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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: 61

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

Author Topic: When will the Arctic Go Ice Free?  (Read 240261 times)

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1900 on: March 24, 2021, 09:55:44 PM »
I have been doing my spreadsheet housekeeping and found a lot of stuff about BoE all over the place. Having put it into better order and updated the data here are some thoughts. (all output derived from data from the NSIDC and PIOMAS standard files.

What is the definition of a BOE? I sort of think it is described as 1 million km2 or less of Arctic sea ice extent for the whole month of September.

BUT. As the melting season progresses sea ice concentration reduces - always.
The Central Arctic region (CAB) at maximum has a concentration of nearly 100%. At minimum, after losing about 25% of its sea ice extent, concentration drops to around 70%.

The Beaufort sea at maximum has a concentration of nearly 100%. At minimum, after losing about 75% of its sea ice extent, concentration drops to around 35%.

An Arctic Ocean with just 1 million km2 sea ice extent is probably to have at most a sea ice area of half that, i.e. a max of 500,000 km2.

So on a definition for the BOE of a maximum extent of 1 million km2, we are talking about just half a million maximum area of sea ice in the 7 central seas with an area of 8.9 million km2, i.e. 94% or more open water.

But, that seems to be the consensus. Ho hum.

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« Last Edit: March 24, 2021, 10:17:26 PM by gerontocrat »
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1901 on: March 24, 2021, 10:16:53 PM »
But what i wanted to show was

Reductio Ad Absurdum - a method of proving the falsity of a premise by showing that its logical consequence is absurd or contradictory:

I have taken the NSIDC sea ice area and PIOMAS sea volume averages for September and combined them to produce the graph of average thickness. The graph uses actuals to 2020 and then projections based on the long-term linear trends. I have done this for the entire Arctic and the 7 central seas of the High Arctic.

In percentage terms the annual reduction in volume is far higher than that of sea ice area. hence the reducing average thickness.

Reduction Ad Absurdum is achieved in around a decade. To avoid absurdity, volume reduction must reduce substantially. On the other hand sea ice area and /or volume reduction could speed up and a BOE happen earlier.

I also looked at October data for the High Arctic for 2 reasons. In the last 2 years October sea ice area has reduced to record lows, and the scientists seem to tell us that late refreezing is likely to accelerate as AGW + Polar Amplification proceeds.

The result is Absurdity is reached just a couple of years later. i.e. a 2 months ice-free Arctic

CONCLUSION ?:
Somethings gotta give, What, where and when?

click images to enlarge
"Para a Causa do Povo a Luta Continua!"
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1902 on: March 25, 2021, 03:53:02 AM »
<snip>
Reduction Ad Absurdum is achieved in around a decade. To avoid absurdity, volume reduction must reduce substantially. On the other hand sea ice area and /or volume reduction could speed up and a BOE happen earlier.

I also looked at October data for the High Arctic for 2 reasons. In the last 2 years October sea ice area has reduced to record lows, and the scientists seem to tell us that late refreezing is likely to accelerate as AGW + Polar Amplification proceeds.

The result is Absurdity is reached just a couple of years later. i.e. a 2 months ice-free Arctic

CONCLUSION ?:
Somethings gotta give, What, where and when?
      If I understand that the question is how to resolve incompatible trends for Area vs. Volume, then my response is: Area gives more than Volume.  (Almost) no Volume dictates (almost) no Area.  And the Volume trend looks robust.
   
      "Almost" because I think trends will break down for the final residual ice Volume and Area in protected inlets etc. along the CAB-CAA border.  But that is pocket change in comparison to the bigger issue, which is "How long can the open Arctic Ocean continue to sustain these loss trends and retain more than a small residual of ice in protected areas?"

      Mathematically the trend lines must meet at zero.  So one trend line has to bend to meet the other.  One mathematical option is for the Volume line to bend upwards so that it does not hit zero before the Area line.  And as noted above, to some degree that may happen.  But I don't think it will happen very much.  Thus, while Volume in September is not likely to reach 0.000 in September, I think it is likely to get so close that it might as well be zero in terms of the effects of ASI on albedo and weather, ecosystem function, ship passage etc.

      So if the Volume line does not bend up to meet the Area line, then the Area line must bend down to meet the Volume line as they both near zero.  I think Area decline will accelerate as the ice that remains becomes progressively easier to melt due to qualitative changes in the ice at the micro level (salinity, density) and also at the macro ice pack level (more fracturing, mobility, export, open water albedo decline, warm air mass incursion, storminess, wave action, Atlantification etc.)

      The Absurdity will be resolved and disappear, as of course mathematically it must.  The real Absurdity is that we would allow such a drastic change to a critically important component of the planet's climate regulatory system.  The irrefutable fact that worries me the most is that the energy required to warm a gram of water by 1 degree C is 1/80 the energy required to melt a gram of ice.  The ice serves as a huge buffer to absorb warming energy being added to the system year after year.  The excess energy going into heating the Arctic Ocean will be more effective at doing so once the ice is gone.

      The observation trends are clear that September loses its ice first, with August and October not far behind.  So by that logic, I raise the stakes by calling Gerontocrat's bet for two months of ice-free Arctic absurdity by the early 2030s, and raise the bet to 3-months of an essentially ice-free Arctic by 2035 or earlier. 

      The CMIP3 to CMIP5 to CMIP6 globals models show a trend of projecting earlier dates for 1M km2 Sept Extent.  But they still don't call for even 1 month of 1M km2 "BOE" much before 2050.  See attached graphs below, from Stroeve et al. (2012), Geophys. Res. Lett., 39, L16502, doi:10.1029/2012GL052676 and SIMIP Community (2020). Geophysical Research Letters, 47, e2019GL086749. https://doi.org/10.1029/2019GL086749.  The blue line in first graph is CMIP3, the red line CMIP5.  In the bottom graph, the brown-gold line for CMIP6 is same RCP4.5 scenario as the red line in the CMIP5 graph.

      On one hand it's "What the heck do I know?"  On the other hand, it's PIOMAS, HYCOM, NSIDC, Wipneus, Gerontocrat, Stephan, and ASIF showing numbers that clearly indicate trends running far ahead of expert projections, and which show no sign of reversing course.  It's like the Arctic modelers are saying "Who ya gonna believe -- Me or your lyin' eyes?"  For me, the Eyes have it.  It is not the math that is Absurd, it is the reality it describes, and the fact that we are creating that reality.  Or as Shakespeare might have said, "The Absurdity, dear Brutus is not in our math, But in ourselves."
« Last Edit: March 25, 2021, 10:17:07 PM by Glen Koehler »

Tor Bejnar

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Re: When will the Arctic Go Ice Free?
« Reply #1903 on: March 25, 2021, 04:55:39 AM »
2 meter-thick ice in the Beaufort Sea in May is more likely to melt out during the summer than 2 meter-thick ice in May that drifts near the North Pole during the summer.

CAB sea ice is more resilient than ice in the surrounding seas - it is farther north and the melting season starts later; northern ice continues to thicken (bottom freezing) after southern ice extent starts decreasing (bottom and top melting). The ice-melt charts (showing rates of volume and extent loss over the years) are usually made for the entire Arctic, so they include  southern areas.  Nearing the BoE, most remaining ice will likely be in the CAB.

Therefore, I suggest volume loss will slow down more than will extent/area loss as we approach a BoE, but both will slow.
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1904 on: March 25, 2021, 06:03:29 AM »
      Good point.  I would have more faith in latitudinal delay if the final ice was centered around the North Pole.  The current HYCOM thickness model shows bulk of the thick ice being well south of 80N in Beaufort and along ESS shore.  PIOMAS thickness is less southerly but somewhat similar to HYCOM, and even CS2SMOS which shows thick ice overall at higher latitude still does not have it centered around 90N.
      Apologies to whomever I copied the attached graph from that shows the expected location of the final 1M km2 ASI Extent.  Current distribution may be a one-year exception, but in March 2021 the thick ice is centered well south of where the final 1M km2 of ice graph says it should be centered.
     While true that higher melt rate in southern locations has affected the Vol., Ext. etc. ice loss trends, in terms of Sept. minimum we are already in the era when almost all the ice remaining ice at end of melt season is in the CAB.  Gerontocrat's "River Valley" Area graphs for individual seas https://forum.arctic-sea-ice.net/index.php/topic,3426.msg303130.html#msg303130  shows that Barents, Greenland, Hudson Bay have been melting out for quite a while.  And that except for the Beaufort Sea and the CAB, the other high Arctic seas (ESS, Laptev, Kara) are already reaching or nearly reaching zero Area late in the melting season.
     Other Gerontocrat Volume graphs make the same point for Chukchi, CAA, and show even the Beaufort getting near zero.  That leaves the CAB as the last wall, and its late-season Volume is also less than what it used to be. 
     If getting down to the CAB as the final stand is going to slow down the trends, that should become apparent in a slowing of the trend lines over the next few years because we are already into the 'CAB last stand' era.  The later the Volume trend starts to slow the harder it has to bend away from zero.  The current straight-line trend has it reaching zero in 2033.
« Last Edit: March 25, 2021, 07:41:16 AM by Glen Koehler »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1905 on: March 25, 2021, 12:37:40 PM »
I may recall the discussion we had some months ago which I had called "trend of the trend lines". All months between July and November show a strong convergence (that means the slope of the "late" values extent and area is getting steeper year by year which means that the BOE date shifts to earlier times in comparison to more or less stable slopes of the "early" values volume and thickness which do not affect the predicted BOE date). I will follow this month by month in my monthly posting of the BOE numbers.

Unlike the summer/autumn months there is a divergence for the months Jan to May...
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1906 on: March 25, 2021, 12:46:52 PM »
      Mathematically the trend lines must meet at zero.  So one trend line has to bend to meet the other.  One mathematical option is for the Volume line to bend upwards so that it does not hit zero before the Area line.  And as noted above, to some degree that may happen.  But I don't think it will happen very much.  Thus, while Volume in September is not likely to reach 0.000 in September, I think it is likely to get so close that it might as well be zero in terms of the effects of ASI on albedo and weather, ecosystem function, ship passage etc.

      So if the Volume line does not bend up to meet the Area line, then the Area line must bend down to meet the Volume line as they both near zero.

False dichotomy: They can both bend up (or down)

And the models tend to show they do both bend up as zero is approached.

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1907 on: March 25, 2021, 02:24:04 PM »
In the end, AGW wins, even in winter
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1908 on: March 25, 2021, 03:22:39 PM »
In the end, AGW wins, even in winter

So sure it shouldn't be:

If GW continues at pace for long enough, yes GW will eventually win.

St Laurence is fairly low latitude. One example is nice, but if it picks lowest latitude place and doesn't show evidence of this moving to higher latitude at a rapid rate ... then why shouldn't I think this will be harder to achieve at higher latitudes that have months longer of darkness and seems to be taking its time to move much further north.

Concentration trends seem to affect wide bands in summer months and only narrow bands in winter.
https://nsidc.org/data/seaice_index/compare_trends

Bands of blue represent 40 years of Northward progress and may look like it will take much less than 40 years in September but that is assuming it continues at same rate. But we have had a fast rate of decline 2000ish to 2010ish and now the rate of retreat seems to be getting slower and that is what models suggest will happen.

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1909 on: March 25, 2021, 03:41:15 PM »
      Mathematically the trend lines must meet at zero.  So one trend line has to bend to meet the other.  One mathematical option is for the Volume line to bend upwards so that it does not hit zero before the Area line.  And as noted above, to some degree that may happen.  But I don't think it will happen very much.  Thus, while Volume in September is not likely to reach 0.000 in September, I think it is likely to get so close that it might as well be zero in terms of the effects of ASI on albedo and weather, ecosystem function, ship passage etc.

      So if the Volume line does not bend up to meet the Area line, then the Area line must bend down to meet the Volume line as they both near zero.

False dichotomy: They can both bend up (or down)

And the models tend to show they do both bend up as zero is approached.

Yes, the models do show that.  I think it is less of a false dichotomy than one has to (mathematically) bend [more] to meet the other.  I feel that it is more likely that volume will bend further to meet area.

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1910 on: March 25, 2021, 10:11:49 PM »
     The ice will decide so our words are like a pea shooter aiming at a battleship.  But FWIW, this graphic gives a nice single view of how all the seas except CAB are already reaching or nearing zero Area for extended periods in latter portion of melt season, and the CAB is also moving in that direction.
   Image from Oren post at https://forum.arctic-sea-ice.net/index.php/topic,3447.msg303886.html#msg303886
« Last Edit: March 25, 2021, 10:46:14 PM by Glen Koehler »

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Re: When will the Arctic Go Ice Free?
« Reply #1911 on: March 26, 2021, 02:44:24 AM »
I value the information provided the regional ice graphs but my experience is its to hard to find information or insights when staring at the whole thing at once. Opening each graph at full screen size and comparing it to images and other graphs is the only way I learn from them.

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1912 on: March 26, 2021, 02:35:01 PM »
I value the information provided the regional ice graphs but my experience is its to hard to find information or insights when staring at the whole thing at once. Opening each graph at full screen size and comparing it to images and other graphs is the only way I learn from them.

Because I downloaded the Wipneus detailed file on regional area and extent (to allow thickness calculations with PIOMAS data) I can give you the CAB graphs according to Wipneus (Area 4.457 million km2)  against the graphs of the NSIDC defined area of  3.224 million km2.

The NSIDC data shows a shallower and somewhat wider profile as the area is more or less confined to North of 80, while the Wipneus CAB extends a couple of degrees farther south and thus includes 1.2 million km2 additional area that now usually all melts out..

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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1913 on: April 14, 2021, 10:34:13 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 March value now includes 2021.

Position of March 2021 towards the long-term trend lines
Thickness, area, volume and extent are above the linear trend line.

Trend of the trends
The "BOE numbers" increased by 1 year (thickness), 2 years (volume), 17 years (area) and by 8 years (extent) compared to March 2020.
So there is once again a divergence between the "late values" (area, extent) and the "early values" (volume, thickness) which seems to be usual as I already posted for the "high winter months".
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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