A few people have already remarked on some pretty surprising numbers in Arctic sea ice extent this year (the New York Times has also noticed). The minimum extent is usually in early to mid September, but this year, conditions by Aug 9 had already beaten all previous record minima. Given that there is at least a few more weeks of melting to go, it looks like the record set in 2005 will be unequivocally surpassed. It could be interesting to follow especially in light of model predictions discussed previously.
There are a number of places to go to get Arctic sea ice information. Cryosphere Today has good anomaly plots. The Naval Sea ice center has a few different algorithms (different ways of processing the data) that give some sense of the observational uncertainty, and the National Snow and Ice Data Center give monthly updates. All of them show pretty much the same thing.
Just to give a sense of how dramatic the changes have been over the last 28 years, the figures below show the minimum ice extent in September 1979, and the situation today (Aug 9, 2007).
The reduction is around 1.2 million square km of ice, a little bit larger than the size of California and Texas combined.
Update: As noted by Andy Revkin below, some of the discussion is about ice extent and some is about ice area. The Cryosphere Today numbers are for area. The difference is whether you count ‘leads’ (the small amounts of water between ice floes) as being ice or water – for the area calculation they are not included with the ice, for the extent calculation they are.
Update: From the comments: NSIDC will now be tracking this on a weekly basis.
http://science.natice.noaa.gov/icImages/qs_07241_nheimsk_00z.png
http://science.natice.noaa.gov/icImages/n2_07242_n_12z.png
Do read the text for information on accuracy, these are _pictures_ after processing data.
These are via the link given in the first post, where it says:
“The Naval Sea ice center has a few different algorithms (different ways of processing the data) that give some sense of the observational uncertainty ….”
Re 293: “While a circle may be merely a useful construct, a Sphere evidently does exist ;-) and can either concentrate on clarifying points or on scoring them.”
I happen to disagree. I’d ask you to prove to me that I exist if that wasn’t so far afield from the topic.
(You might take note that there are people here I’m happy to agree with. It’s just a certain attitude and bogus view of Science with which I disagree. I find Scientism a very disagreeable religion.)
Re 294: “Not that I expect this post to make it to the discussion, mind you…very off-topic, indeed.”
You noticed! :)
Re 296: “[May I suggest Ohshitocene — as in we sure didn’t see this coming!]”
Ever since I bought my house overlooking Boston in 1990 I’ve said that I bought valuable oceanfront property — it was only a question of when. I think I might even live to see when.
Greenland ought to be fairly slow to melt away. So I think two years from now the major topic will be the Antarctic Peninsula, and two or three years after that the Ross Ice sheet and Western Antarctica. I won’t even have retired by then.
On Climate:
It might be the state of climate research that it is about long-term averages, but climate is what the weather will be in the future where you live, not what the weather has been in the past where you live.
Do you live in a cold dry climate or a warm wet climate?
Alastair McDonald 29 August 2007:
“You can argue about whether the climate is chaotic, but it is a non-linear dynamical system with negative and positive feedbacks. So long as the negative feedbacks dominate you have a stable system such as that over the last 10,000 years. But if the positive feedbacks dominate then you have a rapidly changing system just as we had 10,000 years ago at the end of the Younger Dryas. The positive feedbacks cause the system to runaway until it gets into a new state where the negative feedbacks again dominate. The new state is then stable, and it will sit there for perhaps another 10,000 years.”
It’s maybe worth noting here that negative feedback-dominated systems are not inherently stable. It depends on the relative strengths of feedback and damping. Strong negative feedback combined with little damping produces a system that wants to oscillate – and will at the slightest provocation.
Of course, our climate system is strongly damped (by the ocean thermal inertia). Which is presumably why it doesn’t oscillate much on our timescales, despite strong negative feedback from the longwave radiation mechanism. Of course, on longer timescales and in other states, our climate does oscillate. That is presumed ([I]shown[/I], for the ice age cycles) to be due to sub-scale positive feedbacks within the overall negative feedback regime from temperature vs radiation to space.
For any ship captains following this thread who are trying to make their way through the NorthWest Passage (and those of you still following this thread), you better put the engines at 110% because the sea ice is rapidly refreezing.
Don’t believe the images from the Cryosphere Today. You might only have a day or two left.
http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2007242/crefl1_143.A2007242221000-2007242221500.4km.jpg
False-color image with sea ice in Red.
http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2007242/crefl1_367.A2007242221000-2007242221500.4km.jpg
#307: Refreezing? In the last week of August?
What ship’s captains actually use are charts like this:
http://www.natice.noaa.gov/pub/West_Arctic/beaufort_sea/2007/currentcolor.pdf
… and this:
http://ice-glaces.ec.gc.ca/prods/WIS40CT/20070830180000_WIS40CT_0003296413.pdf
The Canadians plot new ice in pink. See any pink there, John?
#307, Mr Wegner I live by the Northwest Passage, and I heard that ships have had pleasant sailing lately. “A day or two left” utter nonsense, more ships are on their way. Is there any reason to believe your reasoning then?
#288 Alastair, I take it you are from the UK? Well I am a little puzzled by the met office no longer displaying sea ice extent yearly projections until 2100. I am getting convinced that the ice and Polar atmospheric models were off by 10 to 20 years, would have really appreciated seeing their projections still, as I am curious about how we take it from here. Is the met office ice model merely wrong timewise? It will be very good to understand where the error is, especially compare the 2007 melt with 2007 projection, it would help narrrow down a bug, and perfect future models. I don’t think its bad yo be wrong, it is terrible when you can’t know why.
Do you have a point? Does refreezing somehow discredit the minimums which have already been recorded?
#310 Wayne Davidson.
The Met Office are still showing ice area projections.
http://www.metoffice.gov.uk/research/hadleycentre/models/modeldata.html
From Hadley Ctr Briefing “Climate change and the greenhouse effect”(Dec 2005) page 44:
“Under the High Emissions scenario we find that ice in the month of September (when it is at its minimum extent in the annual cycle) will have almost completely disappeared on average by the 2080s.”
___Does anyone have any refs about the climate impacts of an ice-free Arctic Summer?___
Leaving sensible warming rate impacts aside: Will changes to heat flux (ice insulates atmosphere from ocean) and availability of water with regards humidity really have no effect on the Arctic Oscillation? I’ve been checking through AR4 and the ACIA, but can’t see this discussed and can’t find anything in Google (although with my day-job and this issue I have been burning the candle at both ends – so apologies if I’m missing the obvious).
PS What’s the contrarist reaction to this news?
Actually don’t answer that.
I don’t care.
RE # 312, Cobbly, thank for the link to the Met Office page but Please help me to understand the March 2100 ice concentration. Is that their idea of a joke?
Wayne, you’ve opened the wrong Talking Points Packet, that “Arctic Freezing Fast” set is from the September Denial series.
All that new to the SW of Banks Is literally showed up overnight. Plus, the ice edge moved south along the Banks shore. I agree, anyone attempting the passage now is a risky gambler.
RE: #308 – The Canadian chart is in error. Areas K and I are definitely new ice. I track this daily.
#313 John,
In the winter there’s still a loss of long wave into space, but no incoming short wave from the Sun so initially it didn’t strike me as odd.
However A1b is 717ppm CO2 in 2100 which brings it up towards Cretaceous levels. And according to this abstract (not read actual paper) http://www.nature.com/nature/journal/v380/n6572/abs/380330a0.html
“We find that the Arctic Ocean was relatively warm, remaining above 0 °C even during the winter months. This implies that there was significant poleward heat transport during all seasons.” That was published in 1996.
#314, Hank, I agree with some previous post, there should be a way to flag nonsense, and warn RC readers of how ridiculous some statements are, this would decrease contrarian useless arguments driven to distract rather to inform.
#312 Cobbly, Many thanks for the link, could not find again, much appreciate this I can’t slow down the projection pace, but I can see where they got at least 2007 melt wrong. The melt of June 2007 occurred over the middle of the Arctic gyre, which is seen as happening in 2038. This is key in understanding what happenned, I believe it is due to unnusually warm air at the usual location where a high pressure system settles North of Alaska almost throughout the entire year. I don’t have June’s weather animation, but I think it is so. Must remind that in 2005 a stagnant High pressure system settled over Northerrn Arctic Quebec, giving +30 C surface conditions in late April early May (if memory serves) . This is serious evidence of a potential catastrophic meltdown to come, if such a “hot” high pressure system settles over the thickess ice in the Polar region. Met Office projection shows strong yearly melting on the Russian side, but not so much on the Canadian side.
In Large I think that it underestimated warming from a very different atmosphere than we are use to…
Many thanks Cobbly, I think its important that contrarians explain their reasoning, this shines a great light on them…. Bookmarked the animation.
Re 306: “It’s maybe worth noting here that negative feedback-dominated systems are not inherently stable. It depends on the relative strengths of feedback and damping. Strong negative feedback combined with little damping produces a system that wants to oscillate – and will at the slightest provocation.”
Um… I think there is a disagreement here about what the term “negative feedback” means.
My understanding of the term is: Any response which tends to increase when a system diverges from a meta-stable state and which tends to pull the system back towards that state.
Positive feedback is any response which also tends to increase as a system diverges from a meta-stable state and which tends to pull it away from that state.
Responses which do not either tend to draw a system back to the meta-stable state or pull it away from that state are uncharacterized by the terminology.
Note that this definition does not define any given response as necessarily positive or negative — but only as positive or negative relative to a given meta-stable state.
By the definition I understand, a system dominated by negative feedback must necessarily remain near some meta-stable state for the duration of the time in which it is dominated by negative feedback. If it wanders off to some other meta-stable state it must have been dominated by positive feedback during the transition. (A transition called re-organization.)
Certainly, strong responses to perturbations can pull a system any which way, but unless the response does a fairly good job of pulling the system back to a specific state from divergences either way it isn’t negative feedback.
[Response: The use of the terms positive and negative feedback in climate and engineering differ, and your definitions aren’t quite what is meant when these things are discussed in climate papers. I recommend the early Hansen papers to get a better sense of the climate usage. – gavin]
Re: “[Response: The use of the terms positive and negative feedback in climate and engineering differ, and your definitions aren’t quite what is meant when these things are discussed in climate papers. I recommend the early Hansen papers to get a better sense of the climate usage. – gavin]”
I’m perfectly satisfied with the “In Nature” section of this Wikipedia entry: http://en.wikipedia.org/wiki/Feedback See also the root General Systems notion of Feedback: http://en.wikipedia.org/wiki/Systems_theory
As you can see, I was not using feedback in the narrow cybernetic sense; which is consistent with the general usage, but much more restrictive.
I have no intention of accepting or using any domain specific notion of feedback which is contrary to the general notion.
As I predicted yesterday, the NorthWest Passage is now closed off by the sea ice (unless you have a good icebreaker.)
There are three different routes to take which are shown on Wikipedia here.
http://en.wikipedia.org/wiki/Image:Northwest_passage.jpg
The Northern route is choked off by the ice in the Beaufort Sea. The middle route is touch and go but appears to be choked off as well. The southern route is iced up the middle (which is what the early explorers always complained about – that the ice seems to come out of nowhere in the inner passage ways of the NorthWest passage.)
You might need to use the 500M resolution of this Terra satellite image to see it given the cloud cover. The 500M resolution allows one to zoom into the different routes and see the ice.
http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2007243/crefl1_143.A2007243193500-2007243193959.500m.jpg
In a way, this situation is no different than that experienced by the early explorers. They might make progress, but then suddenly they are frozen in for two straight years. In the third year, in late August, suddenly the ice opens up and they are able to squeak through. In the last two years, there was no way any ship was getting through the NorthWest Passage. This year, there has been a 2 week window to make it through. If you started at Baffin Island today, however, you are stuck for the next two years.
Noone with a $100M in cargo is going to park a ship off Baffin Island in early August and wait for the satelitte images to tell them which route to take over the next two weeks before the end of August (when everything refreezes) and when there are so many risks of different routes iceing up the next day. With more warming, maybe.
[[As you can see, I was not using feedback in the narrow cybernetic sense; which is consistent with the general usage, but much more restrictive.
I have no intention of accepting or using any domain specific notion of feedback which is contrary to the general notion.]]
Oh, and I suppose you use “work” to mean “any effort” even when discussing physics? And use “culture” to mean “going to the opera and art museums” even when discussing microbiology? And use “theory” to mean “wild guess?” What other technical definitions do you avoid when talking about the fields where those terms are used differently?
No new ice has formed in the Canadian Arctic. However over the next week, new ice (slush) may form in the sheltered bays of the high arctic.
The last time I checked, McClure strait has 1/10 to 2/10 ice, with this ice being thick first year or multiyear ice.
Now the wind can quickly push old year ice around and pile this ice up around islands. You are always in danger of the having the old ice in the beaufort sea, entering McClure Strait and blocking the Northern route of the North West Passage. However the southern route, which is tricker to Navigate, should be clear for several more weeks.
Another point, when the Canadin charts show blue instead of white, it means that its not ice free but less than 1/10 coverage. Once again, wind conditions can push thin
John Wegner (#321) wrote on August 31:
Well, I would certainly hate to use early August pictures to navigate in late August. And that would seem to be the right location, although I see plenty of blue towards the south. So lets see how Nasa describes the ice as of August 30th, 2007 using an image from the day before…
If you check out the rest of the webpage it is clear that the passages were more difficult to navigate in early and mid August than they were on the 29th. If it is choked with ice relative to the earlier part of the month and you were able to see it rapidly closing on the 30th, I gather that it is freezing over at breakneck speed…
Sphere writes:
“I’m perfectly satisfied with the “In Nature” section of this Wikipedia entry”
Someone needs to update that Wikipedia entry to add the usage from climatology, obviously.
Sphere, if you use the search tool at the top, you’ll find a long series of confused postings from an engineer whose definition of “feedback” also differed. It’s much like trying to talk to a lawyer, who has come out of law school with “infer” and “imply” reversed.
You either understand how the field uses the term, or waste time.
Notwithstanding the cruise ship which has just left Resolute Bay today, and more ships to come, it has been the best ice free year in a series of ever decreasing ice coverage in the Northwest passage. The Northwest passage was never traversed in the distant past mainly by its great stigma given by the death of many explorers/whalers daring to penetrate it. Now it is a “walk in the park”mostly ice free sail, recent past huge pack ice floes are none existing of extremely rare… I don’t appreciate comments which are misleading on RC, and I guess responding to them is the only recourse.
Present day met dynamics are very interesting, especially with extremely warm sst’s”
http://www.osdpd.noaa.gov/PSB/EPS/SST/climo&hot.html
Very very warm in the open section of the arctic ocean, we are experiencing a warm september in the High Arctic +7 C again despite a High Pressure
in the SW quadrant of the North American Arctic Ocean. The sun is quite lower than summer just past yet the heat is still on.
Hank,
Feedback was a term invented by electrical engineers to describe non-linear processes long before a butterfly fluttered in Lorenz’ brain. It is quite clear, since they think that they can redefine the term, that climatologist do not understand feedback. That explains why they have so wildly underestimated the melting of the Arctic ice.
The re-closing of the North West Passage is just a minor aberation caused by some loose ice being blown south. You can check out the day by day sequence on my Javascript web page: http://www.abmcdonald.freeserve.co.uk/north.htm by clicking Backward s Day.
The real situation is that the Arctic sea ice has been thinning steadily for about 20 years. Now it is so thin that the edge of the perennial sea ice melts and retreats further each summer. The more ice that melts, then the warmer the sea becomes from being exposed to the solar radiation. This melts more ice, and so there is a positive feedback with warming causing melting and melting causing warming.
This year the edge of the perennial ice stopped its major retreat at the end of July as is normal, but next spring the ice will not have fully recovered because the extra exposed sea surface is warmer than usual, and so will inhibit the regrowth of the seasonal sea ice.
Next year, because the ice melt will get a head start, more ice will be lost before the start of August, perhaps all of it. If not we will surely see the last of the summer ice within a year or two driven away due to the positive feedback from the ice albedo effect. No matter how the climatologists try to define feedback, that will not change the physical system.
They tried to define the adiabatic lapse rate to fit the US Standard Atmosphere, then wonder why they have a tropical lapse rate problem. It is a great pity that the competence of today’s climatologists does not match their hubris :-(
Re #319, #320
Perhaps the disagreement stems not from the definition of a negative feedback, but from the way in which the concept is used. For example, radiative equilibrium is attained when absorption equals emission. If the temperature is increased slightly WHILE HOLDING THE INCOMING FLUX CONSTANT, emission becomes greater than absorption, causing the temperature to fall back toward its equilibrium value. Thus, the increase in emission with temperature represents a negative feedback in the classic sense and the equilibrium is stable. However, if the system warms due to external forcing, e.g., an increase in the incoming flux, the role of a negative feedback is to slow down the rate of increase, eventually causing the system to settle into a new equilibrium.
Re #306
“Of course, on longer timescales and in other states, our climate does oscillate. That is presumed ([I]shown[/I], for the ice age cycles) to be due to sub-scale positive feedbacks within the overall negative feedback regime from temperature vs radiation to space.”
This comment seems to assume that the glacial/interglacial cycle was a free oscillation; it is generally accepted, however, the the oscillations were FORCED by spatial and temporal redistributions in insolation due to the “wobbling” of the earth’s axis. (Milankovitch theory)
Good news today…
The arctic sea-ice seems to be continuing to bounce back rather strongly at the moment.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg
Still, it is rather early in September.
Re #330: Timothy, it’s not bouncing back, not yet anyway. The anomaly plot you linked to does indeed show the ice going up, but that’s in relative terms. The accompanying ice area plot is basically flat.
I wonder if the rebound or the ice area is due to the melt ponds refreezing. One of the problems with the calculating ice area, is that it hard to tell between open water, and melt ponds on the ice. Considering that the rebound is quite small however, it appears that Cryosphere today has a fairly good handle on this problem.
What I find amazing is that places like Alert,NWT (83 North is still recording temperatures above freezing), with the Sun barely above the horizon for most of the day.
This tends to indicate that the Arctic Ocean has good heat content, and is having an effect in extending the summer in the high arctic.
The NSIDC results for ice area should be out in a few days, and I expect the ice area will show a continued but slow decrease in ice for the next two-three weeks.
The Cryosphere results will be up and down depending if new ice melt, melt ponds refreezing, and possible formation of new and nilas ice in the next few weeks, fight it out for control.
But the days of rapid ice decline are over for this ice season. Soon the discussion will turn to how slow the ice recovery is during the winter.
Hank,
I am very surprised to read the postings regarding the definition of feedback, arising once again. Can you provide me a few more pointers on using this site’s search tool, so that I can find the confused postings to which you refer? I would like to follow up this post with a more researched thought-through posting. Unfortunately, I am unable to get the search tool to hone in on the material you reference.
Let me first postulate that all feedbacks in nature have fundamental analogies, based in the mathematics, whether in climate systems, engineering control systems, or as implemented by the helmsman on the Staten Island Ferry in order to minimize his transit time in the presence of wind and currents. This seems to be a wonderful opportunity then to open a cross-discipline discussion and educate those truly curious about climate issues, rather than to create a divisive internet shouting match, without a mathematical basis, on whose feedback belongs to whom.
For instance, even with my limited use of feedback in five or ten engineering classes, I feel that I possess some appreciation for the concern of ice albedo feedback. Yes, I would like to know more details, but I get the idea well enough to understand what I need to, and don’t feel the need to poke at the experts without doing my own research. However, I have a day job and a family so I choose to leave it there. I at least believe for now that my study of feedbacks also enabled me to conceptually understand the post on water vapor as a feedback.
Without looking too far into it, I suspect that the real differences have to do with the complexities and underlying assumptions, including linear vs. non-linear systems, parametric variabilities, and complexities arising from multiple simultaneous feedbacks, rather than whether a feedback is fundamentally unique to a certain discipline. I do remember the blog shouting match with the poster-boy engineer from some time ago, but don’t remember the details other than I discounted the postings because (as I recall) there was very little detail present to underpin that commentator’s assertions and arguments, and a blog is rather ill-suited for resolving such fundamental allegations anyway. Yes, the devil is in the details, and we must have them, but conveying the concepts of global warming to a more broad audience is essential. Feedbacks are an important element of that dialog, and stating that noone but the climate experts understand is to miss a golden opportunity.
Re #327
“The more ice that melts, then the warmer the sea becomes from being exposed to the solar radiation. This melts more ice, and so there is a positive feedback with warming causing melting and melting causing warming.”
This is precisely how climatologists define the ice-albedo feedback. It would appear that some of the bloglodytes who make frequent posts here are just trying to stir up controversy where none, in fact, exists.
> feedback, definitions
Well, interestingly enough, search this with Google:
+realclimate +engineer +definition +feedback
you’ll find there are a lot of postings recently on skeptical sites making comments about this very question. Odd coincidence, perhaps.
I’ll leave it to the climatologists after reminding you of the pointer Gavin gave earlier to Hansen’s earlier papers as a place to start.
Re #291 where Hank Roberts Says:
Alastair, please. That was published last year and there’s an entire thread here at RC about it. “The whole of science” isn’t “hung up on linear trends.” You’re in the mainstream.
and he cites as justification: Arctic Sea Ice decline in the 21st Century https://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/#more-391
It is true that in the commentary by Cecilia Bitz she dismisses the idea behind Figure 3 https://www.realclimate.org/images/bitz_fig3.jpg where a straight line is drawn to meet the zero ice line in 2100. However, what she does do is suggest the ice might go in 2040 which fits to a straight line drawn on Figure 2. Try it with https://www.realclimate.org/images/bitz_fig2.jpg
Of course the results from her experiment do show a sudden collapse. See https://www.realclimate.org/images/bitz_fig1.jpg but that model still has residual September ice well after 2040. This is where the climate modellers do not seem to understand what positive feedback means. When positive feedback takes over, and it has done, the reduction is sea ice area will accelerate until no ice is left. That is what positive feedback means!
Jerry may think that my engineer’s definition of ice-albedo feedback is the same as that of climatologists, but Gavin has written that their definition is different. He has only given us a vague reference to early Hansen papers. Gavin, or perhaps Hank, could you give us a reference to an open access paper where we can read Hansen’s definition?
Re #329:
The intent was the opposite – that the glacial-interglacial cycles are not free oscillations, rather forced by orbital variations, as you say. But Milankovitch alone is way too small to explain the observed amplitude. You need positive feedback to amplify the orbital forcing – the most important being the carbon cycle effect on atmospheric CO2 conc.
Hank, speaking of feedback, the lack of a sudden massive biological feedback may have played a role in the demise of the ice this year. Not well known, however I have seen it for years, there’s a cloud seeding chemical release from under the ice biological activity or simple chemicals like bromides :
http://www.fysik.lu.se/eriksw/aoe2001/EOS_AOE2001_Leck.pdf
In the recent past, a solidly frozen Arctic Ocean gave a mighty release of cloud seeding chemicals at about mid April onwards which nullified the higher sun heat. If these aerosols were released gradually throughout the winter, instead of suddendly in the spring, there would be a greater ice melt by the lowering of cloud albedo. This might have happenned, need a word by those who have access
to high resolution data…….
Further to #336
I have found a paper by Hansen et al. (1984) “Climate Sensitivity: Analysis of Feedback Mechanisms”, Reprinted from Climate Process and Climate Sensitivity Geophysical Monograph 29, Maurice Ewing Volume 5 Copyright 1984 by the American Geophysical Union. http://pubs.giss.nasa.gov/docs/1984/1984_Hansen_etal_1.pdf
They “calculate land ice, sea ice and vegetation feedbacks for the 18k [at the last glacial maximum (LGM)] climate to be f(land ice) ~ 1.2 – 1.3, f(sea ice) ~ 1.2, and f(vegetation) ~ 1.05 – 1.1 from their effect on the radiation budget at the top of the atmosphere.”
My point is that positive feedbacks lead to an increase in the forcings. It is wrong to use an average forcing, when it is increasing exponentially.
This is similar to point that is being make by falafulu in his post at https://www.realclimate.org/index.php/archives/2007/08/regional-climate-projections/langswitch_lang/index.php?p=442#comment-51812
The whole ethos of climate modelling is wrong, and I con only assume that this is because is minly being dome by mathematicians. For them an average temperature is a higher truth than a set of temperature readings becasue it hads been mathematically manipulated and maths is never wrong. However, what they have really done is throw away most of the information, so in fact the average is less true than the original data. This can be seen when the size of the average US family is calculated to be 3.14 people. That answer, with a precision of two decimal places, does not match reality.
But now, not satisfied with taking averages, they have moved on to Bayesian statistics. I am not the only person to object to that method. See http://en.wikipedia.org/wiki/Bayesian_probability#Controversy
RE # 327
Alastair, you said:
[The more ice that melts, then the warmer the sea becomes from being exposed to the solar radiation. This melts more ice, and so there is a positive feedback with warming causing melting and melting causing warming.]
While observers are fixated on the extent of and diminishing rate of Arctic ice melt back, I am wondering about the massive heat about to be given off to the atmosphere and its destination. Can Moscow expect another late and mild winter?
I begin with the 15 million sq km of Arctic Ocean and the now approximate 3 million sq km of remaining ice. The black surface is, in my estimation, about 4.6 million square miles of warm water about to freeze.
Sphere at #239 provided a link to SST anomalies that indicate about a 5C anomaly in the far western Arctic. I do not know the average SST throughout the Arctic but I will assume it is averaging 37F .
The refreeze begins with evaporating water heat. The process of evaporation 7.5 times as much energy as freezing and the latent heat of fusion of ice require 79.6 cal/gm or 143.3 Btu/lb. Evaporation takes away about 540 cal/gm or 975 Btu/lb. I am using 1000 Btu/lb to evaporate sea water.
From NSIDC (All About Sea Ice): the freezing temperature of salt water is lower than fresh water; ocean temperature must reach 28.8 F to freeze. Because oceans are so deep, it takes longer to reach the freezing point and generally the top 100 to 150 meters of water must be cooled to the freezing temperature for ice to form.
Assuming an extreme average Arctic open water temperature at 37 F, the evaporation process could release 636 x 10(18) Btus to bring the surface water to 28.8 F.
Then, the latent heat of fusion of ice takes over. Assuming the nearly 12 million sq km. melted surface froze to a depth of 3 feet (my assumption), would yield an additional 3×10(18) Btu for a total of about 640 x 10(18) Btu released to the atmosphere throughout the entire surface water to sea ice change.
If my assumptions are off base, they do not dismiss the large question of where the freezing open Arctic Ocean heat will dissipate to and what will be its impact.
Any thoughts?
Hank,
I performed the search you recommended and located a lot of blather. If this is about an assertion that positive feedbacks cannot lead to another stable state, then this is untrue in engineering and other disciplines. And feedbacks in engineering control systems can be plenty complex, just ask any designer of a nuclear power plant’s control system. It’s hard to sort through all the comments on those listings to find relevant comments on this topic, but at a glance I don’t see anyone discussing the mathematical underpinnings, again, just shouting. Also, I’m gonna need a better citation than “Hanson’s early work.”
To find the early Hansen papers, first, spell his name right.
Hansen
+climate +NASA +GISS +publications
re 330
I take that to be big ice breaking up into little ice, and the little ice speading out and looking like more ice at the resolution of the sensors.
Both the water and the air are too warm for such significant ice formation. However, there are winds that would facilitate dispersion of broken ice. Look at changes in the ice near ~75 N and ~135 W.
A good treatment of feedbacks in a climate context can be found in section 2.5 of Peixoto and Oort, “Physics of Climate”. For those who are desirous of obtaining a more rigorous understanding of the physical underpinnings of climate change than can be obtained from the internet, this would be a good book to purchase.(It’s still in print and available from Amazon.com)
RE: #341 and others – so, here is what those who wrest a livelihood from (and risk there lives on) northern waters bank on. This is as of yesterday. A good / scary crab fisherman will play chicken with the ice edge (what is shown in “Deadliest Catch” is for real):
http://pafc.arh.noaa.gov/marfcst.php?fcst=FZAK80PAFC
THE MAIN ICE EDGE LIES FROM THE WESTERN COAST OF BANKS ISLAND TO 71.1N 132.5W TO 70.8N 135.9W TO 71.2N 138.2W TO 71.4N 143.0W 71.8N 145.0W 72.3N 149.9W 72.9N 152.0W 74.4N 154.8W AND CONTINUES TO THE NORTHWEST. THE EDGE IS MAINLY 1 TO 4 TENTHS NEW…YOUNG…FIRST YEAR THIN AND MULTI YEAR ICE.
FORECAST THROUGH SATURDAY…EAST WINDS OF 10 TO 20 MPH WILL CONTINUE AROUND THE VICINITY OF THE ICE EDGE FOR THE NEXT 5 DAYS. NEW ICE WILL FORM NEAR THE ICE EDGE AND WITHIN THE PACK AS TEMPERATURES DROP BELOW FREEZING. LITTLE NET CHANGE IN THE POSITION OF THE EDGE THIS WEEK.
The Sept 3 update is out at NSIDC (National Snow and Ice Data center. NSIDC Sept 4 Update
The sea ice extent continues to decline and is now down to 4.42 sq. km, or below what it should be by 2050, according to the UN climate report projections earlier this year.
Sea ice extent is 4.42 million square kilometers, as of Sept. 3, or 0.9 million square kilometers less than the absolute minimum measured for Sept. 20-21, 2005. See: http://www.nsidc.org/news/press/2007_seaiceminimum/20070810_index.html.
Have any climate simulations ever shown such a rapid drop in a single year? If not, what is missing from the models? Heat transfer via ocean currents (i.e. W. Maslowski’s thesis)? Overestimates of sea ice volume in the past?
I’m an RNA biochemist, so maybe I’m over-impressed by this sudden drop. What’s the take-home message for the average RealClimate reader?
“Physics of Climate” is on google books and can be read on-line
http://books.google.com/books?id=3tjKa0YzFRMC&dq=physics+of+climate&printsec=frontcover&source=web&ots=xTDnBwSGHF&sig=tbXe2xyO1LGmqGwTA1v1rUgpFx4#PPA519,M1
Wayne, that’s a fascinating article.
http://www.fysik.lu.se/eriksw/aoe2001/EOS_AOE2001_Leck.pdf
I’ll quote a bit:
“To test the idea that the tiniest aerosol particles
are made of sulfuric acid, they were examined
by electron microscopy during the 1996 Arctic
expedition. It turned out that these very small
particles,when present,were not at all composed
of sulfuric acid. Instead, they were
mostly five- or six-sided insoluble solids, resembling
viruses,and were accompanied by larger
particles such as aggregated compact balls,
bacteria, and fragments of diatoms [Leck and
Bigg, 1999; Bigg and Leck, 2001; Leck et al.,
2002].The most likely source for these particles
is the open water between ice floes. If these
“virus-like”particles, already in sizes 20–50 nm
in diameter, rather than tiny sulfuric acid particles,
served as cores for subsequent condensation
of DMS oxidation products, then the
growth process to cloud-forming particles
would be greatly shortened and all the action
could take place below cloud base. Such a
mechanism would remove the need for
formation and growth of aerosol particles
above the clouds.The simple system proposed
prior to the 1991 and 1996 Arctic expeditions
became suddenly more and more complex….”
Jamie, you asked if any models have shown such sudden drops; see the prior thread, I pointed to it in an earlier response on Aug. 30, saying “linear extrapolations are more optimistic about sea ice than climate model runs and every model includes some runs that show periods of unusually rapid decline (which get blurred if only the average rather than the extreme cases is looked at). This looks at model runs that look much like this week’s Arctic sea ice.”
https://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/#more-391