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Neven

Thanks, Lodger! And thanks for those submarine-links.

The first SIE update of the year is up. It officially replaces these Open Threads, so have at it over there.

Rob Dekker

Artful, Peter,
Thanks for the links guys.

I cannot confirm nor deny the presence of the "freeboard" numbers in Cryosat's data, since I have not found where that number would reside. The level 2 data does not show a freeboard data, and I have not checked level 3 or 4 interfaces yet.

Initially, I thought that the absense of freeboard data is not a big deal. It's not difficult to find sea level on the edges of ice fields, and it's easy to adjust the altitude numbers in ice accordingly to obtain freeboard numbers in ice covered areas. However, the first scientific info as reported by the BBC shows the big problem with that approach. The ocean level changes over the Arctic basin, up till amounts of +/- 0.5 meters.

Ocean currents and wind patterns as well as atmospheric pressure will depress the 'sea level' in some places and raise it in others. If there is 100 % ice coverage over a large area, it will be very hard to estimate sea level there from the Cryosat data, and because of Archimedes law, variability in the sea surface altitude would be amplified by a factor of 8. Thus, on large areas of 100% ice, any ice thickness estimates would thus be mere guesses.

I wonder if the Cryosat team has a solution for this problem. Since the primary objective of building and launching Cryosat was to estimate sea ice thickness, they must have thought of a solution to this problem.

michael sweet

It is simply not true that PIOMAS is "only a model" that is uncalibrated. Every time a measurement of ice thickness is made that data would be copied to U of Washington and the model updated. Ice breakers cross large areas of the ice in summer, measuring it all the way. Sea ice thickness at locations near the coast are measured all winter. Ice camps measure ice thickness in the pack. Submarine data is collected every year. Surface expeditions to the pole measure ice. Aircraft with special equipment measure the ice. All these measurements update and tie the model back to reality. They will have better data when the complete satelite record is available, but they have a lot of data now. We will see sometime this summer how far off they were when the Icesat data is compared to PIOMAS. The fact that PIOMAS was close to the satelite measurements in the past gives us confidence that it is currently close to reality.

The real shame is people who pixel count PIPS (and TOPAZ) and compare that data to PIOMAS. PIPS and TOPAZ are not intended to be used for volume and their accuracy for volume use is unknown (but likely high). The scientists at PIPS and TOPAZ can integrate their data but they choose not to. PIOMAS is intended for volume and the error has been measured. I think the TOPAZ data posted here lately is interesting, but it is not as reliable as the PIOMAS data. PIPS is a navy program and is probably intended for navagation use. A ship cares most about the thickest ice likey to be encountered. If most of the ice is one meter thick but some blocks are 5 meters thick the ship has to navagite at a speed where it can hit 5 meter ice without damage. Therefore a forecast for navagation would say what the thickest ice likely to be found is. For volume calculations you want the average thickness of the ice, which is less. TOPAZ is likely better at volume than PIPS, but the error is unknown.

Artful Dodger

Hi Michael

I appreciate your comments in support of the Pan-Arctic Ice-Ocean Modeling and Assimilation System. However, I don't recall anyone on this blog saying that PIOMAS is uncalibrated... it clearly has been, as anyone can read in detail from links on the PIOMAS page.

Joe Romm posted an Entry on September 22, 2010 on Climate Progress where he discusses the Polar Science Center PIOMAS volume estimates:

I did check with PSC about their confidence level in this relative decline.

They said that they don’t have credible numbers for the uncertainty of the model estimates, so it is possible that this volume drop is within the model error. For them, “The more important point in my view is that 2010 continues a long-term trend of declining sea ice volume.”

Previously on this blog, FrankD, Wipeneus, and Bfraser have provided numerical data for PIOMAS and TOPAZ volume. If you would like to contribute, it would be very useful to calculate the correlation between the two data sets. Doubtless someone will do it eventually, but you could be first...

Cheers!

FrankD

I've compared the two datasets, such as they are. Without attempting a rigourous mathematical treatment (beyond my "skills" anyway), I would say:

There is a cyclical variation in the sets over the course of the year, reflecting either too small a variation over the course of a year in TOPAZ, or too great a variation in PIOMAS. In winter, PIOMAS is as much as 30% higher (this is expected, since it covers a wider area). The values converge in August and by the bottom of the melt, PIOMAS can be 15% lower. Over time the intra-annual variance appears to have increased.

Over the four years of the TOPAZ dataset, I also notice that TOPAZ numbers are falling faster than PIOMAS. Its hard to put a good number to such a short sequence, but I would guess TOPAZ volumes have declined about 10% more than PIOMAS (although TOPAZ started from a higher estimated volume as at the start of that series).

The average difference between monthly totals (TOPAZ vol / PIOMAS vol) is 5.9%, with a standard deviation of 16.0 percentage points (that is, the standard 2-sigma range has TOPAZ between 26% below and 28% above the equivalent PIOMAS figure (however this range is blown out by some particularly high TOPAZ values in the first six months of the sequence).

Notes: PIOMAS monthly values determined by interpolating data from their anomaly graph in accordance with the methodology described in Open Thread 3.
TOPAZ monthly values derived from the spreadsheet posted by bfraser, with 18 missing points inserted and 8 obviously anomalous points corrected using the average of data on either side, .

FrankD

The "28% below" in the previous post should read "38% below", of course.

Stupid fingers - I can't play the holophonor either.

michael sweet

I was responding to this comment:
"However, all these volume numbers are based on models (like PIOMAS, TOPAZ and PIPS). These models do get calibrated with actual satellite altimetry data but not very often. As far as I can see, most of these models have not been calibrated in years, so they could be way off for trends and certainly for absolute numbers of ice volume." I think the models are tied to reality much more than this commenter thnks they are.

I like to read all the analysis on this site but I don't think I have much to add. I think the unknowns from the weather and unknown heat transfer in currents from the Atlantic are too high to calculate what will happen. I wonder about the thin areas of central Arctic ice in the Cryosphere Today image. Is that the Atlantic warm water showing through? I will be very interested in the data on central Arctic ice thicknesses when it becomes available. I hope that the posters here are wrong about ice free Arctic before 2016, but the ice looks thin to me. When the sea ice is gone, how will the Greenland ice sheet react? Faster melting or the same? I don't want to think about methane clathrates, it is too depressing.

Rob Dekker

Michael. So that was my comment.
You may be right that the models are calibrated against actual measurements much more than I suggest. I simply am not aware of the evidence for that though.

Also, FrankD's analyis above (comparing PIOMAS and TOPAZ number) shows 2-sigma variability of -38 % to +28 % between these two models, with the difference in winter even exceeding these. If both models are calibrated against reality, then this wide difference in model outcome is not very a very good assurance that we got the sea ice volume numbers (ore their trend) nailed down with these models.

Frank : Thanks for your comparison of PIOMAS and TOPAZ. Bfrazer posted the numbers for TOPAZ in tabular form. Can you do the same with the numbers you obtained for PIOMAS ?

Rob Dekker

Quick report on my progress to use Cryosat data to obtain Arctic ice volume.
I analysed a few samples (orbits) from Cryosat. Used a few orbit data sets from July 2010.

I have good news and bad news.

The good news is that Cryosat L2 data sets indeed include "freeboard" data (the elevation of ice above the sea surface).
The bad news is that this data is only calculated for the sea ice boundaries, where radar altimetry detects both the ice boundary and the sea surface in one burst.
The worse thing is that this "freeboard" data is useless even when it is valid. It gives freeboard numbers of -8 meter for example. Now what does that mean ?
Even worse, there does not seem to be any regular range data available, and pretty much all other fields that I investigated seem to contain garble and completely inaccurate numbers (for example, sea-surf is estimated as some 200 meters in most places. In general, I cannot get any decent numbers out of Cryosat right now, let alone be able to estimate ice volume.

If anyone can get data out of Cryosat that makes sense, please let me know how you did it. I can't find heads or tail in the data.

On a positive note, I did get reasonable numbers out of Envisat, including a beautiful profile of the Greenland ice sheet and at some orbits, I found some not completely unreasonable "freeboard" numbers for Arctic sea ice...

FrankD

Rob,
I'll take a third try at getting those numbers right - even the correction needs correcting (sigh!) - "between 26% below and 28% above" should read between "26% below and 38% above". (The correction used the right figure, but the "below" should be "above" - facepalm!).

Also, FrankD's analyis above (comparing PIOMAS and TOPAZ number) shows 2-sigma variability of -38 % to +28 % between these two models, with the difference in winter even exceeding these.
With the extra correction, the 2-sigma range is -26% to +38%; that is, TOPAZ is between 74% and 138% of the equivalent PIOMAS figure. This figure covers all complete months (45) between June 2007 and February 2011. The winter difference ("PIOMAS is 30% greater") is included in these figures.

I worked this out in terms of TOPAZ / PIOMAS, but in writing it up (in the second para above), I was talking about PIOMAS so I flipped the ratio. I was talking about all winter months, but to just take Feb 2011: TOPAZ / PIOMAS = 76%.
"TOPAZ is 24% lower than PIOMAS" and "PIOMAS is 32% greater than TOPAZ" are equivalent statements, and since I was talking about PIOMAS, I preferred the second expression. It read better to me at the time, and it is accurate, but I can see it was a bit confusing.

The PIOMAS numbers I have derived were linked earlier in the thread: http://snipt.org/wnoP
The file is a comma-seperated text file. See earlier in the thread for some remarks on the contents.
Wipneus also created a dataset - the link to his is in Open Thread 3, I think.

cheers

Rob Dekker

Thanks a lot Frank, for your PIOMAS numbers. They do reflect the numbers from TOPAZ that Bfraser posted, but they are they make a bit more sense especially for the winter volume numbers. Where TOPAZ seems to suggest that winter volume reduces faster than summer volume (and thus freeze and melt are getting less over time), your PIOMAS numbers show a more consistent reduction in volume on a monthly basis over the years. PIOMAS shows a consistent decline in absolute volume, which made me realize something very profound.

As a result of that realization, I posted the following on William Connolley's stoat blog :
http://scienceblogs.com/stoat/2011/02/this_years_sea_ice.php
---
Not sure if anyone is still reading this, but there I found something that is somewhat disturbing and at the same time very obvious.

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

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

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

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

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

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

idunno

Hi Rob,

Good luck to you and Mrs Rob with the impending arrival.

I think you're probably right, but there is a possible major negative feedback - disappearing ice.

As the ice disappears, more open water is in contact with the atmosphere for longer. i.e. the insulating layer between the liquid seawater and the atmosphere is removed. This should have a very strong cooling influence on the ocean; and a warming influence on the atmosphere.

As the atmosphere warms, more heat should escape into space.

I am not qualified to quantify any of this, and I haven't seen it written down anywhere, so this is just a speculation on my part, and I may very well be wrong.

Rob Dekker

Thanks idunno.
I think you are right about the negative feedback, but it seems to me that this would only occur if sea ice area is reduced faster than volume. For the time being, that is obviously not the case, which seems to suggest that we would need to see significant ice free areas before the decline in ice volume numbers starts to taper off.
That would mean we should see an ice free Arctic in summer way before the quilibrium will be restored.

And moreover, this decline in the equilibrium seems to be caused by our
GHG emissions, unless someone can refure the radiative balance that I suggested.

Gas Glo

Nice reconciliation of GHG forcing to volume reduction. :-) (I don't understand why WC's huge daily and seasonal variations matter to annual change in ice volume.)

Of course, it is the consequential changes to the heat budget that matter, does reduced ice insulation as the ice gets thinner bring the heat budget back into balance or is this outdone by albedo effect?

Your figures indicate that so far we have not seen the ice insulation effect start to reduce the difference. However, we can expect this effect to start kicking in soon and rapidly as the ice thickness falls.

The albedo effect so far has also been limited as a result of the great arctic comb over where area has not fallen much considering the volume fall. So this effect is also likely to become more rapid.

Which wins isn't clear.

Rob Dekker

P.S. Thanks for the good luck with the baby.
We are only days away now, but it seems that we are both already adjusting to the irregular hours that are sure to come our way.
We are ready, and I will go off-line soon..

Rob Dekker

Gas Glo, nice observation.
However, if insolation reduction from thinner ice would dampen the melt or increase the freeze, then the PIOMAS numbers should show a reduction of volume melted during the melt season, or an increase during the freeze. However, Frank's numbers indicatate that that melt amount stays pretty consistent at 15k km^3 loss over the melt season, possibly actually increasing over the past couple of years, and over the year we still loose some 1500 km^3. So for now it seems that the albedo effect is winning...

Gas Glo

Rob,

Yes, albedo is winning for now and also over past several years the amount by which albedo is winning seems to be increasing. But we cannot be sure it will stay that way.

http://farm6.static.flickr.com/5093/5501725499_7aa18a6a63.jpg

Best wishes for you and the baby.

Gas Glo

A really simple model that incorporates albedo changes and ice insulation effects:

Start with PIOMAS volume numbers:
1979 to 2004 (25years) max volume and min volume both declined by ~18000.
2004 to 2010 (6 years) max volume delined 4000, min volume declined 6000 or 1000 pa

The max volume declines of 18000/25 =720 or 4000/6=666 are very similar but the min volume declines have grown faster by 2000 over 6 years = 333pa. I am going to take this extra decline in summer as the albedo effect. I expect this to grow faster in future because of the 'great comb-over' where area has decreased slower than volume but that cannot continue indefinitely. That suggest to me a future increase in this albedo effect that is faster than linear but to avoid crying wolf over arctic ice disappearance, I will use just a linear increase of 350pa increase.

The annual volume increase needs to grow due to reduced ice insulation. I really don't know how to model this easily but as a first stab suppose the heat loss is inversly proportional to the average volume of ice. At least in an extreme respect, this is too hopeful as the heat loss will not increase infinitely if there is no ice.

I am also going to use the average of the minimum and maximum volumes as the average. As volume increases rapidly when volume is low, that underestimates the average and is therefore well of the optimistic side for preserving the ice.

I get:
Year Max Loss Min Gain
2010 20293 16378 3915 15378
2011 19293 16728 2565 17031
2012 19596 17078 2518 16834
2013 19352 17428 1924 17497
2014 19421 17778 1643 17673
2015 19316 18128 1188 18156
2016 19344 18478 866 18420
2017 19286 18828 458 18854
2018 19313 19178 135 19142
2019 19277 19528 -251 19566
2020 19315 19878 -563 19852
2021 19289 20228 -939 20287

Despite 2012 max volume apparently going higher than 2011 max, the ice disappears by 2019. I think it will be practically gone well before then given the way I have tried to err on the more ice side.

Can anyone see major flaws in this that might mean the ice could last longer than this simple model suggests?

Greg Wellman

Gas Glo,

I like your model as you've described it ... but looking at the output, the drop in min volume from 2010 to 2011 appears out of line with the other years. As that's the first year of the model, it suggests there's a flaw in how the model connects to historical data.

This year should give a good test of the albedo effect as it appears we're going to start the melt season with very low ice area and volume.

Rob Dekker

Gas Glo,
I like your reasoning regarding the fight between ice insulation effect and albedo, and your note that albedo effect seems to be winning (as observed by faster reducing minima). But I'm not sure how you got to your assumption that heat loss ice insolation is inversely proportional to the average ice volume, nor do I see that you can validate that assumption in the PIOMAS record.

The way I see it, ice insulation should show it's effect over the freeze season (thin ice growing faster than thick ice), while albedo should show it's effect during the melt season (albedo has effect when the sun is out).

To test your and my assumption I wondered if that effect would be reflected in the PIOMAS freeze numbers over the years.

To check that, I used FrankD's numbers to calculate how much ice freezes and how much ice melts over the years. This is what I got :

1980: max 32634 min 17972 freeze 14566 melt 14662
1981: max 31258 min 15366 freeze 13286 melt 15892
1982: max 30150 min 15575 freeze 14784 melt 14575
1983: max 30826 min 16497 freeze 15251 melt 14329
1984: max 31009 min 15881 freeze 14512 melt 15128
1985: max 31346 min 15896 freeze 15465 melt 15450
1986: max 31305 min 17622 freeze 15409 melt 13683
1987: max 32396 min 17248 freeze 14774 melt 15148
1988: max 32351 min 17059 freeze 15103 melt 15292
1989: max 31174 min 15687 freeze 14115 melt 15487
1990: max 29951 min 14566 freeze 14264 melt 15385
1991: max 30776 min 14584 freeze 16210 melt 16192
1992: max 29787 min 15970 freeze 15203 melt 13817
1993: max 30185 min 13470 freeze 14215 melt 16715
1994: max 29498 min 13806 freeze 16028 melt 15692
1995: max 27214 min 11637 freeze 13408 melt 15577
1996: max 27250 min 14404 freeze 15613 melt 12846
1997: max 28654 min 13714 freeze 14250 melt 14940
1998: max 29595 min 12862 freeze 15881 melt 16733
1999: max 28860 min 12516 freeze 15998 melt 16344
2000: max 27657 min 12361 freeze 15141 melt 15296
2001: max 27560 min 13101 freeze 15199 melt 14459
2002: max 27328 min 11430 freeze 14227 melt 15898
2003: max 26391 min 10709 freeze 14961 melt 15682
2004: max 25182 min 10229 freeze 14473 melt 14953
2005: max 25088 min 9938 freeze 14859 melt 15150
2006: max 24493 min 9672 freeze 14555 melt 14821
2007: max 22805 min 6042 freeze 13133 melt 16763
2008: max 23024 min 6126 freeze 16982 melt 16898
2009: max 21756 min 5583 freeze 15630 melt 16173
2010: max 20814 min 4020 freeze 15231 melt 16794


I have not done much statistical analysis over these numbers, but it seems to me that the amount of ice that freezes (from Sept->March) is fairly consistent over the years. There may be only a minor up-tick in trend in the past few years, which could possibly be attributed to 'ice insulation' reduction due to reduced ice thickness. But the effect seems very minor.

The ice loss during the melt season (March->Sept) is also fairly consistent, but it does show a 'significant' increase of melt over the past couple of years, which may correlate to change in ice albedo due to reduced area.

So if ice insulation is to have any effect in puttin the brakes on ice volume loss, it better starts showing up quickly, because ice albedo is starting to accelerate the already relentless long term down trend of 720 km^3 year over year.
So if these volume numbers are even remotely correct, we will see ice free conditions even faster than your model assumes...

One final note : That long term trend of 720 km^3 can very easily be caused by GHG forcing (which in first order approximation predicts 1400 km^3 annual ice loss) as I noted above...

Gas Glo

>"But I'm not sure how you got to your assumption that heat loss ice insolation is inversely proportional to the average ice volume, nor do I see that you can validate that assumption "

How I got there is very simple, the more ice there is the more it delays heat transfer to space. Validate is sort of difficult when I have been careful to overdo it but also sort of easy:

The important thing is to be sure I have overestimated this effect not underestimated it and my table of numbers does that. The minimum numbers before each freeze up starts is going down. Now I am not sure how strong the ice insulation effect is. However we can say that if the ice catches up with a previous year the lower level of insulation has dissappeared and the rate of freeze should be back down to the level of the previous year. Thus if the minimum is going down the max should not get up as high as the previous year. My maximum is barely declining from the 19293 figure, therefore I am sure I have overdone the ice insulation effect.

Gas Glo

>"the drop in min volume from 2010 to 2011 appears out of line with the other years"

The 20293 and 3915 came from:
http://snipt.org/wkyg
I have used Mar rather than the max in April (D'oh). I think we are on course for 1000 below last year per the piomas graph hence 20293-1000=19293
http://psc.apl.washington.edu/wordpress/wp-content/uploads/axel/ice_volume/BPIOMASIceVolumeAnomalyCurrent.png

Hence I estimate the freeze at 19293-3915=15378.

The max and min in 2010 of 20293 & 3915 are much higher than the 2011 figures of 19293 & 2565 as a result of which my deliberately overestimating effect of ice insulation causes a big increase in the freeze up to 17031 from 15378. In future years the max and min figures are more similar to the last year hence less change.

So the dis-similarity is in accordance with the model I was suggesting and yes maybe it looks a bit odd because I know I have overdone the ice insulation effect as intended.

This means this model doesn't hindcast well but the idea was to make it as robust as possible to any possible accusation that the ice insulation effect is stronger than I have modelled. Of course, someone can just throw in a snow feedback effect that I haven't attempted to model to suggest it is too alarmist....


Using the correct max month April rather than March figures made no difference to speak of:
Year Max Loss Min Gain
2010 21161 17246 3915 16246
2011 20161 17596 2565 17926
2012 20491 17946 2545 17685
2013 20230 18296 1934 18381
2014 20315 18646 1669 18532
2015 20200 18996 1204 19033
2016 20237 19346 891 19282
2017 20173 19696 477 19728
2018 20205 20046 159 20005
2019 20164 20396 -232 20439
2020 20207 20746 -539 20713
2021 20174 21096 -922 21160


Rob Dekker

Gas Glo,
I appreciate your analysis, but once again, I think that there is no evidence in the PIOMAS history to suggest that ice insulation is playing any significant role. Seems that you used Wipneus' PIOMAS numbers while I used FrankD's numbers, but both data sets are very compatible, and neither of them shows any indication of thin-ice insulation reduction having any significant impact on the freeze volume.

Both show a significant accelleration in volume melt during the melt season though, which may be attributed to albedo effects of reduced sea ice area.
In short, I think your projection is admirable, but more conservative than PIOMAS record seems to indicate.

With GHG forcing the way it is, and resulting in some 750km^3 extra melt each year, combined with the significant positive feedback in albedo during the melt season which we see in the PIOMAS record over the past 6 years or so, it looks like we are heading for a complete meltdown and ice-free Arctic in summer within a few (2 or 3) years. After that, it remains uncertain what's really gonna happen, but it looks to me that we would be looking at some 15k or 16k of winter max ice volume while having ice free summers for a while. After all, that is the amount of ice volume that has been accumulating during the freeze season.

Gas Glo

>"is no evidence in the PIOMAS history to suggest that ice insulation is playing any significant role"

I agree, but it might in future. So the exercise is to show it is never significant enough to stop the Sept ice disappearing.

>"is admirable, but more conservative than PIOMAS record seems to indicate"
>" it looks like we are heading for a complete meltdown and ice-free Arctic in summer within a few (2 or 3) years"

Thank you and I agree. Of course, this model isn't directed at people who believe in melt down in 2 or 3 years, it was built for anyone who maintains it won't happen this decade.

FrankD

Rob & Gas Glo,

V. interesting discussion, just wanted to throw in a couple of things. Any numbers refer to my dataset (the one Rob refers to),but Wipneus came up with similar results so I doubt anything here is wildly out.

Ice Melt and Ice Freeze are both increasing: a linear trend through 32 years of data shows the melt (eg September 2009 - April 2009) increasing by 37.8 km^3 per year, while the freeze (eg April 2010 - September 2009) is increasing at 15.7 km^3 per year. Net imbalance of 22.1 km^3.

I would argue that we are already seeing the oft-mentioned negative feedback (the freeze is increasing, and its not like summer minimum is too high to mask the effect completely), but that it is out weighed by the summer feedbacks. The thing is that we are not just seeing albedo changes versus insulation changes:
In summer we are seeing the melt increased by albedo change + warmer inflow + increased GHG blanketing + (I suspect) cloud cover changes (+others?)
In winter we are seeing freeze increased by increased radiation to space - warmer inflow - increased GHG blanketing - (I suspect) cloud cover changes (+others?)

So the effect of insulation change would need to be much greater than the effect of albedo change to produce a balanced change overall. And most of these unbalanced effects will increase over time, IMO.

What we are actually seeing is warmer SST's surrounding the ice minimum, which then radiates into space, which then allows ice formation. Because this dumping of heat takes time, the onset of significant freezing is getting later, but because it happens over a wide area fairly evenly, when SST's finally get down low enough, the ice forms quickly over a wide area.

With (suspected) cloud cover changes - in summer its a mix of a negative effect (reducing insolation) with a positive effect (cutting the heat radiated into space, which happens in summer too, remember). Overall it might be a negative feedback on melt - it certainly seemed that way in 2010. But in winter, I'm damn sure its a negative feedback on freeze - a couple of days of clear weather will drop surface temperatures by 15 degrees or more, so more cloud = less heat loss. If there is more vapour in the atmosphere, it will help trap radiation (whether through clouds reflecting the heat back to the surface or water vapour doing its GHG thing).

I believe the shift from 62% by volume multi year ice in 2004 (Kwok) to ~25% now is also a negative feedback - if salty first year ice melts at a lower temperature and water has a higher specific heat than ice, it stands to reason that you absorb more heat turning -2 C FY ice into 0 C salt water then you do turning -2 C MY ice into 0 C fresh water. However, I don't know if salt water ice has the same specific heat or latent heat as fresh water ice. Does anyone else?

My interpolation of the PIOMAS data started because I don't like the PIOMAS anomaly graph. I mean, the data starts below the trendline, then its above, and then below again. That's a great big flashing neon sign that a linear trend has been fitted to non-linear data. The fit is twice as good using a quadratic (as discussed in Open Thread 3 I don't think it is actually a quadratic but a small-tailed ogive, but I don't have the tools for that). However, it is interesting to compare the quadratic extrapolation (ice-free-September in 2016): http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png with
the linear extrapolation (which yields ice-free-September in ~2030).

I first did this exercise in December, and since then the three extra months of data have all been *below* each respective quadratic curve, reinforcing my belief that a linear fit is just plain wrong and if anything pulling back a prediction inherent in my monthly data to ice-free-Sooner-than-you-think.

Rob - thanks for the hat tip at Stoat's, its appreciated. I respect WC's authority, but so far, all he has really said is "I don't believe it", which is simply the old argumentum ad incredulitatem - appeal to incredulity.
(I think I have the grammar right on that Latin, but its been a while since I studied it. Cue John Cleese's Roman centurion: http://www.youtube.com/watch?v=vsawP_Ew0r4)

Rob Dekker

Frank, Gas Glo,
Nils Bohr stated that "predictions are hard to make, especially when pertaining to the future". I think we should keep this in mind. Considering the political 'climate' opposing climate science, I do understand William's conservative stand. He has taken an aweful lot of flak in the war on science that political forces have unleashed. So I can't blame him for being ultra-careful with his projections, since anything he says will be put through the political meatgrinder.

The political issues seem to stifle the scientific debate, so maybe we as 'amateur' scientists are one of the few that are in the luxurious position of speaking freely scientifically. That said, I think there is still a problem that few dare to debate in the current climate science 'climate'. The issue is the modeling of ice volume.

On the one hand, we have the IPCC general climate models, which predict ice free conditions in summer some 50 years from now. An example of that is the paper that was mentioned at the start of this thread (Tietsche et al) :
http://www.seas.harvard.edu/climate/seminars/pdfs/Tietsche_GRL_2011.pdf
Tietsche et al uses IPCC general climate models to show that ice free conditions in the Arctic will be short-lived, and that ice will recover quickly to some 'mean' that is determined by global conditions in line with long term IPCC projections.

On the other hand, we have the PIOMAS model volume numbers, and Frank just showed us how these numbers are heading straight for an abyss not much later than 2016.

So what's going on ? How can these models differ so much ?
Besides, as I pointed out before, both of these are models, and we are not even sure what is out there in the real world. The Arctic Survey ice measurements suggest that the PIOMAS models are right, and that the Arctic sea ice is really getting thinner very quickly. But is that temporary 'variability' ? Or does that mean that the IPCC models are incorrect at a more fundamental level ? And if so, where do they go wrong exactly ? For example, does Tietsche have the calculated ice volume numbers that the IPCC models suggest ? and how do these compare to the PIOMAS developments ? and did he take into account that GHG forcing may actually still be present (at the 1 W or 2 W/m^2 level), since the Arctic ocean did not have a chance to raise it's temperature like the other oceans did ?

I don't think we figured out why the IPCC models differ so much from what we see happening in PIOMAS. Does anyone dare to approach Tietsche with these questions ?

Rob Dekker

By the way, Frank, which tool did you use to create this slick graph ?
http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png

Artful Dodger

Hi Frank,

Stoat said a little more in his Feb 28 blog post:

"Of course, I may be wrong; this isn't my field any more. And its not as if I'm betting the farm on this."

Artful Dodger

Rob, sea ice thickness has been surveyed by U.S. Navy nuclear submarines since April 1958. Submarine data is discussed in length at the PIOMAS site.

Climate is basically the 30 year trend. Volume reduction is not a short term trend.

FrankD

Rob,

I just knocked up that graph with the 2007 version of Excel (I personally prefer the older version, but 2007 is what I have on this PC, and the default palette for graphs *is* nicer).
Copy/pasted into MS Paint. It doesn't get much more basic. One day I'm going to put on the waterproof pants and download R, or some other sweet tool, and then watch out! :-)

Lodger - Like Neven, the sort of dosh I'd want to wager is beneath Williams dignity to collect. She (who must be obeyed) indulges my blogging time, but she'd have my guts for garters if I started betting on this! Staying happily amateur. But I could wish he'd put a rationale on the table to support his comments to the effect that volume extrapolators are not dealing in reality. I'd say (have said) much the same of people with extent fixation: "Never mind the quality, feel the width!"

michael sweet

The Arctic ocean can become warmer and still be ice covered at the same time. It has layers of water that are dfferent temperatures and salinities. Density differences stabilize these layers. The increasing inflow of Atlantic warm water forms a layer of warm, salty water at medium depths in the Arctic. As more AWW inflows the layer gets thicker and warmer. Eventually that heat comes to the suface, either by mixing or diffusion, and starts to melt the ice. AWW causes ice retreat in the North Atlantic sector of the Arctic even in winter. Is heat from the AWW causing the increase in North Pole temperature this year? Can the submarines measure this under the ice?

Rob Dekker

Thanks Dodger, for that story about the Nautilus. Interesting that they could not cross the Bering strait in June 1958, due to ice extending 18 m below sea level. When was the last time we had more than 18 meter thick ice in the Bering Strait...in June ?

So, if PIOMAS is right, and thus Frank's graph is a valid representation of reality :
http://img543.imageshack.us/img543/2145/piomasmonthlyvolumes.png
then why do the IPCC models (and William) still predict another 50 years of summer ice ?

Artful Dodger

Hi Rob. Please, call me 'Lodger'. Observed sea ice extent has consistently been below even the most pessimistic IPCC model run, which indicates they are too conservative. The models are now at least 10 years old, are missing crucial heat inflows from the Atlantic and Pacific, have low spatial resolution, and have been outpaced by events in the Arctic.

Currently, the High Resolution model developed by the U.S. Navy Postgraduate School's Dr. Wieslaw Maslowski's seems to best track observations. See "The war on Santa Claus".

One caveat as your read this Climate Progress post. As correctly pointed out by Arctic Sea Ice blog Commenter FrankD, U.S. Navy Admiral David Titley DID NOT testify to the US Congress that he believes Arctic Sea Ice will be gone in Summer by 2020.

This is a misquote by a dodgey journalist from the U.K.'s Guardian newspaper, posted on a third-party website. Joe Romm seems to have been duped into posting a link to this website article without fact-checking. In fact, in his Nov 18, 2010 testimony to Congress, Adm Titley said he expects the Arctic to be Sea ice free in Summer by the middle to late 2030's. He also said within 10 years the Navy will have models that predict sea ice accurately from days to decades out. Dr Maslowski's work is NOT mentioned.

Also note that the responsible Journalist also claims on his personal blog to be the source of the incorrect statement in the IPCC 2007 report that Himalayan Glaciers will be all gone by 2030. He seems quite proud of this accomplishment, and happily blames IPCC authors for accepting his word without fact checking...

I will post this, with relevant links, over at Climate Progress later today in Joe's Weekend Open Thread... Enjoy the Weekend, everybody!

Steve Bloom

Lodger, Titley has been discussing an ice-free month by 2035-2040. Obviously the first ice-free day would occur long before that, i.e. his statements are consistent with Maslowski's results.

Steve Bloom

Just to add that the USN would only start caring about sea ice loss when it begins to meaningfully effect operational planning, which much less than a month wouldn't do.

Artful Dodger

Steve: You are missing the point. A Reporter is conflating two separate predictions. Titley does not refer to Maslowski's work. He also never says 2020 for first ice free day. The Point is that this is irresponsible Journalism by a Reporter who has deliberately done this before.

Steve Bloom

Lodger, if you haven't already done so you should listen to Titley's oral testimony to make sure he didn't get asked and answer a question about an initial date for ice-free conditions. The important thing IMHO is what he really did say, not what Pearce or anyone else says he said. Let'[s also be clear that while Titley has not mentioned Maslowski's work, his statements are consistent with it.

As to Pearce's dodginess (note not lodginess!), he has, as they say in Blighty, form.

Could you provide a link to that statement on Pearce's personal web page, BTW? I'd like to keep it handy.

Steve Bloom

Lodger, I went ahead and checked the testimony. At about 3:15:00 Titley starts responding to questions. He adds that there's an expectation for "2 to 3 months" of ice-free conditions by "mid-century" but says nothing about an initial ice-free day. He does mention a 2020 date, but that's for the availability of improved modeling capabilities.

But again, since a 2020 date would be consistent with the Navy's (Maslowski's) current model, did Titley say something along those lines in a different venue? Maybe just email him and ask.

Artful Dodger

Hi Steve

Here's the transcript of the 111th Congress House Hearing (Nov 17, 2010) "A Rational Discussion of Climate Change: the Science, the Evidence, the Response". R. Adm David Titley's verbal testimony and Q&A session is on PDF pp. 159-164: Size: 665 KB (Warning -- slow to load)...

Compare Adm Titley's actual words in the transcript above to those attributed to him by Fred Pearce:

"He predicts an ice-free Arctic in late summer by 2020."

When Adm Titley actually says "2020", he is talking about this:

...how do we look at a next generation of weather, ocean, ice coupled prediction models so that by roughly 2020, in about ten years from now, we can predict that system as a whole and really going — spanning between weather time frames, say hours to days, out to say roughly about two or three decades.

There's lots of video from Cancun (Dec 2010) with Adm Titley (Pearce reported from Cancun). I've watched much of it, including a News Conference where Adm Titley says he expects an Sea Ice free Arctic in late Summer by the mid to late 2030's... just like in his Testimony to Congress above... Military men stay on message.

Pearce's article also claims "the U.S. Navy has a climate change task force. With 450 staff." Adm Titley says he has 2 staff, and works with about 450 people from various Gov agencies... slightly different!

So now that you're warmed up, have a look at Pearce's blog entry regarding the IPCC report and claims of Himalayan glacier melt by 2035: I wrote the offending article. I stand by it (Jan 23, 2010).

You get the idea. I'll leave it to you to sift through the other conflations and misrepresentations. Cheers!

Neven

Ah, Fred Pearce indeed, the man behind the birth of the 'Himalayan glaciers gone by 2035'-clusterfuck. Screwing up accurate reporting on ClimateGate, and recently in the news again for attributing 'the science is settled'-quotes to climate scientists after having a couple of beers with denialists. When is he finally retiring?

Artful Dodger

Hi Steve,

The relevant quote from Adm David Titley's Nov 17, 2010 testimony to Congress appears at the bottom of page 186 of the Transcript: "I have told Admiral Gary Roughead, our Chief of Naval Operations, that we expect to see about four weeks of basically ice-free conditions in the Arctic in the mid to late 2030s"

The entire section is of general interest to Arctic Watchers, so I reproduce it at length here:

And now, sir, as you absolutely have it spot on, we are looking strategically out. So not just three, four, or five days, but what are the next 20, 30, 50 years going to look like?

We can see the signal in the Arctic. The observations tell us what’s going on. We see that the percentage of what’s called multiyear, the thick ice has dropped to levels that, frankly, we have not recorded before. So although 2007 was in area extent the least amount of sea ice that was recorded, in ’08, ’09, and ’10 the levels were slightly higher, when you look at the volume of ice, the volume as of last September has never been lower.

And in respect to Congressman Rohrabacher, I should not say never. In the last several thousand years, it has not been lower.

So we see the probable, probable opening of the Arctic. I have told Admiral Gary Roughead, our Chief of Naval Operations, that we expect to see about four weeks of basically ice-free conditions in the Arctic in the mid to late 2030s. By the middle of the century, we could be seeing quite easily two to three months of ice-free conditions. That’s enough time to allow the trans-ocean shippers, assuming they have governance, search and rescue, charting, insurance, all of those other conditions, but by the middle of the century that’s very, very possible.

Rob Dekker

Guys,
I am sorry that I have not much interest in debating who said what, why and when.

I'm more interested in what the data tells us.
I already noted the big difference between PIOMAS volume developments, and IPCC models, when it comes to projecting the first ice free summer.

I just pulled up PIPS numbers between last year and now :
March 20, 2010 :
http://www7320.nrlssc.navy.mil/pips2/archive/retrievepic.html?filetype=Thickness&year=2010&month=3&day=20
March 20, 2011 :
http://www7320.nrlssc.navy.mil/pips2/ithi.html

Seems that in 2010 the ice was thicker pretty much anywhere.
However, PIOMAS suggests that we are running some 1000 km^3 below last year.
Now which model is right ?

Rob Dekker

Oops. I meant to say (regarding PIPS) : Looks like ice is thicker now than it was in 2010.

idunno

Hi Rob,

I know Neven has mentioned that he might do an update soon on PIPS versus TOPAZ which may help...

There are also striking differences also between PIPS and TOPAZ. I have been keeping an eye on both, and cross-comparing with the satellite images available from Uni Bremen and CT for the past couple of months.

My conclusion is that PIPS is way out. It marks as thick ice areas where there are visible and obvious leads, polynna etc. It will give as 5 metre ice an area where CT has 85-90% ice.

TOPAZ also gets my vote because it is on a scale where I can see it, and the thicknesses and distribution pattern seems to correspond with CT, UniBrem and SST data.

I have also read in passing that PIPS is not actually intended to accurately map actual ice thickness, but is some sort of long-term predictive model, which is often gleefully cited by the denialosphere precisely because it does not reflect current reality.

So, for my money, PIPS is your pup.

Rob Dekker

First of all : vernal equinox is here !
As the first rays of the sun hit the North Pole for the first time in 6 months, it seems that the Arctic is already preparing for a wonderful spring season. At least the temperatures on the east side of the Pole are already approaching 0 C..
It's gonna be a very interesting melting season.

Regarding PIOMAS, TOPAZ and PIPS : Thanks idunno. Great that you keep an eye out for inconsistencies in the records available. I wonder if there would be some way to automate comparisons.
Either way, I hear you regarding PIPS. Still, I thought that PIPS was designed to do short-term predictions, and was calibrated with actual measurements, just like PIOMAS. Also, shouldn't PIPS (like other models) at least be consistent by itself ? I mean, if they always predict too thick ice, then wouldn't it be logical to conclude that at least last year's ice was thinner than this year's ?

Regarding TOPAZ, I share the opinion of other posters in the TOPAZ thread, that it is suspicious that the winter volume numbers decline faster than the summer volume numbers. There does not seem to be any physical explanation for this trend. PIOMAS shows the opposite (summer volume declines faster than winter volume) which does have a physical explanation (albedo and ice insulation effects).
So I tend to trust PIOMAS more than TOPAZ, and for PIPS I have not made up my mind yet (despite your argument, PIPS is used by the military, and they tend to use good stuff).

Neven

Rob, there was a lot of discussion last year (on pseudo-skeptic blogs mainly as they love PIPS of course (but no other models, no no)). You can find some info there, but won't find an answer. Only CryoSat will hopefully be able to resolve this.

But there's one thing from last year: Steven Goddard who went on and on about PIPS ice thickness (counting pixels and making all sorts of graphs) immediately after a WUWT commenter pointed him to it, was almost 1 million km2 off with his prediction (no recovery). Jinlun Zhang of the Polar Science Center was almost spot on with his prediction based on PIOMAS.

This doesn't say anything in itself, but still...

Neven

I'll do the PIPS vs TOPAZ blog post as soon as TOPAZ updates.

Peter Ellis

I have also read in passing that PIPS is not actually intended to accurately map actual ice thickness, but is some sort of long-term predictive model

Quite the opposite: it's a short-term model and is apparently mainly intended for forecasting the position of the ice edge up to 24 hours in advance - i.e. it models extent rather than area/thickness/volume. Even then, it needs daily re-initialisation from satellite data to keep on track. It has never been verified for thickness predictions across the pack.

Peter Ellis

And yes, I'm sure the military use good stuff, but you have to understand what they use it for. They need to know where the edge of the pack is, so surface ships don't get trapped. They might have some use for thickness data for submarines, but I would guess not much. After all, in the central basin, with water over a kilometer deep, does it really matter whether the ice "lid" is 1m or 10m thick? Just hang around 50m underwater and ignore it!

michael sweet

Last year there was a letter from the NSIDC that made the rounds (sorry I do not have a link, can anyone else provide?) that said PIPS was good for showing the movement of ice but not good for extent or thickness. I would point out that PIOMAS claims to measure ice volume and has validation data for that. PIPS and TOPAZ do NOT claim volume. Bloggers pixel count the data and report what they get. If PIPS and TOPAZ were accurate for volume the scientists would pixel count themselves. The fact that they do not means they do not think the volume is accurate enough to report. As pointed out above, the models are made for a reason. If you use PIPS and TOPAZ for volume the data is not validated for that use. The PIOMAS data is recommended by the NSIDC as most accurate for volume.

FrankD

Rob, going back to your question "then why do the IPCC models (and William) still predict another 50 years of summer ice ?", the answer is because many prefer to base their predictions on the much more robust area / extent data than volume data.

Actually, we don't really have *any* volume data, just model results (which are well validated). So people who prefer longer datasets and / or more concrete data naturally focus on those area and extent numbers. And the trends on area and extent are *much* flatter than for volume. So assuming *these* (and not volume) are the mirror of physical reality, September ice will exist for many years yet.

There are some physical realities that come into play; there is an argument that because thinner ice allows the sea to lose more heat to the atmosphere, winter area will only decline slowly from current values. So if there is a (slowly declining) minimum that the maximum extent can be, and the amount of melting that can take place in one season is also relatively fixed (again, growing slowly), then its logical that summer extent *can't* drop below a certain minimum in the near future, but will continue its slow downward trend towards ice free in 2050 or so - each year the maximum will get a bit lower, and the melt will be a bit bigger, so minimum will decline, but only at a rate of, say, 100,000 km^2 / yr^2. Off a ~4 million km^2 minimum (varies with metric and datset), that's going to take 40 years.

Now, while I appreciate the sense of the above argument, it is, nevertheless a load of cobblers, in my humble opinion. It "defends" high extent by allowing one feedback (changing insulation maintaining winter extent, which is probably true), but ignores almost every other feedback you can think of and other dynamic effects (*current* SSTs are enough to cause a decline, but *future* SSTs will be higher).

Personally, I think this is all wishful thinking, as it virtually ignores the critical third dimension. Ice area might hold up okay for a few more years while the remaining ice gets thinner and thinner but in not to many years those who rely on the more robust and extensive area and extent datasets will be shocked to find that "in the end, it will just melt away quite suddenly,"

That's Maslowski's phrase but I expect to be quoting it quite often in the next few years.

Peter Ellis

Walt Meier (NSIDC) did a guest post for WUWT last year covering the differences between PIPS and PIOMAS.

http://wattsupwiththat.com/2010/07/13/nsidcs-dr-walt-meier-on-pips-vs-piomas/

Gas Glo

>"why do the IPCC models (and William) still predict another 50 years of summer ice ?"

The IPCC model runs must have completed about 4 years ago and the processes defining what should be run about 6 years ago and the primary purposes of those models is climate in general not the arctic ice specifically. Around 2004 / 2005 I suspect there was very little in the way of ice volume estimates and what there was was viewed suspiciously. If it is recent volume data that causes concern then it is not surprising that IPCC models have not and could not have built that in.

William's (and perhaps even Admirals) continued refusal to see concern given the new volume data is available to them is more puzzling. Perhaps continuation of viewing volume data suspiciously means they decide upon a cautious 'wait until the extent shows it then you will know it is for real' approach? Or maybe it is us that are wrong and we are just a bunch of alarmists panicing over anything that looks worrying. Time will tell...

Kevin McKinney

". . . it is suspicious that the winter volume numbers decline faster than the summer volume numbers. There does not seem to be any physical explanation for this trend."

I know, I know!--I think.

The warming of the Arctic has been occurring most rapidly in winter, when the temperature is affected most strongly by cooling rates, not insolation (which is of course minimized at that season.) This has resulted in lower rates of ice growth, and hence a decreasing trend in winter ice volumes.

So there is a physical mechanism--and it's in the literature. What I just wrote seems consistent with Comiso, 2006:

http://tinyurl.com/Comiso2006PDF

The Comiso paper looked at the problem of why the winter warming hadn't been affecting the extent & area more markedly. In our current context, I'd suggest that warmer winter temps affect volume much more markedly than extent or area--I don't think Comiso 2006 looked at volume (I didn't read the whole paper, but there was no discussion of volume in the discussion of data used, nor in the figures.)

michael sweet

Frankd:
Thanks for that link. It was not the one I was thinking of. Your link was more detailed and better. I rarely read WUWT and was surprised to see the post there.

Rob Dekker

Hi Kevin,
Thanks for your post.
Unfortunately, TOPAZ does not only suggest reduced freezing during the freeze season, it also suggests reduced melting during the melt season.
And that would be difficult to explain physically, if only higher winter temperatures are to blame.
Also, I don't see how Comiso et al 2006 sustains your explanation. They clearly point out that winter ice does not decline as fast as summer ice (directly opposite from TOPAZ volume trend).

Rob Dekker

FrankD, Gas Glo, Peter, Michael, Neven, Kevin,
Thanks guys, for your comments on PIPS, IPCC models, TOPAZ, and PIOMAS.

I will assume that PIOMAS is still the best we have for ice volume estimates.

Now, PIOMAS suggest a long-term downward trend of some 700 km^3 ice loss per year (recently accellerating to more than 1000 km^3/year).
Also note that such ice loss roughly translate to 1 W/m^2 'forcing' over the Arctic, in terms of heat absorbed by that melting ice.

I've read about a dozen papers now Arctic ice projections based on IPCC models, and
I realized something profound : most of them work with variability in the range of 10 W/m^2 or higher, and they mostly deal with ice area.

They would not even notice the 1 W/m^2 downtrend in volume that we see in the PIOMAS trends.

So, it's very well possible that the volume loss, as witnessed by PIOMAS, fell in the noise of the IPCC models, and thus noone could state a firm yes or no for it's validity.

Now, one step further : PIOMAS suggest that we are going to bit ground-zero (before 2016
) with approximately a 1000 km^3/year slope.
Apparently that is the rate that albedo (and GHG forcing) is stronger than ice insulation.

That suggests a 1 W/m^2 forcing that needs to be compensated for before we reach equilibrium again. That 1 W/m^2 could be accomplished by a 12 W/m^2 forcing for a month of ice-free conditions.

I did a quick calculation based on ocean heating from Tietsche et al, and it looks like that means that ice free conditions should sustain for about 2.4 months, with on average 2.7 K increase in ocean temperature (over the area that is currently covered with ice).

So it seems that if we hit ice free conditions soon, and at the rate suggested by PIOMAS, that we will have immediately 2-3 months of ice free Arctic until equilibrium is restored...

Rob Dekker

I can see that I'm not expressing myself very clearly. Let's try this again :

The current downward trend of PIOMAS suggests not only that we will soon (before 2016) reach ice free Arctic conditions, but also that water in the Arctic ocean will be ice free for 2-3 months in summer, with a 3 C average ocean temperature (before radiative equilibrium is achieved again).
That's 3 C average, so at the peak, some areas will experience 6 C or higher water temperature anomalies.

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

P.S. Winter ice volume should stabilize at about 16-17k km^3, slightly above the current freeze amount.

Gas Glo

>"So it seems that if we hit ice free conditions soon, and at the rate suggested by PIOMAS, that we will have immediately 2-3 months of ice free Arctic until equilibrium is restored..."

Not sure I follow. Does 'immediately' mean equilibrium will be reached rapidly like a couple of years?

>"Unfortunately, TOPAZ does not only suggest reduced freezing during the freeze season, it also suggests reduced melting during the melt season.
And that would be difficult to explain physically, if only higher winter temperatures are to blame."

Huh? We are getting warmer summers it is just that the summers have not warmed by as much as winter. This could explain Topaz volume declining more in winter than in summer.

However it also suggests that temperatures have already risen and will be partly offsetting the 1W/m2. Why then does the 1W/m2 seem to reconcile? Because it is augmented by albedo change. So .... don't you need to figure in the albedo effect of your 2-3 months ice free before declaring that this with 2.7C average temp rise will be enough to reach equilibrium?

I could be completely misunderstanding what calculations you have done.


Gas Glo

Besides which, if we have grown to 1W/m2 over the period 1970-2010, then by the time we get to your equilibrium in 2016 plus a couple of further years, the forcing could have grown to 1*48/40 = 1.2 W/m2. 20% more forcing causes ... which causes albedo effect of .... ...

idunno

Hi all,

I have a strong suspicion that the heat reaching the Arctic from the Atlantic water flowing North has been increasing at a rate greater than extra heat caused by the effects of sunlight within the Arctic.

This may be a relatively temporary phenomenon, as the Atlantic Multidecadal Oscillation is currently around its crest.

If this is the case, I would expect the winter volume to be decreasing faster than the summer volume.

Winter volume = a function of (say 0.5 Centigrade higher) water temperature caused by a naturally peaking AMO, unnaturally amplified by AGW.

Summer volume = a function of water temperature as above, AND increased solar input due to AGW and albedo

I had thought that Bfraser's figures showed something like this. Winter volume is falling faster, showing that the constant all-year-round erosion due to water temperature is rising faster than the seasonal erosion due to solar factors.

Patrice Monroe Pustavrh

idduno, I am not disagreeing with you, but Tamino has done some nice analysis of AMO. From what I've read, AMO is actually detrended, meaning that high temps in NA, which we are observing now are sum of oscilation and upward trend.
Here is link to a nice analysis:
http://tamino.wordpress.com/2011/01/30/amo/
Yes, if AMO is positive, we may observe some acceleration of trend (and vice versa). But I would bet also on trend itself.

Rob Dekker

Hi Gas Glo,
I reasoned that albedo changes are (one of) the reasons that PIOMAS shows an accelleration in volume loss over the past decade. If albedo changes of the melting of the last 4M km^2 of Sept minima would need to be accounted for, then the post-ice free picture looks even worse than what I painted. I did not dare to go that far :o|

Patrice, and idunno, you guys may be right, that TOPAZ faster declining winter volumes have a physical explanation. I'm not sure though, since it seems to me that a decrease in melt (as TOPAZ shows) could only be explained by a cooling in summer (or a decrease in heat influx in summer). And we have no evidence for that. On the contrary, I would say. Besides, TOPAZ trends do contradict PIOMAS trends, so you would also have to prove PIOMAS wrong.

All in all, I'm not sure what's gonna happen. We may be staring ourselves blind on these volume numbers, which may still be off.

Besides, maybe Nature has some tricks up her sleeve which will turn around the seemingly imminent collapse indicated by PIOMAS and TOPAZ. Like if the Beaufort gyre turns around and keeps all ice in the basin, rather than pumping old ice out through Fram Strait as she has been doing over the past decade.

But it's gonna be a very interesting melt season for sure.

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