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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 200183 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.