Poof, it's gone

One of the reasons for setting up the Arctic Sea Ice Forum, was to increase interaction and make more space for visual gems that do not fit the narrow comment section of this blog (check out for instance the Jakobshavn glacier thread).

One of those gems was posted yesterday by commenter epiphyte, who for the past month tracked one single ice floe in the Laptev Sea. What I like about this, beside the visual appeal of the images of course, is that it shows that ice doesn't disappear gradually, but suddenly. That's to say, for those who are watching from above.

Here's epiphyte's explanation of what he did:

It troubles me that so much weight is given to the rate of decline in area+extent as an indicator of the progress of the melt season. I think that this is becoming less and less relevant as the volume distribution becomes more even every year - I.e. you would expect that the year there is an ice-free September, there might still be a very high percentage of the April area/extent in early August.

Here today, gone tomorrow. I'm not saying it's this year - but on the year it happens, it will happen fast - and IMO anyone tracking progress by comparison with past years CT area decline will be very surprised to see it go.

To illustrate what I'm reaching for at I followed the melt progression of a large, high-albedo ice floe under favorable conditions. The image below is a series of snapshots of a ~300km^2 ice floe on the Laptev/CAB boundary  (~79N , 110E) taken from worldview between 01-jul and 01-aug. (see images below). For each image, I counted the number of pixels with > 50% luminosity on a 140x140 pixel array centered on the floe, cut from that day's 7-2-1 Terra/MODIS image.

As Peter Ellis pointed out earlier on the thread - anything you can see on EOSDIS is not slush. The floe we are looking at here is a contiguous, high-albedo (snow-covered?) ~300km^2 chunk of ice at the edge of the pack. It remains so from 01-26 jul. On Jul 27, it becomes a little less bright and loses 10% of its area. Three days later - poof. It's gone.

Click the image for a larger version.

In the meantime, the Arctic seems to be on for some of the most powerful melting weather we have seen this melting season. A prelude of it has already led to most of the Northern Sea Route opening up (just some last ice blocking Vilkitskiy Strait).

How things play out exactly, and what happens after that, will be discussed in the next ASI update.

Comments

[Jim Hunt]

Most interesting Neven. Thanks too to epiphyte for all that hard work.

I've only just posted a picture on your previous post that seems to be relevant here too. Instead of looking at the Arctic sea ice from above there are all sorts of buoys spread across the Arctic measuring all sorts of things about the sea ice they are sitting on.

At the risk of repeating myself, here's British Antarctic Survey ice mass balance buoy 4, currently in the Beaufort Marginal Ice Zone:

Perhaps this helps explain how an ice floe gradually gets thinner, but can then suddenly melt away into nothingness?

[Espen Olsen]

It is not that I want to repeat myself, but I always believed the sea ice will disappear overnight, in the same way lake and river ice behaves.
So what Epiphyte discovered I totally agree upon, despite what other say about slush, in this phase it behaves like slush, no matter the size of it.

[D]

Ice on the interior of the pack doesn't go poof overnight because the ice around it buffers both the air and the water temperatures. Ice goes poof on the margins because it is melted from above and below.

The pressure and wind patterns are setting up for a low just south of the Kara sea and high pressure over the Arctic. This will enlarge the large area of open water in, and north of, the Laptev sea. The present ice distribution is capable of losing area fast because ice has piled up on the islands on the Atlantic isde of the Arctic. Storminess in the Barents sea could mix in a lot of warm Atlantic water that has pushed into the Barents sea below the surface. A sudden melt event is possible in part of the Arctic now, but not the on the cold Canadian side of the N pole.

[PrévisionsMeteo Belgique]

Probably Peter Wadhams was saying the same thing when he was interviewed by the BBC :

http://news.bbc.co.uk/2/hi/7139797.stm

"In the end, it will just melt away quite suddenly. It might not be as early as 2013 but it will be soon, much earlier than 2040."

And in an email to The Guardian he predicted an ice free Arctic toward the end of this decade :

http://www.theguardian.com/environment/2012/sep/17/arctic-collapse-sea-ice

"This collapse, I predicted would occur in 2015-16 at which time the summer Arctic (August to September) would become ice-free. The final collapse towards that state is now happening and will probably be complete by those dates".

It seems he thinks that Arctic will do a 'poof it's gone' like this floe. An ice free Arctic in 2015 or 2016 is perhaps a bit short, but there is a real possibility that sea ice will go 'poof' in a short time.

[iceman]

On a geological time scale of "poof", we're already at the first "o".

[wayne]

PrévisionsMeteo Belgique, the preceding point when this will happen must the North Pole Ice free, so one must wait for this step. The ridging Ice pack, where the thickest ice remains, must be surrounded by water for this to happen as well. Ice in small packs melt far more faster than large ones, as this proof above shows. There has to be lots of warmer sea water about enveloping the moving ice, so no chance for the pack to create a colder sea water from the shade it makes.

[Neven]

What would the chronological prerequisites be for large parts of the Arctic to go poof towards the end of the melting season?

Perhaps something like this:

1) Previous melting season ending low
2) Mild winter, lots of transport
3) Very sunny start to the melting season from May to mid-June, lots of melt ponds and deformed snow
4) A couple of strong cyclones dispersing the ice pack from mid-June to end of July, causing holes in the ice pack
5) Lots of insolation and heat from mid-latitudes during August, with large parts of the ice pack breaking off (like we saw in 2012)
6) Then, as a bonus, perhaps a big GAC-2012 type cyclone at the end of August

Would that be the perfect melting season for getting the Arctic close to ice-free?

I find Chris Reynolds' writing with regards to the Slow Transition very convincing, but at the same time (still) think that one freak year could get the Arctic very close to ice-free. Remember, CT SIA was down to 2.2 million km2 in 2012. That's just 1.2 million km2 shy of the ice-free definition.

So one question is whether we will see that slow transition now that most of the multi-year ice is gone. The other question is when a freak year occurs. Is it a 1-in-20-years event? 1-in-50? 1-in-100? It's impossible to know. And even if we did know it, we wouldn't know if the effects of Arctic sea ice loss are distorting these statistics.

Either way, I posted this because I liked the idea that there are things we don't see when looking from above (something I tend to forget). I might try and post something on Chris Reynolds' Slow Transition idea, but I'd have to re-read everything everyone wrote about it on Dosbat and the ASIF, and my brain is still somewhat occupied with wood, screws, electric cables and water pipes. ;-)

[Colorado Bob]

Cracker Jack work epiphyte

[Colorado Bob]

Arctic Emergency: Top Scientists Explain How Arctic Warming is Wrecking Our Weather and Pushing World To Rapidly Cross Climate Tipping Points

(Must-watch video that includes direct observation and analysis of Arctic tipping points provided by a number of the world’s top climate scientists.)

You don’t want to mess with Arctic warming. It’s an engine of destruction straining to be set loose. A mad burning beast of a thing. One whose fires we are now in the process of stoking to dangerous extremes.

Don’t believe me? Then just listen to top scientists like Dr. Jennifer Francis, Dr. Jason Box, Dr. Jeff Masters, Dr. Natalia Shakhova, Dr. Igor Semiletov, Dr. Peter Wadhams, Dr. James Hansen, Dr. Steve Vavrus, Dr. Ron Prinn, Dr. Kevin Schaefer, Dr. Nikita Zimov, Dr. Jorien Vonk, and a growing list of many, many more (also see above video).

http://robertscribbler.wordpress.com/2014/08/04/arctic-emergency-top-scientists-explain-how-arctic-warming-is-wrecking-our-weather-and-pushing-world-to-rapidly-cross-climate-tipping-points/#comment-19626

[Colorado Bob]

"What would the chronological prerequisites be for large parts of the Arctic to go poof towards the end of the melting season?"

Neven
I would add large fires burning around Arctic Ocean burning deep into tundra, to yoor list.

[Colorado Bob]

UPDATED: Nine volunteers were rescued on Monday afternoon after they’d been trapped for over an hour by the flames of the worst fire in Sweden’s modern history.

The fire began on Thursday in Sala, Västmanland, central Sweden. It is unclear how the fire began, but the flames now engulf somewhere between 5,000 and 10,000 hectares.

Emergency services trying to control the fire have called it the “biggest fire of modern times” in Sweden.

“It’s burning deep down into the ground and across large surfaces,” fireman chief Per Hultman told newspaper Expressen. “It’s going to take months to extinguish.”

http://www.thelocal.se/20140804/five-day-forest-fire-rages-out-of-control

[Neven]

Thanks for that, CB. Will re-post that video tomorrow.

[Colorado Bob]

Note what the fire chief said , "It's burning deep into the ground." This fire behavior in the far North I have been watching for 7 years now. The trees are not the only thing burning now , the fires around the far North are burning 5 and 6 feet into the Earth. In the poorest combustion conditions one will ever see. The same kind of poor combustion , killed 58,000 Russians when their peat deposits burned in 2010 around Moscow. These fires make really , really nasty smoke.

[fredt34]

I had exactly the same reaction about Waddhams and "at the end it will melt away quite suddenly". It will be Poof Day, or Poof Year.

Neven, I think you describe exactly the sequence of events which may or will lead to this catastrophe. So far they didn't happen in this sequence - but if I'm right, all these events happened at least once in the, say, 5 or 10 last years. So it might just be a matter of being unlucky... but I think we're already at Step 1.

[Ostepop1000]

Espen Olsen, you say:

"It is not that I want to repeat myself, but I always believed the sea ice will disappear overnight, in the same way lake and river ice behaves."

This is irrational.

Lake ice does not disappear overnight. It slowly thins during spring.

So does ice on rivers.

Thick river ice will usually be gradually undermined by warm water until it breaks up and gets flushed downstream.

There is no difference when it comes to Arctic sea ice.

It melts when the conditions get adverse, and it grows again when conditions eventually turn around again.

It is simple.

[Jim Hunt]

The Sala fire is visible using Aqua MODIS, via WorldView:

[Hans Gunnstaddar]

"Don’t believe me? Then just listen to top scientists like Dr. Jennifer Francis, Dr. Jason Box, Dr. Jeff Masters, Dr. Natalia Shakhova, Dr. Igor Semiletov, Dr. Peter Wadhams, Dr. James Hansen, Dr. Steve Vavrus, Dr. Ron Prinn, Dr. Kevin Schaefer, Dr. Nikita Zimov, Dr. Jorien Vonk, and a growing list of many, many more (also see above video)."

CB, where's the link? The one provided goes to something else.

[Hans Gunnstaddar]

Sorry, CB, didn't find it at first. It turns out the link is at top, so for everybody that hasn't gone to it yet, scroll all the way up to the top to find it. Thanks.

[Ostepop1000]

2014 still trailing above 2013.

http://ocean.dmi.dk/arctic/plots/icecover/icecover_current_new.png

The turnaround continues.

As expected.

[epiphyte]

"Would that be the perfect melting season for getting the Arctic close to ice-free?"

epiphyte here - (Can't figure out how to use my favorite pseudonym on this blog... Ah, well...)

It seems to me that there might already be enough energy in the mix to melt all of the ice - but the many antagonistic mechanisms playing tug-of war across the balance point make modeling even the day-to-day outcome pretty much chaotic.

In other words, the closer we are to the boundary between ice and no-ice, the harder it becomes to know in advance on which side of it we are going to end up at the end of the season.

[aside - maybe this could be part of the reason that the ECMWF and GFS medium range models have been doing so poorly this year]

Neven's list of prerequisites looks as good as any to me - but I'm a rank amateur. Even to a professional the last straw might come from somewhere unexpected.

If I was being Machiavellian I might add something to reduce the previous winter freeze - e.g. have the previous season end with very low volume but high area, and extent higher still, with much open water scattered throughout the whole arctic.Start the winter with a big storm to get the surface salinity up, then a dead calm + short deep freeze to get a skin of salty ice on the surface, quickly followed by a couple of feet or so of dry powder to insulate the water underneath.

On the tail end of the next melt I'd want a just what Neven suggests - another big storm - something to stir in as much sub-arctic and deep water as possible.

[Ostepop1000]

[snip]

Edit Neven: Last warning. You behaved appropriately so far. I don't know what is ticking you off all of a sudden.

[Jim Hunt]

Not on CT Area Ostepop. As predicted!

http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html

For further details please see:

http://GreatWhiteCon.info/2014/07/shock-news-breathtakingly-ignorant-deranged-blogger-batting-1000-this-summer/

[Ostepop1000]

Fair enough Neven.

Was just pointing out unreasonable and unsupportable viewpoints.

[Neven]

It was a bit short, Ostepop. And not very friendly. And the Arctic shows time and again that none of us know and understand enough about to say something conclusive. Which means that some of our viewpoints will always turn out to be unreasonable and/or unsupportable. And this, of course, should also have implications for risk management. Especially given the trends so far.

What, according to you, would the melting season look like that gets SIA below 1 million km2? How would large parts be there for weeks and months on end, when viewed from above, and then suddenly go poof towards the end of the melting season? I'm not asking when, I'm asking what that particular season would look like.

But I'll do a separate blog post on that subject some time.

[Ostepop1000]

Jim Hunt:

So on average we are equal to last year.

My bet is we will surpass last years arctic sea ice.

I will wager:

A bottle of norwegian beer.

Up for the bet?

[Jim Hunt]

Why does everyone want to challenge me to a bet today?

Specify things more tightly please. Which metric for example? I presume you mean the minimum, but it would be nice to have it in writing.

I only have West Country cider here I'm afraid. I prefer charitable donations to booze at the end of the day.

[Ostepop1000]

"What, according to you, would the melting season look like that gets SIA below 1 million km2? How would large parts be there for weeks and months on end, when viewed from above, and then suddenly go poof towards the end of the melting season? I'm not asking when, I'm asking what that particular season would look like.

But I'll do a separate blog post on that subject some time."

First of all I think it is a great idea to ask all of your followers this exact question.

The answers will no doubt be both diverse and enlightening in both a spiritual and a scienitific sense.

[Ostepop1000]

West country Cider?

Somthing you made yourself, fermenting under the planks of your seldom visited biathouse?

No thanks.

[Ostepop1000]

"What, according to you, would the melting season look like that gets SIA below 1 million km2? How would large parts be there for weeks and months on end, when viewed from above, and then suddenly go poof towards the end of the melting season? I'm not asking when, I'm asking what that particular season would look like.

But I'll do a separate blog post on that subject some time."

These are the biggest ICE KIllers:

- Transport through the Fram would be NR. 1.
- Transport of warm air through the Chukchi.
- Movement og ice from Canada/Greenland towards Russia/Svalbard, where it melts.

- High pressure with blue skies and sun.
- Low pressure with rain and no sun.
- Cluded, dry weather.

[Ostepop1000]

http://www.youtube.com/watch?v=qBvnJpDR-1Q

[Espen Olsen]

I migth be irrational, but where I live Scandianavia, of course ice do thin during the spring, but in the end of that process it suddenly disappear overnite, in most cases. And since we watch sea ice from above (from satellites)it will look the same way!

[wayne]

Epsen, its not unreasonable to witness ice simply melting fast in one day, its a matter of sea ice temperature, sea ice can actually look solid, white, not dark, and just crumbles to pieces from something of weight above it. Likewise under the ice may appear solid, but can be in such a fragile state a mere touch make the bottom layer vanish instantly . Generalizations such like "this doesn't happen" is due to lack of experience or study from the commenter. As far as spiritual implications in a computation of sorts please comment about that at WUWT, I am sure they welcome such acts of faith.

[Chris Reynolds]

Thanks Epiphyte, and thanks to Neven for re-blogging. I don't see this as having any impact on the fate of the whole pack though, such rapid disappearances are not uncommon.

PIOMAS volume holds no surprises, now above 2007.

[Gideon Low]

"This is irrational.

Lake ice does not disappear overnight. It slowly thins during spring"

Oste, the concept here is very easily understood as "rational". Hopefully, boiling it down to these points makes it easier to understand:

1. An expanse of ice reaching the end of the freeze season at certain close to uniform thickness.

2. Factors driving the rate of melt conspire to melt the expanse at a relatively even rate.

3. During most of the melting, this expanse of ice holds together. The expanse then reaches the critical threshold where it very rapidly disintegrates and melts across its entire area at nearly the same time.

Epiphyte has clearly already shown us one excellent example of this.

The greatest impediment to this scenario is finding an expanse of ice whose freeze and and subsequent heat influx (melt) distribution is close to uniform. And what body of water is far and away most likely to meet such a condition? Why, a lake! Even a fairly big one is quite likely subject to very similar weather across its area throughout the freeze and melt cycle. And, the fact that the ice is confined by immovable shores helps to keep it intact until it is quite thin.

Barring (often only localized) factors such as streams and rivers emptying into the lake, the most rational conclusion must be that the expanse of a melting lake does typically reach the "critical" threshold between intact ice and no ice at about the same time. The mobility (and probably also albedo change) that occurs once break-up does begin only accelerates finishing the job quickly and dramatically.

Having myself grown-up in Northern New Hampshire, I have seen lakes and rivers very quickly go from 100% coverage to 99% clear with my own eyes. My experience is that same lakes regularly exhibit this melting behavior—more frequently when the threshold is reached during strong melt conditions. The "breaking of the ice" (whether lake or river) is in-fact a much celebrated annual event as the harbinger of Spring in many northern communities.

Oste--One should be careful about throwing-around words like "irrational" when in a personal frame-of-mind that might be considered, well, at least a bit erratic. It comes-off like pure projection.

It would have been much easier to pick on the likelihood of the entire remaining pack going (to use the non-technical term) "poof"--you would need only to refute the possibility of this remnant pack experiencing the combination of rapid enough melting coinciding with relatively homogenous thickness/strength.

I think us "rational" readers all recognize that the larger an expanse, the smaller the chances of a very sudden transition from very high concentration to nearly none. So there's that . . . But, is such a scenario really so outlandish? Perhaps not.

Even having studied this subject only as an amateur and only for a limited time, I feel confident in stating that the chances of such an event are steadily increasing. The trend is clear enough: average ice thickness is decreasing, average ice thickness is becoming more uniform (mainly 1st yr ice), and average summer melting is increasing. These are exactly the trends most favorable for enabling an "overnight" (or close to that) melt-out of a quite large remnant ice pack. Will it happen? Only the Arctic knows. Is the notion "irrational"? Far from it. I hope this is O-1000% clear(ly rational)!

One last thing: I'm pretty sure it was here on Neven's blog where somebody posted a time-lapse video of their local lake melting-out in a very short period of time (I think here because I think it was before Neven started the separate forum, but I could be wrong). I'll bet somebody else reading this either posted that video or will know where to find the link :-)

[Gideon Low]

[Your wish is my command - Mod]

[Otto Lehikoinen]

there's the ~70% area limit commonly seen near area/extent edge, that looks to be a potential limit for this to happen, once the Central Pack gets to this limit the clearance could happen any week, of course not saying it couldn't happen with larger concentrations.

[seattlerocks]

Ostepop, Espen,

Sustained freezing during winter and melting during summer are gradual processes. However, the transition from freezing to melting is abrupt, especially when a wave of warm temperatures comes in Spring and sustains the environment about melting point for more than a few days. Change of phase is a pretty non-linear process, right? Phase state as a function of temperature is a square-wave shape. And weather patterns are also non linear right? Temperatures do not rise up linearly during Spring (usually)

[seattlerocks]

How do I edit here? I should say abrupt instead of "non-linear", and gradual instead of "linear".

[Jim Hunt]

Ostepop,

"No thanks"

Is that to the bet, the booze or the charitable donation?

[P-maker]

Gents ( and remaining ladies…)

Sitting here on the Normandy coast with a cold beer helps to clarify your thoughts and systemize your reflections.

Experiences from a long list of field experiments in the Arctic puts some of your remarks above into context. Here are my main views:

1) The potential rapidity of melt is a reflection of the ice formation process
2) The mixed bag of current Arctic sea ice qualities precludes any robust statements about a “poof” this year
3) The future may guide us to a more clever risk management approach

Ad 1) The Russians have a wonderful word: “Naled” (pronounced naljot! I believe). It is a type of ice which is formed in the middle of winter, when freshwater breaks to the surface. In Greenland, I have seen this type of ice formed in front of a glacier, when late summer melt water eventually emerged from underneath the front and spread out over a lake already covered with ice. The vertical ice crystals were > 0.5 m long and 2-3 cm across – like a white, clear and crisp version of columnar basalt. During the summer “heat” (0-5 C), these columns would tumble down in front of your eyes. In less the a day half a meter of solid ice may disappear, if the formation process is of this type.

Ad 2) As A-team has so vividly demonstrated on the Forum, glacier ice at the bottom of the Jakobshavn Isbræ is a mélange of various sorbet types. It is evident that the crystals in this type of glacier ice consist of all kinds of tiny, agile, flexible and scalable pieces. Above this dynamic zone near the bottom of the glacier, you will find clear, cold, crisp and big ice crystals. I believe that x-ray pictures show these to be 2-3 cm across. Thus when you walk down the glacier, your boots will meet melting ice similar to glass in the beginning and then, when you start walking into sorbet ice, the sound from your boots change immediately. Thus the history of deformation of the ice will also make an imprint on the ice quality. Apparently small and big ice crystals melt at the same rate on the surface, so it is not easy (apart from the sound) to say whether you have crossed the line.

Ad 3) As time goes by, we will have to await how the Arctic sea ice is formed in the next few years. Some of it will be based on “flash freezing” – leading to amorphous ice - like when a cold katabatic wind comes off the Greenland ice sheet in the autumn. Some of it may be formed from regular “plate ice”, as we have seen in open ocean situations over the years, and some of it may be of the “Naled”-type, if the Greenland ice sheet delivers freshwater on top of already formed sea ice in the middle of the winter.

I think I’ll go to the beach now and see the tides come in.

Cheers P

[George Phillies]

And now the end-of-July PSC graph shows we are still more or less at the long term declining trend, while today's (8/5) Bremen picture shows extensive areas of partial coverage. On the scale of the Bremen image, the Northeast passage is now open, though at one point the opening is really narrow and close to shore. The Northwest passage is still closed on the scale of the Bremen map.

[Chuck Simmons]

I would add a few possible scenarios to the Ice Free pre-requisite possibilities.

How about a cold low sitting over the mouth of the MacKenzie in the Spring so that an ice dam keeps waters warming in the south for longer than usual leaving a 2014-laptev-like hole early in the season?

How about a nice rainstorm and flooding in the Lena watershed in late spring to gush water earlier and in greater volume into the Laptev.

How about a mild storm in late August at the edges of the arctic to blow tall waves across the open sea, cracking the far ice and making it more mobile.

I like the point someone made about the soot. Soot that would end up on top of multi-year ice.

And a nice hot high sitting over the northern Archipelago for a week might do wonders for the thick ice.

[Pete Williamson]

Pre-anthro-forcing did ice melt differently?

[Jim Hunt]

Ostepop,

I had yet another wager suggested to me today. This is all getting rather tiring, so I'm preparing a "challenge" of a slightly different sort. Please see my initial report on the showing of "Thin Ice" at Free Cinema Exeter this evening, over on the Arctic Sea Ice Forum:

http://forum.arctic-sea-ice.net/index.php/topic,578.msg33420.html#msg33420

[epiphyte]

Chris Reynolds writes:

"Thanks Epiphyte, and thanks to Neven for re-blogging. I don't see this as having any impact on the fate of the whole pack though, such rapid disappearances are not uncommon.

PIOMAS volume holds no surprises, now above 2007."

...Please don't get me wrong. I wasn't trying to say that thin ice in favorable conditions is disappearing any more rapidly than it has in the past.

I'm just trying to illustrate the argument that as the pack grows more uniform in thickness, more fragmented and diffuse in extent,more mobile and more subject to incipient energy from outside the arctic, the larger the fraction of the remaining ice that is at risk of melting at any given moment.

PIOMAS is a case in point. From what I can see, almost everywhere PIOMAS modeled a significantly lower June-July melt anomaly in 2014 vs. 2013 is now open water - which makes me less inclined to rely on it as a guide to what's coming next.

[Chris Reynolds]

Hi Chris,

Ahh, I didn't realise your are Epiphyte, good work. I was initially confused as to why you were addressing me!

I'm a bit lost by what you say above, surely if the thinner ice than 2013 has melted out that supports PIOMAS volume/thickness?

Anyway, there is a fairly fundamental limit to the volume of ice that can be melted.

Consider the following graph.
https://farm4.staticflickr.com/3856/14548870398_4ae3450902_o.png

I did it to show how unusual a total melt out from an average 2m thickness of the pack in April would be, for completeness I'll go over that, but for now...

The graph shows the difference between the start and end data of successive ten day periods from January through to December. This is basically the rate of change of sea ice volume. Note how it dips around the summer solstice and peak around the winter solstice. It is worth comparing it with insolation in the Arctic.
http://2.bp.blogspot.com/-k_S7N0VlMRg/UH4RNvJ3cjI/AAAAAAAAFjk/lqjQhGqLWOk/s1600/insolation_latitude.gif

It is clear that what drives the seasonal cycle of sea ice volume is insolation.

Looking at the years listed on the graph, years in the past are deeper blue, lighter blue in recent years. Now take, say, 20 June, which is the difference between 11 and 20 June. Within that band of blues are all years from 1979 to 2014, you can see that from 1979 to 2014 volume loss in the period 11 to 20 June has increased. Early melt season losses have increased significntly, but later in the summer volume loss has decreased.

My point is that insolation drives the annual cycle. Things like albedo affect the amount of sunlight absorbed, but the changes these factors have are small. Note that what drives the long term trend of volume loss need not necessarily be linked to what drives the seasonal volume loss.

The red plot was intended to show a possible scenario where by an April volume of 19.3k km^3 could be reduced to zero by September.

Yes, rapid melt out of peripheral ice floes happens. It does happen on a large scale in models, in the PIOMAS model when ice in April is thinned by 1m across the pack the Arctic Ocean is virtually sea ice free by the end of July. But at present with ice thickness of around 2m for much of the pack (more in the coming winter) the rate of progression of melt is limited by available insolation and the mass of ice that needs to be melted to give largescale ice free conditions early enough for the Central Arctic to have time to experience large extent loss.

[Chris Reynolds]

Pete,

"Pre-anthro-forcing did ice melt differently?"

Good question. I'll think about it.

Things that come to mind...

Define 'melt' - do we mean the seasonal cycle? Obviously with regards multi-decadal trend the ice hasn't always been declining. Yes there have been recent changes to the seasonal cycle.

The holocene climatic optimum when the ice was probably in a worse state than in summer 2012. But that was caused by increased summertime insolation, not a global warming that was year round and affected night time temperatures as well.

The Barents Sea and Atlantic ice edge has been declining since at least the early 1900s. When did anthro-forcing start to have an effect?

[Blaine]

Here's a centered link to the particular referenced floe, so people can play with stepping back and forth. The floe is blown first a bit north and south, so that it absorbs the heat from an ocean area of a 2-3 times its own area, but it's still clear that the area of the floe must be decreasing much more sharply than its volume. Surface imagery is not terribly informative about thickness, particularly when the melt is mostly bottom melt and not top melt. At around 25x20km, the floe would all experience roughly the same weather, and barring edge effects would reach zero thickness everywhere at roughly the same time, hence, go "poof".

On an Arctic Ocean-wide scale, obviously the spread in both initial thickness and melting weather is going to be wider, but is still the case that with most of the ice being first-year ice, thickness will converge to near 2m. With good weather, insolation isn't that different, and sometimes a whole lot of this ice tends to melt out at around the same time. I would say August and September of 2012 can reasonably be described as the ice across the Arctic Ocean going "poof". Even as insolation had fallen substantially from its peak and thickness decreases were declining rapidly, extent decreases accelerated to a record high as more and more area hit zero ice thickness at around the same time.

For 2014, with sea ice extent currently well above the post-2007 average (considered "normal" hereafter), I think we have both more area that is about to go "poof" than normal for this time of year, and more area which is clearly too thick to do so, and will survive. The southern parts of the Beaufort, Chukchi, and East Siberian sectors normally melt out, so it's not a surprise to see them melting out this year, even if it's a bit late. The "Marginal Ice Zone" and CRREL bouys, confirm the ice thinness here.

A lot of the ice closer to the pole in these sectors just never had the melt pond albedo feedback I would have expected, despite getting decent sunlight, and still has thick ice as confirmed by, for example O-Buoy #10.

Here's the ice edge in the East Siberian sector, on July 29th and on August 6th. Here's deep in the East Siberian icepack around 76 North on July 29th and on August 7th. Clearly, it's a significant meltback, although not that unusual for this time of year, and the forecast is for continuous Arctic Dipole.

[George Phillies]

The 8/7/2014 and 8/8/2014 Bremen AMSR2 figures for the area north of Alaska and Khamchatka are suddenly showing a remarkable reduction in the ice extent, now down to 50% over impressively large areas. YMMV.

[Jim Hunt]

Here's the current Bremen AMSR2 concentration:

I dont think extent is down 50%!

[George Phillies]

I said: "Now down to 50% over impressively large areas."

Readers can clearly see the *impressively large area*on the pretty color picture.

Looking at the picture, the area is from slightly above 9 o'clock much of the way to 12 o'clock and (if the circles are 5 degrees of latitude each) roughly from 73 to 77 N. That is a huge area of green and yellow (close to 50% coverage) relative to some other periods.

Whether the area in question goes below 15% remains to be seen.

The open Northeast and close northwest passages are both clearly visible.

[iceman]

@ Chris Reynolds
Pete,

"Pre-anthro-forcing did ice melt differently?"

The most recent peak in summertime insolation was around the time of the first anthropogenic forcing, if it's true that land use changes from agriculture and grazing affected climate. By the time of the industrial revolution, it had dropped off at the higher latitudes. We're lucky we didn't "poof" all those fossil fuels during a time of increasing insolation.

The graph is from www.realclimate.org; cites Source: Marcott et al., 2013.

[Kevin McKinney]

OT for sea ice, but possibly of interest to some here--I've just published an essay mulling the denialist meme of 'puny humans.'

Comments welcomed--particularly if you spot a mis-statement of some sort!

http://doc-snow.hubpages.com/hub/Puny-Humans-Can-We-Change-The-Course-Of-Nature