When will the Arctic Go Ice Free?

[crandles]

The more I think about it, the less I am able to see why there should be a stall in melt, whether it's the minimum we focus on or the annual average (which I believe is still trending downwards - when did I last see a graph showing the annual average? - Gerontocrat has a running 365 day average which is definitely tending down, but annual calendar year average?)

• Loss of MYI should cause a speed up of melt.
  

Agreed.

Now if the loss of MYI slows down again?

Has/Will the loss of MYI slow down? Well it can only decline at a fast rate for so long at some point it has to slow down because it cannot go negative. I can see scope for it slowing down near current levels per posts above.
[/list]

[Tom_Mazanec]

A FFA would be a sign of a paranormal incursion into our spacetime, heralding the appearance of zombies, yokai, vampires, and MIBs. 

[crandles]

A FFA would be a sign of a paranormal incursion into our spacetime, heralding the appearance of zombies, yokai, vampires, and MIBs. 

Doesn't even depend on what. With those threats, perhaps I would argue against 1+1=2 

[Tor Bejnar]

When I studied computers before they were personal, I learned that 1+1=10.   

[oren]

Binntho, you keep saying once the MYI is gone FYI loss should accelerate. This does not necessarily follow. As crandles explained very well above, once the MYI is gone or shrunk considerably, there could be a new equilibrium of FYI, on a smaller area, but losing it only slowly. FYI near the pole manages to survive the current strength of the melting season, and if some of it is gone, next winter will grow it back. The ice is still on a downward trend because of growing heat content all around, and because freezing seasons are shorter and warmer, but ice area loss is not expected to accelerate. Chris Reynolds covered this very nicely with his "Slow Transition" theory back in 2014, and while I think he was optimistic in his assumptions about the freezing season, I think the basic premise still holds.

[wili]

We are not measuring the same thing as we were ten or so years ago.

Then, we were mostly measuring ice. Now we are more and more measuring slush.

[oren]

Indeed. And one year there will come such weather that will wipe it all away, and we'll have the first BOE. It could have been this year, it could be next year, I expect it before 2030. For a consistent BOE we may have to wait a bit more, maybe another decade.

[Glen Koehler]

      FWIW, the Wipneus linear PIOMAS volume trend chart at
https://sites.google.com/site/arctischepinguin/home/piomas
suggests that by 2029 any individual year would have a 50% chance, by 2032 an 84% chance, and by 2036 a 97.5% chance, of going below 1 million km3 by the end of melt season.

     Given the argument that last phase of CAB will be the toughest to melt out, it would be interesting to graph CAB minimum volume over the years (or is such a graph already posted here and I missed it?).  That eliminates the influence of the peripheral sea contributions that could inflate loss rate relative to rate when the remaining late season ice is limited to CAB.  But it would also remove the effect of that ice in those peripheral seas has provided to protect CAB ice from open water melting effect (I think, not too sure about that).  Therefore, CAB rate of loss could increase once it loses that surrounding ice earlier in the melt season.

     The argument that the final CAB ice is at higher latitude does not seem to completely apply because the end of season CAB ice is not centered around North Pole, but is centered at lower latitude of triangle between NP, northern Greenland and northern edge of CAA. 

     Way above my knowledge, but my gut says that reinforcing feedbacks of wave action, open water albedo decline, fractured ice, increased exposure of remaining ice to transport currents, winter cloudiness or other factors giving weaker refreeze seasons, increasing SST (and with it increasing chance of GAC), and of course the ever increasing GHG levels in the atmosphere and monotonic warming-- esp. as 2 year lag in currently bottomed-out solar cycle starts to push temperatures up starting around 2023 -- will take a toll on the ice.  And by the late 2020s ENSO cycle could be trending towards El Nino phase adding even more push to surface warming (though I have no idea how surface air temperature effects from ENSO relate to SST and impact on ASI.  But at least it gave me an excuse to use 3 acronyms in the space of 8 words).   The point is, all those feedbacks working together seem likely to be more than enough to overwhelm any increased resistance of the final CAB core to melt. 

     And I suspect that measurement errors introduced by higher percentage of "rotten ice" are inflating reported extent values and thus suppressing the more recent rate of decline.  The remaining CAB doesn't look like a resistant pack, just a bunch of aggregated chunks.  All pure conjecture of course.

   The NASA animation up thread shows the Pacific side of ASI being an overwintering stronghold of MYI before 2007, taking a big hit in 2007 but recovering, taking another big hit in 2012, but coming back a bit in 2013-2015, then taking a third big hit in 2016 and not coming back after that.  Of course 3 years may be too short to say it won't come back, but with the one way trend of lessening ASI I doubt it will.  The loss of the Beaufort nursery seems to be a functional system change with major impact.  The MYI chart updated next spring could bring dramatic news on the MYI story, showing the virtual extinction of the oldest categories.

   Extent is declining less rapidly than Volume, but eventually will have to catch up it as both get closer to zero for September minimum (because 0 Volume forces 0 Extent).  Given the difference in trends between Ext. and Vol., it is important to specify which is being referred by BOE, though I guess the "official" definition is Extent.  By the time Volume gets close to 1 million km3, Extent should have mostly caught up, though I can also imagine a future with almost all FYI that by end of melt season still has large Extent but is approaching zero thickness and thus zero volume. 

    Even though 2019 is falling into 3rd or maybe 4th place for Extent, it is a solid second place for volume and will likely finish only about 200 km3 and about 5% above 2012 (and slightly below the Wipneus straight line trend).   As for 2019 Extent minimum, it is not over until the fat lady sings, and while she is standing close to the exit, she is still on stage. Given high SST and recent/forecast weather, a late finish such as 2007 looks very possible.   

[binntho]

Binntho, you keep saying once the MYI is gone FYI loss should accelerate. This does not necessarily follow. As crandles explained very well above, once the MYI is gone or shrunk considerably, there could be a new equilibrium of FYI, on a smaller area, but losing it only slowly.

I must admit that I didn't understand the explanation that crandles put forward, and I wasn't sure if we were talking about the same thing:

• Loss of MYI should cause a speed up of melt.
  

Agreed.

Now if the loss of MYI slows down again?

When I said "loss of MYI" i meant "when all MYI is gone" as in post 2012 (and I know that it isn't all gone, but there is so little of it left that it makes no difference).

But crandles seems to understand me as saying "while the MYI is melting, ice loss accelerates", understandable given how badly I formulated my self, but not what I was trying to say.

FYI near the pole manages to survive the current strength of the melting season, and if some of it is gone, next winter will grow it back. The ice is still on a downward trend because of growing heat content all around, and because freezing seasons are shorter and warmer, but ice area loss is not expected to accelerate.

That last bit about ice area loss not expeced to accelerate. Not expected by whom? And as opposed to say volume or extent?

Anyway, I'd like to try to explain a little better why I find it counter intuitive that the rate of extent loss should slow down once MYI is gone. Or another way put this is, why can one use the loss of MYI to explain the slower trend in extent minimum (or even possible flatlining) since 2012 2007/8.

Every year the ice melts, and melting uses up a hell of a lot of energy (heat) and is facilitated by mechanical factors (waves, drift etc.) And every year the ice grows back (FYI) and the bits that didn't melt that year becomes MYI.

In some earlier era, MYI kept increasing every year so you'd have 5 year or 10 year or even 20 year old MYI or even much older - as long as the Arctic ice was increasing in volume every year (which I guess would have been ongoing upt to the beginning of the last century, given that Arctic glaciers were increasing up to that point as well) then every year more MYI would be trapped.

Volume propably started to decrease about 100 years ago or even later, but at some point during the last century the annual increase would turn to a decrease in volume. Summer extent starts to fall around the middle of the century as well (https://www.carbonbrief.org/guest-post-piecing-together-arctic-sea-ice-history-1850).

So since the middle of the last century apparently this historical baggage of MYI starts melting out, and since only so much heat is available every summer, the melting of MYI was in competition with the melting FYI.

The MYI baggage meltout finished in 2012 or thereabouts. But every year the available heat keeps increasing, and now that all the historical baggage is gone, FYI melting no longer has any competitors other than the "normal" MYI from the previous year. And since melting a km3 of FYI takes less energy than melting a km3 of MYI then melt should even accelerate (if that difference in melt energy is significant - I've no idea).

And finally for the kinetic part, as we all know FYI is brittle and fragile and since we have larger areas of open water every summer now, and no tough MYI to withstand the battering, the remaining FYI should be melting ever faster.

[binntho]

Chris Reynolds covered this very nicely with his "Slow Transition" theory back in 2014, and while I think he was optimistic in his assumptions about the freezing season, I think the basic premise still holds.

I find that Chris's theory is very convincing, but isn't it mosly about the regrowth of ice in autumn? Every year, the ice grows very fast to cover the whole Arctic with, on average, 2m ice (at a total volume of about 19 MKm2).  The dynamics of the Arctic are such that this will continue for quite some time, even after our first BOE.

My thoughts have mostly revolved around extent, and particularly about the minimums (although the average annual and the running 365 day average are also very interesting). And it all started because some people maintained that the annual minimum had stalled since around 2010.

But not only that, the same people jumped on a rather naive (and erroneous) attempt at an explanation based on a supposedly major flaw in the science of meteorology. Which made me think that they had no better contenders.

And since then, having thought about it, I have come to the conclusion that there is only one underlying force that we can rely on, i.e. the steadily increasing global (and particluarly Arctic) temperatures. All the various explanations for a hypothetical stall do not hold water. The two most common are "loss of MYI" and "loss of the periphery" or something along those lines, but to my mind that should produce exactly the opposite effect!

So claiming a stall since 2010 does not hold water, neither statistically nor, to my mind, physically.

Therefore I have made (and will make again) my prediction that the SIE minimums will continue to fall by about 0.8 Mkm2 every decade. In the 20's the minimums will mostly fall between 3 and 4 Mkm2, in the 30's between 2 and 3 - and when the numbers become that small, a BOE event will become quite likely.

And finally in the 40's, a BOE should be an almost annual event. Which of course means that I don't belive in linear projections any more than most other people. We may be experiencing a linear trend (or as close to as we can tell), but at some point it's going to plunge downwards as far as summer extent is concerned.

As Chris Reynolds says himself:

by a slow transition I do not expect the summer sea ice to last into the 2050s, I suspect that around 2030 we will see the first summer with an extent of less than 1 million km^2.

[Stephan]

     

     Given the argument that last phase of CAB will be the toughest to melt out, it would be interesting to graph CAB minimum volume over the years (or is such a graph already posted here and I missed it?).  That eliminates the influence of the peripheral sea contributions that could inflate loss rate relative to rate when the remaining late season ice is limited to CAB.  But it would also remove the effect of that ice in those peripheral seas has provided to protect CAB ice from open water melting effect (I think, not too sure about that).  Therefore, CAB rate of loss could increase once it loses that surrounding ice earlier in the melt season.

   
[...]

   Extent is declining less rapidly than Volume, but eventually will have to catch up it as both get closer to zero for September minimum (because 0 Volume forces 0 Extent).  Given the difference in trends between Ext. and Vol., it is important to specify which is being referred by BOE, though I guess the "official" definition is Extent.  By the time Volume gets close to 1 million km3, Extent should have mostly caught up, though I can also imagine a future with almost all FYI that by end of melt season still has large Extent but is approaching zero thickness and thus zero volume. 

   

Glen,
thank you very much for this interesting posting, which comes very close to my opinion.
I also played around with a "division" of CAB form all the other seas for a separate BOE evaluation. Unfortunately I also miss monthly volume data of CAB to perform this evaluation. If there is a source for that information please give me a link or a data file. I will asap make this BOE estimation for the CAB with these data (and by calculating the difference "Arctic (total) minus CAB" I will get the sum of all the other seas, which then can be "BOE evaluated" as well).

[binntho]

Perhaps I should venture to add that I also agree with Glen's posting. 

A few thoughts:

     And I suspect that measurement errors introduced by higher percentage of "rotten ice" are inflating reported extent values and thus suppressing the more recent rate of decline. 

A very reasonable suspicion. It's quite possible that the minimums will continue to stubbornly avoid dropping because of increased dispersion caused by a more fractious ice.

    Even though 2019 is falling into 3rd or maybe 4th place for Extent, it is a solid second place for volume and will likely finish only about 200 km3 and less than 5% above 2012 (and slightly below the Wipneus straight line trend).   As for 2019 Extent minimum, it is not over until the fat lady sings, and while she is standing close to the exit, she is still on stage. Given high SST and recent/forecast weather, a late finish such as 2007 looks very possible.

And volume is after all what we should be looking at, not SEI, if we want to know how fast the ice is melting.

[oren]

There is a regional daily volume file published by Wipneus on the PIOMAS thread every time the data is updated. I can make a chart tomorrow if no one else posts it by then.

[Archimid]

I hope this is what you want to see. CAB loses from the max to the end of August is lowest highest on record but by a very small amount.

[crandles]

When I said "loss of MYI" i meant "when all MYI is gone" as in post 2012 (and I know that it isn't all gone, but there is so little of it left that it makes no difference).

But crandles seems to understand me as saying "while the MYI is melting, ice loss accelerates", understandable given how badly I formulated my self, but not what I was trying to say.

I realised that you were drawing a different conclusion to me and I wanted to point out the difference.

It isn't a complicated argument, but you don't seem to be getting it, so I will try again with a few more words.

When MYI is rapidly declining, there is your cause for other effects to follow via albedo feedback and therefore for extent decline to follow the MYI decline.

You seem to be ignoring the point than once the MYI decline slows down substantially you are removing the cause so the effects should also largely cease, though if there is lots or inertia in the system the effects may continue for some time before ceasing.

Removing sea ice in models has it recovering within a couple of years so there isn't much inertia in the system. So removing the cause should make the effects cease.

So returning to you arguments:

Loss of MYI should cause a speed up of melt. MYI is "stored" ice from previous years and takes a hell of a lot of energy to melt out. Once it's gone, the FYI should melt all the faster.

Once the MYI has leveled off, all the 'FYI should melt faster' effect has already happened and you are left with little decline in MYI and FYI so this causes little increase in FYI melting faster.

2. Melt-out of the peripheral seas also has the potential to speed up melt

Again, once you have lost the cause of fast changes, you are left with marginal changes.

[El Cid]

I attach CAB piomas volume until 2019/06 (havent updated it in the last 2 months but it doesn't change the big picture).
This is not really going anywhere since 2010

[dnem]

Maybe better for Stupid Questions but is there a way to bin up extent by coverage for each grid cell?  Rather than just totaling up every grid >15% and calling that "extent", get a frequency distribution of grids by coverage? E.g. 0-15%, 16-30, 31-45 etc.?  Wouldn't that help address the "extent method is making the decline in ice quality" argument?

[binntho]

When MYI is rapidly declining, there is your cause for other effects to follow via albedo feedback and therefore for extent decline to follow the MYI decline.

You seem to be ignoring the point than once the MYI decline slows down substantially you are removing the cause so the effects should also largely cease,

I'm not getting this at all. The effects (albedo feedback etc.) are not caused by MYI rapidly declining,  but by the entire ice pack declining.

So once MYI is gone, that fact alone has no effect on albedo and what have you. Besides the MYI decline slows down because there isn't any MYI left, and the melt moves all the more vigorously against the rest if the ice.

[binntho]

Removing sea ice in models has it recovering within a couple of years so there isn't much inertia in the system. So removing the cause should make the effects cease.

You presumably mean "there is a lot of inertia in the system", since the Arctic just keeps freezing up every year.

And removing the cause of what effects? What does melting of MYI cause that melting of FYI does not cause? And what effects are these, that are caused by MYI melting and not by FYI melting?

I feel that you are turning things totally on their heads: Global warming causes melting, while the ice has a high proportion of MYI then a lot of MYI will melt, but ice sill melts every summer - more and more as the temps goes up. And once the MYI is all gone the FYI continues melting.

So returning to you arguments:

Loss of MYI should cause a speed up of melt. MYI is "stored" ice from previous years and takes a hell of a lot of energy to melt out. Once it's gone, the FYI should melt all the faster.

Once the MYI has leveled off, all the 'FYI should melt faster' effect has already happened and you are left with little decline in MYI and FYI so this causes little increase in FYI melting faster.

Why and how did "allt the FYI melt faster" happen - and why are we left with little decline? You claim that we are left with this or that, where is the argumentation for it, what are the physics that suddenly slow down melting just because the hardest-to-melt ice is gone?

2. Melt-out of the peripheral seas also has the potential to speed up melt

Again, once you have lost the cause of fast changes, you are left with marginal changes.

What cause of fast changes are you talking about? The rapidly warming Arctic? Has that stopped? The increased wave activity, the increased storminess, has that stopped?

Saying things like this is meaningless, crandles, if you do not describe a physical causality. Which is what I have been doing, and you just answer with contentless claims such as "once you have lost the cause of fast changes, you are left with marginal changes".

Word salad, nothing more.

[Comradez]

It just occurred to me today that, while this stall in sea ice area and extent declines that we have seen in August and early September 2019 may be frustrating for those of us who predicted a lower minimum this year, this year's melt chronology and the sort of shallow, saucer-shaped trajectory of sea ice area and extent is sort of "ideal" from the standpoint of encouraging heat accumulation in the arctic.  The peripheral seas opened up very early and started soaking up the sun not long after the summer solstice, resulting in sky-high accumulated albedo warming potential for this season, but the CAB has been resistant to melting.  Consequently, not as much heat will be lost from the CAB now that the sun is setting.

By contrast, a pattern of melt that would not favor heat accumulation would be where declines in June, Juy, and early August are sluggish, but where the arctic witnesses a sudden spurt of melting in late August and early September from bottom-melt and wind-driven processes, after the sun has already become ineffective. 

2012 was more of the second type of melt chronology, and I bet the GAC ended up venting a lot of heat from the ocean...perhaps accounting for the rebound of ice coverage in 2013.  I would not expect a similar sort of rebound this time around in 2020.  Quite the opposite, in fact.  Next year will have even more melting momentum.  I anticipate the Bering and Chukchi seas will be especially fragile and prone to melting unprecedentedly early.  I question how far south the ice will even get in the Bering Sea this winter...

[SteveMDFP]

. . .2012 was more of the second type of melt chronology, and I bet the GAC ended up venting a lot of heat from the ocean...perhaps accounting for the rebound of ice coverage in 2013.  I would not expect a similar sort of rebound this time around in 2020.  Quite the opposite, in fact.  Next year will have even more melting momentum.  I anticipate the Bering and Chukchi seas will be especially fragile and prone to melting unprecedentedly early.  I question how far south the ice will even get in the Bering Sea this winter...

+1

[Glen Koehler]

     Thanks El Cid and Archimid.  What I want to see is annual minimum volume (not loss from max, though that too is interesting) with straight line trend extended out 20 years.  (I know, extending trendlines past data range is fraught with potential error, but less so for straight line and certainly worth looking at.)

      To harp further on the Wipneus annual volume graphs (they are not written on a stone tablet from Mt. Sinai, but are worth attention as predictors IMHO):

1.  The annual minimum graph is lowest single day volume.   The Wipneus average volume chart for all the months shows average monthly volume, not single day min. for each month.
(also at https://sites.google.com/site/arctischepinguin/home/piomas
       For September the volume is nearly flat across the month, so the average monthly value is  almost the same as lowest single day annual minimum.  Thus, going below 1M km3 could be a multi-day event, not just a single day.   

2.  But the day after refreeze begins, some idiot will say the ASI is recovering.  The all-months volume graph shows August and October reaching the September value about 3 years later.
 Thus (combining this with the straight line graph for annual minimum), August and October could reach 50% chance of going below 1M km3  by around 2035, and 84% chance by 2039.  Open water in September won't change ocean water heating much, (and may even allow faster cooling) because solar radiation is so low after August 15.  But having the average August volume below 1M km3 would be a much bigger effect on insolation and SST, at least for the first half of August.
   {Wipneus - if your'e listening, can we have the all-months graph with straight line trends?}

3.  Torturing the data a little more shows that July and November track behind September by about 12 (Nov.) and 13 (July) years.  Adding 13 years to the Sept. values gives 50% of less than 1M km3 in JULY and November around 2045, and 84% chance around 2049.  Now that really gets us into hot water.  Literally, at least in comparison to pre-warming Arctic SST.  There is plenty of sunlight in the Arctic in July at a pretty decent impingement angle for solar warming.

4.  Extending my ignorance one more step, there is already talk that more open water in fall is affecting winter weather patterns.  If so, then if/when the Arctic is essentially ice free (i.e. < 1M km3) in November, the effect on winter weather patterns would seem to be much stronger.  Even though polar air masses should be a warmer by then, having the North Pole send its cold air over me in eastern U.S. is not a happy thought.  I had pipes freeze last year that cost me serious $.  Ironic to pay a bill like that because of global warming. 

5.  More important is the effect that such swings (if in fact they increase with Arctic warming as per Jennifer Francis et al.) can have on agriculture and other sensitive systems.  When the jet stream pattern lands to the east or west of the eastern U.S., instead of pulling polar air down, it can pull tropical air much farther north than usual, giving a freakishly warm extended period in winter or spring.  This happened in 2012.  Apple budbreak is remarkably stable between years despite big swings between cold and warm winters and springs, varying within no more than +/- 7 days between years.  That was until 2012 when we not only broke the previous earliest budbreak record, we broke it by 3 WEEKS.  Absolutely unprecedented in records as far back as anyone had.  Then after the early start, the last frost occurred at a relatively normal time, by which time the buds were far advanced and thus much more susceptible to frost.  As a result, growers in New England, PA, NY, and esp. MI lost their crop.  And not for first time in recent years. 

     So all this ice volume number crunching eventually turns into effects on the food we eat and other tangibles.  That's why we should let our politicians know in no uncertain terms that no climate change mitigation policy = no money and no vote for them.  And annoy our family, friends, neighbors by harping on the climate crisis.  it took all of us to screw this up and it will take all of us to turn it around.  That requires it being a topic of regular conversation, not just the latest altered weather report by Trump.  (By the way, what gets lost in that fiasco is that his misreprensentation of the hurricane track could have lulled people on the U.S. east coast into thinking that the danger was not heading towards them when indeed it was.  Though by now I think even the red-hat gang knows not to put much credence in the factual reality of his ramblings.)

[Shared Humanity]

Maybe better for Stupid Questions but is there a way to bin up extent by coverage for each grid cell?  Rather than just totaling up every grid >15% and calling that "extent", get a frequency distribution of grids by coverage? E.g. 0-15%, 16-30, 31-45 etc.?  Wouldn't that help address the "extent method is making the decline in ice quality" argument?

Dispersion at the end of the melt season  captures this and dispersion is increasing.

[Stephan]

I played around with the area and extent data from NSIDC.
I separated the CAB from all the other seas ("Rest") and plotted the August averages from 1989, 1999, 2009, and 2019 (to keep it simple I used only four years, hoping I did not do any cherry-picking by that selection). The resulting graphs and the calculated BOEs (individually performed for CAB and for the "Rest") are quite surprising and may explain to some extent the different opinion in this forum about a stalling of the annual sea ice minima in the past years and whether a linear, a log or a Gompertz fit may represent the data best.

Facts: The area and the extent of CAB in August changed only very slightly. Applying a linear fit will leave this part of the Arctic Ocean ice covered until the year 2383 (area) or 3796 (extent; in this case the slope is very very small).
On the other hand the "Rest" is declining fast and almost linearly. BOE of this part of the Arctic Ocean can be expected for 2031 (area) or 2040 (extent), respectively.

If I combine all seas the BOE (linear extrapolation) will be around 2065-2070 (area) or 2085-2090 (extent), respectively. See my posting from Sep 06. (Reply #1080)

What I need is the regional volume chart of the CAB. I guess with the loss of most of the MYI which used to be concentrated in CAB the BOE will occur here much earlier than only extrapolated by extent. Asap I have the data I will generate a comparable chart.

See attached graphs

[crandles]

You presumably mean "there is a lot of inertia in the system", since the Arctic just keeps freezing up every year.

No I meant not a lot of inertia.

And removing the cause of what effects? What does melting of MYI cause that melting of FYI does not cause? And what effects are these, that are caused by MYI melting and not by FYI melting?

I feel that you are turning things totally on their heads: Global warming causes melting, while the ice has a high proportion of MYI then a lot of MYI will melt, but ice sill melts every summer - more and more as the temps goes up. And once the MYI is all gone the FYI continues melting.

GHGs, ocean temp increases are slow effects that continue throughout periods we are considering
Air temp changes are mainly caused by ice extent decline, but there may well be some two way causality.

The fast changes are:

Melt thick (over equilibrium thickness) MYI and it doesn't come back in winter. Compare with FYI which might melt faster in summer (saltier, thinner) but the vast majority of it comes back each winter. So year on year the change when melting FYI is slow. If it keeps coming back, you are not making much progress. (old Navel saying: A stern chase is a long chase)

Approaching the state change MYI in the Beaufort gyre that happened to be in East Sirberian/Laptev over the summer may have thinned over the summer but didn't melt out and then got thickened by compresssion over winter and other parts of Beaufort Gyre.

When the slow thinning reached point where MYI did melt out in Laptev, then things moved quickly, the area, age and thickness of the MYI rapidly fell til vast majority of MYI is only in Western Arctic. This has knock on effects - because East Sirberian/Laptev had more FYI, it melts out every year and sooner allowing albedo feedback to get to work. So extent decline follows the MYI decline.

These effects are conditional on MYI declining at a fast rate. When the MYI stops declining at a fast rate then the knock on effects of faster melt out, albedo feedback, increased storminess remain in place. However, we have already had all these effects in the last few years. Therefore the difference of this year to previous years in now down to just the slow effects (GHGs and ocean temperatures).

Not sure how else to describe it.

[Archimid]

but the vast majority of it comes back each winter.

But what if the ice stops coming back, like the Barents, Bering and Chukchi are suggesting?

[crandles]

but the vast majority of it comes back each winter.

But what if the ice stops coming back, like the Barents, Bering and Chukchi are suggesting?

What is reason for it not coming back?

Weather? = noise, will probably return to normal.

A long period of slow changes to GHGs, ocean temperatures? Yes over a long period, you will get cumulative small slow changes.

Something else?

What makes your question any different from saying 'But what if sun doesn't rise tomorrow' ?

[crandles]

Had a go at Tamino's method on PIOMAS volume.

My adaptive seasonal pattern is just average of 49 dates, 3 days before/after and 3 years before/after.

I am sure this can be done in a better way.

Haven't managed to optimise 6 parameters for 3piece linear trends.

Root Mean Square Error (RMSE) for 4 parameter Gompertz at 0.94 is noticeably better than linear trend at 1.25 but has 4 parameters rather than 2 so it should be better.

RMSE for 3 piece linear looks like it will be similar to gompertz fit but has 6 parameters rather than 4

[oren]

As requested, the regional CAB volume chart. I have chosen to provide several charts at once, each one for a different date, as the dynamics are different between the various months. (Scroll to the right for the scale).
Thanks to Wipneus for the data.

I think these charts show very well a major change in the CAB in the last two decades, with early season volume dropping from ~12.5 to 10 and below, and late season volume dropping from ~8 to ~4. A downward trend is obvious and the end obvious as well - a BOE. On the other hand, a semi-flattening is also evident since the 2010 crash, with new minima still being created (2017, 2019) but with the overall rate of decline much lower than it was in the first decade. Some will protest this semi-flattening, but a look at the graph until 2012 explains why there were expectations of an imminent BOE within a few years, while now expectations are more tempered.
Chris Reynolds came along in 2013 (or 2014?) to postulate that winter volume will plateau when most of the Arctic Ocean will be FYI that grows to the same thickness every year, with summer losses growing slowly due to increase in overall energy, and thus the reduction in volume (and hence area and extent) will be "slow" - a decade or two until a BOE, rather than an imminent crash.
A look at the early season chart shows that the postulation was only partly right - the winter of 2016/2017 showed that the freezing season is not a constant, with the plateau broken by a whole 500 km3. (Charts for the whole Arctic Ocean show the same breakdown). CAB thickness was lower that winter at 2.2m compared to 2.3m-2.7m in previous years mainly dependent on the preceding melting season (2.3 after 2012, 2.7 after 2014). 2016 had a middling thickness during the melting season, but crashed to a record low since the beginning of October due to poor refreeze. I expect such winters to happen again and frequently, thus the "slow transition" should be "medium transition". A confluence of a bad winter season 2016/17-style and a bad summer season 2012-style could get a near-BOE any year now, with chances growing each year as AGW marches on.

[Tor Bejnar]

I mostly skimmed the last 24 hours of posts in this tread, and think you all all missing a very important piece, that being export of ice, especially MYI out of the high Arctic (roughly 83N to the pole).  For 'ever', export of MYI into the Atlantic was the major method of losing MYI, not Arctic melting.  Once upon a time, export from the high Arctic into Beaufort Sea (and then back into the CAB) was a loop for making MYI thicker, but that changed a decade ago or so, and now all the peripheral seas are killing grounds. 

This past year (or at least the first six months of the past year) saw much transpolar movement of ice (per A-Teams graphics posted in May 2019), basically exporting North Pole ice, and the North Pole receiving ESS ice (or course, it got thicker along the way).  I think the most cohesive ice remaining in the Arctic is between the North Pole and the Atlantic.  If what happened this past year happens again, this remaining cohesive ice will be exported. 

It used to take a decade to export 'all' the MYI (and therefore a decade available to replace it) now it looks to me like it is mostly an approximately 2-year process.  Still, ice near the North Pole at the start of the melt season pretty much doesn't seriously melt (although it moves towards the Atlantic some) and does not turn to slush (as ice does elsewhere)

[oren]

Indeed Tor you are absolutely correct, I meant to write something about it and then forgot. It's not just a question of available energy for melt in the CAB, but also one of the ice moving to where it will eventually melt.
MYI is continually exported, mostly down the Fram and some to Nares, Barents and Beaufort. It is supposed to be replenished by newly named MYI that managed to survive a season or a few. But the replenishment is much lower than it used to be, and a mobile winter (as 2019 had) can actually reduce MYI rather than add to it.

[petm]

Indeed, MYI is already largely a thing of the past...

[binntho]

Thank you for your excellent post, oren!

[binntho]

A couple of days ago I was complaining about not remembering having seen (or if having seen, where I had seen) any graphs showing the calendar year averages for SIE.

Then I woke up this morning realising that I could just make them myself from NSIDC monthly data. So here they come, both for extent and area.

Instead of taking the calendar year, I took September - August. So the first datapoint is Sept. 1979 to Aug 1980, and the last point is Sept. 2018 - Aug. 2019.

Two major points arise: The fall shows no stall at all since 2012 or 2007 or 2010 or whenever. Neither extent loss nor area loss is stalling. So any and all attempts at explaining the now missing stall by talking about mysterious MYI speed-melting etc. are hereby null and void.

The second major and, for me, mystical point is the sharp rise in area in mid- to late 1980s. This has me completely mystified, so I've included a version of the graphs where area prior to 1988 is ignored.

Making a linear extrapolation from the two linear trends from the bottom graph gives me 0 average extent in 2187 and 0 average area in 2176. So let's wait and see!

[oren]

Surely it's the dreaded pole hole, which for some reason is added to NSIDC's extent numbers but you need to add it manually to their area numbers...

https://nsidc.org/data/g02135?qt-data_set_tabs=2#qt-data_set_tabs
Check out the user guide tab. Look under heading 4.2.3

4.2.3 Arctic Pole Hole
4.2.3.1 Relevance of the Arctic Pole Hole to Ice Extent and Ice Area Values
Due to orbit inclination, the satellite-borne instruments that collect the brightness temperature data that go into creating the Sea Ice Index do not image a circular area over the North and South poles. This area is referred to as the Arctic pole hole. With three different generations of instruments, there are three different Arctic pole hole sizes through the time series. See Table 8.
To account for these holes in the spatial coverage of the data, three Arctic pole hole masks are used, one mask per instrument. They are termed masks because they are overlaid onto the input GSFC and NRTSI ice concentration data by the Sea Ice Index processing code prior to calculating ice extent and area. The holes are significant because, in calculating Northern Hemisphere monthly ice extent, it is assumed that the entire region under the Arctic pole hole is covered by ice at greater than 15 percent concentration. In calculating Northern Hemisphere monthly ice area, however, the region under the Arctic pole hole is not included. Because of this, there is a discontinuity in the time series of
38
Northern Hemisphere ice area recorded in the Monthly Sea Ice Extent and Area Data Files. This discontinuity, or apparent jump in ice area, occurs in August 1987 when the data source changes from SSMR to SSM/I and in January 2008 when the SSM/I Arctic pole hole mask changes to the SSMIS Arctic pole hole mask. Although SSMIS data begin in 2007, the smaller SSMIS Arctic pole hole mask is not implemented until 2008 to allow for a year of intercomparison between the SSM/I and SSMIS data streams.

[binntho]

Thanks for that oren! So with the dreaded pole hole covered, here are the latest results. Still no stall at all.

EDIT but the linearly projected 0 area now falls in 2164 (as if ...)

[oren]

Two major points arise: The fall shows no stall at all since 2012 or 2007 or 2010 or whenever. Neither extent loss nor area loss is stalling. So any and all attempts at explaining the now missing stall by talking about mysterious MYI speed-melting etc. are hereby null and void.

An annual average of the whole NH SIE can be an excellent tool but in this case it combines several trends and may gives the appearance of saying something that it doesn't.
The adjacent seas inside the Arctic Basin (Chukchi, Beaufort etc.) are melting earlier each year. This causes the annual average to drop.
The peripheral seas outside the Arctic Basin (Bering, Barents etc.) have lower extent in winter. This causes the annual average to drop.
However, the CAB trend in summer is what drives the chances of the first BOE. This is masked in the annual average. I recommend separating the outer seas in total, the inner seas in total, and the CAB, and focusing not just on the annual trend but also on specific month trends.

[binntho]

Two major points arise: The fall shows no stall at all since 2012 or 2007 or 2010 or whenever. Neither extent loss nor area loss is stalling. So any and all attempts at explaining the now missing stall by talking about mysterious MYI speed-melting etc. are hereby null and void.

An annual average of the whole NH SIE can be an excellent tool but in this case it combines several trends and may gives the appearance of saying something that it doesn't.
The adjacent seas inside the Arctic Basin (Chukchi, Beaufort etc.) are melting earlier each year. This causes the annual average to drop.
The peripheral seas outside the Arctic Basin (Bering, Barents etc.) have lower extent in winter. This causes the annual average to drop.
However, the CAB trend in summer is what drives the chances of the first BOE. This is masked in the annual average. I recommend separating the outer seas in total, the inner seas in total, and the CAB, and focusing not just on the annual trend but also on specific month trends.

I agree (almost) totally. My exercise has not really been to try to predict BOE but to show that a stall in melting in general has not taken place. I believe the same can be read out of your graphs from your posting #1128

But I did make a monthly analysis (but still of the whole dataset) as can be seen below. The decline in March is only half that of the decline inSeptember, and the large variations (and percieved stall) mostly appears in the late summer/autumn data (August, September, October), and the least exciting month seems to be June!

As for the not total agreement: I don't think looking at the CAB isolated from the other seas is going to say any more about when a BOE will happen. My argument is the same as re. MYI - once the peripheral seas start to melt out earlier, the CAB will start melting seriously. But dividing the CAB from the Periphery is besides totally artificial. It's all just ocean with ice on it, and the ice is melting from all directions.

[binntho]

And here is the area version. A few surprises: September and August follow each other very closely with a big gap up to July and October which again are very similar, and an even larger gap up to June and November, again in close agreement.

I guess the difference between this graph and the one for extent above says something about dispersion (presumably, that dispersion goes radically up during summer - but then we all knew that), but it raises the question: Is despersion on the increase during the summer months?

Stay tuned!

[oren]

As for the not total agreement: I don't think looking at the CAB isolated from the other seas is going to say any more about when a BOE will happen. My argument is the same as re. MYI - once the peripheral seas start to melt out earlier, the CAB will start melting seriously. But dividing the CAB from the Periphery is besides totally artificial. It's all just ocean with ice on it, and the ice is melting from all directions.

I agree, the inner seas will drive the CAB. The earlier they go, the higher the chances of a
CAB crash.

[Archimid]

What is reason for it not coming back?

Global warming due to GHG generating greater heat intrusions into the Arctic Ocean combined with a warming Arctic.

faling to come back Weather? = noise, will probably return to normal.

You think the changes in the Bering and Chukchi are due to weather?

A long period of slow changes to GHGs, ocean temperatures? Yes over a long period, you will get cumulative small slow changes.

Ok. Small temperature increase over a long time causes small changes. True. But do small changes cause further small changes, or do small changes cause large changes? Sadly the answer is both. Small changes can cause further small and large* changes. On top of that, all systems have a saturation point. Some of them gradual, some of them sudden. Do you really don't know this?

 The earth has been warming unnaturally for 100 years, very strongly in the last few decades, extremely strong in the last few years. Earth systems are already changing, some of them slow, some of them sudden. Everyday the earth warms more system reach saturation points.
 

What makes your question any different from saying 'But what if sun doesn't rise tomorrow' ?

Because, that I know off, there is no object threatening the sun, or the Earth or their orbits, so I'm very certain that the sun will come out tomorrow.  Also, if there was such an object, It is beyond my power to do anything about it.

The Bering, Chukchi and Barents are already seasonally ice free, with the Bering showing very concerning changes in the last two years. The Blob is probably not going to help it this year. SO I have evidence that validates my concern. I also have a real threat, accumulated global warming producing global climate change. And more important, I can do something about it.

*edit

[binntho]

And here comes dispersion - my very own index of area divided by extent (I'll bet nobody ever thought of that one before!)

Dispersion is indeed increasing very rapidly, with August leading the pack.

This time it's July, August and September that cluster around the bottom, with June and October making up the middle tier.

The winner is August 2016 with an index of 0.621, second place August 2011 with 0.62 and third is same month 2012 with 0.627

I was expecting 2012 to stand out more clearly, given the very low minimum that year (which I assumed had at least something to do with the ice being very compact as well as having melted a hell of a lot) but it doesn't.

On the other hand, the constant increase in dispersion will cause the minimums to fall slower than before, and will hide some of the actual ongoing melt from a long term SIE comparison.

[binntho]

One more, this time showing dispersion during the "summer months" of June - November (the months showing any action in the previous graph). This time 2019 is not included, but the three first places are clearly visible (and marked with red, 2007, 2012 and 2016). All three years had very low dispersion on average these 6 months.

Another graph, titled "minimum months" (July, August, September) show the exact same thing. The three prizewinners had exceedingly low dispersion (high compaction) which just goes to show that melting alone is not enough to win prizes!

EDIT:
The amount of rubbish that can be created from a simple but fundamental misunderstanding. The graphs do not show what I said they did, but exactly the opposite.

The three lowest years extent wise show markedly higher dispersion than other years, so less compaction. I was so very much expecting the opposite that I was totally blinded to what the graphs actually show. Now I'm just lost and confused.

[Klondike Kat]

Thanks for that oren! So with the dreaded pole hole covered, here are the latest results. Still no stall at all.

EDIT but the linearly projected 0 area now falls in 2164 (as if ...)

You are averaging stretches of high and low to get your linear fit.  From 1992-2004, you have plotted 13 consecutive years where the extent is above the linear fit, followed by 9 straight years being above the fit line.  Does that not tell you something above the possibility of a change in slope?

[gerontocrat]

I have a bunch of open water graphs, that look at how much open water there is in each sea at various times of the year. I usually only give them an outing at milestones during the year.

But here is the one for the Central Arctic Sea.  Note this is the 3.2 million km2 area as defined by NSIDC, (not Wipneus' 4.4 million km2 CAB). i.e. we are looking at the ocean North of 80 as near as makes no difference.

As one can see, there was a permanent shift upwards in open water in 2007, but no permanent shift after the peaks in 2012 and 2016.

You can also see that there is a long, long way to go to the +70% open water required for a BOE.

Perhaps when surrounding seas such as the ESS and Beaufort lose all ice by early summer we will see a real shift?

[binntho]

Thanks for that oren! So with the dreaded pole hole covered, here are the latest results. Still no stall at all.

EDIT but the linearly projected 0 area now falls in 2164 (as if ...)

You are averaging stretches of high and low to get your linear fit.  From 1992-2004, you have plotted 13 consecutive years where the extent is above the linear fit, followed by 9 straight years being above the fit line.  Does that not tell you something above the possibility of a change in slope?

Nope. I'm not saying there hasn't been an ever so slight change from the linear (and who is to say that it has to be linear rather than something else?) but Occam's razor says go with the simplest explanation, which is that there is what appears to be steady downwards slope and no evidence whatsoever to the contrary.

But overly active pattern matching humans may well be able to see all sorts of fancy stuff in there!

[binntho]

Perhaps when surrounding seas such as the ESS and Beaufort lose all ice by early summer we will see a real shift?

That'd be my guess as well.

[crandles]

Thanks for that oren! So with the dreaded pole hole covered, here are the latest results. Still no stall at all.

EDIT but the linearly projected 0 area now falls in 2164 (as if ...)

You are averaging stretches of high and low to get your linear fit.  From 1992-2004, you have plotted 13 consecutive years where the extent is above the linear fit, followed by 9 straight years being above the fit line.  Does that not tell you something above the possibility of a change in slope?

Nope. I'm not saying there hasn't been an ever so slight change from the linear (and who is to say that it has to be linear rather than something else?) but Occam's razor says go with the simplest explanation, which is that there is what appears to be steady downwards slope and no evidence whatsoever to the contrary.

But overly active pattern matching humans may well be able to see all sorts of fancy stuff in there!

Really?
13 coin tosses in a row come up the same way and you don't see the very low probability of that as being any evidence at all?

5 in a row (4 the same as previous) gives 1 in (2^4) 16 not statistically significant
6 in a row  (5 the same as previous) gives 1 in (2^5) 32 reaches 95% level for being statistically significant.
If there are lots of chances for it to happen, then you may well need 7, 8 or 9 in a row.

13 in a row - not evidence at all ?

[binntho]

Really?
13 coin tosses in a row come up the same way and you don't see the very low probability of that as being any evidence at all?

5 in a row (4 the same as previous) gives 1 in (2^4) 16 not statistically significant
6 in a row  (5 the same as previous) gives 1 in (2^5) 32 reaches 95% level for being statistically significant.
If there are lots of chances for it to happen, then you may well need 7, 8 or 9 in a row.

13 in a row - not evidence at all ?

Evidence of what? That there was an acceleration 2002 - 2007 as Tamino has shown? He used different data (seasonally adjusted daily values) and showed that there was acceleration in 2002, with a corresponding deceleration in 2007 or thereabouts.

But I was talking about the presumed stall in the fall since 2008 or thereabouts which at lot of people have tried to explain to me why happened. But as my graphs clearly show, there was no stall in the fall at all after 2008. So all the various explanation can be tossed on the heap.

And just to remind you - my involvement in this discussion started when somebody tried to explain the percieved stall since 2010 (or whenever) based on a totally erroneous posting, and since I pointed out that a) there was no stall, and b) the explanation was erroneous anyway, a lot of people have used a lot of effort to convince me of the mechanisms behind this stall that they claim is there for all to see.

But - my graphs show a steady decline since 2010 or whatever. No stall. As I stated very clearly:

The fall shows no stall at all since 2012 or 2007 or 2010 or whenever.

[Glen Koehler]

    Folks - we don't need to go around the wheel again about whether the recent apparent flat lining in annual minimum Extent and Area is real or not. (I don't think anyone is arguing that volume has flat lined).  Yes it looks like the trend has flattened out in recent years, and maybe it has.  The point is that given the degree of inter-annual variability between individual data points (i.e. years), the paucity of data points does not provide support for the assertion of a change in long term trend with any acceptable degree of statistical certainty (i.e. less than 5% or even 20% chance of a Type I false assertion error). 

     That said, just drawing a straight line trend through the 1979-2018 Extent data that looks like it points down is not a statistically based conclusion either.  But just from an eyeball view I bet it is significant.  (I know, I know, the hypocrisy is astounding!)  I admit I didn't actually run the tests, I'm too lazy and not enough time to do so, but Tamino has already covered this ground with far more skill than I could.
   
    Tamino has addressed the parallel issue of the so-called pause in global surface temperature warming after the El Nino driven high value in 1998.  I think that controversy is exactly analogous to this discussion about a possible flattening of the ASI Extent trend.
https://tamino.wordpress.com/?s=pause

    One of the best of those blog articles also discuss the same phenomenon at play with ASI https://tamino.wordpress.com/2019/01/07/fooled-by-noise/

   Appearances can be deceiving with noisy data.  As for rolling the dice 13 times, I think that is a false analogy due to the multiple testing problem. Again, see Tamino.

   The ice doesn't care what any of us think it's doing anyway, so let's just wait and see.  But that takes years, and inquiring minds want to know now, so here is a pseudo-answer. 

   I will bet the price of a lifetime subscription to the ASIF that the average of the 2019-2021 ASI Extent, Area, and Volume will each be less than the average of their respective values in 2016-2018.  Even with a statistically significant downward long-term trend, short term noise could lose that bet for me, but I don't think so.  I think too much damage has already been done, with more on the way. I agree with others who have noted that the remaining ice "doesn't look good".