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The 500mb level is found at approximately 18,000' (ranges from near 5,000 meters to 6,000 meters) but is * NOT * where the polar and tropical jet streams form.

The (polar) jet stream forms along and just below the Tropopause and is THERMALLY driven. During the winter, the maximum jet stream winds are typically found in the 250-300mb level (30,000-35,000 ft) and is the predominant, global jet stream. The tropical (actually referred to as the sub-tropical) jet forms around the 150-200mb level - and is almost always confined to the cold season.

During the winter, an arctic jet can found at times around very deep upper level Lows and associated troughs - generally at the 450mb level.

Ridging refers to an area of upper level high pressure (for example, where the actual height of the 500mb level, along with temperatures, is highest). Ridging can be north-south orientated or east-west, as is currently found with the sub-topical high over the Atlantic ('Bermuda High').


Evening Ron,
Hope my rant wasn't personally disturbing. At least, I still sleep well at night (except the last few nights, while it's hot and filled with stinging insects).
To add to Allen's cooperative explanations, here's an ECMWF model run for 25 July:

 photo GAC-2013A2507500Mbanalysissmall_zps2af77978.jpg

In my own crude way, I circled the "Polar Cell" and marked the axes of ridges (red) and troughs (blue). It all rotates around a relatively small Polar Cyclone. The ridges are best analysed on 500Mb pressure level (about 5-6 km high in the Polar cell), the Jet is situated a little higher (mind, in the climo!) on 300-250Mb.

One of the QED challenges is to analyse whether the Rohrschach-image is different from the climo.
I've been trying some all winter, but other priorities wilhhold me from really testing my assumptions.

Sleep well!


BTW, as I've been trying to learn on the web about "wave momentum flux" related to the transfer of energy through the ridging, I found this orographic map of the Arctic:

 photo Orographicmapfromauragsfcnasagov_zps958355de.jpg

It is from a http// site aura.gsfc.nasa.gov/images/science/Gravity_wave_polar-lg.jpg

I think it visualises the extreme position of the GIS in relation to the circulation pattern.

Another potentially nice source on the matter is " kiwi.atmos.colostate.edu/group/dave/at605pdf/Chapter_8.pdf "

Lots of reading...


Thanks, sgregory,for being more specific.
There's so much knowledge that can be deepened!
BTW your remark on the Bermuda high ridge is easy to see on the ridging model I inserted above. Actually, it fits quite well with the big spike in GIS-melt area just a few days ago!


Walt Meier on "Are scientists conservative about sea ice?": http://nsidc.org/icelights/2013/07/29/are-scientists-conservative-about-sea-ice/

"Sea ice models, though far from perfect, are the best tools we have to understand and project the future changes in sea ice. While the models on average show a slower trend, a closer look provides a more subtle view. Looking at averages can mask important variations in the sea ice that occur in the real world. Individual model simulations do show periods of rapid ice loss lasting several years, but they also show periods of stasis, with little or no trend, over several years.


Thus the observations that we are seeing may be a period of rapid ice decline that models indicate will happen from time to time. And we may be due to experience a period of slow down. There is no certainty of this and scientists have been surprised by the dramatic record lows in 2007 and 2012."

I suppose Walt's post may deserve a more focused discussion, but it's a sticky issue for sure. I have great respect for Walt, but I have a hard time reconciling chalking up the recent decline to a "period of rapid decline" and that we may be overdue for a slow period. Analogous to this, I suppose, would be the global surface temperatures and the "rapid warming period/hiatus period" duality. This seems valid enough. And I don't suppose there's any way to really falsify this notion until we see several more years of sea ice data come forth. My sinking feeling is that--from the now famous sea ice observations versus models graph--observations being consistently below the models one standard deviation line is a red flag that the models did not expect the Arctic to be as vulnerable as it actually is.

But if it's variations that's sagging the extent numbers so aggressively below the transient sea ice "sensitivity" that models expected from the GW signal, I'd be interested to know what they may be. Incidentally, only from 2007 to present do the satellite data suggest any sort of rapid decline that is so shockingly deviated from the norm. From 1979 to 2006--the relative "good old days"--the pace of ice loss had already been tracking well below the ensemble mean of the models. So I find myself reverting to my strong hunch that the case here is that the Arctic is far more vulnerable to global warming than had been anticipated. Any slow period of melt would be more relative to the pace of the 1979-2006 years than what is being suggested in the models. This is exactly the kind of unsettling thought I have that has kept me on the edge about the Arctic, and it no doubt fuels what I notice is maybe a consensus here on the ASIB that ice-free summer conditions are mere years away, not decades.


This discussion of a transition to a single cell northern hemisphere is, unfortunately, news to me, and has indeed added to my feelings of dread. Thank you so much for bringing this to my attention (not being sarcastic btw).

So, as pointed out, if the earth can exist in a dual climate state (NH hot-house, SH ice-house) then global warming is not the immediate concern, but northern hemisphere warming is!

Instead of getting concerned as we watch the global average temperatures rise, should we be focussing (for now) on solely the northern hemisphere temperatures, and, having filtered out the more moderate increases seen in the SH, be getting even more concerned!

I wondered what a graph showing warming by hemisphere would reveal (a quick google found data sets for hemispheres from NASA GISS, and also this graph: http://www.giss.nasa.gov/research/news/20100121/418334main_hemi-temp-full.jpg )

So, as already said by others, tipping the NH climate into a new state is much closer than a 'global' change seemed to be. And with it come huge changes to weather patterns, and enough warmth to unleash the arctic carbon.

Seems that it really is NH warming that needs to be at the forefront of discussion, not global warming.

Is there any indication that climate science is picking up on this? If not we need to get much more scientists to get to work on this.


One question, in the hothouse/icehouse dual state, what effect would this have on the ENSO, and its effect on global temperatures?


2009 had a minimum above 5 million sq km. This year is currently close on extent to that year but it appears on area its lower so I don't expect a repeat. I think high 4s is possible this year though.

Henry and also Lord Soth.
Totally agree with you. Unless something unexpected happens (such as a repeat of GAC 2012), we can now write off the possibility of a minimum under 4 million. I stick to my earlier prediction of an SIE minimum in the 4.8- 5.2 bracket. There are about 30-40 days of melt left, even if we average 65 k a day for that period, this will bring us to 4.8 million.


Has anyone seen any discussion of this recent paper?


seems to be one of the most recent on the topic.

This is the MIT News article about his research that Rose links to from his website:



In search for more info on possible cell-rearrangement and the role of planetary waves in transfer of energy I just struck on this:
by jaiser et all, AWI pub. 01 July ‘13


"Stratospheric response to Arctic sea ice retreat and associated planetary wave propagation changes"

Also a lot of interesting references.


As Allen's second link points out, conservation of momentum makes a single cell impossible unless there is a massive increase in friction. Farrel's theory relies on an arbitrary, unexplained increase in friction to solve this problem, and the first link doesn't claim to be operating near the correct frictional parameter for the Earth. I don't find this theory completely implausible, as increased heat will lead to increased moisture and increased convection, and hence increased friction, but I would still be cautious about accepting the theory as fact for the Earth.

Regarding the actual jet stream configuration this summer, the Polar cell has pretty clearly been going backwards all summer, with rising air near the pole. This means we need an even number of cells, and it's pretty clear to me on Jai's "Find the Jet Stream" link that there are four.

There is always a jet stream for each cell boundary (except the Equator, by symmetry), so normally there are two. The northern jet between the Ferrel and Polar cells is usually stronger, and we normally call it just "The Jet Stream", while southern jet stream between the Hadley and Ferrel cells is called the "Subtropical Branch of the Jet Stream".

At the moment, we have three distinct jet streams, the polar branch (along the northern tops of Werther's purple line), the middle branch (along the bottoms of his purple line) as well as the subtropical branch (not marked). Also we have extreme amplification, with each cell mostly divided into vortices.

This configuration isn't all that unusual in summer, but I can't recall it ever staying in this configuration all season almost non-stop like this year.



I'm interested in the difference in "weird weather" explanations.

The Hadley Centre seems to say "Nobody understands it. It might be cyclic."

Jennifer Francis says "The deceased temperature difference between temperate and Arctic regions is causing it."

Do Jaiser et al. lean towards the Hadley or the Jennifer Francis view?

Allen W. McDonnell

Long lecture by Jennifer Francis Phd. at the climate summit 2012
and this year 2013

I found her lecture's to be both informative and persuasive. Be prepared for a long listen if you want to hear the whole thing, I watched it a couple months ago while doing a long workout and it still wasn't done when my timer ran out so I had to finish it later lol. The 2012 lecture is about the Arctic Paradox, the second is about Sea Ice and Jet Stream dynamics.

Klon Jay

Storm seems to be having some effect in thickness.


Geoff, Hi,

You’re "a politician"… it is so hard to fathom the inclination of a discours.

I’ve given Jaiser et al a short glance and was occupied this evening further compiling decadal (10 day) 500Mb images, filling in troughs/ridges in an attempt to get a grip on what’s going on up there.

So I have to give a superficial answer; Jaiser et al have cleared a different pattern over two periods and thus conceive a relation between planetary wave propagation and sea ice cover. It could very well match to Dr. Francis'work

I’ll get into the piece soon.

From my 500Mb compilation, I’d like to express the obvious late SSW through March, the linear set-up in April (effectively shutting Atlantic influx) and especially the late May deep inclination of geopotential height (deep = ca. 150 m), concentrated over what we knew as PAC-2013.

It looks like a pinwheel with the ridges/troughs as spikes and a Rohrschach-like Polar cell.

How anomalous is it???
How does it transfer energy???

Jon Hurn

No recent open thread so thought this one was the next best as it was probably triggered by the recent stormy weather.

Melt pond emptying captured during the past few days at the North Pole Environmental Observatory, National Science Foundation NPEO webcam #2.
You have to drill into the archive at the foot of the page http://psc.apl.washington.edu/northpole/NPEO2013/webcams1and2.html to see it as the “latest images” on that particular page are not so latest. Between late evening 27th July and early morning 28th the pond level abruptly dropped. The ablation poles in the last image before the emptying are under water, and then in the next frame are totally exposed leading to a drop in excess of 80cm (I think I read somewhere these show 10cm gradations).


Would this type of event result in (1) an increase in sea ice area measurement due to the pond no longer being “seen” as water, and (2) a decrease, increase or no change in measured ice thickness?

Jai Mitchell

Fascinating. I think that this year's jet stream activity (or lack of defining activity) is a new reality. I have been flabbergasted at the number and propensity of blocking highs and cutoff lows. It seems that there hasn't been a U.S. weather map that did not show some kind of cut-off low pressure, high altitude energy in it.

This is almost historic now. I would bet that if they extended this data through 2013 then these values would basically blow up on the charts.

Still, a pretty good read.


Measurements of the movement of the jet streams at mid-latitudes,
in the Northern and Southern Hemispheres, 1979 to 2010
R. D. Hudson


On re-arrangement of the atmospheric cells...
I've given it a shot based on some NCEP/NCAR data.
It's on the Forum

I'm sorry, it's become quite long since I thought it best to insert some illustrations with my line of thinking...

Whether this season the ice gets the headlines or not... this system is reacting!

[fixed the link; N.]



I'm more of an unpaid political lobbyist than a politician but I have made some important contacts. Looking forward to you considered opinion ... or any further comment.

Allen McDonnell

I think a big part of the uncertainty is that we are approaching or very close to a tipping point, so the climate is entering a period of instability. If we push the climate hard enough we will pass through the tipping point and settle into a new quasi stable regime, or if we quickly stop using fossil fuels we will back away from the tipping point and things will return to say 1950 regimes.

This makes predicting weather almost impossible on a year by year basis because any two years can be divergent. That doesn't mean we shouldn't try and figure things out, but I believe the uncertainty will remain very high until we either stop perturbing the system or flip it into a different state.

Climate changes in the geological record are always presumed to be caused by long slow processes, but even in the long slow change pattern the actual step change from one state to the next is fairly abrupt. Most epochs are defined by an extinction event that makes geological dating of the strata distinct from the prior layer. Because most extinction events took some time to effect the entire species there is uncertainty about he exact dates, the key species may have persisted for thousands of years in some favorable climate spot after it died out everywhere else for example. Over geological time scales the climate uncertainty effect would be a gradual shift from one state to the next and the unsettled period would be spread out over many generations, but the human CO2 impact is incredibly fast. Current CO2 levels would be normal for a northern hemisphere in the single cell configuration, but in the course of a natural change it would take thousands of years to increase as much as we have done in 250.

Between 20,000 ybp and 12,000 ybp CO2 increased from around 180 ppm to 275 ppm. Over those 8,000 years 2/3rds of the ice sheets on the whole planet melted. From 1760 to 2010 humans changed the CO2 from 275 ppm to 395 yearly averages. The system has not had time to react to this very rapid change, especially considering he rate of change has been going up the whole time. If the change had occurred over a geologically rapid 8,000 years as it did at the end of the last major glaciation there probably wouldn't be much ice left in Greenland by now and the climate patterns wouldn't be so chaotic as the tipping point approaches. The way things stand now the CO2 forcing is in strong conflict with the albedo forcing, if the change had taken thousands of years the albedo would have smoothly decreased as the CO2 forcing increased.

John Christensen


Thank you for the link to the article in Huffiington Post (in your entry of 7/26).

However, I was amazed that one of these scientists, Matthew Asplin, has found that cyclones "are usually stronger in winter", which is incorrect, and also that he claims the ice "is thinner and weaker" than last year in August, which is also incorrect.

We know this cyclone has held up SIA and SIE numbers in a significant way, and it will be interesting with the August PIOMAS update to see what happened with the volume..

John Christensen

Sorry, but I cannot resist the urge to clarify:

Beaufort was gone a year ago, while current SIA is about 20kkm2 below norm:

CAB was 500kkm2 lower last year:

We have three times as much ice in Laptev compared to a year ago:

And we have 390kkm2 in ESS rather than about 250kkm2 a year ago:

Only Chukchi had perhaps 15kkm2 more ice last year, so since we know from the last PIOMAS update that average thickness is higher as well this year, the reference in the article is for the Chukchi Sea alone perhaps?

However, I was amazed that one of these scientists, Matthew Asplin, has found that cyclones "are usually stronger in winter", which is incorrect

Is it? I was under the impression that Arctic storms are much more intense during winter.



"if we quickly stop using fossil fuels we will back away from the tipping point and things will return to say 1950 regimes."

When we stop the emission tomorrow, the current trends in sea level rise and temperature change are going to continue for probably a couple of decades, just to respond to the current 400ppm CO2 level (and I am not mentioning the temp rise due to the change in aerosols when we stop emitting them).
The CO2 concentration was around 310 in 1950; it is my understanding that it will take very long (>100s of years?) for nature to get us back there.

John Christensen


From everything I have read, while the winter storms are truly terrifying due to the temperatures, there are less of these, they do not go as low and do not span as wide areas as summer cyclones.

Please share if you have articles or other material pointing to the opposite.

John Christensen

On highs and lows:


So Asplin is mixing cyclones (taking place during melting season and typically over ice-covered seas) with polar lows (taking place during winter over open water).

The polar lows during winter are typically centered around either the Aleutian Islands on the Pacific side or Iceland on the Atlantic side, while the high Arctic is dominated by the Beaufort High and the Canadian Archipelago High (anticyclones) during winter.

The polar lows require arctic cold air to pass over warm open water, so are not likely to take place in the CAB.

Wikipedia and many other sources do not define the split between cyclones and polar lows as clearly as NSIDC, but due to the difference in how these are formed, and where they occur, I would agree with NSIDC on this.

Kevin O'Neill

John, Matthew Asplin's area of interest is Arctic Cyclones. His PhD thesis was: Cyclone Forcing of the Ocean-Sea Ice-Atmosphere Interface

A Cyclone’s central barometric sea level pressure reflects its intensity. Cyclone intensity is considered a key property of cyclone strength, and the intensity of cyclogenesis can be characterized by the change in a cyclone’s intensity over a period of time. Summer cyclones are found to exhibit little regional variability in mean central pressure and are typically 5 – 10 hPa weaker than their winter counterparts (Serreze et al., 1993). Zhang et al., (2004) classified relative seasonal cyclone intensities by regional origin (Fig. 7)

He works with and has published with Dr David Barber:Fracture of summer perennial sea ice by ocean swell as a result of Arctic storms


John, I don't have the time to do a proper search, but I did remember this piece on Climate Central from a couple of months ago (which I re-blogged), and there it says:

A study published in Geophysical Research Letters looks at no fewer than 19,625 Arctic storms and concludes that in terms of size, duration and several other of what the authors call “key cyclone properties,” the Great Cyclone was the most extreme summer storm, and the 13th most powerful storm -- summer or winter -- since modern satellite observations began in 1979.

So if the Great Arctic Cyclone of 2013 was the most extreme summer storm, but still came in 'only' 13th, this would imply that winter cyclones are much more frequent and intense. The GRL paper probably has more info on that.

I can't remember what I wrote in my piece on persistent cyclones (I have a terrible memory, because of my Internet addiction and doing too many different things at once), but maybe there's some info here too.

Allen McDonnell


Based on the lecture series by Dr. David Archer and his book The Long Thaw the CO2 will drop off by 50% over three centuries. That is half the slug added by humanity, but after that the ocean is saturated to equalibrium with the atmosphere. To drop from 400 half way to 280 only gets you down to 340, but in essence if we could stop adding today we would stop making it worse. Even better the drop would be steeper at the beginning and slow down as h 300 years went by.

However we all know humanity isn't going to stop releasing CO2 tomorrow or in all likelyhood any time before fossil fuels run out.

John Christensen


Yes, you are correct, but as always the devil is in the details: The data in the Geophysical Research Letter is based on the broad definition of 'Arctic', which includes winter storms caused by polar lows in the Atlantic (originating between Greenland and the Faraoe Islands) or in the Pacific (originating around the Aleutian Islands).

Your reference from the 'persistent cyclone' entry specifies the central Arctic Ocean as the area of interest for their research, and here is where they find that cyclonic weather events are much more frequent in summer than in winter. The cold of winter and lack of humidity simply do not support very strong lows, but rather the typical highs over Beaufort and the CAA.


It only makes it so much worse that this is his field of expertise. Look also at the claim that the ice is thinner this year.. How can e.g. Beafort be thinner than last year where it was completely gone before GAC-2012 kicked in? But his press release has certainly made the rounds - plenty of papers eager to announce an ice-chewing cyclone.


I see what you mean, John, it could very well be that storms are more intense and frequent during summer in the Central Arctic.

To be fair, the ice was thinner in the Beaufort Sea at the end of winter (CryoSat, SMOS, PIOMAS all agree there), but because of weather conditions it's probably thicker now, or at least, there's more of it than last year.

John Christensen

Yes, if he was making a March to March comparison I would agree, allthough the quote is:

"The effects of (the storm) are nowhere near what we saw last August," said Asplin. "But because the ice is thinner and it's already been pre-conditioned, and because there's less volume, it's much more vulnerable to impacts from this sort of thing."

Well, things can slip, and it certainly make the article more interesting and the event seem more extreme.


Allen, Jai, Jon, Kate, Sam, SH, Steve, Tenney, Werther and others

Thank you all indeed for keeping this thread open at such a high level.

After re-reading most of the background material you provided, I feel encouraged to try to tie a few knots on the Hothouse issue.

1) We have been sweating here in Denmark for the past few weeks. The reason is quite obvious from this link: http://synoptic.envsci.rutgers.edu/site/sat/sat.php?sat=nhem&url=../imgs/wv_nhem_anim.gif . There has been a more or less constant advection of warm and moist air masses from the Caribbean. Since about a week ago, it has even been possible to follow the same air mass advection all the way to around Svalbard. Essentially this constant flow of latent heat has been an example of the one-cell system, you have been discussing over the same period.
2) Concerning the two-cell configuration, I think there may be a connection between the persistent Arctic spring low (http://neven1.typepad.com/blog/2013/06/on-persistent-cyclones.html ), which - to my knowledge - was a cold-core feature, which actually led to strong warming aloft and “convection” over the North Pole. It may - or it may not - be a coincidence, that PAC-A Jun13 ended around the 16th of June, at which time the two-cell configuration of the Jet Streams was most clearly developed (around the 17th June as described here: http://www.popularmechanics.com/science/environment/climate-change/how-the-dual-jet-stream-sparks-this-weird-summer-weather-15634917#ixzz2XRu4pxGC ). We may thus have seen a rare glimpse of future – but temporary - two-cell configurations including all the havoc associated with this type of extreme event.
3) Since the appearance of the second persistent cyclone (PAC-B Jul13), we have essentially had a weak and chaotic jet stream configuration, although with some persistent features - such as recurring cut-off lows - and ridges dominating the picture. This pattern has provided more persistent and predictable extremes, although the impacts - in the long run - may seem more severe, when you consider the big unknowns related to the thawing of permafrost, methane releases and soot deposition in the Arctic (see a fresh example here: http://earthobservatory.nasa.gov/IOTD/view.php?id=81736 ).

To sum it all up, I support the view, that a major tipping point wrt. the global circulation systems has been reached this year. It will be critical to examine in detail the forthcoming third persistent Arctic cyclone (PAC-C Aug13 to appear next Wednesday) to see how long this embryonic single cell configuration continues into the autumn. In most recent years (e.g. 2012, 2010-06 and 2003), the autumn “shoulder” in the DMI Arctic Mean Temperature graph (http://ocean.dmi.dk/arctic/meant80n.uk.php) has been at a level well below freezing. Should it happen this year, that the “shoulder” sticks out close to freezing, we may be able to identify a mechanism, through which a perennial ice-free Arctic may be sustained.

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