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Alais Elena

As someone who peered at photos from 4 different satellites nearly every day for the past 5 years, this information comes only as a shock to my innate hopefulness that things were not as bad as they really are.

Time for the modelers to do major mea culpas and get out of the way!!!

Kris

Needs to be corrected though:

The route designed on Giulio Frigieri map isn't the NWPassage but Amundsen's route

idunno

Eh?

The figures given in the article are far higher than PIOMAS, surely?

Artful Dodger

"CryoSat-2 is the world's first satellite to be built specifically to study sea-ice thickness"

... so presumably CryoSat-1 was to study what, launch failures? How about IceSat? Huh, howzat? What a Gaurdian!

Where's the ESA PR"?

Apocalypse4Real

The Cryosat 2 findings generally support what is being depicted in the Godiva2 ice thickness iamgery.

I don't know about the PIOMAS results, but perhaps someone can help.

One thing is clear, this has tremendous impact on climate, crop production and socio-economic stability as the trends develop. Far worse than most of us want to consider.

Time to reread the National Intelligence Council reports on climate change.

Wayne Kernochan

Reading between the lines, I believe that this validates PIOMAS more than it calls it into question. PIOMAS' extrapolation is the only one I have heard of that projects volume to head to zero between 2013-2016 (although that's just extrapolating a curve). All the folks in the article say is that "very soon now" the Arctic will be essentially ice-free sometime in summer. If they meant this year, they'd say so. So they're saying "next year or soon after".

Artful Dodger

Agreed, Wayne. Just by eyeballing the PIOMAS graph, it looks like PIOMAS has 2012 about 800 km^3 below 2011 for July 31.

The CyroSat/CPOM-UCL analysis says -900 km^3 in the last year, so if anything PIOMAS underestimates the observed change.

Anna May

I'm looking at today's UBremen SSMIS map (at http://www.iup.uni-bremen.de:8084/ssmis/index.html) and wondering how long it will be before we have no areas with 100% coverage. We still have 2-3 more weeks of high summer before melting slows down...

Steve Bloom

Yep, "in a few years," maybe, um, 2016 =/- 3 years? Hmm, sounds familiar...

martinw

Newbie here, great blog and insightful posters.

Just a couple of observations on the new data compared with PIOMAS.

For the past winter, PIOMAS has 22000km^3, Cryosat 2 has 14000km^3. That is quite a big delta.

For the current summer, PIOMAS is now 5800km^3 and Cryosat 2 is 7000km^3. Since this summer minimum is still not achieved, and it is not clear what date the Cryosat 2 summer number is from, it is not possible to compare directly with the PIOMAS value, but I'd guess the Cryosat number is at least a few days older than the latest PIOMAS number in the database, which would suggest they are in remarkably good agreement, as are the extremely high summer decline rates.

So overall this looks like strong validation for the worst-case scenarios implied by PIOMAS that I suspect many had secretly hoped were too bad to be true.

martinw

Reading a big more on the winter extent in other blog posts and comments here, it appears that Cryosat 2 covers a smaller area than PIOMAS, so it is unsurprising that PIOMAS shows a larger winter extent.

Chris Reynolds

To add to MarinW's numbers.

From the Gaurdian article:
"However, the summer figures provide the real shock. In 2004 there was about 13,000 cubic kilometres of sea ice in the Arctic. In 2012, there is 7,000 cubic kilometres, almost half the figure eight years ago. If the current annual loss of around 900 cubic kilometres continues, summer ice coverage could disappear in about a decade in the Arctic."

For PIOMAS - Summer (JJA) 2004 was an average of 16.79k km^3. End of July was 13.49k km^3. Summer up to end of July has an average of 11.32k km^3, end of July 5.78k km^3. So the Cryosat figures probably aren't for the summer as a whole but are for a specific date. Which I suspect is end of July.

With regards the 2012 figures, bear in mind that PIOMAS at 7000 km^3 is only 11 days before the end of July. i.e. a small time evolution difference in the seasonal cycle at that time of year could account for the difference between Crysat and PIOMAS.

As Martin says, and I've long suggested PIOMAS is giving us reliable information. PIOMAS validates well with the earlier DRA submarine data, and with ICESat. This new data supports the idea that the PIOMAS acceleration of volume decrease is real and is not a new deviation from 'reality'.

Wipneus

Re: comparing PIOMAS with Guardian numbers.

PIOMAS calculates more than the Arctic Basin. So winter figures are bigger, for summer it should not matter.

PIOMAS numbers have stated uncertainties:

The uncertainty of the monthly averaged ice volume anomaly is estimated as ±0.75 10^3 km3. Total volume uncertainties are larger than those for the anomaly because model biases are removed when calculating the anomalies. The uncertainty for October total ice volume is estimated to be ±1.35 10^3 km3

I'd say taking this into account the numbers do not disagree. Not to mention any uncertainties in the "new" figures.

Al Rodger

I'm with martinw & Chris Reynolds & Wipneus on this one.
The winter numbers are only for the central Arctic which is only a portion of POIMAS winter ice count.
The summer looks like late July & fits POIMAS spectacularly well.
It's the 2012 figure that is important as the 2004 one is not derived from Cryosat 2.
The accuracy of PIOMAS appears much tighter that their error bars. Well done PIOMAS!

Neven

I've asked a round a bit, but haven't found out much more for the time being. So no update as of yet.

dorlomin

Our friends are a little quiet on that Guardian thread. Took them a while to get going. Unusual, perhaps a bit of daylight has sunk into one or two of them (posting as Hithlum on there)

Mariaferdinanda

My mind goes to northern extension towards Europe of Gulf Stream. I ask to myself and I ask you: is this big melting affecting the Gulf Stream?
(sorry for my poor English!)

L. Hamilton

So Cryosat sees 900 km^3 of ice lost since last summer.

PIOMAS July 2011 mean (8.911) minus July 2012 mean (8.093) equals 818 km^3 of ice lost.

Although the absolute PIOMAS and Cryosat measures are not comparable, in terms of change it looks like they're on the same page.

Kris

Maria Ferdinanda asked:


Is this big melting affecting the Gulf Stream?

Good a question, but allow me to rephrase to:

"Would the big melt affect the convection circle of the Gulf Stream?"

We know in the past and the very past the convection system had been interrupted by a sudden and massive burst of fresh water into the Atlantic (cfr Dry Falls). With as a consequence a "little ice age" for about 10 à 20 years, due to the interrupted convection.

But as the fresh water flood coming from the melting sea ice is far behind the convection turning point, and isn't nor suddenly nor massive, in my opinion there won't be any noticable consequence, other than perhaps the convection turning point moving a bit deeper into the Arctic.

Glenn Tamblyn

Maria

It's more likely the other way around. Warming of ocean currents that travel up to the Arctic is a significant part of what is causing the steadily increased melting. The Gulf Stream is a part of this system of currents but it is further south.

There is the possibility that adding more fresh water to the arctic (sea ice is still fresh water) may cause a slowdown of a process called the Thermo-Haline Circulation that drives all the worlds currents, including the Gulf Stream.

Some years back there was concern that this circulation may have been slowing due to extra fresh water being added to the Arctic; not just from melting sea ice but also from large increases in the flow from rivers in Siberia. But at present the evidence for this slowdown is very small.

Mdoliner43

As a pure amateur I might be totally wrong about this, but here goes. The arctic is like an ice cube in a glass of water in a warm room. That ice cube cannot grow by giving up heat to the room. It can only grow by giving up heat to space through infra red radiation. Thus refreeze is entirely dependent upon greenhouse gas concentration over the arctic. If this were to remain constant the total volume of recovery would remain constant, but unless it declines the volume of recovery cannot increase. And if concentration increases that volume can only decrease.

On the other hand the ice cube can gain heat not only from insulation, but also from the rest of the “room" through ice being removed (driven through the straits), and warm air and water infiltration. Thus volume declines, in propitious years, can not be recovered unless there is a decrease of greenhouse gases over the arctic.

Kris

Mdoliner43 wrote:

That ice cube cannot grow by giving up heat to the room

Why?

The glass passes energy from it's contents to the room or vice versa the glass passes energy from the room to it's contents.
Elementary.

Sorry, but your first assumption is totally wrong.

Mdoliner43

Because the room is warmer than the ice cube.

crandles

>"may cause a slowdown of a process called the Thermo-Haline Circulation that drives all the worlds currents, including the Gulf Stream. "

Gulf stream and Thermohaline circulation(THC) are pretty much different things - different directions at different ocean levels.

The gulf stream is mainly wind driven and that isn't going to change unless there is some major change in Hadley and polar cells (or earth stop turning or sun stops shining).

THC is mainly driven by meridional overturning circulation (MOC).

There has been speculation of possible MOC turn-off or slow down due to change in fresh water in Arctic. The models don't show turn off unless you force them with ridiculously too large volumes of fresh water.

The models could be wrong, but the evidence seems to be against a sudden turn off. It has happened in the past but it is likely there was a much more sudden release of much larger volume of fresh water from dam burst following glacial retreat in North America. Current changes, even if we include a simlar dam burst from Greenland, wouldn't release as much water in same locations.

So, a slow reduction in speed of MOC seems more likely than some sudden dramatic effect. This might have effect that Britain and nearby countries gets some reduction in the global warming effects rest of world suffers.

This seems to me to be a case of media thinking 'disaster stories sell' and not letting the science get in the way of them telling a good disaster story.

Chris Reynolds

Crandles,

I'm in 100% agreement.

Artful Dodger

Hi Mdoliner43,

Sometimes it's good to make a simplified model to understand the dominant characteristics of a system. To wit, read about the SHEBA Project (Surface Heat Budget of the Arctic), an NSF observation experiment conducted in 1997. Some good modelling papers came out by 2003, and SHEBA is still providing data used in current papers.

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

Aaron Lewis

crandles,

I disagree. "Ice dams" cannot hold a head of more than ~6 meters of water (at equilibrium). When the water gets deeper, the water forms a moulin through the ice and drains, as we see on the super-glacial lakes on Greenland. On Greenland water depth in the lakes of 15 m has been reported, but this is likely a result of runoff accumulating faster than the ice under the lake could come to equilibrium.

Thus, the large fresh water flows were likely actually the progressive structural collapse of large ice structures. The process occurs as large ice collapse under their own weight as the ice weakens as it warms. The process is fast and ejects a slurry with very large horizontal velocities.

This concept has not bee accepted by the guys that study ice. If you want to see it in writing, look in Feynman's journals. He considered it too basic to publish. However, there is good data in the USACE observations on ice jams in rivers. The concept of ice dams holding large lakes has a common sense plausibility to it, but it does not work when you do melting point calculations. This is university level physics.

The bottom line is that very large chunks of the GIS will go from ice to slurry without fully melting into liquid water.

Mike Constable

The experiment with ice-dams is performed in S. America - http://earthobservatory.nasa.gov/IOTD/view.php?id=78754
The water elevation on the high side is up to 30 metres, but not an equilibrium situation.

Chris Reynolds

Aaron Lewis,

That doesn't change the fact that the Gulf Stream isn't the same as the MOC. And the heat transport to Europe isn't going to be affected even if the MOC slows or shuts down.

For further reading, and argument against the MOC shutdown paradigm see Wunsch, Abrupt Climate Change: An Alternative View.

http://ocean.mit.edu/~cwunsch/papersonline/abrupt2006.pdf

"...Further suggestions that D–O events in Greenland are generated by shifts in the North Atlantic ocean circulation seem highly implausible, given the weak contribution of the high latitude ocean to the meridional flux of heat. A more likely scenario is that changes in the ocean circulation are a consequence of wind shifts."

crandles

>"I disagree. "Ice dams" cannot hold a head of more than ~6 meters of water (at equilibrium)."

I am no expert, you may well be right. Does this mean that subglacial lakes in Antarctica are all less than 6m deep or is this some different feature that wouldn't have applied to North America?

I also thought there was a known large lake that has been named which I forget. That could be less than 6m above sea level at the time.

I am curious rather than having knowledge to disagree.

NLPatents

Wipneus,

Can I prevail upon you to update you PIOMAS monthly averages with exponential trend to include projections for all months and an extended time scale until 2030?

The chart (not that I necessarily agree that the exponential curve is the right fit) certainly is foreboding.

For those of you who haven't seen Wipneus's extrapolations for the PIOMAS data - they are pretty cool, and are what accidentially lead me to this excellent site when I was looking for his latest and greatest showign the July data.

Anyway, the exponential fit curves projects that by 2020, plus or minus 3 years, the monthly averages (not just one day) for sea ice in the artic are zero from June until October. All that open water, all the extra humidity, all the questions raised.

Any way, I would love to see the projections for all months until 2030 if it is something you are interested in doing in your update when the August data comes out.

Cheers,
Nick

Aaron Lewis

crandles,

Not at all, the sub glacial lakes may be sitting on rock the holds the pressure head, or the local temperature may be lower than melting point of the local phase of water. see en.wikipedia.org/wiki/Ice#Other_ices and scroll down to "Phases".

The classic example is Lake Missoula (with its wave benches hundreds of feet above the valley floor. see http://vulcan.wr.usgs.gov/Glossary/Glaciers/IceSheets/description_lake_missoula.html) However, those wave benches could have been formed by shallow super-glacial lakes sitting of top of hundreds of feet of ice. Not something the geologists considered.

Their idea was that: ice floats, and ice is always on top of water, and water is never on top of ice. I had this explained to me in great detail in September 1994.

wca

Ice dams enabled Glacial Lake Missoula to reach a depth of about 600m many times around 14,000 years ago. Any 6m limit to ice dams presumably applies to a specific set of circumstances.

Artful Dodger

The Daily Mail has picked up the CryoSat-2 ice volume report:

http://www.dailymail.co.uk/sciencetech/article-2187346/Arctic-sea-ice-disappear-10-years-global-warming-increases-speed-melting.html?ito=feeds-newsxml

The article is more popular tripe and rambling disconnected factoids, striped of context. Poor show.

GeoffBeacon

You won't find Cryosat-2 or the storm on the BBC news website: http://www.bbc.co.uk/news/science_and_environment/

I've been tweeting them to complain.

Their article on Hansen's latest: http://www.bbc.co.uk/news/science-environment-19146256

I would say "The article is more popular tripe and rambling disconnected factoids, striped of context. Poor show." Except that I detect much more pretention.

Wipneus

NLPatents:

I would love to see the projections for all months until 2030

Nick, there are reasons why there is a limit to 2020 and only some months are extrapolated.

1) It matters whether you extrapolate 5 or 15 years. My guess in this case is that errors will at least grow *exponentially*;
2) After August to September ice volumes have shrunk to (near) zero, the question is whether this has an influence on the remaining ice months. If the exponential behavior is the result of some positive feedback amplification, you should expect some slowdown in further melting.

For discussion, here is the graph with trends for all months and up to 2030:
https://sites.google.com/site/arctischepinguin/home/piomas/piomas-trnd2-1.png

Al Rodger

A strange BBC radio interview talking about the Cryosat-2 data that was linked at RealClimate. I assume it was this morning's Radio 4 Today programme, an interview between the BBC's Evan Davis & Seymour Laxon of the Centre for Polar Observation and Modelling UCL. Link to audio here. Laxon does stutter & spurge through the proceedings but with one of the essential Cryosat-2 numbers he says "... at the end of last summer, so that's after the melt season had happened, we were looking at a number round about 7,000 cu km."
Now that isn't what the Guardian article said. They said the 7,000 cu km was 2012. And if it were 2012 the melt season cannot have happened as it is still in progress.
As I say, a strange interview.

NLPatents

Thanks Wipneus.


For those interested: CBC has an article on last week's storm
http://www.cbc.ca/news/technology/story/2012/08/12/north-arctic-cyclone-beaufort-sea.html

NLPatents

Wow, Wipneus, that's a scary looking prediction - let's hope you are right that it has some inherent flaws more than a few years out.

Neven

"... at the end of last summer, so that's after the melt season had happened, we were looking at a number round about 7,000 cu km."

And PIOMAS had around 4000 km3, so there's a bit of a discrepancy there. According to PICT (PIOMAS volume divided by Cryosphere Today area) average thickness was 1.38 metres for the remaining ice. If that 7000 km3 is correct, average thickness would have been 2,41 metres.

I hope things will become clear.

Bob Wallace

I recall someone on this or another site stating that numbers had been cranked and one person/group was stating that once the first summer melt out occurred, a year round ice-free Arctic would follow in about ten years.

Does that ring a bell with anyone? Is there a published paper that presents those numbers?

Jeffrey Davis

reply to Bob Wallace August 13, 2012 at 18:21

Until the climate changes radically, most of the Arctic will refreeze each year.

Is it despairing or hopeful to say that nobody on this board will witness a year round ice free Arctic?

crandles

>"the first summer melt out occurred, a year round ice-free Arctic would follow in about ten years.

Does that ring a bell with anyone? Is there a published paper that presents those numbers?"

I don't believe there is such a peer reviewed paper. I think I may recall someone from AMEG: A??? Methane emergency group stating something like this was what PIOMAS data showed. Dr Schweiger head of PIOMAS promptly called this nonsense and asserted something like modeled 30 year timeframe to summer ice free was entirely consistent with PIOMAS data.

Bob Wallace

Jeffrey - someone apparently calculated that the climate would change (is changing) radically. I'm wondering if that the claim of near future year round ice free has any merit.

The claim could easily have been a dismiss-able nutcase one. Or the numbers could have been solid. I'm just wondering.

After all, we're very short years from the time when common belief was that we wouldn't see an Arctic meltout until at least 100 years from now. Very short years ago few seemed to take the "2016 +/- 3 years" prediction seriously. And now some of us are starting to fear a "-3" year event next year.

Aaron Lewis

Jeff Davis,
We have seen 6-sigma changes in the weather over last 30 years. Now, we are just starting to see some big feedbacks kick in. These would include albedo feedback and changes in the Rossby waves. Given the CH4 spikes on Nome hourly data in 1986 and 2012, I would not be surprised to see methane in released in time and quanity to have an effect on the weather within our projected life time.

Since Wipneus's charts do not include these effects, I expect that they are a bit conservative. Thus, a year round sea ice free Arctic is plausible with in less than 30 years.

WCA, I know the Lake Missoula Floods story in excruciating detail, I just do not believe it. I trust my melting point and structural strength of ice calculations more than I trust the Harlen Bretz hypothesis.

Jeffrey Davis

There was a paper discussed on Real Climate about the consequences of a summer melt out. Would the Arctic stay unmelted etc? The study suggested that, absent huge changes, that the ice would simply refreeze. (One caveat: I'm old and my memory is not as good as it used to be.)

OTOH, one need only look at those charts of the relationship between CO2 and temps over the last several hundred thousand years to know that climate state can change very quickly in the Arctic. Geologically speaking, change occurs instantly. To not refreeze though would demand warming such that we won't around to witness it.

Artful Dodger

Bob, the possibility of a perennially sea ice free arctic has been discussed many times on this blog. The 'Search' feature at the top right is handy, and easy to use with a few deftly chosen keywords ;^)

Eisenmana & Wettlauferb (2009) "Nonlinear threshold behavior during the loss of Arctic sea ice" is a seminal paper. It shows that an increase in forcing of only 3 watts per sq. meter would be required to push the Arctic ocean from a seasonally ice-free state to a perennially sea-ice free state.


(click the img above to read more)

Further papers by these authors and others have shown that a shift to a climate state with seasonally sea ice-free Arctic Summers is reversible if forcings decrease, but one the climate warms further to the point of a perennially sea ice free Arctic, the state-change is irreversible, because of the bifurcation described in the paper above.

And yes, paleoclimate data show that this has happened in the past. Your question goes to timing of the events. The answer is "Which emissions scenario will mankind choose to follow"? The forcings are well known for increases in GHG concentrations. Feedbacks count too, but that's the tipping point issue.

Bob Wallace

Dodger, my elementary questions seem to be bothering you. I'll take that hint and cease posting.

Timothy Chase

Bow Wallace wrote:

I recall someone on this or another site stating that numbers had been cranked and one person/group was stating that once the first summer melt out occurred, a year round ice-free Arctic would follow in about ten years.

Does that ring a bell with anyone? Is there a published paper that presents those numbers?

You might want to check:

http://soa.arcus.org/sites/soa.arcus.org/files/sessions/1-1-advances-understanding-arctic-system-components/pdf/1-1-7-maslowski-wieslaw.pdf

It is just a presentation. There may be a peer reviewed paper by the same author.

Timothy Chase

That is for 2016 +/- 3 years. 2019 seems quite reasonable given the current rate.

Al Rodger

Jeffrey Davis,
Was the paper you had in mind Recovery Mechanisms of Arctic Summer Sea Ice. Tietsche et al (2011)?
They modelled what would happen if the Arctic was magically made ice-free and concluded the Arctic would return to the 'declining ice' scenario. Their study was the basis for a lot of talk of "no tipping-point" in the Arctic.

Chris Reynolds

I've not been able to find any peer reviewed backing to Maslowski's extrapolation. It's possible such a claim wouldn't get past peer review. The extrapolation is simple enough but it may lack physical backing.

I've certainly not read any paper supporting the claim that the Arctic will become perennially ice free within ten years of the first seasonally ice free occurrence. I think AMEG or someone else of the same ilk is the most likely source.

I think we may know by September whether we face a rapid transition, as implied by volume extrapolation. If, as happened in 2007 and 2011, there is a stall in the loss rate leading to a levelling after the last week of August, then it probably means we'll see an inflection in the volume loss trend of PIOMAS - because the central Arctic will prove resistant to melt in late season (due to insolation factor). This would imply that area loss would have to proceed more rapidly than at present in order to achieve a minimum of near zero before the end of August, effectively sidestepping the last 2-3 weeks of the season. The years taken to reach that new state would imply a reduction in the rate of summer volume loss.

Jeffrey Davis

re: Al Rodger | August 13, 2012 at 21:02

The mechanism -- artificially zeroing out Arctic Ice in models -- sounds like it.

I'd disagree with any assertion that it wouldn't a "tipping point" simply because refreezes would follow. We don't need to swelter on an ice free Earth for there to be a huge toll in human lives. We're not following a science fiction script.

Daniel Bailey

Agreed with Lodger on Eisenmana & Wettlauferb: a sobering read, indeed.

Chris R, as for Maslowski's peer-reviewed/not peer-reviewed status, there is this:

The Future of Arctic Sea Ice
(Open copy here)
Wieslaw Maslowski,1 Jaclyn Clement Kinney,1
Matthew Higgins,2 and Andrew Roberts1
1Department of Oceanography, Naval Postgraduate School, Monterey, California 93943;
email: maslowsk@nps.edu, jlclemen@nps.edu, afrobert@nps.edu
2Cooperative Institute for Research in Environmental Sciences, University of Colorado,
Boulder, Colorado 80309; email: matthew.higgins@colorado.edu

Annu. Rev. Earth Planet. Sci. 2012. 40:625–54
The Annual Review of Earth and Planetary Sciences is
online at earth.annualreviews.org
This article’s doi:
10.1146/annurev-earth-042711-105345


Note that full disclosure for Maslowski is likely difficult due to the proprietary hardware (and possibly software/code) used to run his model. The US Navy takes a rather strict view on security classifications.

Steve Bloom

IIRC, Chris, Maslowski makes no special claim for the extrapolation, but has (still unpublished AFAIK) model results pointing to the same thing. He has stated that the reason for his (regional) model's results relative to the GCMs (the best of which still falls short of the reality as just confirmed by the new sat data) is that it accounts for warm water inflows.

As for the lack of publication, he's not in a publish-or-perish position, and I suppose it's also possible that he relies on classified data unavailable to other researchers.

But this year sure does make him look good, doesn't it?

Agreed completely about late season central pack persistence, but I expect Maslowski accounted for that. Whether he (or anyone else) accounted for it correctly remains to be seen.

Steve Bloom

The thing I really wonder is how stable the Arctic atmospheric circulation will be as we see less and less ice in the summer. It's been pointed out that overall atmospheric pressure is shifting in the Arctic. How stable is the polar cell itself as that process continues? Even short of that, it's not too hard to imagine a very rapid state change.

Chris Reynolds

Thanks Daniel,

I am aware of the problems Maslowski faces in publication. I'll give that paper a read in due course, I'm fairly sure I've never seen it.

It is significant I think that both PIOMAS and NAME project a rapid loss of volume. And that now Cryosat seems to be backing up that modelled volume loss.

It's amusing that the media are now picking up on the volume loss. I'm sure most of us here have accepted the volume loss shown by PIOMAS for some time. I expect more Cryosat data to back up the qualitative message from PIOMAS - accelerating volume loss.

Steve,

I think the central pack persistence is the reason Maslowski has indicated a residual remnant in the FreshNor poster:
http://freshnor.dmi.dk/handout_freshnor.pdf

I'm a lot more open to the idea of a rapid transition to a virtually sea-ice free state this decade. But I think it's too early to say what's happening this year is in support of the 'extrapolation to zero' argument. I still think we could see the volume loss trend break in the next few years. I'm prepared that events may overtake this timescale, if shown wrong I'll change my opinion.

I agree with Neven that it really looks like the ice pack is 'doing what it wants' regardless of weather. I also think it's significant that PIOMAS lost its thick ice over the winter of 2009/10 and that since then we've had two substantial losses (this year and last). However I still think that what we're seeing could be epiphenominal of the thinning of the ice, rather than part of a concerted process of transition to a seasonally sea ice free state.

I think we should be prepared for both scenarios - either rapid transition, or an era of extreme volatility.

We're seeing extreme warming events now happening regularly on a global basis (Hansen Climate Dice) due directly to AGW. Prolonged synoptic patterns causing floods and heat waves due to the warming in the Arctic (Francis). WACC pattern winter outbreaks (Cohen). Petoukhov/Semenov pattern winter outbreaks (Europe this February due to open water in Barents). Increasing tendency to +ve Arctic Dipoles, with the Arctic dipole being associated with weird weather in mid lattitudes (my opinion FWIW). The term Global Weirding is one of the most apt phrases coined about our predicament. And the evidence is clear, AGW itself aside, the Arctic is a large part of what's going on.

Last year and 2010 were notable for weird weather. I recall reading something by Jeff Masters in which he said this year might be calmer - it's not been. A few more years like this and blind eyes will be turning.

If we do face Arctic ice volatility with a residual (~1Mkm area) summer pack - that's not ice free, but the atmospheric heat fluxes in Autumn would dwarf what's been seen up to date. We don't need a rapid transition to a seasonally sea ice free state to invoke 'climate chaos'.

Artful Dodger

Hi folks,

No offense intended Bob, I had actually typed in a reply to your question before I scrolled down far enough to even see your name. Your contributions and your questions are ALWAYS welcome here!! Hope you're having a good day. :^)

Several Contributors refer to the concept of "late season central pack persistence", based on earlier reduction of insolation at extreme latitudes. There are several problems with this position:

  1. the oldest and thickest sea ice is not at/near the pole, it is pressed against the Cdn Archipelago
  2. late season melt is bottom melt, which doesn't require insolation, only winds and warm water, such as carried poleward with the transpolar drift in 2007
  3. sea ice does not need to melt completely to be lost in the CAB. It only needs to be broken up and exported through Fram strait to be lost to later melt, which occurs in the E. Greenland sea well into Autumn.

So the last bastion of Arctic sea ice is likely to be the Northern shores of Canada and the Lincoln sea. But we're already seeing signs of significant sea ice mobility there, now that Ward-Hunt and other ice sheets have broken up and set sail.

Just a reality check, but I see Central pack persistence as being unlikely.

Klon Jay

I was just looking at the northern shore of Greenland, which has some interesting cloud formations, and a surprising amount of open water.
http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r03c03.2012226.terra.250m

K.

Steve Bloom

Thanks for those, Klon. Yes, a surprising amount of open water, especially comparing to the graphs. The photos seem to be a little fresher, but a gap of hours doesn't seem sufficient to explain the difference.

Hopefully someone more informed can comment.

I notice that the ice has now broken away from the coast all the up to the northeastern cape (don't know the name). It'll be interesting to see if it can turn the corner in the coming days.

Timothy Chase

Daniel Bailey, thank you for the link to Maslowski's paper. Didn't know about it. To the extent that I am able to follow it, I am impressed.

Twemoran

Klon - Steve

An image from last year of the Cape Morris Jessup area may provide perspective.

http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r03c03.2011240.aqua.250m

Terry

Chris Reynolds

Artful Dodger,

Long term the bastion may well be off the CAA - that is after all what the models show.

But evidence is always the best reality check.
http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html

Tell me what the notable feature is about years crossing the 3M kmsq mark, and day 236.

Steve Bloom

Not so much, Terry, due to too much cloud and not even being able to tell exactly where that cape is in the image. Thanks for the effort, though.

Clare

Crandles: belated reply
"Does this mean that subglacial lakes in Antarctica are all less than 6m deep or is this some different feature that wouldn't have applied to North America?

I also thought there was a known large lake that has been named which I forget."

Lake Vostok, is below sea level, & deeper than 6m. I think pressure is a factor there, and was a feature in the design of the sampling method they planned to use in trying to avoid contaminating the system.
http://en.wikipedia.org/wiki/Lake_Vostok
Clare

Kris

Clare made the remark:


Lake Vostok, is below sea level, & deeper than 6m I think


Lake Vostok itself must have about 750 m depth.

In the course of times the lake has been buried under a 3000 m thick ice layer.

On 5 February 2012, a team of Russian scientists claimed to have completed the longest ever ice core of 3,768 m .

I wonder who might have created the "6 m maximum" stupidity.

Twemoran

Steve

The Cape is cloud free - lower right of the image, but not to the extreme.
Perhaps backing it off to 1K resolution would help.

Terry

Jim Williams

The Navy's CICE ice thickness has shown the ice pull away from Greenland and the islands more than once this summer. I think it's just the wind.

http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif

AmbiValent

Extent seems to be down a century, but area remains in place. Do we have refreeze in the heart of the main pack?

Espen Olsen

Are we having a refreeze?

I think so, Deep Purple is entering the stage, where Pink Floyd finished, so now Simply Red is watching from the edges, and the show will be over before Green Day gets a chance!

http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png

Superman

Wipneus,

"For discussion, here is the graph with trends for all months and up to 2030:"

How did you get a data point for September 2012?

Superman

Bob Wallace,

"After all, we're very short years from the time when common belief was that we wouldn't see an Arctic meltout until at least 100 years from now. Very short years ago few seemed to take the "2016 +/- 3 years" prediction seriously. And now some of us are starting to fear a "-3" year event next year."

I've both done and tracked long-range predictions in other disciplines, and their temporal trends can be interesting. For example, if you track the predictions of when fusion power will be demonstrated commercially starting from the 1950s, you will find the date keeps receding further into the future as time proceeds. My question here is: has anyone documented historical predictions of when the Arctic would be ice free even for a few days? Let's say, predictions made in 1971, 1981, 1991, 2001, 2011. I suspect these results would be the converse of the fusion results.

Wipneus

Superman:

Please look again: last point for September is 2011.

Tick marks on the x-axis are at begin of January, monthly data are plotted at the middle of the month.

Superman

Aaron Lewis,

"Since Wipneus's charts do not include these effects, I expect that they are a bit conservative. Thus, a year round sea ice free Arctic is plausible with in less than 30 years."

If your system is described by nonlinear dynamical equations, wouldn't the omission of even relatively 'small' terms potentially result in large errors in the solution? Especially when we know the directions that these missing terms would take the solution. Couldn't Wipneus' charts be far more than a 'bit conservative'? We are witnessing extreme events in all the markers of climate change, and they are coming fast and furious.

crandles

>"My question here is: has anyone documented historical predictions of when the Arctic would be ice free even for a few days? Let's say, predictions made in 1971, 1981, 1991, 2001, 2011. I suspect these results would be the converse of the fusion results."

Contemporaneous papers can reach different conclusions so you would want a good synthesis effort. So I suggest IPCC reports

First assessment report 1990:

Chapter 7.8.2 Variations in sea ice extent and thickness

"Changes and fluctuations in Arctic seaice
extent have been analysed by Mysak and Manak
(1989); they find no long term trends in sea-ice extent between 1953 and 1984 in a number of Arctic ocean regions but substantial decadal time scale variability was evident in the Atlantic sector. These variations were found to be consistent with the development, movement and decay of the "Great Salinity Anomaly" noted in Section 7.7."

Observations are not the same as modelling or projections. Much of the modelling was equilibrium climate modelling (Chapter 5) so that is warned not to viewed as projection. 3.5.7.2 (p88) mentions time dependant modelling but I haven't found any mention of modelling of future sea ice level.

So perhaps we are left with taking 'no long term trends' and mangling that into projections for 1990 and previously as projected never?

Maybe second, third and fourth reports would yield better modelling/projections information:

http://www.ipcc.ch/publications_and_data/publications_and_data_reports.shtml

crandles

If your system is described by nonlinear dynamical equations, wouldn't the omission of even relatively 'small' terms potentially result in large errors in the solution? Especially when we know the directions that these missing terms would take the solution. Couldn't Wipneus' charts be far more than a 'bit conservative'?

Well, yes it ***could*** be. But when the projection is basically curve extrapolation, this is very dangerous to use this to go far into the future. More than a couple of years (if not just one year) looks dangerous to me. Therefore, it ***could*** also be far more than a little aggressive.

Yes, there is more reason to worry about it being conservative than aggressive.

Dr Schweiger liked this Wipneus' graph in preference to wild extrapolations:
https://sites.google.com/site/arctischepinguin/_/rsrc/1332318605624/home/piomas/piomas-trnd1.png

I like Wipneus' graphs; but this is provided the cautions he has given against longer term extrapolations are heeded.

George Phillies

Lake Vostok: That's under the ice, with the ice on top of it, and if it is under sea level, with water on the far side of the ice pushing back. That's very different than how thick a vertical plate of ice you need to support a hydrostatic pressure head, and how thick and cold the ice needs to be to do this.

Perhaps Greenland will give us some experimental examples. Has anyone seen recent data on the Watson river flood?

Artful Dodger

Chris Reynolds asked "Tell me what the notable feature is about years crossing the 3M kmsq mark, and day 236."

Just the typical noisy observations, fitting the general downward trend. Did you have a specific observation, Chris?

BTW, the Aug 7-13 MODIS Composite image is out at EnvCda: (large JPEG)

http://ice-glaces.ec.gc.ca/prods/MODISCOM-F/20120813000000_MODISCOM-F_0006593535.jpg

Cheers,
Lodger

Al Rodger

Superman,
The ice-free predictions of old, I know not. The first I can date is a '2030 prediction' made in 2002 but I cannot say by who. 2007 did draw some "at this rate there will be..." type predictions but in December 2007 a '2013 prediction' was made by Professor Wieslaw Maslowski. I believe his latest predictions are 2016+/-3, which is not entirely inconsistent.

Neven

Maslowski made his prediction in 2006, with data up till the 2005 melting season, so well before the 2007 monster melting season (source).

cynicus

Re how much waterpressure can an icesheet withstand?

Isn't the collapse of the Antarctic Larsen & Wilkins iceshelves attributed to meltponds working as wedges opening cracks from the top of the shelf to the bottom?

Because water is heavier then ice, water works much like a peg splitting wood; pressure at the tip forces an existing crack to widen. Water seeps down newly formed cracks which increases the column of water and thus increases the splitting force at the tip. The splitting will continue as long as the meltpond is replenished while water is seeping deeper into the shelf.

When melting on the top of the sheet stops then the waterlevel in the meltpond lowers as the crack deepens and ice-collapsing-forces on the crack will come in balance at some point with the pressure of the watercolumn and the crack will stop progressing. It might even refreeze. If melting continues there is not much to stop the watercolumn to reach the bedrock.

See e.g. http://earthobservatory.nasa.gov/Features/WilkinsIceSheet/

Because of this mechanism I find it hard to believe that a deep glacial lake can be sustained for any longer timespans.

Al Rodger

Hi Neven,
You could well be right. Certainly his data didn't include 2007.
A lead on the '2030 prediction.'
A nod from somebody with a good memory gives me the name Robert Hunter and a book Thermageddon: Countdown to 2030. as the source of the '2030 prediction'. (I have no memory of this source. I'd imagine back in 2002 I read it in New Scientist or something like that. But definitely before May 2002.) It seems Hunter is the co-founder of Greenpeace.

dorlomin

50% grabs you by the throat and says "something is happening".

Klon Jay

Jim says: The Navy's CICE ice thickness has shown the ice pull away from Greenland and the islands more than once this summer. I think it's just the wind.

Perhaps I shouldn't have been too surprised. Wind, and the snow-less land absorbing sunlight. Last year there was more snow in N. Greenland around this date.
http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r03c03.2011228.aqua.500m

Daniel Bailey

@ kris

"I wonder who might have created the "6 m maximum" stupidity."
Not having been able to keep up with you guys (d*mn frickin' day job!) someone may have already addressed this. So pardon if this is redundant. I think this is a conflation of supraglacial lake depths vs sub-glacial lakes.

Krawczynski et al 2008 looked at constraints on the lake volume required for hydro-fracture through ice sheets (i.e., supraglacial lakes). What they found:

"We find that the cross-sectional area of water-filled cracks increases nonlinearly with ice sheet thickness. Using these results, we place volumetric constraints on the amount of water necessary to drive cracks through 1 km of sub-freezing ice. For ice sheet regions under little tension, lakes larger than 0.25–0.80 km in diameter contain sufficient water to rapidly drive hydro-fractures through 1–1.5 km of subfreezing ice. This represents 98% of the meltwater volume held in supraglacial lakes in the central western margin of the Greenland Ice Sheet."
And their conclusions:
"Our calculations show that lakes that are only 250–800 m across and 2–5 m deep contain a sufficient volume of water to drive a water-filled crack to the base of a 1 km-thick ice sheet. Lakes that are smaller may also be drained, however it requires fractures that are fed by multiple basins. This range in lake sizes represents the majority of supraglacial lakes in the ablation zone along the western margin of the Greenland Ice Sheet. Thus we propose that a large fraction of the melt water produced in the summer (on the order of several cubic kilometers) could rapidly reach the base of the ice sheet via this mechanism."

Kris

George Phillies wondered:

Perhaps Greenland will give us some experimental examples.

There is no need for, as we had already a real-life example in 1996 from Iceland.


Back in 1996 a subglacial eruption under the Vatnajökull glacier triggered an enormous flood.

The Vatnajökull glacier/icecap is about 8300 m² and has a depth of 500 à 600 m.

The eruption created a giant lake, a lake kept in place solely by the ice dam (glacier) present there.

But at a certain instant the entire glacier had been lifted up by the sheer power of the water mass and it's pressure, mainly it's pressure, and the entire lake was drained away then underneath the glacier.

The "hole" the spill made at the bottom of the glacier has been visitable for years and perhaps still is visitable.

The reason why a huge water mass is capable in uplifting an entire glacier is yet another chapter. But it's about the very same dynamics for "normal" dams. cfr the Val di Stava dam collapse.

Anyone who doesn't know has to educate himself now, and Internet and Google are his friends.

Neven

Important update to this blog post. I have received some clarifications from Dr. Laxon which he has allowed me to share here:

1) The numbers are PROVISIONAL but are our best estimates right now. We are working hard to finalise (i.e. check the details of) the numbers at which point a paper will be submitted which will hopefully be published in due course. At that point everyone will have access to the whole story/figures etc.

2) The trends are from the period 2004 to 2012 and are obtained by combining CryoSat ice volume with ice volume from NASA's ICESat mission for years 2003-2008 (see Kwok et al, JGR, 2009).

3) The trends are for the two campaign periods which ICESat operated in each year that overlap with the times of year when CryoSat-2's provides data. That is a month during October/November (ON) and February/March (FM).

4) The numbers refer only to the central Arctic (the ICESat domain) and cannot always be compared with the PIOMAS "whole arctic domain" available on the PIOMAS website (i.e. there are times of year when some ice lies outside the central Arctic).

5) Both ICESat and CryoSat-2 measurements have been validated (checked) against data gathered by aircraft and undersea moorings.

6) IF the trends we appear to be seeing continue then the Arctic may become (largely) ice free within a decade. HOWEVER to make a "prediction" of the date at which the Arctic might become ice free it will be necessary to get our data into models which are capable of making such a prediction. We are working on that also with colleagues.

7) From point 3) you may assume that our last data points are for ON11 and FM12. For the current condition of the sea ice there are many websites which show the current extent of the ice (CS-2 cannot measure thickness at this time of year with our current processing).

That's all I can say right now, but I hope that helps and I would encourage all now to wait for the paper where all of the data, methods and uncertainties will be clearly laid out (though for those who can't wait see [Giles et al., GRL, 2008] and [Kwok, et al., 2009] where measurements derived in a similar way are presented).

Wipneus

So the 7000 km3 figure that was discussed above would be October/November 2011 ?

Very comparable with PIOMAS.

Neven

Bingo, Wipneus!

crandles

Antartica was a bad example if the lakes are below sea level. Sorry about that.

Perhaps this would be a better example for 150m high morraine dammed lake:

There are a number of imminent deadly GLOFs situations that have been identified worldwide. The Tsho Rolpa glacier lake is located in the Rolwaling Valley, about 110 kilometres (68 mi) northeast of Kathmandu, Nepal, at an altitude of 4,580 metres (15,030 ft). The lake is dammed by a 150 metres (490 ft) high unconsolidated terminal moraine dam.

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

Superman

Crandles,

"Yes, there is more reason to worry about it being conservative than aggressive."

It seems to me 'much more' reason. The presence of full cover thick ice serves to insulate the water from the heat flux from the Sun and atmosphere. The presence of full cover thick ice serves to minimize additional heat transfer from the water that could fuel stronger cyclones. The presence of full cover thick ice serves as a fixed no-slip boundary condition that minimizes the mixing in the water due to the presence of winds and serves to brake the winds at the ice surface, and minimizes the lateral heat transport by underwater currents and brakes these currents near the bottomside surface. The ice is effectively the 'scab' that protects the 'body' of the Arctic Sea.

Once the ice starts going, all these identified processes (and many others) start to heat the Sea and feed off each other in a self-reinforcing manner. This will result in methane release from myriad vertical and lateral regions within, and adjacent to, the Arctic Sea. These releases may be smooth, or they may be abrupt.

I don't see intuitively how catastrophic runaway can be avoided. Any curves that don't show this have to be questioned for accuracy. Has the 'community' become 'gun shy' in their predictions because of the presence of the skeptics and deniers? I ask this here, because I know this has happened in other communities, where the presence of powerful opponents results in presentation of only the most conservative watered-down findings and predictions.

Neven

Superman, I'm quite the alarmist (that's a code word for 'alarmed'), but as the janitor of this blog I see it as my duty to not be too confident when writing about things I'm not 100% sure will happen. I do try to stress the risks wherever I can, as much as I can, of course.

Chris Reynolds

Artful Dodger,

If you're going to cast aspersions that someone isn't in touch with reality (i.e. they need a reality check), you really need to pay attention to what they're saying. Need I observe that I'm the second person you've riled on this very thread (i.e. Bob Wallace)?

So here we go again...

Both 2007 and 2011, record low area years in the CT dataset show a cessation of the summer loss trend around day 236, then the loss rate shifts into a more gradual and far more noisy levelling. This doesn't affect the actual date of CT area minima which is between 250 and 255 for all years after 2007. But it is a notable feature of loss profile in thos two years. It is this that I had hoped you' have noticed, given my preceding comment, when I linked to CT's interactive area plot.
http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html

What I am saying is that this may happen again this year, and if it does it needs an explanation. Indeed I think this feature of 2007 and 2011 needs an explanation as it is, because it stands out that these were two sub-3Mkm^2 years with different weather profiles that nonetheless show this behaviour. Do I expect such a levelling this year? I'm about 55% on that. We'll know by early September.

My tentative explanation is that at such low extents, when the ice is restricted to a small zone virtually within the 80th parallel, insolation in late August is no longer able to win the battle against heat loss. If this is the case then to lose that ice we'll need to have the seasonal cycle shift earlier so that before the end of August the ice edge has made it into that region. i.e. to lose the ice in that region the Arctic must be virtually ice free by mid August at the latest.

If this is the case how can the August volume loss trend continue to zero? We'd actually see a break point in the trend as the volume loss abates while the melt process shifts earlier in the year.

Superman

Neven,

"Superman, I'm quite the alarmist (that's a code word for 'alarmed'), but as the janitor of this blog I see it as my duty to not be too confident when writing about things I'm not 100% sure will happen. I do try to stress the risks wherever I can, as much as I can, of course."

I never use terms like optimist, pessimist, alarmist, etc. The only term I like to use is 'realist'. Yes, in pure science, perhaps in a timeless discipline like cosmology, we would stay within the bounds of only the data and analysis we have, and extrapolate out in time only to the point where we felt completely comfortable. But, these criteria cannot hold for science that have time-critical policy implications.

I have examined a number of diverse areas, including etiology of chronic diseases, etiology of cell phone and other EMF-induced illnesses, etiology of climate change, etc. All of these problems are characterized by extreme complexity, many variables, special interests that manufacture research results and, especially, long latency periods.

If we waited for definitive proof that smoking causes lung cancer (as we did), about 20-40 years would have passed before we had enough epidemiological data to make evidence-based policy decisions. We would have (actually, did) condemned many people to premature death who spent that latency period merrily puffing away.

If, as we are doing now, we wait until we have definitive proof that cell phones, perhaps in conjunction with other toxins, cause higher brain cancer rates, then we will similarly end up condemning many innocent people to premature death and unnecessary suffering. Hardell has shown that after one decade of cell phone use, adults double their rates of brain cancer, and children more than quintuple their rates. The manufactured research tries to counter these data, but it is no more valid than WUWT for climate change. Given that lung cancer latency periods typically start at about thirty years from onset of smoking (although some papers suggest twenty years), the fact that cell phone cancers start to appear only after a decade of use is alarming indeed. The point here is that we need to err on the side of caution in cases like this, and intuition must play a key role along with hard data.

I suspect that, for climate change, if you wait for data with which you are fully comfortable before informing policy-makers, it will be like the cases above. It will be too late, perhaps for the planet. The consequences of what appears to be happening now have to be laid out in the most stark terms possible. Otherwise, when people believe they have time remaining to make a decision, they will delay to the last minute.

There is a limit to the quality of the data you will get for a base. For all the literatures above, I have found a combination of good research, poor research, and manufactured research, and it is not always easy to differentiate among the three, especially for complex systems. We need to look at the data, add in a heavy dose of experience and intuition, and go with that. When I see the recent acceleration of myriad extreme events, it tells me the pins are starting to fall in place on Pharoh's tomb. That's the word that needs to get out at this time.

Artful Dodger

Chris Reynolds, the data set you point to is for the entire CT Arctic region. I'm not sure how you are extracting trends from it for the North pole region, which is the topic.

My 3 points above go to what is likely to be the failure mode when we see the first ice free Summer at the North Pole. Will it be insolation, or will it be bottom melt, or will it be breakup and advection.

Your point seems to be that if the sea ice is to be lost at the N. Pole, it must happen before about day 236 (Aug 23 ) due to decreased insolation.

I disagree with that position, for the reasons outlined above. I think it can occur later. See Neven's 2010 Series on the "North Hole". Notice that those images were taken just days before MODIS sunset, on Day 250...

Just sayin' ;^)

Cheers,
Lodger

crandles

>"I have found a combination of good research, poor research, and manufactured research, and it is not always easy to differentiate among the three, especially for complex systems."

Then I say get out the message: IPCC reports = good research, long curve extrapolations without much physical modeling built in = poor.

While "it tells me the pins are starting to fall in place on Pharoh's tomb" is dramatic language (and maybe that is appropriate), how/does someone distinguish yourself from someone who would ban the progress made in the industrial revolution just a few years into it on safety grounds? Weren't all the positive feedbacks still in place back then and yet it didn't prove risky for many decades?

That the current situation is risky comes from careful IPCC reports. Sea ice volume observations, a few curve extrapolations and a bit of dramatic language shouldn't frighten anyone and trying to do so can just make you look like someone with extremist views, or perhaps a bit of a wacko. The science is in, we don't need to risk looking a bit loony. I think it is better to call it what it is and point people to IPCC reports rather than have them dismiss what they see as loony extremism. OTOH perhaps it is advisable to have a few people using dramatic extremist jargon to make people wonder, be curious and want to find out more. It takes all sorts.

Chris Reynolds

Artful Dodger,

"Chris Reynolds, the data set you point to is for the entire CT Arctic region. I'm not sure how you are extracting trends from it for the North pole region, which is the topic."

At the risk of stating the bleedin' obvious: At minima what's going on in the surrounding water is just blank space in terms of area. What happens in the central Arctic in 2007 and 2011 is indisputable - why it happens is debatable.

Your three reasons were:

1.the oldest and thickest sea ice is not at/near the pole, it is pressed against the Cdn Archipelago

A There is good reason to believe that what is left off the CAA is not particularly thick. If you take the thickness calculated from CT area and PIOMAS volume since 2010 the late summer thickness has crashed. This can only be because PIOMAS has lost the thickest ice, which previously biassed the thickness upwards. Even if we doubt PIOMAS, Maslanik's timseries of thickness shows that ice over 3-4 years old will be gone within a few years.

2.late season melt is bottom melt, which doesn't require insolation, only winds and warm water, such as carried poleward with the transpolar drift in 2007

A. As soon as insolation input goes net flux turns negative and heat starts pouring out of the surface layers into the atmosphere, thence to space. Bottom melt might continue in whatever thicker ice is left, but open water will freeze rapidly. Likewise, thin, fractured ice will conduct heat well and will transfer heat from the ice/ocean interface to the ice surface, it won't melt out. Just look at how fast the open ocean develops a thin covering of ice in October and November. e.g. US Navy HYCOM thickness plots.

3.sea ice does not need to melt completely to be lost in the CAB. It only needs to be broken up and exported through Fram strait to be lost to later melt, which occurs in the E. Greenland sea well into Autumn.

A. No conceivable Fram Strait transport is going to empty the central Artic. Even the Polar Express of 2007 didn't achieve that.

As a further case in point, consider the fragment left from the recent cyclone. It's in a far better position to melt than ice within 80degN after the last week of August. It's in pre-warmed waters at a relatively low lattitude. It's going, but not that fast.

In years to come at the end of the melt season the whole of the Arctic pack will be like the images in Neven's post "North Hole", that doesn't mean that as insolation falls the ice will still melt away. It's instructive to ponder the significance that the minima of 2007 - 2011 all lie between day 250 and 255 despite the massively varying circumstances of those melt seasons.

opensheart

"OTOH perhaps it is advisable to have a few people using dramatic extremist jargon to make people wonder, be curious and want to find out more. It takes all sorts."

Crandles

Hello, I'm a lurker who just subscribed to comment on this. Just last night I was lying awake thinking about trying to sell bumper stickers and t-shirts and stuff with just such an edge. Looking through what bumper stickers were available on the subject I was depressed and the number and cutting edge of the global warming deniers. I'm thinking about jumping in to balance that out as a way to do something with all that I'm learning. So far my best idea is a sticker that says:

Global Warming
has killed before

Chris Reynolds

Actually with regards my answer to point 1. I have information I can't divulge right now. That's why I'm saying PIOMAS has lost its thick ice - the reduction in thickness I describe could in theory be due to thinning of thinner ice, it is not.

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