011 or a little above it.

Why is the 2012 projection of September volume so much lower than 2011? Are the big drops in 2007 and 2010 skewing the line?

The second largest manner in which the Arctic loses ice volume is through the Fram Strait. The year to year loss through the Fram Strait is highly variable. See http://www.cgd.ucar.edu/cas/cdeser/Docs/climdyn_tsukernik-framstrait.pdf (Vinje 2001; Brummer et al. 2001, 2003; Kwok 2009).

Given that the ice is thinner in 2012 than prior years and the diminished ice cover in the Barents Sea, is it possible that less ice volume will be lost through the Fram Strait in 2012 than in previous years and this will operate as a negative feedback that prevents ice volume from falling as quickly as it has in the past?

Chris Reynolds


I agree that delayed effects may be important, IIRC it takes about 2 years for Svalbaard Atlantic Waters (AW) to reach the Siberian Shelf. My earlier criticism was on trying to link the AMO to current influxes in Bering - IIRC the person I directed my post to said they were using AMO in rather a looser term than the formal definition, which is fine by me.

As I've posted elsewhere here, Mercator might prove to be a useful tool.
I use anomalies of salinity to try to estimate what AW and Bering Strait (Pacific Water (PW)) influxes are doing. I do this on the basis that temperature changes associated with AW may be small, though the volume of the water can still have signficant overall heat content. So it seems to me that salinity is probably a good proxy for AW. However this technique is useless for long term monitoring over the period of that system because they've upgraded the model twice in the period of data there - and the upgrade times are by far the greatest changes in all indices there.

I've also said in my blog's post 'Musings about Models' that AW and PW influx increases may have had a pivotal role in the events of 2007, this is a feature of model simulations of Rapid Ice Loss Events (RILES). So to predict RILES in the real world looking at AW and PW influxes could be a key tool. Mercator is the best I've seen. It's some way off the ideal - regularly published observations of AW and PW heat fluxes - but if used with caution could be a reasonable tool provided people don't run away with conclusions drawn from it.

Chris Reynolds

William Crump,

I have some sympathy with your position. However I'm not as sure as you seem to be that we won't see a September with below 1Mkm^2 this decade.

Consider the recent few years PIOMAS volume.

You can see that 2007 was ahead of 2008 & 2009, a descending order that's been occurring since 2001. 2007 broke the order because of exceptional conditions.

There's some background to the 2010 issue here, in case you've not seen it.

However, going back to the first graph I link to, it can be seen that 2010 deviates from the preceding year early in Spring 2010, after that it follows roughly the same trajectory as 2011. Now even with April's PIOMAS data it's a bit too early to draw any conclusions about 2012, especially given events in the Atlantic sector.

I agree that curve extrapolation is not a preferable option, I still find it unconvincing. However I am willing to concede what Maslowski (et al) actually says in that paper: "Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover."

Bear in mind that the models used by Wang and Overland were chosen for their reproduction of sea ice response to another forcing - insolation's annual changes. It is quite possible that even their estimate is too late. Indeed I consider it so and for some time have said I expect the first virtually sea ice free state in the 2020s. There are two reasons for this, firstly the models used are subject to biasses (e.g. Boe et al) and the insolation forcing being cyclic may not be invoking amplification to the same degree as the continual intra-annual forcing of CO2.

Daniel Bailey


There are reasons why the vast majority of models do not reflect what is actually occurring in the Arctic...yest Maslowski's does. It is understandable having reticence to put much faith into a model which poorly does what it's supposed to do. But Maslowski's model has been closely tracking to the developments that have unfolded in the Arctic since 2006...which have followed an exponential curve of volume demise rather than a linear line.

Doesn't take a rocket science degree to figure these things out. Just letting go of preconceptions that are tied to the existing paradigm (i.e., the IPCC GCM's that have failed - through no fault of their own - to explain the rapid "death spiral" [for that is what it is] of Arctic sea ice volume).

And the operative phraseology is "largely ice free". Meaning an Arctic free of cap (but not necessarily devoid of some cover) except for a peripheral fringe of ice near the Canadian Archipelago and Greenland (and scattered other bits). And remember, it was 2016 3 years for the "lower bound".

Which, barring a massive volcanic eruption in the tropics or a global nuclear exchange, we are on-track for.

I suggest reading Maslowski's paper that Kevin was kind enough to provide a link to.

Daniel Bailey

That was 2016 ± 3 years. And "yet".

And at September minimum.

Ye gods, my typing skills have gone to sh*t...

R. Gates

Werther said:

"On your suggestion that negative AMO could block 40 years of forcing... that seems hard to imagine while CO2 is creeping up to the 400's."

It would seem the association of fluctuations in Arctic sea ice extent with the AMO is about correlations between natural variability of the system. The AMO/Arctic sea ice correlation is useful to look at, especially when trying to identify external forcing on system and parse it out of natural variability. The fingerprint of an external forcing (i.e. anthropogenic greenhouse gas emissions) on the decline in Arctic Sea ice is strong to very high level of confidence, and given the slower rate of the cryosphere to respond to a forcing such as increasing greenhouse gas concentrations, it is still responding to 392 ppm and will be for some time. I would expect the cryosphere to continue to respond (i.e. declining Arctic sea ice) for many decades, even after greenhouse gas emissions have stabilized. The AMO may be natural noise that rides on this longer-term signal.

Tor Bejnar

So has Arctic ice. And that is much worse.


William: Given that the ice is thinner in 2012 than prior years and the diminished ice cover in the Barents Sea, is it possible that less ice volume will be lost through the Fram Strait in 2012 than in previous years and this will operate as a negative feedback that prevents ice volume from falling as quickly as it has in the past?
Except that the flow out of the Fram contains lots of thick ice slipping along the coast:


William Crump


Amazing graphic, but I am not sure it answers my question as it only shows 2012 flow. Below is 2011 flow:


It looks to my biased and untrained eye that the thin stuff is moving fast while the thicker ice along the coast is not moving that much. Also, there does not appear to be much of the thicker stuff.

I am relying on NSIDC statement that much of the oldest and thickest ice is gone.


Is there a 365 day graphic for 2007 and 2010 that I can compare with 2012?

William Crump


What Maslowski model are you talking about? There is no Maslowski predictive model in the article posted by Kevin for future ice prediction.

Maslowski took data points for mean October-November ice volume per a model he uses to estimate current ice volume for the period 1996 through 2007 and drew a straight line. The NAME data points are estimates of actual ice volume, not projections of future ice conditions. He added data from Kwok et al for the period 2004 to 2008 to fill in missing data from NAME. Note the Kwok ice volume estimates for 2004 and 2005 are higher than the NAME volume estimates

Maslowski calculated a decline of 1,120 km3 per year using the period 1996 through 2007 (he left out 1979 through 1996 since it showed an increasing volume amount per the red dashed line in Figure 9. He also states the standard deviation is plus or minus 2,353 km3 which is an extremely large range), and stated that the 2007 October-November mean was under 9,000 km3. At this rate of decline, he stated that it would reach a zero point in nine years (2016).

There is no model.

Please answer the question, the data points used in Maslowski's line drawing exercise used mean estimated values for October-November ice volume. His line predicts the arctic will be "ice free" in the months of October and November by 2016 plus or minus 3 years.

Since the ice volume has expanded in every month following August in every year of the satellite record, I do not think a claim of an ice free October and November by 2019 is supportable.

William Crump


I am taking my time to go through the thoughtful information you have provided.

With natural variability, I guess it is possible for the ice to drop though a 1,000,000 km2 threshold (a size 43.6% bigger than Texas, which seems rather large to me as my state, Maryland, is just over 32,000 km2 including the water) by 2020, and it would only take a volume of 500km3 if the ice is half a meter thick to generate an area/extent this large, but it does not appear that the Arctic would maintain this condition year in and year out, so I would not say the Arctic reached a steady state of ice free existence.

What I am looking for is a data set on volume or better yet, thickness, for the region Cryosphere today calls the Arctic Basin.


I would like to see a trend line for the thickness of first year ice for this region that shows that the extent will fall below 500,000 km2 (an area larger than California) before joining the "ice free" by 2016 to 2019 bandwagon. I can not find such a data set, but the area figures from Cryosphere today indicate that the region is maintaining a minimum area of approximately 2.5 million km2 since the big plunges in 2006 and 2007.

I do not think the Arctic wide volume data set is appropriate for generating a prediction of when the Arctic Basin will be ice free as it includes many regions which have already reached a zero volume level at the minimum and it is skewed by the disproportionate loss of thick multi-year ice.

The Arctic Basin will not be "ice free" until it reaches a point that the ice that forms in winter does not survive the melt season. Provide a graph of first year ice thickness for the Arctic Basin that shows that first year ice that forms in winter does not reach a sufficient thickness to allow it to consistently survive the melt season by 2019 and I can agree with the Maslowski extrapolation.

Daniel Bailey


"Since the ice volume has expanded in every month following August in every year of the satellite record"
Dude, what kind of meds are you on?
"There is no model"
Unless you are channeling Yoda, every thought experiment or drive to the supermarket involves a model. Part of life, my man. For Maslowski, the name of his model, run on the US Navy's supercomputer, is NAME (love how they hide proprietary code run on ghosted hardware in plain sight with an acronym like that!).

If your takeaway was that there was no model of the name NAME, then you should read the paper...again.

I understand you play the contrarian role. That's your choice. But you now cross the line into denial. And waste our time.

William Crump


NAME is a model to estimate current volume conditions not a forecasting tool.

The data points in Figure 9 for NAME stop in 2005. There are no data points from NAME in Figure 9 after 2005 - notice how the blue line and dark blue asterisks stop in 2005.

Maslowski uses Kwok current estimates of volume (light blue asterisks and magenta asterisks) for data points in 2004 through 2008. There are no data points after 2008.

You should give the article a good reading. I too thought Maslowski had a model that generated multiple scenarios for forecasting future ice conditions until I read the article provided by Kevin and realized that this characterization is a sham. NAME is being used to generate historical data points from which a linear extrapolation is performed by Maslowski. The NAME model does not generate future data points in the manner that the models discussed in the Maslowski article create multiple forecasts of future ice conditions. Maslowski's article does a good job of slamming all predictive models; however, Maslowski is just line drawing based on historical NAME and Kwok data points. His 2016 claim is not based on a model simulation of 2016 conditions, it is based on a cherry pick of data points and a linear extrapolation with no consideration of the complex and dynamic factors affecting ice behavior. The models discussed in the article generate multiple future outcomes. Maslowski is just drawing lines for his "prediction.".

William Crump


I see the issue you are working on and I have wrestled with it myself.

"In the above figure you can ignore ExtentThickness as I’ve moved over to calculating AreaThickness, using area alone. Kevin O’Neill (a commenter at my blog) and I have been referring to the relatively flat area through the Summer as the ‘roof’. Its implication being that during the Summer volume loss has been largely accounted for by loss of area, hence thickness changes little. However in 2010 and 2011 this changed, with loss of thickness being ‘needed’ to account for the loss of volume. As the above graph shows this is unusual behaviour in the context of the full PIOMAS series.

Using NCEP/NCAR reanalysis the only weather that stands out as being anomalous is a high pressure system over the Arctic in 2010 presumably related in some way to high temperatures. However as the area was ice covered at that time increased insolation wouldn’t have caused high temperatures, although inflow of air or large leads/polnyas could. Spring 2011 was rather unremarkable from what I can see."

Please consider that a possible explanation for what you are seeing is the disparity in the types of ice that are declining and how their decline is contributing to the average calculation.

An underlying assumption of the "thickness" analysis is that it assumes that all ice types are declining in volume and thickness at uniform rates.

I do not think this is the case. The disproportionate losses of thick multi-year ice, which the NSIDC indicates below have nearly disappered:


"After the near-record melt last summer, second-year ice declined again, but some of the ice that had survived the previous few summers made it through another year, increasing the proportion of third- and fourth-year ice. However the oldest, thickest ice, more than four years old, continued to decline. Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%. First-year ice (0 to 1 years old) this year makes up 75% of the total ice cover, the third highest at this time of year in the satellite record. In 2008 the proportion of first-year ice was 79%, and in 2009 it was 76%."

may be driving a disproportionate portion of the volume and thickness decline. Very thick multi year ice has been replaced by thinner first and second year ice and the thickness of the remaining multi-year ice is considerably thinner on average than the thickness of multi-year ice that used to cover the Arctic.

If a disproportionate amount of the thickness decline is attributable to multi-year ice, then the thickness of first and second year ice is not declining as fast as the graph would indicate.

What is needed is a direct measurement of the rate of decline in the thickness of new (ice formed in the current year) and first year ice (ice that survived the prior September). If the thickness of this ice is not declining as fast as the rate of decline from the average of all types of ice, then it may be possible to maintain a much larger area of thin young ice at the minimum for a much longer period of time than the extrapolation of Artic wide volume and average thickness data would indicate.
The last area to disappear will likely be the Arctic Basin region as defined by Cryosphere today.


A substantial majority of this ice appears to be first and second year ice. The big unknown is how fast the thickness of this young ice that survives the September minimum is diminishing. If the thickness of new and first year ice in the Arctic Basin is declining at a slower rate than the Arctic as a whole, then that would explain why the area of the Arctic Basin ice has not declined since 2007 in the face of the extreme volume decline experienced by the Arctic as a whole.

Is there any manner in which your area thickness chart can be altered to generate a thickness decline curve for young ice in the Arctic Basin?

Bob Wallace

"If the thickness of new and first year ice in the Arctic Basin is declining at a slower rate than the Arctic as a whole, then that would explain why the area of the Arctic Basin ice has not declined since 2007 in the face of the extreme volume decline experienced by the Arctic as a whole."

An alternative explanation of why Arctic Basin area has remained high is because that's where what ice remains in the Arctic gets shoved by the wind.

Chris Reynolds


I have to second Bob Wallace, it's all too easy to forget that the pack is a dynamic system.

The problem with seeing the Spring 2010 volume loss as being from a certain category of ice is the mechanism - how did the high pressure 'single out' the old ice. Such a melt process may incindentally hit old ice, but it wouldn't target it.

Maslanik's work suggests that the Drift Age Model found no massive loss of older ice.
See plate 2 of figure 5.

As PIOMAS only gives gross overall figures there is no way to generate thickness declines for categories. The same goes for where the ice loss occurred, which has implications for the age of ice hit. I have to add here the caveat - if the ice loss is real. The April increase Neven shows suggests PIOMAS is still corectly diagnosing weather impacts. But the September thickness implications are so severe I really find it difficult to believe. That's before I get on to the implied change in seasonal cycle.

The key question for me is will these Spring volume losses repeat this year, May's figures will be the earliest possible indication.

Daniel Bailey

Essentially, Maslowski's model (NAME) uses high-resolution (9 km) numerical modeling and compares output to observational estimates through 2009. Try comparing Fig. 9 from Maslowski 2012 to PIOMAS, or to Wipneus' PIOMAS graphic here:

[Click to enlarge]

Still a model. And still shows an Arctic sea ice death-spiral.

And you still have not addressed your throwaway comment from earlier:

"Since the ice volume has expanded in every month following August in every year of the satellite record"
Or do you simply call winter by another name?

William Crump


I agree that I do not have a mechanism for why the oldest ice is disappearing at such a high rate and Bob Wallace is correct that the ice is moving from other regions into the Arctic Basin. The diminished Barents Sea should not impact this analysis as winds generally do not push this ice into the Arctic Basin.

In this regard, perhaps the Laptev Sea is worth watching since:

"The Laptev Sea is a major source of arctic sea ice. With an average outflow of 483,000 km2 per year over the period 1979–1995, it contributes more sea ice than the Barents Sea, Kara Sea, East Siberian Sea and Chukchi Sea combined. Over this period, the annual outflow fluctuated between 251,000 km2 in 1984–85 and 732,000 km2 in 1988–89. The sea exports substantial amounts of sea ice in all months but July, August and September.[7]"

(sorry this is from wikipedia).

I am just repeating the observation by the NSIDC that the oldest and thickest type of multi-year ice has almost disappeared, regardless of the mechanism that caused it to disappear:

"Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%."


This should have a disproportionate effect on the volume loss and thickness figures making the use of average figures for the Arctic as a whole or extrapolations based on continuing the historical rate of volume loss suspect.

The contributions that the loss of this thickest and oldest ice made to the PIOMAS volume decline from 2007 to 2011 can not be repeated because this type of ice is no longer there to be melted or otherwise transported out of the Arctic.

It will take several years of PIOMAS data and not just one more month to see if there is a slow down in the rate of volume loss.

That the ice will diminish is not in doubt, we are only discussing how fast it will go.

William Crump


Yes it is winter indeed. I think you are getting at the problem with the graph in Figure 9, it flies in the face of the physical process of winter.

I am saying winter will have a
stronger influence on the October-November mean volume than the lines drawn in Figure 9 for the October-November mean which show no volume by 2016 or 2019 at the latest.

What do you believe will win out in determining the future October-November mean volume, winter or the lines in Figure 9?

As for Wipneus diagram, it is very pretty, but it does not factor in that prior volume losses have occurred due to a type of ice that is virtually non-existent in the Arctic and therefore it is incorrect to assume that the rate will continue.

You have yet to show me the physical processes that will cause the ice in the region Cryosphere Today calls the Arctic Basin to suddenly drop from the 2.5 million km2 level it has maintained at the minimum since 2007 to almost nothing in the next three years.

Other than saying the lines reflect historical rates, none of you have shown what physical processes will occur in future years that will allow this rate of decline to be sustained.

Even though the models have not matched the actual rate of decline, it does not necessarily follow that they do not have the correct rate of decline for future periods.

You can draw all the lines you like, but they prove nothing unless they are backed by a model employing the physical processes that justify the shape of the lines; otherwise, they are just lines.


You have yet to show me the physical processes that will cause the ice in the region Cryosphere Today calls the Arctic Basin to suddenly drop from the 2.5 million km2 level it has maintained at the minimum since 2007 to almost nothing in the next three years.

Rather than focusing on physical processes, I would say it's a question of timing, after having followed the last two melting seasons quite intently.

At the end of the 2011 melting season as well as that of 2010 I had the feeling that if the melting season would only last a few weeks longer we'd see a much further intrusion into the central ice pack. In that sense the Arctic sea ice in the Arctic Basin was saved by the winter bell, just before the accumulated heat and winds could further diminish the ice cover. Both times there was also a MYI barrier in the Chukchi and Beaufort Seas ('The Arm') that shielded the ice behind it.

So, I guess what I'm trying to say, is that when we get to this point a few weeks earlier (because for instance weather patterns stay conducive to ice melting, and don't flip like they did in 2010 and 2011), there will be still a couple of weeks left for the sea ice in the Arctic Basin to take a beating.

For instance 2007 lasted a couple of weeks longer than the other years, with perfect conditions all the way to the end of September. We saw what happened then. If that happen this melting season, I think the ice in the Arctic Basin has a problem.


In other words: loaded dice. A question of timing.

When has all the ice on the edges of the ice pack in the Arctic Basin melted out? August 10th? August 31st?

And when do low temps come in and save the ice that is left? September 5th? September 27th?

Peter Ellis

William: Can I encourage you to think about the logic of your prediction?

You seem to be saying that:

a) The Arctic will lose all its multi-year ice and enter a state where it is predominantly covered by first-year ice.

b) This first-year ice will however form rapidly enough (and thicken enough through the winter) that it won't melt out.

Therefore, Arctic ice area will overall be sustained even though the ice will be predominantly younger, thinner first year ice.

However, there's a contradiction embedded in your logic. If the ice survives through the summer melt season then next year it isn't first year ice any more!

The only way to get a pack of the sort you describe (i.e. all first- and second-year ice with no MYI) is if all the second-year ice melts out every year, and only some of the first-year ice melts out: i.e. there is preferential loss of second-year ice every year. That is unphysical. Second year ice is less saline and harder to melt, and also is located in regions less susceptible to melt.

It's useful to play around with toy "population pyramid" models when visualising these things. Plug in some assumptions about the proportion of each cohort of ice that gets lost each year, and see how it ends up.

Daniel Bailey


Apologies for becoming a distraction on your fine blog. Dealing with deniers on a daily basis in my role at SkS brings out the bulldog in me and I become the antibody to the invading infection. But that is not my place to behave so here; for that, I apologize and recuse myself from this conversation.

William is free to carry on in his beliefs in non-physical processes and only the certain models he is happy with.

Bob Wallace

I've spent a bit of time watching this gif today.


Of course, one year is not necessarily representative of all, but what I seem to see is a lot of moderate thickness ice being transported out the Fram and a lot of the thickest 'close to land' Arctic Basin ice melting in place.

In May, 2011 when the gif starts there's a lot of red, ~4.5 meter ice in the western side of the AB and over the melt season I don't see much movement of that ice. The ice that gets transported seems to be from areas more to the east, with the thickest ice somewhat locked in under the northern point of Greenland.

Like Nevin, I think the AB is barely dodging a bullet. As volume drops overall the melting is going to get to that thicker ice earlier. Warm the air up a bit more (we're moving into an increased solar output period and El Nino conditions) and it could make for a spectacular melt.


Neven wrote:

For instance 2007 lasted a couple of weeks longer than the other years, with perfect conditions all the way to the end of September.

Do allow me to contradict you.

In 2005 the minimum extend was reached on the 24th september. In 2007 on the 11th, in 2008, 2009 and 2010 from 5th to 11th, and last year 2011 on the 19th of September.

Moreover, in October 2007 the ice shell recovered at warp speed leading to the second largest maximum extend in March 2008.

Bottom line, the melting continuing deep into September started alreday in 2005.

Since 2009 the recovering started to slow down substantionally, but of course 3 years in a row is a period to short to have conclusions based on.


In 2005 the minimum extend was reached on the 24th september. In 2007 on the 11th, in 2008, 2009 and 2010 from 5th to 11th, and last year 2011 on the 19th of September.

What data set, Kris? I was saying it from the top of my head, but looking at my old IJIS extent spreadsheet, I have:

2007: Sep. 24
2008: Sep. 10
2009: Sep. 13
2010: Sep. 18
2011: Sep. 9

In 2010 the melting season got extended somewhat after the weather switched radically from mid-July to the end of August. Minimum was hit one week earlier than 2007. Last year the melting season was cut short by another radical switch in weather patterns and ended two weeks earlier than 2007. Had it lasted two weeks longer like 2007, records would have been broken in all datasets (not just Uni Bremen extent and CT area), and that would probably have meant that the Arctic Basin would have dipped below the post-2007 plateau that William mentioned earlier.

Mind you, 2011 also had a lull of a couple of weeks in August. 2007 was completely lull-less, I believe. That was just Arctic Dipole from start to finish.

So again, besides physical processes, timing is also of the essence. If we get anything that comes near 2007 this year or the next, that plateau in the Arctic Basin will be short-lived.

Kevin McKinney

Will Crump wrote: "You can draw all the lines you like, but they prove nothing unless..."

No offense, Will, but why would you expect any sort of 'proof?' I think it's pretty clear that full understanding of the dynamics of sea ice loss is a good way off--perhaps far enough that the ice will be gone first.

I know--you think the ice in the Basin is privileged somehow. Clearly, you haven't persuaded anyone so far (and vice versa.) Requiring those discussing it with you to achieve an impossible standard of 'proof' simply ensures that this impasse will continue indefinitely.

All any of us have at this point is 'indications' and 'suggestions.' Some are more specific and detailed than others. Shall we take them for what they are worth, and glean what insight we can?

William Crump

Peter Ellis:

The current state of the Arctic ice appears to be doing exactly what you state in items a. and b. If you extrapolate the trends in the ice age charts below, what is the trend that you see?

Please note that when I use the term multi-year ice I am referring to ice that is more than 2 years old.

Perhaps some of the line drawers can provide a chart for ice in the various age categories that incorporates the percentage of ice ages in the chart and the decline in area/extent for each year. This would at least provide a clearer picture of the area trend line for ice younger than 2 years and ice older ice.

Both points a. and point b. appear to be confirmed by the NSIDC charts and narrative's in various press releases.

I agree this does not make intuitive sense that younger ice is able to regrow and regenerate and survive better than multi-year ice; particularly the subset of multi-year ice that is made up of ice that is older than three years, but isn't that exactly what the charts below and the NSIDC narrative are saying?

Per the NSIDC, the age of ice in September of 2011 and March of 2012 are close to the situation where the Arctic is dominated by thinner young ice.

The March 2012 ice age chart shows that ice 2 years old and under makes up 80% of the ice and the NSIDC says that ice more than 4 years old has gone from 25% of the ice pack to 2% of the ice pack. Per NSIDC:

"However the oldest, thickest ice, more than four years old, continued to decline. Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%."

March 2012 chart is at:


The September 2011 Ice age chart is at:


On the September 2011 chart, ice that is 4 years old or older has gone from close to 50% of the ice pack at the minimum to less than 10% of the ice pack. The NSIDC noted in their October 2011 press release the following:

"First- and second-year ice made up 80% of the ice cover in the Arctic Basin in March 2011, compared to 55% on average from 1980 to 2000. Over the past few summers, more first-year ice has survived than in 2007, replenishing the younger multi-year ice categories (2- to 3-year-old ice). This multi-year ice appears to have played a key role in preserving the tongue of ice extending from near the North Pole toward the East Siberian Sea. However, the oldest, thickest ice (five or more years old) has continued to decline, particularly in the Beaufort and Chukchi Seas. Continued loss of the oldest, thickest ice has prevented any significant recovery of the summer minimum extent. In essence, what was once a refuge for older ice has become a graveyard. "

Given that the older thicker multi-year ice has declined more than the thinner younger ice, isn't it possible that the volume decline lines are more indicative of when the Arctic will become "ice free" of the oldest thickest ice (with the exception of the older ice that winds drive up against the Canadian Archipelago and Northern Greenland) and not indicative of when the Arctic will be "ice free" of ice less than 3 years old?

The following is my guess for how the September 2012 age of ice chart will play out:

5 plus years old will continue to decline as it is not being replenished as fast as it is being melted and transported out of the Arctic. This type of ice will continue to be a marginal portion of the ice - under 5% of the September ice pack

4 year old ice will increase in percentage because at the September 2011 minimum there was more three year old ice in 2011 than there was in 2010, but it will not be a significant proportion of the ice pack (I am guessing it will be under 5% - yes I know this is a simplistic assessment

3 year old ice will remain close to the 2011 percentage since the amount of 2 year old ice at 2011 is about the same as 2010. I would guess that it may decline slightly as the Arctic no longer appears to favor making older ice.

2 year old ice will decline in percentage because there was less one year old ice at September 2011 than 2010. Less first year ice in the prior year means less second year ice the following year.

Ice making it to its first September, one year old ice, will increase in percentage; but this increase is not occurring because the Arctic is recovering, it is simply a function that there is less area taken up by older ice so there is more area for first year ice to develop.

As for volume and area/extent, the weather will determine what these values are. If we get weather like 2008 and 2009, whatever that is, we may see a slight increase in the volume at the minimum. If we get weather like 2007 and 2010 then there will be a drop in volume, but not as much as in the past because there is less of the thickest ice to be blown out of the Arctic down the Fram Strait.

William Crump


If by "privileged" you mean that the northernmost region of the planet has lower air temperatures and water temperatures than regions in lower latitudes and therefore less ice melting and more ice formation occur in the Arctic Basin than in other regions, then certainly ice in the Arctic basin is "privileged". Also, this region receives a significant influx of ice from the Laptev Sea, close to 500,000 km2 per year. While the Greenland Sea also receives a large influx of ice through the Fram Strait, this ice flow is on a "death march" as less than 100,000 km2 of ice survives in the Greenland Sea at the minimum (I am not certain any of this transported ice survives the minimum as it looks like the ice at the minimum in the Greenland sea is ice that is close to the shoreline and the transported ice, which is further off the coast just disappears in the fascinating video mentioned in Bob Wallace's comment).


By contrast, a higher percentage of ice transported into the Arctic Basin from the Laptev Sea survives at the minimum. This is another factor that maintains the Arctic Basin above 2.5 million km2 at the minimum since 2007. If the Laptev Sea ice fails to form, then there will be steep declines in the Arctic Basin.


What is the area trend line for the Arctic Basin region (which has an area in excess of 2.5 million km2 at the minimum) per the following graph from Cryosphere today:


When does this trend line suggest that the Arctic basin will become "ice free" - say below 500,000 km2?

And yes, if we had thickness data for the various types of ice in the Arctic Basin I would prefer trend lines based on these measures rather than area, but this data is not available so I will make do with the data at hand.


"Rather than draw a single line, the 2012 prediction line should..."
"Please answer .."
"I would like to see a trend line for the thickness..."
"Provide a graph..."
"Is there any manner in which your area thickness chart can be altered to generate..."
"You have yet to show me the physical processes..."
"Perhaps some of the line drawers can provide a chart ..."

Shorter William Crump: "Do my homework!"

Do your own. Instead of tabling a long list of demands for proofs that support your argument, how about doing some heavy lifting of your own, instead of simply p***ing on people who have tried to glean something useful from the data. Go do your own graphs, and when they support your argument come and tell us. That will be interesting. Your latest outpouring handwaving and footstomping is pretty UNinteresting.

William Crump: "none of you have shown what physical processes will occur in future years that will allow this rate of decline to be sustained."

I can do you better than "sustained". How's "increased" work for you?

Norbert Untersteiner: "A linear increase in heat in the Arctic Ocean will result in a non-linear, and accelerating, loss of sea ice."

Your turn, William. What physical (not unphysical, please) processes will occur in future years that will slow the rate of decline to linear or less?


Kevin, please...William has a long history of demanding rigourous proof while offering flimsy opinion. Why would he change?

Williams's not a denier. But you'd never know it from his tone.

"All any of us have at this point is 'indications' and 'suggestions.' Some are more specific and detailed than others. Shall we take them for what they are worth, and glean what insight we can?"
Wonderfully put.

William Crump


It is not just my flimsy opinion, it is the opinion of the scientists who create the volume data being used in the various line drawing exercises on this web site. They have posted a warning that their data should not be used in the fashion displayed on this website and have directly referenced the PIOMAS Monthly Arctic Ice Volume with exponential trend graph as not being a valid forecasting method.

You, of course, may choose to ignore the warning of these scientists and go your own way, but you risk becoming as irrelevant as Steve Goddard's web site, which would be most unfortunate.

I am submitting as proof that my position is not the mere ravings of a mad man (although I may fit part of that description) the comment letter posted on Real Climate at:


The authors of this letter say that extrapolations made in the manner that the various line graphs displayed on this web site using the PIOMAS volume data are not valid. They lay out in better detail than I why such lines are not valid.

Please explain why these scientists are wrong and you are correct.

Since these people are the scientists involved in the PIOMAS volume data, I will accept their opinion over the various bloggers on this site, although I appreciate the information and points often brought to light on this site.

They warn that:

"Natural variability at these time scales (order of 30 years) may very well make prediction by extrapolation hopeless."

In summary they state:

"In summary, we think that expressing concern about the future of the Arctic by highlighting only the earliest estimates of an ice-free Arctic is misdirected. Instead, serious effort should be devoted to making detailed seasonal-to-interannual (initial-value) predictions with careful evaluations of their skill and better estimates of the climate-forced projections and their uncertainties, both of which are of considerable value to society. Some effort should also target the formulation of applicable and answerable questions that can help focus modeling efforts. We believe that substantially skillful prediction can only be achieved with models, and therefore effort should be given to improving predictive modeling activities. The best role of observations in prediction is to improve, test, and initialize models.

But when will the Arctic be ice free then? The answer will have to come from fully coupled climate models. Only they can account for the non-linear behavior of the trajectory of the sea ice evolution and put longer term changes in the context of expected natural variability. The sea ice simulations in the CMIP5 models are currently being analyzed. This analysis will reveal new insights about model biases, their causes, and about the role of natural variability in long-term change.It is possible that this analysis will change the predicted timing of the “ice free summers” but large uncertainties will likely remain. Until then, we believe, we need to let science run
its course and let previous model-based predictions of somewhere between “2040 and 2100″ stand”

The authors of the letter are:

Axel Schweiger

"Dr. Schweiger is the current chair of PSC. His research focuses on the interaction of sea ice with clouds and radiation. He is using satelite data, models and in-situ observations to improve our understanding of sea ice and cloud variability. He has developed the PSC Arctic Ice Volume Page . He has been working to impove estimates of the surface radiation balance in the Arctic. To this end he has been developing and evaluating satellite-based algorithms. He has been assembling the TOVS Polar Pathfinder data set, a 20-year data set of polar temperature, humidity profiles and cloud information. Previous research includes work on microwave-based sea ice concentration algorithms and the application of artificial intelligence methods to remote sensing problems. Dr. Schweiger has been with the Polar Science Center since 1992."


Ronald W. Lindsay, Senior Principal Physicist for the University of Washington APL


Cecilia Bitz

I am an Associate Professor in the Atmospheric Sciences Department, an Affiliate Physicist for the Polar Science Center, and part of the Program on Climate Change, all at University of Washington.


You may choose to follow the line drawn in Figure 9 of the Maslowski article using October-November mean ice volume which indicates that the mean for these months will be zero (or close to it) by 2016 (or 2019 if you need some extra years).

I find this claim to be unrealistic when the satellite PIOMAS data show increasing volume of 8,000 km3 for the last two years for the period September 1 to November 30 as the ice begins its annual rebound from a low of 4,000 km3 to 12,000 km3 at November 30.

No force discussed on this web site is going to reverse this gain of 8,000 km3 over this period.

Chris Reynolds


I see you're now aware of the discussion I'm having with Rob over on the PIOMAS April thread. I don't think there is any need to propose a mechanism for the loss of MY ice, because the generally accepted mechanism is that posited by Bitz & Roe.

Incidents like 2010 (if real) also pose a problem for the idea that some process is singling out MY ice and melting it. Because the SPring 2010 melt seems to have been driven by a high pressure system.

It is notable in the NSIDC graphic your present -
- that up to 3/4 year ice isn't losing much now, whereas the decline of older ice is nearly at zero. Nghiem has show the decline of MY ice (excluding mixed ice).

These issues suggest to me that the process of transition from a mainly MY pack to a mainly FY pack is near completion. The longest typical lifetime of MY ice is now around four years, some residue of older ice will be maintained off the Canadian Arctic Archipelago and North Greanland.

The physical process that probably will increasingly oppose further loss of ice is the ice growth feedback and Tietsche effect. Since 2007 in both area and volume the greater losses during Spring & Summer have been compensated for by greater gains in Autumn and Winter.
Sea Ice area. http://farm9.staticflickr.com/8149/7166567668_57c78e8761_o.jpg
Sea Ice volume.
This is on top of a less pronounced compensation during the preceding decades.

The only reason I have concerns we may see a rapid transition are the recent losses shown by PIOMAS. These happened in Spring and have changed the seasonal profile, leading to greater volume melt during Spring and Summer. So they may have th power to answer the remaining question in this puzzle - how fast can melt progression during the Spring/Summer proceed so as to result in a virtually ice free state in September?

Chris Reynolds

Sorry but the two graphs of area and volume don't really do it.

Here's volume, area's similar.

Loss is the difference from min the preceding year to max in the year (e.g. 1980), gain is the difference between max and min in the same year.

R. Gates

This discussion on the final decline of Arctic sea ice to some seasonal ice-free state is quite interesting. Will it end sooner (say, between now and 2030) with a sudden crash or will it hold on and bounce along the bottom until becoming ice free "sometime" between 2040 and 2070? Really, very interesting, but only in a rather "does it really matter" kind of way. I think it's always best to keep things in perspective, by considering that overall, it has been a very rapid and dramatic decline by any standards and any measure, regardless how it finally ends. This graph of the longer term perspective of the modern decline in Arctic sea ice, which all of you are no doubt well aware really says it all, and should be shared widely and often with those who suggest there is "nothing unusual" about our current warming period and the state of Arctic sea ice:


William Crump


I am struggling with the Bitz & Roe article, but I will get through it. This is the same Bitz from the comment letter on Real Climate about the perils of extrapolation.

How does the late start to the melt season in 2010 affect the loss numbers, did this pile up extra thin young ice that was quickly removed from the system once the melt season started?

If the transition from a mainly MY ice pack to a FY ice pack is nearly complete, does this mean the volume decline should flatten out?

I understand your concern that freak weather conditions could result in an abnormally low single year, but the Bitz & Roe paper and the Tietsche paper appear to suggest that any such single year decline would not result in a switch to a permanently ice free Arctic at the minimum.

Maslowski and other line drawers appear to be stating that the "ice free" status as they definite it will constitute a permanent feature once it occurs. These particular papers appear to suggest that single year perturbations do not result in a permanent "ice free" status and that a limited rebound can occur as subsequent year ice growth exceeds subsequent year ice melting and a new equilibrium point is obtained.

Thanks for the posts.

Perhaps what is needed is a standardized definition of "ice free" (I do not mind excluding the coastal areas of the Canadian Archipelago and Northern Greenland from areas to be considered in the determination of "ice free"). Included in this definition should be a requirement that this "ice free" state should occur in at least three consecutive years.

Daniel Bailey

a standardized definition of "ice free"
The obvious one that springs to mind is
"navigable without an icebreaker"

Bob Wallace

William, by attempting to move the goal posts are you signaling that you're loosing faith in your predictions?

Chris Reynolds


I struggle with the maths in the Bitz/Roe paper.

> late start to the melt season in 2010

Dunno. Any growth in the peripheral seas in March / April can largely be ignored. Compared to the massive swings in volume of the seasonal cycle thin peripheral ice will melt without much impact.

> I understand your concern that freak
> weather conditions could result in an
> abnormally low single year

I've not explicitly said that here. Without preparatory thinning such weather couldn't result in near ice free conditions. 2007 wasn't the strongest Beaufort high on record, nor (IIRC) the sunniest, but the ice was 'ready' for a crash because of the decades of thinning. Even if we question the details of PIOMAS, I don't think a serious argument can be made that volume hasn't decreased since 2007. So the ice is even more ready to be hit by weather. I view Spring 2010 in this context. We can expect more.

Not long before we find out. But yes I suspect that once the MY ice older than 4 years is reduced to near zero - a few years at most - we'll see an inflection in the volume loss. That is a reduction of the rate of loss, not a cessation of loss. Then with a mainly FY pack what remains is for CO2 forcing amplified and mitigated by feedbacks positive and negative to bring the equilibrium thickness of FY ice down to a point where losses in the season will be enough to make part of September virtually ice free. Yes I think the first instance will be weather related and will be followed by higher minima ice levels. Although as 2007 showed such drops can manifest themselves as step drops by virtue of volume loss.

I've argued that 1Mkm^2 is reasonable for a virtually sea ice free state. This is also argued in Overpeck & Wang. Is anyone really expecting no ice at all within decades? Or can we consign that expectation to the category of a straw-man argument?

Perhaps we should use the NSIDC/Maslanik graphic.
Use the yellow area of 4th year ice, but cut off the spread into Beaufort around Banks Island, the Greenland side is problematic, surely flow would continue towards Fram? As for what that area is - I guesstimate it to be around 600,000km^2 using Google Earth.

Kevin McKinney

"Maslowski and other line drawers appear to be stating that the "ice free" status as they definite it will constitute a permanent feature once it occurs."

Dr. Maslowski isn't a 'line drawer;' he's very well-respected as a regional modeler specializing in the Arctic Ocean (and in sea ice specifically.) Dr. Wadhams called him "the best modeler around."

And I don't recall seeing anything that would indicate that he thinks that one ice-free season will be the end of the sea ice.

Rob Dekker

Thanks Kevin,
In the discussion I have with Chris Reynolds in the PIOMAS April thread, we specifically discuss the difference between atmspheric heat flux (such as warmer winters) and ocean heat flux (due to increased heat from Atlantic/Bering water) getting under the ice, and the effects that these two sources of increased heat have on thick (MYI) and thin (FYI) ice.

Basic physics suggest that under-ice ocean heat flux has a profound effect on thick ice, thus affecting mostly volume, and atmospheric heat flux has a more equal effect on ice thickness, thus affecting mostly extent/area.

From all the modelers, Maslowski probably has the highest resolution models and also focuses more than anyone on ocean heat flux. And incidentally his models are also the most 'alarming' w.r.t. further collapse of MYI and an ice-free Arctic...

Rob Dekker

The only thing I find frustrating about Maslowski is that he does not seem to (be allowed to?) present any of his model (NAME) projections beyond 2005. (See Maslowski 2012 link above; even his figure 9).

William Crump

Rob Decker:

Is NAME a forecasting tool or is it a model for estimating current ice conditions?

I thought it was the latter.

Maslowski's "forecast" in Figure 9 appears to be an extrapolation - line drawing exercise and not a forecast based on future data points from a model of physical processes.

William Crump

This graph shows the volume of first year ice was increasing in winter from 2004 to 2008. This is not the same as thickness as extent was likely expanding.


William Crump

Here is the graph for thickness for 2004 through 2008.


Peter Ellis

NAME, just like PIOMAS, is a tool for estimating ice volume. The lines from extrapolating one are as valid as the lines from extrapolating the other (i.e. not very)

On the other hand, fully coupled models get the current rate of ice loss badly wrong, so it's hard to know what the best approach is.

My naive suggestion would be to take the shape of the curve from the fully coupled models (i.e. pretty near a sigmoid), and then re-scale the X axis to fit the volume models of the current rate of loss. That is, use the climate models to tell you how ice is lost, but the volume models to tell you how fast it's happening.

The overall upshot would be something similar to the Gompertz extrapolations of PIOMAS ice volume estimates: i.e. loss of the summer ice the in very near future, but a much slower loss of winter ice.

(has anyone done a Gompertz fit to March PIOMAS data yet?)

Chris Reynolds


I'll leave it to you whether we continue here or on the April 2010 thread.

Both PIOMAS and NPS (NAME?) show substantial thinning and volume loss, both suggest an imminent ice free state when volume trends are extrapolated. Yet PIOMAS has a significantly lower resolution.

So I'm not persuaded resolution is the key issue. For me the key issue seems to be assimilation of atmospheric variables.

Sea Surface Temperature is also assimilated. However Schweiger et al find:
"Both Model-Only and IC-SST runs have nearly identical validation statistics when compared with in-situ ice thickness observations..."

"Both ice concentration-only (IC) and no-assimilation (Model-Only) runs have long term trends that compare more favorably with the concatenated time series of KR09."

So it seems that adding SST merely makes runs behave like atmospheric forced only model in terms of thickness. And in terms of agreement with the KR09 thickness series SST isn't needed to agree with thickness changes.

As PIOMAS is mainly forced by the atmosphere it can't account for changes in ocean heat flux that are not driven by the atmosphere.

I understand NAME to be the NPS model, although i two post graduate theses the model is called NPS, not NAME. If so it is very like PIOMAS - it assimilates atmospheric variables (PIOMAS = NCEP/NCAR, NPS = ECMWF) and possibly ice concentration and SST, and uses the assimilated variables to drive ice/ocean response.

Maslowski is on record as stating in one of his projection graphs that an unknown amount of ice 'may' be left as the volume trend approaches zero (State of the Arctic Meeting, Miami, FL, 16-19 March 2010).

Chris Reynolds

Peter Ellis,

"use the climate models to tell you how ice is lost, but the volume models to tell you how fast it's happening"

I agree and don't think it's naive at all.

Daniel Bailey

"The only thing I find frustrating about Maslowski is that he does not seem to (be allowed to?) present any of his model (NAME) projections beyond 2005."
I share the frustration, as well as your interim conclusion. Having worked on classified systems for the military before it is routine for all output (even from unclassified code) to retain the minimum classification of the system it is run on. I.e., "Confidential, Secret, Top Secret" or one of the many SCIF classifications. Given that he is running his code on one of the USN's supercomputers it would not surprise me at all if this were the case.

Given a pressing need, the San Board (Sanitization Review Board; responsible for review and declassification of classified material) could release any or all of the output with whatever level of excerpting they saw fit to perform.

Or none of it at all.


Having some connection problems (expected fix is a couple of days off) so will need to be (relatively) brief.

Willliam - We'll suppose for the moment Axels criticisms are valid*. Your previous critiques have been based on entirely different grounds, advancing some personal incredulity mixed with a little recourse to magic. Now that Axel has posted his criticisms you suddenly cry "See, I was right!", but that is opportunistic BS. The fact that your unreason converges on more sensible arguments cannot make it reasonable.

But really, my post was not to argue your position, but your unhelpful approach to the discussion. Once again, you post a rapid series of virtually substance-free payouts on other peoples observations, yet you ignore or are unaware of what those people are and aren't arguing - despite repeated explanations. Nor have you ever shown any rigour in your own analysis - you eyeballing short time periods on a few graphs and cherry picking factoids that support your argument is simply weak (hence "flimsy opinion"). Adding demands that other people do your analysis for you, rather than actually tackle it yourself is simply tiresome.

You've spent two years wafting assertions and disparaging other peoples attempts at analysis (and again, see Kevin's excellent take on those). Isn't it time to start using your brain instead of your mouth? Perhaps your criticisms of others are fair. Personally, I've become massively uninterested, because you have not offered anything constructive in their place. When you do, I'll be very interested to reconsider my appreciation of your position.

Finally you have shown a repeated habit of verballing people: eg. "You may choose to follow the line drawn in Figure 9 of the Maslowski article..." - this comment is presumably directed at me, but I have not commented on figure 9 of the Maslowski article, so how about you don't put words in my mouth, hey?

*Actually, I thought Axel's RC article dealt out some grave, and rather ironic, injustice have been wondering whether it was worth responding to, either here or at RC. I may post at more length in a few days (ie once decent connection restored). Or not - I'm pretty jack of the whole thing, TBH.

Tor Bejnar

It appears to me from the ARC Ice Thickness gif animations that much more multiyear ice (MYI) is lost through export than through in-situ melting (exported from where it develops). MYI is exported through Fram Strait at a higher rate than is first year ice (FYI), it seems to me, because of prevailing winds that first stack up and press together ice onto and near the North America and Greenland (NA&G) coasts creating thick ice that can survive, thus becoming MYI [therefore most MYI exists near NA&G] and then move ice near NA&G eastward then southward through Fram Strait where it melts in “warm” Atlantic water. Much, if not most, of the MYI that melts within (or near) the Arctic Basin, it appears to me, moves westward in the Beaufort Gyre, thence toward Siberia where (I’m guessing) it gets exposed to wave action (thus broken up and scattered) where it melts in solar heated surface water in a couple of summers. I may under-appreciate ocean heat flux concerns as I am extremely ignorant of the physics details; I currently lean toward the explanation that under broad sheets of sea ice, there is not much vertical mixing due to layers with different salinity. Near the edges of the ice and in open water, we “watched” last November (was it?) a large storm mix up a lot of water (or did I fall for a commenter's enthusiastic projections of what was happening?). Less ice area allows for more potential mixing by storms, for sure.

I’ve come to accept that when a functionally ice-free Arctic Ocean (less than one million sq. km. at area minimum) happens, most Arctic sea ice will be in the Arctic Basin. Therefore, looking at influences on Arctic Basin ice may be more relevant to projecting ice-free timing than focusing on pan-Arctic data. From the CT Arctic Basin ice area graph, eyeballed average minimum area was ~3.4 (million sq.km. – [Mkm^2]) from 1979 to 1997, ~3.25 from 1998 to 2006 and ~2.5 from 2007 to 2011. What caused those “permanent” drops in 1998 and 2007? I’m guessing the answer is “near perfect weather conditions” (certainly true for 2007). With a lot more FYI (vulnerable due to being thinner and saltier than MYI) to melt or at least break up and move, it set up conditions advantageous for moving MYI away from near NA&G more quickly. In addition, global warming induced melting along the NA&G coast allows for less fast ice and more freedom of movement of MYI.

I propose these processes are integrally involved in the decline – exponential decline – of Arctic ice volume in the satellite record. Will the next year of “near perfect weather conditions” create a lower Arctic Basin minimum area paradigm allowing for faster movement of MYI to the melting fields in all subsequent years? Or will “perfect condition” records of Arctic Basin minimum sea ice area be followed by rebound (e.g., the following year area minimum goes back to 2.5 Mkm^2 in the Arctic Basin), per published study conclusions. If this rebound always happens (over the next decades), then even as deepening global warming allows only 1.5 meters of ice to form where currently 2 meters of ice form, winds will continue to pile it up to make thick resilient ice that won’t melt out until moved towards "warm" open water.

Rob Dekker

Very good points. Thanks for you post !
It it very likely that ALL factors are involved in the long-term decline of Arctic sea ice : direct increased atmospheric forcing due to AGW, increased atmospheric heat influx from lower latitudes (due to AGW), increased ocean heat flux (due to AGW warming waters?), thinning of ice due to all these factors, which increases ice dymamics (increased ice export, increased melting due to albedo effects in summer, de-stratification due to open water, leading to increased heat flux from the deep, decreased 'recovery' after "perfect condition" weather events etc etc etc).

Exactly how much each of these components contribut(ed) may be too difficult to quantify, even after the facts.

Maybe this year's melting season will teach us something about some aspects of Arctic ice behavior. We have the situation where the West experienced a brutal winter with ice extent larger than ever recorded in modern history, while the East seemed to have been very much gripped in a "death spiral" with warm Atlantic ocean water swept deep into the Arctic by "perfect condition" pressure areas over Europe, Siberia and the central Arctic, maintaining open water up to 82.5 N all through winter, which only recently froze over (with thin ice) due to changing winds.

Pete Williamson

In the spirit of 'indications' and 'suggestions'. I wanted to lay out a just so story based on physical processes and maybe people can tell me where I'm going wrong.

So to start, simply speaking, the arctic warms due to extra energy being transported north from a warming sub-polar NH. Positive feedback processes work on top of this in the Arctic to amplify this warming.

A good place to start is to look at what is happening in tropical and mid-latitude NH. If you take a look at 0-60 degrees N using any data set on KNMI climate explorer you can see a warming NH since late 1970's but that warming has paused since the turn of the century.

If you look at the arctic (60-90oN) amplified warming since the late 1970's is clear. It's a little harder to say what's happening more recently due to the much larger inter-annual swings and the short time period but it looks as if warming has also slowed since about 2005.

Somebody earlier pointed out that model studies suggest that some ice processes act on a very quick time scale. The example went something like if you remove all the ice in a model that the system quickly forgets this pertubation in a few years. Sorry I can't find who or where the point was made. That suggests to me that important ice feedback processes may be happening on a fairly quick time scale, for the sake of my just so story lets say 5 years. This also looks true when you consider the temperature profile of the arctic over the whole 20th cenury. It seems to very quickly turn around, think about the early/mid 20th century warming of the arctic.

So here's the just so story. A warming NH sends more energy into the arctic this stops when the NH stops warming around the turn of the century. The Arctic continues to warm due to positive ice feedbacks until 2005 (or so). The Arctic is now in a new 'equilibrium' WRT NH temperature as a whole. We are in a phase were year to year changes in the arctic ice are in response to weather. Given that 2007 was an extreme weather year in the arctic this could represent a low for the present regime. As caveats I could say that it's very possible that there is still more warming of the arctic 'in the pipeline' from feedbacks that could melt more ice. But in order to be sure that arctic ice is going to continue on it's downward trajectory it seems that we need to see a resumption of warming in the lower NH.

At the very least it seems like what is happening outside the arctic has been neglected so far in this discussion and I'd be interested in knowing what importance people think that has?

(Apologies if this is actually uninformed BS ;) )



Nice point.

Maybe the story below is also uninformed BS.

I am not sure but maybe the main focus on this blog is more on ‘local factors on the northpole’ and much less on mondial factors, although I read something about e.g. the possible effect of the influx of warmer Atlantic water into the arctic ice.

Some specalion about possible ‘build up inertia’ to cooling effects in the Northpole region:
Maybe, like you suggest, the north pole is lagging behind the tropics partly because the northpole region has ‘build up inertia’ to cooling effects because of its weather history (a lot of melted ice because of the relative warm history).
The build up inertia has an effect on the local wheather in the Northpole region.
That because of e.g. less ice cover (and other related factors) there is less sustained colder weather in the Northpole regio. A lot of sea ice has disappeared with a strong effect on the summer albedo.
To compensate for the build up inertia due to e.g. the lost ice and warmer water (and other related factors), a period with sustained colder weather is needed to significantly increase the amount of northpole ice.
But when there is suddenly a longer period with sustained colder weather in large parts of the northpole region, your suggestion that the amount of see ice will increase very fast will in my opinion be very true.


@Pete, part 2 of my possible BS speculations...

Some speculation about mondial factors …

On a yearly basis the tropical and subtropical zones receives much more energy than the ‘other’ zones.
Out of my head some so called experts ( I have no link available at this moment) suggests that an increase (or decrease)in the temperature in the tropics will lead with some lag in time to resp. an increase (or decrease) in the temperature in the more northerly and southerly regions and not (or much less) the other way around.

Very warm (tropical) air saturated with water vapor contains much more latent heat than colder air saturated with water vapor.
In the tropical zone there is much more very warm air saturated with water vapor than it is the case in the other (not tropical zone) parts of this world.

If I am correct, when 1 m3 of very warm air of e.g. 27 degrees Celsius ‘saturated with water vapor’ cools down 1 degree (e.g during a La Nina), the amount of water vapour that condensates is about 1,39 gram (in this case the amount of about 1,39 x 2256 Joule of energy is released during the condensation). A part of this energy (warmth) is transported outside the tropical zone to more northerly and southerly areas.

When 1 m3 of cooler air of e.g 5 degrees Celsius ‘satured with water vapor’ cools down 1 degree, the amount of water vapour that condensates is about 0,45 gram (in this case the amount of about 0,45 x 2256 Joule of energy is released during the condensation).
So, temperature is not 1 to 1 to the amount of energy.

General speaking, it cost less energy to warm cold air 1 degree than warm air.

Also acording to so called experts, ocean currents transport energy from one place to other places. The suspicion is that it takes many years before the effects of a warming or cooling tropical zone is manifested in the very northern latitudes.
Not talking about the very complicated dynamics of clouds.
All combined (mondial and local factors) creates in my view a very dynamic and complicated proces.

Kevin McKinney
A warming NH sends more energy into the arctic this stops when the NH stops warming around the turn of the century. The Arctic continues to warm due to positive ice feedbacks until 2005 (or so). The Arctic is now in a new 'equilibrium' WRT NH temperature as a whole.

But has NH warming actually stopped since 2000? There are statistically non-significant *warming* trends by most measures. And notably, ocean heat content keeps rising. Moreover, the ice lost since 2000 represents a large heat increase for the Arctic independent of measured temperature change. To what 'feedbacks' is this due? Or does advection of heat into the Arctic from those warming oceans play a larger role?

Finally, how likely is a serious 'cold snap?'

We're just now out of a double La Nina, and also on the increasing leg of the solar cycle:


That suggests that .2-.3 C worth of short-term warming wouldn't be at all unexpected. "Indicators," to be sure--but I'm not going to bet on a cooling outbreak in the next couple of years, that's definite. And meanwhile, the GHG burden keeps getting bigger.

Chris Reynolds


Of anyone else that can help.

The second graphic in the main post suggests that PIOMAS April figures are/have been available. I'd expect this as they usually release the figures when they update the date on the graph.

Since that was updated I've been trying to get the PIOMAS figures for April but the zip I download only contains figures to day 91, the end of March.

Has anyone been able to download the figures for April? Were they issued and then withdrawn?

William Crump

Pete Williamson:

Recovery mechanisms of Arctic summer sea ice
S. Tietsche,1 D. Notz,1 J. H. Jungclaus,1 and J. Marotzke1


is the source of the recovery period, which they say is two years.

4. Conclusions
[23] In our perturbation experiments, we observe how different feedbacks in the Arctic compete to enhance or
dampen a strong negative anomaly in sea ice, equivalent to a strong positive anomaly in oceanic heat content. In summer,
the oceanic heat anomaly is enhanced by the ice–albedo feedback, but in winter the excess oceanic heat is lost to the
atmosphere due to a lack of insulating sea!ice cover. This leads to an anomalously warm atmosphere, which in turn
causes increased heat loss by longwave radiation at the top of the atmosphere and decreased heat gain by atmospheric
advection from lower latitudes. A lasting impact of the ice–albedo feedback is not possible because the large scale heat
fluxes quickly adapt to release the excess oceanic heat from the Arctic.

[24] Hence, we find that even dramatic perturbations of summer sea ice cover in the Arctic are reversible on very
short time scales of typically two years. This suggests that a so called tipping point, which would describe the sudden
irreversible loss of Arctic summer sea ice during warming conditions, is unlikely to exist.

[25] These results also have implications for the value of sea ice initial conditions for climate predictions on decadal
time scales: if even the strong anomalies in sea ice cover that we examine here are reversible within a few years, then
small errors in sea ice initial conditions should not affect the predictions significantly. Intrinsic memory of the thin Arctic sea ice cover of the 21st century seems to span only a few years.

Chris Reynolds

Thanks Wipneus,

When I go to PSC the link I get leads to a zip with the same name but an underscore appended to the end of it.

Now I can finally add the data to my spreadsheet - better make a brew while it updates.

Bob Wallace

"A lasting impact of the ice–albedo feedback is not possible because the large scale heat
fluxes quickly adapt to release the excess oceanic heat from the Arctic."

Perhaps not a lasting impact for water temperature, but as we increase greenhouse gas levels less and less of that extra heat is going to escape the system.

Additionally, if warmer temperatures are increasing cloud cover then more of the released heat is going to be trapped close to the ice.

Higher air temperatures will slow the release of heat from water over time. The refreeze cycle will be later to start meaning less time to thicken the ice that does form.

Tor Bejnar

From time to time, a comment indicates that much multiyear ice was lost through the Fram during the winter. Rampal et al (2011) - see Neven's "Papers" - indicate increasing ice movement over the historical record and " ...this could accelerate the export of sea ice through Fram Strait with a significant impact on sea ice mass balance." "Could", of course, is a different word than "does"! Previous studies are not consistent as to whether export rates are changing, but with less ice in the Arctic, a constant rate of export will have an increasing effect on remaining ice volume. [gotta go, more maybe later]

Pete Williamson

Kevin McKinney,

"But has NH warming actually stopped since 2000? There are statistically non-significant *warming* trends by most measures."

Specifically I said warming had stopped in 0-60oN. Honestly it has, check all the data sets on KNMI Climate Explorer. I'm happy to agree with a non-significant warming trend for the NH but that includes the Arctic.

Your point about ocean heat content and Atlantic advection is important so I checked them.

Here is the NH (0-60 degree N) OHC since 1980

And here is a plot of changes in temp of Atlantic Waters thru' Fram Strait.

It's a screen grab from this 2012 paper

But I'd still suggest that since 2007 (and most likely a couple of years before) we aren't seeing the same increases in energy being advected into the Arctic than prior to that and ultimately this is the engine that's going to drive arctic warming and melting.

Interesting the Beszczynska-Moller paper points out there are time lags asociated with the energy entering the Arctic from the Atlantic so the idea of melting in the pipeline from the warm water pulse in 2006 looks likely.

I guess what I was objecting too was a discussion that focuses solely on internal arctic process like sea-ice feedbacks, sea ice condition etc. It seemed to me it can start to look like it's describing runaway positive feedbacks rather than just positive feedbacks. If you take Neven's analogy of loaded dice then the loading just doesn't happen once it needs to be further loaded to achieve the next state. I'm just pointing out that loading has slowed (I actually think it's stopped) since the 2007 low.

But maybe the dice have already been loaded enough to melt all the ice by internal feedbacks. I'm happy to be convinced on that argument.

"Finally, how likely is a serious 'cold snap?'"

I was really trying to avoid predicting were sub-arctic NH temps will go in the near future. But this discussion seems to be about were sea-ice will go in the near term (e.g. extrapolation of trends over the next decade or so) and I thought it was important to point out that the engine driving the whole process had seriously slowed compared to the galloping pace in the 1980's and 1990's.

Daniel Bailey

I smell cherries.

Pete, I'm still trying to grasp why you maintain that:

"I said warming had stopped in 0-60ºN. Honestly it has"

Because looking at GISS LOTI (Land+Ocean Temperature Index) since 2000 I see this:

Parameters: GHCN_GISS_HR2SST_1200km_Anom0112_2001_2011_2000_2000

Note that since 2000, the vast majority of the globe (even most of the NH, 0-60ºN) shows warming.

Looking at OHC (Ocean Heat Content), we can turn to Levitus 2012 to see what the greatest heat sink in the world, the oceans, have been doing:


That's funny, the oceans gaining heat since 2000 doesn't seem to support your statement, either. How about looking at ENSO, or La Nina:


So the evidence does not support your contended assertion. At all.
Unless you mean NH 37º-40.5ºN (between some unspecified longitudinal bands as well)?


Thanks from me too, Wipneus. I have updated the PICT graph and added it to this blog post.

I was also wondering about that warming stopped in the NH between 0 and 60 degrees, but unfortunately I couldn't check it, as I have no idea how that KNMI Climate Explorer thing works.

Rob Dekker

KNMI Climate Explorer is an interactive toolset into a variety of climate data sets. Quite nice actually. Starts here :

Seems that the self-proclaimed skeptics have found this to be another tool to confuse and obfuscate reality, as WUWT recently used it to mis-represent the Notz and Marotzke paper that you recently did a post on. Note that the very same KNMI data can also be used to expose WUWT's accusations against scientists as self-fabricated nonsense, as I did here :

At this point, I'm just very curious to see where on the KNMI Climate Explorer Pete obtained his data, and how that comparesto Daniel's excellent overview.


>"PIOMAS data running up to April 15th have enabled me to update the PICT"

I, and I expect you, have PIOMAS to day 121=30 April and area to 2012.3206=28th April.

I thought we had established that 15th April is a misinterpretation of graph marks.


Crandles, I forgot I had some more CT area data, so I have now updated the PICT graph to April 27th.

I have for CT area April 27th: 12,650,822 km2. Anyone else has that too? Lodger explained once, but I keep forgetting how it works with CT area. Please, tell me I don't have to adjust my spreadsheet again...

William Crump


NASA study reveals that the oldest and thickest Arctic sea ice is disappearing at a faster rate than the younger and thinner ice at the edges of the Arctic Ocean’s floating ice cap.


Comiso found that perennial ice extent is shrinking at a rate of -12.2 percent per decade, while its area is declining at a rate of -13.5 percent per decade. These numbers indicate that the thickest ice, multiyear-ice, is declining faster than the other perennial ice that surrounds it.

As perennial ice retreated in the last three decades, it opened up new areas of the Arctic Ocean that could then be covered by seasonal ice in the winter. A larger volume of younger ice meant that a larger portion of it made it through the summer and was available to form second-year ice. This is likely the reason why the perennial ice cover, which includes second year ice, is not declining as rapidly as the multiyear ice cover, Comiso said.

"The rapid disappearance of older ice makes Arctic sea ice even more vulnerable to further decline in the summer, said Joey Comiso, senior scientist at NASA Goddard Space Flight Center, Greenbelt, Md., and author of the study, which was recently published in Journal of Climate."

Seke Rob

PIOMAS May'12 is out. 18,100 Km3 as at the 31st.

-- Rob

Seke Rob

Corr. Seems to be last day is the 30th. Also prior month data was reworked.

-- Rob


Thanks, Rob. PIOMAS June 2012 is up.

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