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When will the Arctic Extent dip below 1,000,000 Km^2

2018-2019
12 (17.9%)
2020-2025
21 (31.3%)
2026-2030
13 (19.4%)
2031-2040
15 (22.4%)
2041-2060
2 (3%)
2061-2080
0 (0%)
2081-2099
1 (1.5%)
2100-beyond
3 (4.5%)

Total Members Voted: 62

Voting closed: July 27, 2018, 07:46:32 AM

Author Topic: When will the Arctic Go Ice Free?  (Read 210630 times)

gandul

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Re: When will the Arctic Go Ice Free?
« Reply #1750 on: September 13, 2020, 04:14:13 PM »
It wouldn't be much of a rebound anyways when you consider how thin all of the ice is.

What good is 4 year old ice that's under a meter thick
It’s more resilient than FYI under a meter.

That difference is more academic than practical, at 1m.

Quote
Anyway, the notion that Western CAB ice is homogeneously under a meter thick is misleading.
I can imagine a field of mixed floes of different thickness, surviving tall  ridges, ... the closer to CAA the thicker and older in average.

*Mostly* true, I'll agree, but I think you are overstating  how much of that melange is actually MYI and of significant thickness.

Quote
The region between the NP and the Beaufort sea has suffered surface melting but has stayed relatively protected compared to the other side of the NP. It stayed substantially colder during July even when it was 24/7 under the sun.
Now this 1 millon km2 of extent has several years of being stretched, exported to Beaufort sea or the CAA channels until it completely melts. It is a region of slow turnover time compared to the Gyre or the ice on the transpolar drift. It is a buffer against abrupt apocalypse scenarios.
You are making an awful lot of assumptions there, in the face of evidence - like the melt out of thick, MYI north of Greenland this year - which don't support your rosy interpretation of the ice's survivability.

Other posters have pointed out that Transpolar drift is broken.  The Gyre is broken.  Pretty much every mechanism we are used to watching and basing assumptions on, is broken.

And then there is the raw question of how much what we see in models is diverging from what's actually visible where we have "feet on the ground".

The only buffer we have against "sudden apocalypse" scenarios is the weather. 1 million km2 of 1m thick MYI or the equivalent simply doesn't have the thermal inertia to stop an apocalypse if the weather isn't cooperative.

The net enthalpy in the system has exploded, between additional solar uptake, and the huge inputs implied by the salinity data we see around Atlantification, as well as less dramatic inputs through the Bering straight on the Pacific side.

At this point, it really all hinges on seasonal uptake and existing heat.  Not extent.  Not area.  Not thickness.

We burned through ~15,000 km3 worth of ice this season already.  The ice you are citing (1,000,000 km2 of more or less 1m thick MYI) would represent less than 7% of that.

Even if I'm generous, and assume say, an average of 3m thickness, (which is VERY generous), we are talking about less than 20% of what has been lost this season already (PIOMAS figures).

It's not a bastion.  It's barely a cushion.  At best, averaged out, it's about 4 weeks of melt.  That's how thin a margin the Arctic pack's survival hinges on.

So back to my point... even if you are correct about quantity, at this stage in the evolution of the Arctic, it is weather, not ice volume which will determine any given year if we can avoid a BoE. 

That's been true pretty much since 2012.  Many of us have been holding our breath every year since 2012 in fear of a BoE.  So far, we've lucked out.  Increasingly, the deck is being stacked against us.

Some years ago, during one or another poll, I indicated that I thought there wouldn't be a BoE until sometime after 2029, and probably not before 2050.  At this point, I'll be surprised if we make it to 2029 *without* a BoE.  MYI won't help prevent it.

Weather will be the determinant of the pack's survival, not the existing ice.

jdallen pretty convincing. I agree with almost everything you explain. Still that does not negate that, if we have that 7% of ice that has become older in the Western CAB post-2016, let’s count with its existence for future years. My belief is that it does matter, it is one of few negative feedbacks that the Arctic ice has to avoid imminent oblivion, that is: some regeneration of old ice if several years seasons do not push it away one direction or another.

I just happen to believe we are in for a gradual decline, which I know is not a popular opinion here. Yet some folks are noting that “this year would be creating big news if it wasn’t because of 2012”, yes, and that’s because of the current gradual decline of which 2012 was the exception.

I Used to believe 2030 was a good BOE prediction, but I am not so sure when one counts some negative feedbacks: extended falls after bad seasons lead to enormous late heat release, increased snowing, later springs, rebound years; years in a row with low or moderate CAB ice export lead to MYI rebound; warm ocean currents not easily reaching the western CAB ice...
mind you, I agree that a very bad year before 2030 might come and ice extent can go down even 1 m km2 but that would probably be exceptional, followed by rebounds, back to the gradual downhill track as it has happened post 2012, clearly.
Anyway, this is all speculation, reason why I post it here.

Juan C. García

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Re: When will the Arctic Go Ice Free?
« Reply #1751 on: September 13, 2020, 07:26:14 PM »
Nothing that is new in this Forum, but I like the videos he makes. A good summary of what is happening in the Arctic.

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

jdallen

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Re: When will the Arctic Go Ice Free?
« Reply #1752 on: September 14, 2020, 12:24:42 AM »
It wouldn't be much of a rebound anyways when you consider how thin all of the ice is.

What good is 4 year old ice that's under a meter thick
It’s more resilient than FYI under a meter.
<mass snippage>

Weather will be the determinant of the pack's survival, not the existing ice.

jdallen pretty convincing. I agree with almost everything you explain. Still that does not negate that, if we have that 7% of ice that has become older in the Western CAB post-2016, let’s count with its existence for future years. My belief is that it does matter, it is one of few negative feedbacks that the Arctic ice has to avoid imminent oblivion, that is: some regeneration of old ice if several years seasons do not push it away one direction or another.

I just happen to believe we are in for a gradual decline, which I know is not a popular opinion here. Yet some folks are noting that “this year would be creating big news if it wasn’t because of 2012”, yes, and that’s because of the current gradual decline of which 2012 was the exception.

I Used to believe 2030 was a good BOE prediction, but I am not so sure when one counts some negative feedbacks: extended falls after bad seasons lead to enormous late heat release, increased snowing, later springs, rebound years; years in a row with low or moderate CAB ice export lead to MYI rebound; warm ocean currents not easily reaching the western CAB ice...
mind you, I agree that a very bad year before 2030 might come and ice extent can go down even 1 m km2 but that would probably be exceptional, followed by rebounds, back to the gradual downhill track as it has happened post 2012, clearly.
Anyway, this is all speculation, reason why I post it here.
Thanks for shifting the discussion here.

I still think 2030-ish is the way to bet as far as a BoE is concerned, and agree that we'll get years if not decades of "dead cat bounces" while the Arctic as a system languishes in a marginal condition between the previous and next "stable" state.

I think my primary criticism about the value of MYI is more nuanced than may have come across in my OP.

There is no question that MYI was key to buffering and balancing the Arctic as a system, especially pre-2007.  The key function it served really didn't have to do with the implied latent energy uptake it represented.  MYI doesn't absorb more energy that FYI when melting.  The heat budget for phase change remains the same.  Rather, it was it's mechanical strength, across vast stretches of the pack which helped stabilize the system as a whole.

Part of that strength depended seriously the temperature of the ice as much as it did on its salt content - ice at -20c is almost as hard as bedrock - and has nearly the same mechanical strength.  So, pre-"modern" era conditions with millions of KM2 MYI and sub -10c temperatures meant that wind and other kinetic forces could be spread across very large areas with relatively little damage, and, that there would be little movement or disintegration of the ice outside of the pack margins.  This has made the system  more or less stable since the last of the Laurentide ice sheet vanished over 4500 years bce. (Prior to this, it was probably stronger.)

It's thickness ->at scale<- was important as well, as it meant year over year, it could lose 2+m of thickness, still remain in place, and provide a similarly broad-scale platform for re-deposition of new ice from below and new fresher ice refrozen from melt above.  It tended to stay in place.  It tended to keep albedo high, and by nature of strength and coverage, limit seasonal uptake of heat.  These last were as if not more important than the thermal inertia the ice itself provides.

Scroll forward now to the modern era, particularly at key junctures like 2007, 2010 (an underrated melt year), 2011 and 2012.  I'm adding a link to one of my favorite graphics by Jim Pettit here to help illustrate:

http://iwantsomeproof.com/extimg/siv_annual_max_loss_and_ice_remaining.png

Those years mentioned are key in they are points in which the melt season destroyed large areas of MYI.  2010 in particular is notable for that, as even though extent and area did not drop to record levels, it was the first year we observed volume drop below 5,000 km3.  2007 was the first below - WAY below - approximately 9000km3 (2006 was 8993km3).  2011 and 2012 were years that continued the trend, dropping volume under 5000km3 and progressively chipping away at what some of used to call "matrix pack"; called such because of the very regular way it would fracture, essentially creating what could be considered fault lines in the ice while mostly retaining strength and coherence.

Those losses of volume and by extension MYI are critical to set the stage for what we see starting most dramatically in 2016.  The winter pack now fractures and recombines at much lower scales, eliminating the resistance it used to have to mechanical forces, and making the entire pack as a whole far more mobile.  Combine this with increasing advection of heat from southerly seas, and you have the new seasonal regime we now see. 

The result is, we have nothing like the larger expanses of MYI we used to see, which unbroken might cover 10's of thousands of km2. We are lucky if we see blocks of more than about 2500.  And because of warmer temperatures overall, for longer periods of both the melt and refreeze seasons, that relict ice has nothing like the mechanical strength of the old pack.

So, to finish my thought for the moment and conclude, MYI was far more important for the structure and mechanical characteristics it provided than it was for any sort of thermal component.  So while it exists now, it has nothing like the structure it had in the past, and because of that is only marginally less vulnerable than FYI when exposed to the conditions we now see during the melt season.  Without that structure, it doesn't really provide a buffer against loss as it used to.
« Last Edit: September 14, 2020, 12:33:20 AM by jdallen »
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Tor Bejnar

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Re: When will the Arctic Go Ice Free?
« Reply #1753 on: September 14, 2020, 02:01:06 AM »
great summery, jdallen!

An element focused on in the video Juan posted, MYI in 2020 is much thinner than MYI was in 2012 and earlier.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1754 on: September 14, 2020, 03:03:53 AM »
Yes, excellent post jdallen.

uniquorn

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Re: When will the Arctic Go Ice Free?
« Reply #1755 on: September 14, 2020, 01:24:20 PM »
nsidc ice age for the week to sep1 (or sep2), 1984-2020

gandul

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Re: When will the Arctic Go Ice Free?
« Reply #1756 on: September 14, 2020, 03:29:22 PM »
Last four years. Note 2017 conditions after 2016 summer and winter, in a position to melt all FYI and dump most two-three year ice... but was a relatively cold static year.
2020 sees a buildup of 4+ year MYI. No comparison to 1980, obviously, but it’s some rebound and it will take time to have a ice distribution as ready for meltout as was 2017

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1757 on: September 14, 2020, 04:42:33 PM »
Last four years. Note 2017 conditions after 2016 summer and winter, in a position to melt all FYI and dump most two-three year ice... but was a relatively cold static year.
2020 sees a buildup of 4+ year MYI. No comparison to 1980, obviously, but it’s some rebound and it will take time to have a ice distribution as ready for meltout as was 2017

Yes, significant growth in 4+ year old ice but 3-4 year old ice has dropped by a similarly dramatic amount and the 2021 melt season will open with more first year ice than any year except 2013. I would not describe this season which blew by the 2nd lowest ice minimum as any kind of rebound.

This freeze season and next years melt season will be fascinating as the entire Siberian side and Pacific side of the central Arctic is ice free, excluding the lonely branch of rubble hanging out in the Beaufort, and SST's are very high. Let's hope for a bitter freeze in the Laptev, ESS and Chukchi. This is the area I will be watching from now through February.
« Last Edit: September 14, 2020, 04:51:43 PM by Shared Humanity »

uniquorn

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Re: When will the Arctic Go Ice Free?
« Reply #1758 on: September 14, 2020, 09:20:26 PM »
Last four years.
You have a reasonable point that the ice age product shows a possible increase in 4+ year ice.
A technical graphics question. What made you choose to insert a transition that ignores the other 51 weeks into that animation? It makes no sense (and increases the file size).

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1759 on: September 14, 2020, 09:43:02 PM »
Last four years.
You have a reasonable point that the ice age product shows a possible increase in 4+ year ice.
A technical graphics question. What made you choose to insert a transition that ignores the other 51 weeks into that animation? It makes no sense (and increases the file size).

It makes perfect sense when we talk about minimum sea ice and ice-free conditions.  They will not occur during the other 51 weeks.

gandul

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Re: When will the Arctic Go Ice Free?
« Reply #1760 on: September 15, 2020, 01:47:21 PM »
Last four years.
You have a reasonable point that the ice age product shows a possible increase in 4+ year ice.
A technical graphics question. What made you choose to insert a transition that ignores the other 51 weeks into that animation? It makes no sense (and increases the file size).
Nothing special. I grabbed your gif, selected the last four frames in ezgif, and added transition between frames for aesthetic reasons. The result was not *that* big... but thanks for the lesson from the Graphics Olympo.

Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1761 on: October 05, 2020, 07:05:47 PM »
2032 seems like the year, again.
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1762 on: October 05, 2020, 08:58:20 PM »
Thanks a lot for these animations. Very informative indeed.
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1763 on: October 05, 2020, 11:15:01 PM »
Here is a graph of Arctic sea ice volume, area & thickness.

Volume - note that the trend value for September 2021 is close to the Sept 2012 record low.

Surely, at some time or other if the volume continues to reduce at around 300 km3 per year, the thickness will reduce to a tipping point and area/extent loss will accelerate - a lot ?
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RichardStamper

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Re: When will the Arctic Go Ice Free?
« Reply #1764 on: October 05, 2020, 11:40:23 PM »
Not sure that thinking about volume as being decreased is the right approach. 

To first order, so ignoring pesky complicating factors like winds and currents moving ice around, isn't maximum ice area a measure of how much space gets cold enough, and maximum ice thickness a measure of the amount of heat loss in that area? The slow decline in area says that it still gets cold enough to create ice in much the same area, but the relatively rapid decline in ice thickness says that nonetheless there is a lot more heat in the system so less ice can be made. Both are likely to keep heading as they are and volume just is the result of combining the two. 

kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1765 on: October 06, 2020, 03:00:26 AM »
Well if you extrapolate from the historical numbers they miss things like way more fractured ice , much more vulnerability to wind directions etc during the melting season and the general failure of the old ice regrowth factory.

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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1766 on: October 06, 2020, 01:19:58 PM »
If the Arctic Ocean was a nice calm pond with a nice calm gradually warming climate and ocean, one could see the linear projections continuing until the ice was extremely thin, but...

The litany of anecdotal evidence from the MOSAIC project, the lunatics on skis, the abandonment of the Russian Barneo North Pole encampment and others suggests that this is the first evidence that the ice sheet is beginning to lose its integrity, even in winter. My speculation is that there is a tipping point at which time the remaining ice starts to disintegrate big-time and the linear projections are broken.

And yes, I have zero scientific evidence to support this, though many natural systems are very resilient up to a point, and then rapidly collapse (e.g. eutrophication of water bodies).
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1767 on: October 06, 2020, 01:42:17 PM »
My speculation is that there is a tipping point at which time the remaining ice starts to disintegrate big-time and the linear projections are broken.

This has also been my feeling for quite some time. And when you see the linear extrapolations pointing to BOE2032 then we should, if we are right, see something major happening before then.
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Re: When will the Arctic Go Ice Free?
« Reply #1768 on: October 06, 2020, 01:49:11 PM »
And if something unusual happens before then, like in 2012 we would see it sooner.
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blu_ice

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Re: When will the Arctic Go Ice Free?
« Reply #1769 on: October 06, 2020, 03:24:25 PM »
Maybe the tipping point wasn't so far this summer? CAB ice looked weak all the way up to the pole, as witnessed by the Mosaic crew.

Maybe with just a little bit thinner ice to start the season, or more favourable weather late season, or a strong storm to clear the rubble...

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1770 on: October 06, 2020, 03:25:32 PM »
Not sure that thinking about volume as being decreased is the right approach. 

To first order, so ignoring pesky complicating factors like winds and currents moving ice around, isn't maximum ice area a measure of how much space gets cold enough, and maximum ice thickness a measure of the amount of heat loss in that area? The slow decline in area says that it still gets cold enough to create ice in much the same area, but the relatively rapid decline in ice thickness says that nonetheless there is a lot more heat in the system so less ice can be made. Both are likely to keep heading as they are and volume just is the result of combining the two.

Agreed.  While a linear regression has volume falling below 1M km3 by 2032, area does not fall below 1M km2 until 2060.  Volume and area must approach zero at the same time.  As the ice becomes more confined to the northernmost latitudes and the CAA, past trends may not hold.  Thickness appears to be the key.  Can the heat in the system melt that last stretch of ice before the refreeze commences?

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1771 on: October 06, 2020, 09:58:38 PM »
Maybe the tipping point wasn't so far this summer? CAB ice looked weak all the way up to the pole, as witnessed by the Mosaic crew.

Maybe with just a little bit thinner ice to start the season, or more favourable weather late season, or a strong storm to clear the rubble...
I'd like to take you back into summer 2016. At this time the CAB ice also looked very damaged and fragmented. Maybe it has never really recovered since then, although the melting seasons 2017 and 2018 were not too strong. Could it be this was the first step on the way into a BOE?
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blu_ice

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Re: When will the Arctic Go Ice Free?
« Reply #1772 on: October 07, 2020, 12:50:22 PM »
Or one step among many. It seems Arctic ice is in terminal decline.

As you pointed out the recovery years are not really recoveries at all.

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Re: When will the Arctic Go Ice Free?
« Reply #1773 on: October 09, 2020, 09:18:02 PM »
It is time for the monthly update of my extrapolation when the extent [Ausdehnung], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume and thickness, not for extent and area in the winter months). The September value now includes 2020.
Volume and thickness in September 2020 are (slightly) above the long term trend lines, area lies almost at the long term trend line, whereas extent dips slightly below it. The "BOE numbers" did not change relevantly compared to September 2019. Interestingly my linear extrapolation for volume matches zero in 2032, which is in line with postings of other members in this thread some days ago.

The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table, now widened to see the linear function value (y-AA) at t = 0. stg = slope.

Click to enlarge it.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1774 on: October 19, 2020, 05:56:01 AM »
Cross posting, an interesting paper.

I don't think I've seen this new Jennifer Francis paper referenced on the ASIF:
https://www.woodwellclimate.org/why-has-no-new-record-minimum-arctic-sea-ice-extent-occurred-since-september-2012/

https://iopscience.iop.org/article/10.1088/1748-9326/abc047
Abstract
One of the clearest indicators of human-caused climate change is the rapid decline in Arctic sea ice. The summer minimum coverage is now approximately half of its extent only 40 years ago. Four records in the minimum extent were broken since 2000, the most recent occurring in September 2012. No new records have been set since then, however, owing to an abrupt atmospheric shift during each August/early-September that brought low sea-level pressure, cloudiness, and unfavorable wind conditions for ice reduction. While random variability could be the cause, we identify a recently increased prevalence of a characteristic large-scale atmospheric pattern over the northern hemisphere. This pattern is associated not only with anomalously low pressure over the Arctic during summer, but also with frequent heatwaves over East Asia, Scandinavia, and northern North America, as well as the tendency for a split jet stream over the continents. This jet-stream configuration has been identified as favoring extreme summer weather events in northern mid-latitudes. We propose a mechanism linking these features with diminishing spring snow cover on northern-hemisphere continents that acts as a negative feedback on the loss of Arctic sea ice during summer.

Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1775 on: November 02, 2020, 08:29:55 PM »
If the Arctic Ocean was a nice calm pond with a nice calm gradually warming climate and ocean, one could see the linear projections continuing until the ice was extremely thin, but...

The litany of anecdotal evidence from the MOSAIC project, the lunatics on skis, the abandonment of the Russian Barneo North Pole encampment and others suggests that this is the first evidence that the ice sheet is beginning to lose its integrity, even in winter. My speculation is that there is a tipping point at which time the remaining ice starts to disintegrate big-time and the linear projections are broken.

And yes, I have zero scientific evidence to support this, though many natural systems are very resilient up to a point, and then rapidly collapse (e.g. eutrophication of water bodies).

yep.
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Re: When will the Arctic Go Ice Free?
« Reply #1776 on: November 05, 2020, 10:08:23 PM »
It is time for the monthly update of my extrapolation when the extent [Ausdehnung], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times (valid for volume and thickness, not for extent and area in the winter months). The October value now includes 2020.
Thickness in October 2020 is slightly above the long term trend, volume lies almost at the long term trend lines, whereas extent and area dive deeply below it. The "BOE numbers" did not change (volume, thickness) and decreased by 3-4 years (extent, area) compared to October 2019.
So there is a further convergence between the "late values" (area, extent) and the "early value" (volume).
The order (earlier → later BOE) generally is volume < thickness < area < extent.

Please note that this is not a forecast but a trend!
See attached table, now widened to see the linear function value (y-AA) at t = 0. Stg = slope.

Click to enlarge it.
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1777 on: November 16, 2020, 11:20:09 PM »
<snip>As sea ice declines, a new Arctic state is emerging which due to the positive feedback mechanism outlined above may be pushing the system toward a tipping point."

1.  Uh oh.  "Weakening halocline stratification" and "Tipping point" in the same abstract sounds ominous.  The decay trends we've been watching, while rapid relative to most natural transitions, are slow and incremental compared to what a halocline tipping point could bring. 
     I may be incorrect in viewing halocline and thermocline as directly related, but my guess is that is how the summer ASI will get obliterated.  Not by a gradual continuation of the forcings and trends monitored and analyzed so far, but by transition to a new functional system state where multiple factors work in concert to melt sea ice at a MUCH faster rate and by different mechanisms than the processes monitored in recent years.   

2.  Different topic:  I know that the Arctic drift pattern can change greatly between short time periods, but the counterclockwise pattern in the drift pattern in A-Team's Nov. 16 MOSAIC post seems unusually strong and in the wrong direction. 
    Is this another indication/consequence that the Beaufort Gyre no longer exists or has been transformed into a new pattern?  Or am I overinterpreting a short term condition?

3.  Vertical disruption (i.e. halocline stratification reduction)
     x Horizontal disruption (odd drift pattern)
     = an altered Arctic. 
     IMHO none of this bodes well for ASI.  BOE by or before 2030 seems not only increasingly possible, but inevitable.
« Last Edit: November 16, 2020, 11:38:25 PM by Glen Koehler »

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Re: When will the Arctic Go Ice Free?
« Reply #1778 on: November 16, 2020, 11:32:42 PM »
<snip>As sea ice declines, a new Arctic state is emerging which due to the positive feedback mechanism outlined above may be pushing the system toward a tipping point."

1.  Uh oh.  "Weakening halocline stratification" and "Tipping point" in the same abstract sounds ominous.  The year to year decay we've been watching, while rapid relative to most natural transitions, is slow and incremental compared to what a halocline tipping point could bring. 
     I may be incorrect in viewing halocline and thermocline as directly related, but my guess is that is how the summer ASI will get obliterated.  Not by a gradual continuation of the forcings and trends monitored and analyzed so far, but by transition to a new functional system state where multiple factors work in concert to melt sea ice at a MUCH faster rate and by different mechanisms than the processes monitored in recent years.   

2.  Different topic:  I know that the Arctic drift pattern can change greatly between short time periods, but that counterclockwise pattern in the Beaufort seems unusually strong and in the wrong direction. 
    Is this another indication/consequence that the Beaufort Gyre no longer exists or has been transformed into a new pattern?  Or am I overinterpreting a short term condition?

3.  IMHO none of this bodes well for ASI.  BOE pre-2030 seems increasingly possible.

Hard to say which (if any) of these short term conditions will have the greatest impact on the sea ice.  The trend in the sea ice decline has slowed considerably over the past 15 years, compared to the previous 15.  Every year, the possibility of a BOE increases.  However, the recent trend shows that it is highly unlikely prior to 2030.

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1779 on: November 17, 2020, 02:44:17 AM »
RE":  <snip> The trend in the sea ice decline has slowed considerably over the past 15 years, compared to the previous 15.  Every year, the possibility of a BOE increases.  However, the recent trend shows that it is highly unlikely prior to 2030.
       Tamino/Grant Foster is/was the king of change point analysis.

And he did an analysis in 2015, based on extent anomaly data. For sea ice minimum, he found one change point, in 1996 if I read the graph correctly.

 https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

      I do not see the slowdown in the two Volume graphs shown below.  It looks like a consistent ongoing trend to me.  All the data points since 2005 are well within the expected variability of the downward linear trend.  The Volume minima for all of the last 6 years, and 7 out of the last 8, are within one standard deviation (=close) to the trend line.

      As for annual average Extent, the great Tamino did not find a slowdown when looking at data through 2015.  He did find a temporary slowing for 2002-2006, then for 2006-2015 it was back to the original downward rate of decline.  See whisker graphs in the 3rd graph below. 

      When Tamino looked at annual Extent minima, he found a statistically significant increase in the rate of decline in 1996 (see the downward kink in the blue line of the 4th graph below).  He did comment that a smoothing of the data hinted at a possible plateauing in the final few years of those data, but there was too much variability to conclude anything about a rate change based on so few points in such variable data.  The Extent minima in the subsequent years (2016-2020) proved that his caution about concluding anything about the long term trend from those few years was justified.  When 2016-2020 are added, the trend resumes its linear downward slide, thus refuting that hint of a rate plateau (to my eyes, not statistically tested, but I'd bet my lunch money on how that test would come out).  See the NSIDC graph in the next post.  I wish we still had Tamino or someone with his skill set putting such questions through the statistical blender.

      While it is possible that "negative" suppressive feedbacks to slow further losses will strengthen and dominate as Volume gets closer to zero, it seems more likely that the reverse is more likely, i.e. that "positive" reinforcing feedbacks are more likely to strengthen and dominate to accelerate losses. 

      Most ASIF folks already know the list of potential reinforcing feedbacks, so I won't repeat them.  The weakening of halocline stratification is a more recently recognized (to me at least) addition to that list.  Based on studies by Polyakov et al., Timmermans et al., and others, the surface - subsurface water characteristics and relations seem to be of increasing importance for at least some locations in the Arctic Ocean, though I have not read those studies closely or recently enough to comment on the scale of their potential impact relative to entire regional seas or to the Arctic Ocean overall. 

      My question about unexpected drift pattern may be unjustified alarmist arm-waving, but with people in the Forum more familiar with the historical record it seems worth asking to either confirm my suspicion or dismiss it.  (The only "dumb" question is the one left unspoken.) 

      Even if the November 2020 drift graph posted by A-Team is just a meaningless blip, that still leaves the weightier statement about decline of halocline stratification in the Polyakov et al. abstract (and by my inference, the consequent decline in isolation of ASI from interaction with subsurface water).  Seeing an expert like Polyakov use the term "tipping point" about any aspect of the ASI is enough to give me the willies. 

      I do admit that my ears are tuned to hear that dog whistle, because I fully expect that by pushing the climate system, and the Arctic in particular, beyond its previous "performance envelope", then something is going to snap in a non-linear, non-incremental, and very abrupt and "surprising" (but we knew it was coming in one form or another) way.
« Last Edit: November 17, 2020, 05:27:03 AM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1780 on: November 17, 2020, 03:29:46 AM »
NSIDC Extent minima, including 2016-2020 that Tamino did not have available for his analysis through 2015, showing that adding 2016-2020 continues the long term linear downward trend.
« Last Edit: November 17, 2020, 04:26:10 AM by Glen Koehler »

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Re: When will the Arctic Go Ice Free?
« Reply #1781 on: November 17, 2020, 04:11:26 AM »
Thanks for this excellent refutation Glen of that eternal canard, the "slowdown".
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Re: When will the Arctic Go Ice Free?
« Reply #1782 on: November 17, 2020, 04:52:23 AM »
NSIDC Extent minima, including 2016-2020 that Tamino did not have available for his analysis through 2015, showing that adding 2016-2020 continues the long term linear downward trend.

IMHO the slowdown is quite evident from that graph.  Even extending that trend line for 40 years, it will not cross one million square km.  Hence, a BOE is still unlikely in the next 10 years.

<Slight edit. O>
« Last Edit: November 17, 2020, 05:40:46 AM by oren »

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Re: When will the Arctic Go Ice Free?
« Reply #1783 on: November 17, 2020, 06:30:00 AM »
NSIDC Extent minima, including 2016-2020 that Tamino did not have available for his analysis through 2015, showing that adding 2016-2020 continues the long term linear downward trend.

IMHO the slowdown is quite evident from that graph.  Even extending that trend line for 40 years, it will not cross one million square km.  Hence, a BOE is still unlikely in the next 10 years.

What slowdown? Are you still claiming the following:

The trend in the sea ice decline has slowed considerably over the past 15 years, compared to the previous 15. 

Perhaps you need a new pair of glasses? No slowdown from 2005 is visible by any stretch of the imagination, neither by looking at the graphs nor by running the statistics as Tamino has done. To help you focus, I've added vertical lines on the years 1990 and 2005 in the graph below, just to make it doubly obvious that no slowdown is visible whatsoever when comparing the two 15 year periods.

If one were willing to make spurious claims based on what ones imagines one sees in the squiggles on the graph below, one could be excused to claim that the last 15 years have seen a significant increase in sea ice decline, totally the opposite of what the whiskers think they see.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Re: When will the Arctic Go Ice Free?
« Reply #1784 on: November 17, 2020, 07:07:03 AM »
As I mentioned numerous times (to no avail), any trendline whose residuals are autocorrelated is statistically WRONG (I am quite surprised that this is so routinely ignored on a scientific forum). Your trendlines on the above charts obviously have autocorrelated residuals, I do not need my statistical software for that because it is plain to see. (plain language: you cannot have many dots above the trendline, one after the other and then after a while many of them under the trendline, all following each other, because if you do, your trendline is wrong).

The only way to make those trendlines right is to break the chart into 2 parts: before 2007 and after 2007 and use two trendlines, because a state change obviously happened then.

You could also argue that ther will be another state change at some point in the future but using the above trendlines to prove anything is just scientifically faulty

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Re: When will the Arctic Go Ice Free?
« Reply #1785 on: November 17, 2020, 07:36:49 AM »
The only way to make those trendlines right is to break the chart into 2 parts: before 2007 and after 2007 and use two trendlines, because a state change obviously happened then.

Not being the big statistician myself, I still find myself strangely reluctant to reconcile your post with what little I do know.

To begin with, I don't think it is the done thing to break a time series into two just because there is a series of points above the line, then a series of points below the line. You first have to decide if this behaviour is outside the bounds of statistical randomness, and I think Tamino has shown conclusively that it isn't.

Secondly, you don't just create breakpoints because you think they should be there. You run the appropiate statistical analysis, which Tamino has done, and apparently there is no statistical grounds for assuming a state change in 2007. Which is not to say that one did not happen, only that without the statistics and a well-grounded causal relationship we simply cannot know.

But mostly I take umbrage with the claim that the residuals of the trendline in the above graph are autocorrelated. Please explain what you mean by this, preferrably with a concise argument underpinned by sound mathematics so the rest of us can understand what you mean.
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Re: When will the Arctic Go Ice Free?
« Reply #1786 on: November 17, 2020, 07:48:53 AM »
Oh to have enough cash to pay  the highly esteemed Tamino for his time.
Tamino has not been active for a while may he return once again and cast his highly evolved ability to discern reality from noise and clearly illustrate the statistical   significance contained within  data.

Focusing on one or two outlaying data points and ignoring the long term trend is looking at weather not  climate.
 With out Tamino's help  mark one eyeball will have to do.
Look  carefully folks and see in the above charts .

More date points bellow  the line in the first third.
More data points above the line in the second
Returning to   predominantly under the liner trend  in the third.

That gives us a  curve .
Slow down my smegin arse it is clearly a case of acceleration.


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Re: When will the Arctic Go Ice Free?
« Reply #1787 on: November 17, 2020, 01:47:37 PM »

But mostly I take umbrage with the claim that the residuals of the trendline in the above graph are autocorrelated. Please explain what you mean by this, preferrably with a concise argument underpinned by sound mathematics so the rest of us can understand what you mean.

Ok, I thought this was basic statistics stuff. Second google hit describes it pretty well:

https://stats.stackexchange.com/questions/55658/how-to-interpret-autocorrelation-of-residuals-and-what-to-do-with-it

"In general, after fitting a time series model the residuals should be white noise. So they should have no autocorrelation. If you have significant autocorrelation (you have to test this) and not just one spike at high lag order in your acf/pacf this maybe an indication that you specified your model wrong."

To add some more:

If you have a linear model, the residuals (the differences from the predicted value by the model, in this case the trendline) should have no correlation between them, ie. the residuals should be a white noise. If eg. the first ten residuals are all positive values and the next ten residuals are all negative, then you know that your model is wrong.

Conclusion: The usual ice volume and extent trendlines all over this forum are all statistically wrong. They are NOT a linear process, that is sure. If they were, the residuals should be a white noise. They are not.


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Re: When will the Arctic Go Ice Free?
« Reply #1788 on: November 17, 2020, 01:59:03 PM »
A small visual analysis of possible years for state change using Wipneus' piomas modeled ice thickness (Zhang and Rothrock 2003). I think there are data and charts that show roughly the same thing though limiting the observed area to that of the thickest remaining ice near the september minimum may be instructive.

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Re: When will the Arctic Go Ice Free?
« Reply #1789 on: November 17, 2020, 02:55:19 PM »
As mentioned by others, the state change has resulted in a change to the trend line.  Compare Tamino's earlier trendline to those today.

https://tamino.wordpress.com/2010/07/26/summer-ice/

Extrapolating the curve forward, Dikran Marsupial had the trendline falling below 1M sq km around2032

https://skepticalscience.com/print.php?n=1038

Later, Gavin Cawley had the same trend crossing 1M in 2026.

https://skepticalscience.com//2013-arctic-sea-ice-prediction.html

The trend has obviously been changing over the past 15 years, and likely due to the state changes mentioned in previous posts.

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Re: When will the Arctic Go Ice Free?
« Reply #1790 on: November 17, 2020, 03:28:05 PM »
The only way to make those trendlines right is to break the chart into 2 parts: before 2007 and after 2007 and use two trendlines, because a state change obviously happened then.

Not being the big statistician myself, I still find myself strangely reluctant to reconcile your post with what little I do know.

To begin with, I don't think it is the done thing to break a time series into two just because there is a series of points above the line, then a series of points below the line. You first have to decide if this behaviour is outside the bounds of statistical randomness, and I think Tamino has shown conclusively that it isn't.

Secondly, you don't just create breakpoints because you think they should be there. You run the appropiate statistical analysis, which Tamino has done, and apparently there is no statistical grounds for assuming a state change in 2007. Which is not to say that one did not happen, only that without the statistics and a well-grounded causal relationship we simply cannot know.


https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

linked earlier specifically says

Quote
The downward trend is quite clear. And yes, it can (easily) be confirmed statistically — it’s not just a visual impression.

But there’s also a visual impression of more than just a linear decline. This can be confirmed in multiple ways, including changepoint analysis, which finds not one but two changes in the trend rate. Let’s plot a smooth curve fit to the data in red, and a piecewise-linear fit estimated by changepoint analysis in blue:

So Tamino has shown that it is statistically significant by the changepoint analysis he did and probably multiple other methods.

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Re: When will the Arctic Go Ice Free?
« Reply #1791 on: November 17, 2020, 03:42:35 PM »
More Tamino goodness (referring to annual average ASI Extent):
"....annual average sea ice extent is not only still well below what it was 30 years ago, it’s well below what it would have been had the downward trend at that time continued unabated:" 
Bolding added.  See graph below.  And remember that adding 2016-2020 to the data in the Tamino graph keeps the linear trend heading downward.

    As for the Extent line requiring >40 years to go below 1M km2, look at the Volume graph.  It reaches 0 in mid 2032.  No Volume means no Extent.  (Digression - for some reason I'm reminded of Firesign Theatre's Porgy and Mudhead going to MoreScience High School the day before graduation, only to find that the Communists have stolen it!).

    As for which curve rules, remember that as average Thickness gets below 1M the ice is less resistant to melt.  Volume dictates Extent, not the other way around

    Tamino slammed the door shut on any notion of slowdown.  Arguing about the details really misses the point I think we all agree upon - the Arctic Sea Ice is getting destroyed.  The first BOE is just a day that will come and go.  The more pertinent questions are -

1) What can we do to slow the process? (I'll defer any mention of reversal until we do the first step of slowing the acceleration). 
     Of course, we already know.  Slow, then stop, then reverse greenhouse gas emissions.  The one good thing about loss of ASI is that it provides easily relatable visual demonstration of the progression and effects of climate change.

2)  What does diminishing ASI mean for weather patterns and other ecosystem changes that will affect all of us far beyond the Arctic?     
« Last Edit: November 17, 2020, 04:33:14 PM by Glen Koehler »

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Re: When will the Arctic Go Ice Free?
« Reply #1792 on: November 17, 2020, 03:51:10 PM »


The only way to make those trendlines right is to break the chart into 2 parts: before 2007 and after 2007 and use two trendlines, because a state change obviously happened then.

The problem with this statement is that you can choose it arbitrarily
for example

The only way to make those trendlines right is to break the chart into 2 parts: before 1996 and after 1996 and use two trendlines, because a state change obviously happened then.

Un ou deux points isolés ne suffisent pas pour déterminer une tendance ou une cassure
Sorry, excuse my bad english

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Re: When will the Arctic Go Ice Free?
« Reply #1793 on: November 17, 2020, 03:51:34 PM »
Focusing on one or two outlaying data points and ignoring the long term trend is looking at weather not  climate.

September Average data
A few months ago, for reasons best known to themselves, the NSIDC people decided to muddy the waters by using 2 overlapping 13 year periods,1999-2012 and 2012 to 2019. The average linear trend was sea ice falling at 203 k per annum in the years 1999-2012, and just 1.2 kn per annum in the years 2007 to 2019. (see attachment 1)

This provoked some comment. My take on it  was - outliers. There is a standard methodology for identifying outlers that I sort of followed, and ended up with just 3 - 2007 & 2012 (-very much below trend values), and 1996 (very much above trend value).. (see attachment 2)

When I excluded those years from the graph it reinforces the validity of the long-term linear trend - a better R2 value emerges and a better fit all round. I am content to stick with the linear trend for the time being, until it no longer has value. See attachment 3

If volume keeps on reducing at the current linear rate (approaching double that of sea ice extent) it won't that many years before the trend collapses. I'm still saying 2029 for a September average of less than 1 million km2 sea ice extent.
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Re: When will the Arctic Go Ice Free?
« Reply #1794 on: November 17, 2020, 04:02:04 PM »


But mostly I take umbrage with the claim that the residuals of the trendline in the above graph are autocorrelated. Please explain what you mean by this, preferably with a concise argument underpinned by sound mathematics so the rest of us can understand what you mean.

Attached is what happens when you fit a straight line to a curve. Residual stays one side of 0 for consecutive data points and only changes sign a few times *twice with this simple curve). White noise would have it changing sign roughly 50% of time then roughly 25% of time is stays same sign twice before changing sign and so on.

What is being pointed out is that residual stay same side of 0 far too frequently and this is a sign that you are fitting a straight line to a curve.

Edit also added a straight line fit where as it happens residuals change sign 16 times for 32 data points. (should be 15.5 times but 16 is as close as you can get)
« Last Edit: November 17, 2020, 04:23:49 PM by crandles »

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Re: When will the Arctic Go Ice Free?
« Reply #1795 on: November 17, 2020, 04:22:48 PM »
Strongly autocorrelated data vs Arctic Extent, plotted as an ACF
Bunch of small python Arctic Apps:
https://github.com/SimonF92/Arctic

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Re: When will the Arctic Go Ice Free?
« Reply #1796 on: November 17, 2020, 05:29:33 PM »
As Glen showed in his post previously, the dip below the trendline started around 2005 and has continued to today.  Above, Simon showed the residually strongly skewed in recent decades.  All told, the sea ice minimum appears to be reverting to the long term trend after a short term accelerated loss.  Whether the long term trend will be maintained or a new trend associated with a state change dominates remains to be seen.  Stay tuned.

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Re: When will the Arctic Go Ice Free?
« Reply #1797 on: November 17, 2020, 06:41:36 PM »
I think many have noticed this already, and maybe it has been said.
but just now i just realized that we now have as much ice volume at the annual March maximum as we had at the September annual minimum in the years 85-95
Sorry, excuse my bad english