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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 230566 times)

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1800 on: December 02, 2020, 03:37:52 AM »
Quote
Beckwith is not the most accurate or reliable source and his commercializing the catastrophe is offputting.
I agree.

BTW, Paul Beckwith is registered in the ASIF and has made a few posts some years ago, though he's not been seen since.

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1801 on: December 02, 2020, 08:38:09 AM »

Quote
Beckwith is not the most accurate or reliable source and his commercializing the catastrophe is offputting.

And that is putting it very mildly...

Tom_Mazanec

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Re: When will the Arctic Go Ice Free?
« Reply #1802 on: December 05, 2020, 03:40:51 PM »
Interestingly, I thought that if the Arctic was not ice free in the Holocene (at least so far) at least it probably was in the Eemian, so it would not be completely novel in "recent" Earth history.
Seems I was wrong:
https://phys.org/news/2012-06-climate-cold-arctic-eemian.html
So AFAIK the Arctic may be about to be ice free for the first time in a couple million years?
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Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1803 on: December 16, 2020, 05:22:21 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 November value now includes 2020.
Extent and volume lie slightly below the long term linear trend, thickness is lower than the long term trend line, whereas area dives deeply below it. The "BOE numbers" did not change (volume, thickness) and decreased by 4-5 years (extent, area) compared to November 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 #1804 on: December 16, 2020, 05:49:57 PM »
    Thanks for tracking the data Stephan. 

    I don't expect the "Great Convergence" between Extent and Volume trends until closer to the endpoint as Volume gets below about 0.8 km3 and when the average thickness is below 0.8 meter.  But you mentioned that the Ext and Vol trends are already converging. 

     Do you have a record over recent years of the difference between the extrapolated zero-year estimates for Extent and Volume trends?  That would be interesting to see, and would correct the mistaken (IMHO) assumption by some who think the Extent trend is an accurate predictor for the first, and then regular, BOE status in Septembers.   

     My view is that Vol. dictates Ext., not vice versa.  And that as Thickness declines there will be an acceleration of Extent decline until it catches up to Volume at zero.  Thus, first <1m km2 Extent BOE around 2030 or earlier, not around 2060 as estimated from extrapolation of the Extent trend.  Multiple other correlated indicators such as global average surface temperature and cumulative atmospheric CO2 ppm also point to BOE status being reached around the same time as the Volume trend estimate. 

     The problem with Extent, as noted in JC Garcia's tagline, is that Extent alone hides about half of the ice losses because it does not account for simultaneous Thickness reduction.
« Last Edit: December 16, 2020, 06:03:12 PM by Glen Koehler »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1805 on: December 16, 2020, 06:31:56 PM »
         Do you have a record over recent years of the difference between the extrapolated zero-year estimates for Extent and Volume trends?  That would be interesting to see, and would correct the mistaken (IMHO) assumption by some who think the Extent trend is an accurate predictor for the first, and then regular, BOE status in Septembers.   
Glen,
unfortunately no. I save the actual screenshot of the values under the same file name. So the only way to look back is to look at my postings in this thread which began roughly two years ago...

kind regards Stephan
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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1806 on: December 16, 2020, 09:08:08 PM »
         Do you have a record over recent years of the difference between the extrapolated zero-year estimates for Extent and Volume trends?  That would be interesting to see, and would correct the mistaken (IMHO) assumption by some who think the Extent trend is an accurate predictor for the first, and then regular, BOE status in Septembers.   
Glen,
unfortunately no. I save the actual screenshot of the values under the same file name. So the only way to look back is to look at my postings in this thread which began roughly two years ago...

kind regards Stephan

If you look at the data over the long term, the trend in extent has stayed relatively constant (actually slow slightly, but not much). Conversely, volume decline has slowed considerably, bringing it closer to extent.  This is not surprising, as volume is three-dimensional, and will decrease faster than either extent (area) or thickness which are two- and one-dimensional.  For this reason partly, and also that volume is an estimated value whereas extent and area are measured, I am one of those that view extent dictates volume.

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1807 on: December 16, 2020, 11:13:44 PM »
    Thanks for the reply Stephan.  If/when I get around to addressing what is really just a statistical fetish, it would not be difficult to get the extrapolated BOE dates from regressions of annual values for Ext, Vol, and Thickness for incrementally later sets of years
(e.g. calculate the Ext and Vol/Thickness trends with data for 1978 - 1988, then 1980 - 1990, 82-92, etc., then for each set of years record the difference between estimated BOE year based on Extent trend minus estimated year based on Vol/Thickness trend).
 
    The point of this obsessive number crunching would be to see if the difference between the Extent-based vs. Volume-based BOE estimate is already getting smaller through time, aka the
'Great Convergence".  But since I don't really expect the convergence to emerge until closer to the endpoint, I won't be convinced that my theory is incorrect even if that difference is not yet diminishing.  Which is troubling because it means that in a way I am as situationally immune to math as certain psychiatrically-damaged morally-void politicians who shall remain nameless in order to keep this forum apolitical.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1808 on: December 17, 2020, 05:39:48 PM »
Glen,
I just did a "quick and dirty" experiment with a set of reduced data (1979-2008) versus 1979-2020.
I calculated the "BOE numbers" for the time period 1979-2008 and compared it with the full period (1979-2020). I reduced the evaluation on extent and volume and just performed the linear evaluation. Finally I compared the differences (column Delta) for each month (extent versus volume). If the Delta in extent is larger than the Delta in volume, the "BOE numbers" converge. If it is the other way round, the values develop apart.

Conclusions:
1. The slope of almost all months has grown steeper from 1979-2008 to 1979-2020.
2. This results in earlier "BOE numbers" for most, but not all of the months. The "BOE numbers" for extent increased in Jan, March and April!
3. There is a clear season for convergence: summer and autumn, marked in green. In winter and spring the values go even further apart, marked in pale magenta (column "Delta"). June and Sep are more or less undecided.

See attached table.
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1809 on: December 18, 2020, 10:27:43 PM »
Dear Stephan - Nice work and much appreciated.  I think that this addition to your monthly trend posts really gets to the heart of the issue.

       Everybody else - especially Arctic amateurs like me:  Take enough time to understand what these numbers are saying.  What may appear at first glance may appear to be an innocuous table of numbers, in truth says major and disturbing things about the future of the Arctic, this planet, humanity in general, and the not-very-distant future for each us individually and the people we love.

    1) Lots of talk by IPCC and elsewhere about sea level rise by 2100.  No disagreement with that, it is a huge impactful manifestation of our insane management of the planetary life support system.  But also consider what it means to have ZERO Arctic sea ice volume in June, the month of maximum solar energy injection, by 2067.  Moreover, that the date for that catastrophic milestone gets 20 years earlier when you add 12 years to the straight-line trend to go from 1979-2008 to 1979-2020.  Will adding another 12 years, i.e. 1979-2032 put that date at 2047? 
       A planet without its reflective polar cap in June is a different planet than the one we were born on.

    2)  If 2047-2067 is too far off to get your interest, how about 2032-2035?  And what about 2026?  Is that close enough to get your attention as being real?

        ZERO Arctic Sea in August - October is also a radically different planet. While far below June, there is still considerable solar energy input in August.  And an ice-free Arctic Ocean in October (and with much reduced ice in November) venting heat into the atmosphere is bound to have strong effects on mid-latitude weather patterns. 

        The table highlights the fact that adding 12 years to the dataset used to define the trend pushes the zero volume dates 9-14 years earlier.  2032-2035 is already close at hand, but will those trend endpoints continue to get earlier as each new year is added?  Where will those endpoint dates be in just 6 more years in December 2026?  The "trend of the trends" suggests that the estimated ice-free Sept date by then could be another six years earlier, i.e. 2026.  At risk of piling extrapolations on top of each other, does that suggest that we could already have had a zero-ice September by then?

        One of the problems in conceptualizing climate change is that the perceived impacts are in the future.  People already dealing with wildfires, heat waves, droughts, hurricanes, crop failures etc. will have a more immediate perspective, but for many/most of us, the climate changes that worry us are said to be decades ahead and so bring a bit less visceral fear. 

        The dates shown for zero ice volume are nothing new to me, so I've long had the mental concern.  And perhaps I am misinterpreting and over-reacting to seeing the earlier progression of endpoint dates that result from adding 12 years to the dataset.  But my visceral fear just went up.  My emotional operating principle has been that the proverbial poop could hit the fan if global average surface temperature reaches +1.5C over preindustrial circa 2030.
 
       I keep thinking that my understanding of climate change and Arctic Sea Ice decline has reached a level of stability at which I can at least see the horror for what it is, and at least define the problem.  But the damn problem keeps growing like a cancerous tumor.  Seeing that date migration of the Sept. zero ice year has me wondering if I should recalibrate my gut-level fear threshold and "poop in the fan" date more towards August 2026 - less than 68 months from now. 

       Of course, ranting aside, the "Now" is all that we can change to affect the Future.  I hope your data serves as that one additional piece of alarming evidence that tips the scales to wake up the political and business powers to realize that the money won't do any good if there is not a livable planet on which to spend it.  Sorry for such a bleak message as we head into the traditional western holiday season.  I would highlight the fact that some good things are also underway, but this message is already long.  So yes, there are also some good possibilities emerging.  We MUST make those possibilities real.
« Last Edit: December 19, 2020, 12:25:09 AM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1810 on: December 18, 2020, 11:55:37 PM »
To get back to the Convergence question:
      The hypothesis is that the number of years remaining until the zero ice date estimated by the Extent trend will decrease relative to the date estimated by Volume as we get closer to that date.
The hypothesis says that until they meet when both Volume and Extent trends reach zero, it is the Extent date that will shift to meet the earlier Volume date, not vice versa.

      Here are the relative zero date migrations for 1979-2008 vs. 1979-2020 for each month.
The values for Extent and Volume are the number of years earlier the end date became by adding 2009-2020 to the 1979-2008 dataset.

      By subtracting the Volume shift from the Extent shift, a Positive value means that the Extent estimate moved earlier by a greater amount, which is what the hypothesis predicts.  A negative difference means the opposite, that instead of drawing closer to the Volume-based estimate, the Extent-based estimate is moving away from it. 

Jan: -2 (for Extent) minus 13 (for Volume) = -15 
    The Vol. estimate got 13 years earlier, but Extent est. became later not earlier, and thus farther away from the Vol estimate.  This is the opposite of convergence and NOT what the hypothesis predicts.

Feb:   12 minus 15 =  -3
Mar: -22 minus 15 = -37 
Apr: -45 minus 15 = -60  (Wow, Ext estimate became 45 years LATER).
May:   6 minus 19 = -19
Jun:  21 minus 20 =    1
Jul:   24 minus 15 =    9
Aug: 20 minus 11 =    9
Sep: 13 minus 14 =   -1
Oct:  30 minus 9  =   21
Nov: 27 minus 11 =  18
Dec:   4 minus 10 =  -6 

      As you noted, the winter and spring months are doing the opposite of convergence.  While summer and fall are generally showing convergence.  That makes sense in that we would expect the "thin ice" months to show convergence between Extent and Volume before the "thick ice" months.  It is when thickness reaches a critical low threshold that Extent losses increase causing it to begin to catch up to Volume.

      June being a neutral month with respect to the "Extent trend must bend down to catch Volume trend" hypothesis makes sense because it is the transition between the thick ice and the thin ice months.

      But September is a brain twister.  It seems like it should show a full expression of the 'Extent catches Volume as ice thins' trend.  My guess is that those bays in the CAA and other ice traps that are the reason for setting the BOE definition at 1M km2 of residual Extent instead of zero, are already constraining reduction in September Extent.  Those areas may be superficial thin ice that add to the Sept. Extent value without adding much to the Sept Volume because they are so thin.  As a result, the Sept. Extent value does not decline as much as it "should", but Sept. Volume does not as effectively hide the loss of ice.

      It is also a bit mysterious to see the peak "thick ice" months going the opposite direction, i.e. the Extent-trend zero date is getting farther away not closer to the Volume date.  And for March and April, the zero Extent estimate is getting absolutely later, not just getting earlier at a slower rate than the Volume date. 

      My guess is that happens because once the Arctic Ocean fills up with ice, it is full.  Even in the colder, higher ice volume past, it could not add more Extent because the Arctic Ocean is surrounded by land.   These days, the ice Extent comes from thinner low-volume ice, but that change is not reflected in the Extent value.  It still counts for Extent.  The March and April constraint on Extent in the past means that as the ice declines now, relative to the previous years, March and April don't show much if any Extent loss.  So as more years are added to the dataset, with little change in the constrained monthly Extent values for March and April, the trend towards a Zero Extent date for those months is essentially no trend at all with termination dates over 300 years from now vs. decades for the other months. 

      Actually, that point applies to ALL of the maximum ice months of January through May.  For each of them, the zero Extent year estimate is past 2300, and for Feb-May, in the late 2300s.  Thus the negative trend slope is so minor that there really isn't much trend at all due to the constraint on maximum Extent in earlier years.

      The "land bound Arctic Sea Ice" argument conveniently ignores the potential for additional Extent in the peripheral seas not bound by the coast of the Arctic Ocean.  Are your Extent and Volume data for the entire Arctic, including the peripheral seas, or are they limited to the (mostly land bound) central Arctic Ocean?

      If the data are limited to the central Arctic, then I don't have to explain away that potential for additional Extent.  But if your data also include those peripheral areas (Greenland, Okhotsk, Bering Seas) that the "land bound Arctic Ocean" argument does not address, I won't even attempt to concoct some reason to explain them away as I have already used up my daily allowance for fabricating "evidence".
« Last Edit: December 19, 2020, 03:11:32 AM by Glen Koehler »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1811 on: December 19, 2020, 09:39:17 PM »
Glen,

thank you for your excellent reply and thoughts.
I have performed a second experiment on the data. I only used the first twenty (instead of thirty) years. One of the reasons is to omit the super melting year 2007 which, lying almost at the end of the 1979-2008 series, may have influenced the statistical analysis. And, the years 1997-1998 have been unspectacular, both extent- and volume-wise.

Please find the same evaluation, which has to be taken with a certain grain of salt as only 20 years were used. Especially the April value seems not to be very trustful, but I double-checked the data.
But the general trend is comparable. Please notice that the slopes (column stg) are again much smaller than the slopes 19291979-2008 have been. This results in a massive time shift of the "BOE numbers" compared to what they are calculated today. And who may know whether this tendency goes on like that in the next decade?

Evaluation:
Spring months still develop apart. June is still undecided. Summer, autumn and winter values converge.

Please note that I used the NSIDC data for the whole Arctic including all peripheral seas.

One final note to the "undecided" September from the 1979-2008 evaluation: The slope has been higher than it should have been because Sep 2007 was so low. This resulted in a "BOE number" close to what it is estimated today.

See attached table.
« Last Edit: December 20, 2020, 03:44:18 PM by Stephan »
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kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1812 on: December 20, 2020, 10:38:11 AM »
Please note that I used the NSIDC data for the whole Arctic including all peripheral seas.

Is there a way to do this data but without the 4 B´s (Baffin, Barentz, Bering and (B)Okhotsk?
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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1813 on: December 20, 2020, 02:29:41 PM »
Please note that I used the NSIDC data for the whole Arctic including all peripheral seas.

Is there a way to do this data but without the 4 B´s (Baffin, Barentz, Bering and (B)Okhotsk?

That would be nice, as there is some belief that the trend change was due largely to the melting out of these areas.  If I remember correctly, it was gerontocrat who show a graph of just the central arctic.  Perhaps, he can help.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1814 on: December 20, 2020, 03:43:24 PM »
I do not have the regional data in my PC. Maybe I can download them from somewhere or there is a file that someone could share with me. Then I'd like to do this evaluation.
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kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1815 on: December 20, 2020, 11:30:30 PM »
I went looking back to what Oren used before but NSIDC regional data is extent only so that is not going to help.

Jan: -2 (for Extent) minus 13 (for Volume) = -15
    The Vol. estimate got 13 years earlier, but Extent est. became later not earlier, and thus farther away from the Vol estimate.  This is the opposite of convergence and NOT what the hypothesis predicts.


But it is consistent with melting stuff. Volume is hard to make and extent not so much. Extent chases area chases volume.

On another note there must be some thickness which leads to trouble. What is the average thickness to disappear in a year? At some point all kinds of processes that were not important are going to play a role. The summer ice will become ever more shattered and drift more.

Of the 4 measurements i would totally go with volume as the best predictor.

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Rodius

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Re: When will the Arctic Go Ice Free?
« Reply #1816 on: December 21, 2020, 10:35:56 AM »
I think I located the first one, so I saved it and the latest one for those who want to compare.
The first one was Sept 2018

EDIT: One is 2018 (top)
Two is 2020 (Bottom)

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1817 on: December 21, 2020, 02:30:40 PM »
Thank you rodius,
I did the same and wrote down the "BOE numbers" from Feb 2019 (they contain the whole year of 2018) into my spread sheet.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1818 on: December 21, 2020, 03:39:36 PM »
The amazing Wipneus has all sorts of regional data on his website, including the regional NSIDC extent and area numbers.
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data/nsidc_arc_nt_detail.txt

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1819 on: December 23, 2020, 02:36:51 AM »
      Here are the relative zero date migrations for each month using Stephan's revised data.  The values for Extent and Volume are the number of years earlier the extrapolated date for reaching zero migrated due to changing the period of years used to define the trend from 1979-1998 (= a midyear of ca. 1989) to  1979-2020 (midyear 1999). 

      By subtracting the amount of change in the projected zero Volume date from the amount of change in the Extent zero date, a Positive value means that the Extent zero date moved earlier by a greater amount, which suggests that Extent losses accelerated to catch up to Volume.  A negative difference means the opposite, that the Extent trend estimate changed at a slower rate than the Volume-based estimate.   

      The original hypothesis was that as ASI declines, eventually the Extent losses will accelerate to catch up to Volume losses, and that Volume is a more reliable predictor for reaching extreme low values such as a BOE (i.e. < 1M km2 Exent and < ca. 0.8M km3 Volume) or the first date with zero ASI.  The mechanism for this happening was attributed to accelerated Extent losses as ice thickness gets below a threshold value at which rapid Extent losses can occur.  That threshold is incremental, but the effect probably becomes noticeable for a given area of ice when its average thickness gets below about 1 meter.  (If I recall correctly, across the Arctic Ocean as a whole, the average thickness during a melt season declines by about 2 meters before ice accumulation and thickness increase begins in late autumn.)

BEGIN THICK ICE MONTHS
Jan: 152 (for Extent) minus 101 (for Volume) = 51    Positive difference.  Extent CONverged 
      The date for zero Extent moved 152 years earlier, while the date for zero Volume moved 101 years earlier.  Thus, Extent advanced 51 years more than the Volume date. 
Feb:   182 minus 119 =   63  Extent CONverged.
Mar:    20 minus 105 =  -85  Extent DIverged, Extent migration was slower than Volume. 
Apr:   -60 minus 93 =  -153  Big DIvergence.  (Ext estimate became 63 years LATER).
May:   11 minus 90 =    -89  Extent DIverged.
END THICK ICE MONTHS
THICK to THIN TRANSITION
Jun:    72 minus 69 =      3  Slight CONvergence, but essentially Ext and Vol had equal change.
BEGIN THIN ICE MONTHS
Jul:     73 minus 46 =   27  Extent CONverged.
Aug:  120 minus 38 =   82   Extent CONverged.
Sep:  123 minus 45 =   78   Extent CONverged.
Oct:   190 minus 55 = 135   Extent CONverged.
Nov:  157 minus 73 =   80   Extent CONverged.
END THIN ICE MONTHS
THIN to THICK TRANSITION
Dec:  243 minus 98 = 145   Big Extent CONvergence.

      The hypothesis that Extent losses during the thin ice months appear to be accelerating to eventually converge with Volume losses seems to hold up.

      In the first comparison (using 1979-2008 vs 1979-2020), the Sept difference between the relative change in extrapolated zero date for Extent and Volume was contrary to the hypothesis.  In this second comparison (1979-1998 vs 1979-2020) the relative Sept change supports the hypothesis.  And this time, the relative changes in Dec, Jan, and Feb Ext vs. Volume zero dates show convergence even though those months were expected (by me at least) to be neutral because the thin ice mechanism expected to drive convergence does not yet exist for those months. 

      More important than the hypothesis is the larger point is that if we want to estimate when ASI losses will reach some extremely low (never seen in human history) level, then the Volume straight-line trend is a more reliable predictor than the Extent trend.  Extrapolating the Volume trend estimates that a first complete or near-complete loss of late-summer ice will occur by 2029-2034.  It is interesting and disturbing to see estimates from the straight-line Volume trend getting even earlier as more years are added to the data. 

      It is too bad we apparently do not still have Tamino available.  This is the kind of stuff he would slice and dice and pull whatever meaning exists from the numbers.  He might say we are sword fighting with shadows, i.e. the net differences are based on too few years of data to make conclusions.  But my guess is that these differences in trend-based estimates would pass statistical muster (my guess being worth exactly nothing, that is why we have statistics - to get past guesswork based on intuitive hunches).

      We may have squeezed this lemon dry, but the patterns are interesting.  If Stephan or somebody else is up for one more round, it would be interesting to see what comes from comparing non-overlapping periods, i.e. 1979 - 1999 vs 2000 - 2020.
« Last Edit: December 24, 2020, 06:56:18 PM by Glen Koehler »

kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1820 on: December 23, 2020, 08:17:47 PM »
Quote
if we want to estimate when ASI losses will reach some extremely low (never seen in human history) level, then the Volume straight-line trend is a more reliable predictor than the Extent trend

But this also just completely follows from physics.

Another problem is that purely looking at ASI you miss part of the data. Of the simple prediction models that used to play in the yearly poll the best one ran of NHEM snow cover. So here we are looking at the reactions of a system (the ASI growing back its extent).
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1821 on: December 26, 2020, 03:38:27 PM »
https://forum.arctic-sea-ice.net/index.php/topic,2245.msg296662/topicseen.html#msg296662

There is a big lump of ice in the Antarctic called A-68-A. Ok, so it is a lump of ice sitting in a cold ocean and it is melting. But just about everything else is different from the ice and its environment in the Arctic

Nevertheless, in the years since 2017 when it started its voyage, ice extent is down by 54%, ice volume down by 64%.

The two large bits that broke off on 21 Dec were much thinner than the averge, so before that happened volume loss difference from extent loss would have been even higher. Looking at the graph in the post linked above suggests that on Dec 20 the extent loss was about 32% and volume loss about 45%. (Why don't they provide the data in a table?)

So my speculation that belongs to me is that if you put any old lump of  ice into water the volume loss exceeds area loss (until?) It will be fascinating iff we get to see the end of days of this berg and see how long this excess of volume loss over area loss continues.

Is this relationship between volume and area universal simply because
Quote
this also just completely follows from physics.  Kassy
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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1822 on: December 27, 2020, 02:53:07 PM »
Excellent example gerontocrat.  I have been arguing that same point for years.  The example I would use is an ice cube.  If every side melted 30%, any one side would decrease 30% (thickness), while any surface area would decrease 51%, and total volume would decrease 66%.  That real life example is close, and it would be real interesting to follow it to completion to help settle the area/extent vs volume debate.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1823 on: December 28, 2020, 08:15:35 AM »
Good idea Gero to use that big floating lump of ice as an experiment in seeing how the extent / volume ratio changes leading up to the inevitable convergence at 0 of both measures.

We should be careful, though, not to draw too many conclusions, the big Antartic lump is not sea ice (it is fresh-water glacial ice that has broken off an ice shelf), and it is very much thicker than normal sea ice will ever be.

I would expect the ice to disappear very quickly once structural integrity breaks down. Due to the excessive thickness, extent might actually increase temporarily, specifically if distances between breakup fractures is less than the thickness at the time (the narrow wedges will simply fall on their sides as they break away).

The rush to convergence will possibly start while the ice is signifcantly thicker than our normal sea ice due to it's location in the middle of an open ocean with the concomitant swells and wave action.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1824 on: December 28, 2020, 02:47:17 PM »
The example I would use is an ice cube.
Sea ice is not a cube, it is very thin compared to its length and width, which is why the analogy and the insights derived from it are irrelevant.

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1825 on: December 28, 2020, 02:54:40 PM »
The example I would use is an ice cube.
Sea ice is not a cube, it is very thin compared to its length and width, which is why the analogy and the insights derived from it are irrelevant.

True, it is a simplistic examples.  In actual sea ice, extent is more relevant than volume, due to the very thin thickness.  Large percentage changes in a very small number can have a profound effect on the volume, while the extent (or area) appears to be little changed.

P-maker

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Re: When will the Arctic Go Ice Free?
« Reply #1826 on: December 28, 2020, 03:07:14 PM »
Oren,

the relative dimensions for individual sea ice-floes are not that different from those of A68-A.

In the Southern open ocean, also swells and currents are stronger than in the Arctic ice-pack during melting.

I guess it is premature to rule out a new learning experience from this ongoing devastation.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1827 on: December 28, 2020, 04:06:42 PM »
P-Maker, I agree with the A68 analogy and find it interesting, but the ice cube analogy is irrelevant.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1828 on: January 10, 2021, 09:48:17 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 December value now includes 2020.
Extent and area lie slightly below the long term linear trend, thickness and volume are close to their trend lines. The "BOE numbers" did not change (volume, thickness) and decreased by 5 years (extent, area) compared to December 2019.
So there is a further convergence between the "late values" (area, extent) and the "early values" (volume, thickness).
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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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1829 on: January 14, 2021, 01:30:14 AM »
https://xkcd.com/2048/



Quote
Logistic: I need to connect these two line but my first idea didn't have enough maths.


Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #1830 on: January 14, 2021, 10:08:55 PM »
Luckily the Arctic Sea Ice graphs look much less scattered and chaotic than the ones in your sketch.
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Re: When will the Arctic Go Ice Free?
« Reply #1831 on: January 27, 2021, 11:14:11 PM »
From:
Slater, T., Lawrence, I. R., Otosaka, I. N., Shepherd, A., Gourmelen, N., Jakob, L., Tepes, P., Gilbert, L., and Nienow, P.: Review article: Earth's ice imbalance, The Cryosphere, 15, 233–246, https://doi.org/10.5194/tc-15-233-2021, 2021.
https://tc.copernicus.org/articles/15/233/2021/tc-15-233-2021.pdf 
<snip>     RE: the table shown below comparing Gt/year ice loss between periods.  I find it odd that the amount of ASI loss in 2000s is higher than for the 2010s.  Even multiplying the 2010s number by 1.1 since it only accounts for 2010-2018 (missing 2019) gives a much smaller value of ca. 103 vs. the 384 for the 2000s.

    Wipneus' PIOMAS volume graph for Sept. minimum volume shows a change from 2000 to 2009 of ca. 11 to 7 M km3, and ca. 7 to 4 for 2010 to 2019.   That is not directly relevant since the study used the winter (October -April) average ASI volume trend not the summer minimum trend for their ice loss measure.  But I don't see how the losses in 2000-2009 could so much exceed the 2010-2018 value.  And even the 1980s and 1990s rates of winter ASI loss are almost 1.5 and almost 3X higher than the extrapolated Gt/year for 2010s. 

    Even though it is measuring a different month of the year, I do not see why the Wipneus Sept minimum chart would show a consistent trend in losses while this study apparently finds a much lower rate of ASI loss in the 2010s. 
    I posted this in the What's New in the Arcitc thread.  Kassy suggested moving to the "When will the Arctic Go Ice Free" thread.

   Here is the subsequent discussion:
Kassy:  Well the winter ice was thicker overall so there was more to melt out then.

Glen:   Yes, but there was also a lot more summer ice in the earlier decades, yet the PIOMAS volume (e.g. Wipneus chart) shows a steady rate of decline.  So why would winter (Oct-Apr) losses show a 2/3 reduction in loss rate for the most recent decade compared to prior decades, while September minimum losses continued to follow a consistent trend?

Kassy:  They are not so much winter losses as snapshots of the overall loss only taken in winter.

Back to me this time:  I still don't get it.  Why would the trend for Oct-Apr average volume values be so radically different from the trend of Sept. minimum values? 

    OK, I can almost get that if within a single time period (i.e. one decade in the table) there were strong winter compensatory increases after September minima each winter.  That way, even with a trend in Sept. minimums, the Oct-Apr values would not change as much.  Which I guess is what's happening, but the strength of that compensatory factor is surprising.

    Restated: Why do Oct-Apr losses show a strong rate of decline in 1990s and 2000s, then decline to about 1/3 of those loss rates per year in the 2010s, when the September minimum trend continues going down?

   Here is what I see in the Wipneus monthly PIOMAS trend lines for some example months.
Granted the exponential trend overtates the rate of decline and is not accurate for the most recent 3 years, but I think it does so more or less equally for all months and still captures the bigger comparison between decades well enough (values rounded for clarity):

SEP:  1980: 16      1990:14      2000:11       2010:8     2020:3
Nov-  1980:20,      1990:18,     2000:15,      2010:12,     2020:8
Jan-   1980:26       1990:24,     2000:22,       2010:19,     2020:15
Mar-  1980:31       1990:29      2000:27        2010:23       2020:20

Which gives these decadal declines
SEP- 1980-1990:2       1990-2000:3      2000-2010:3      2010-2020:5
Nov- 1980-1990:2       1990-2000:3      2000-2010:3      2010-2020:4
Jan- 1980-1990:2         1990-2000:2      2000-2010:3      2010-2020:4
Mar- 1980-1990:2         1990-2000:2      2000-2010: 4     2010-2020:3

   Part of my brain is saying, "Of course there is no difference in the decadal trendline values dummy, each trend line is drawn to smooth out any such differences."  Which is true, but the individual years within each decade for each month are roughly 50:50 above and below the trend line through the trendline in that decade, so I don't think that is a major problem.

    Partial brain fart:  The individual years are NOT 50:50 for the final years of the 2010-2020 trendline.  Instead for each of those month/years (and also Oct,Dec,Feb,and Apr), the individual monthly values for the final 1-3 years are above the trend line, thus showing a lower rate of decline than the trend line for the final period 2010-2020, which is the whole point.  But that is also true for September, so I think the original argument still stands.

    In summary: I don't see a big drop off > 66% in the rate of decline Oct-Apr monthly PIOMAS between 1990-2000 and 2000-2010  vs.  2010-2020.  But that is what is indicated by Slater et al. (though their data stop in 2018).

 

     
     
« Last Edit: January 28, 2021, 12:43:52 AM by Glen Koehler »

crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1832 on: January 28, 2021, 12:41:36 AM »
« Last Edit: January 28, 2021, 03:56:20 PM by crandles »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1833 on: January 28, 2021, 12:54:59 AM »
Thanks, crandles, I see it now.  Always good to look at the data twice before speculating out loud  (the scientific equivalent of another rule I have often violated, "Measure twice, cut once."  :D

You beat me to it while I was crafting the extraction below... but that also leads to a new mystery.

UPDATE:  Oh, I see it now.  On the Wipneus monthly PIOMAS chart, the last 10 years for Jan-April are pretty much a flat line, i.e. No negative trend.  Dec, Oct, Nov. and Sep are only slightly negative.  And looking back at the linear Wipneus Sept. minmum chart, and blocking out years prior to 2010, ALSO shows an essentially flat trend.

     Now the Slater et al. table values make sense.  But as usual in science, that solution leads to another question.  Is this reduction in rate of volume loss since 2010 because the system is still adjusting to massive loss of MYI in 2003-2007?  Or because there is less ice to lose and/or because the most vulnerable ice has already been "harvested", leaving less vulnerable ice which has a slower rate of loss?

    Which leads to: What happened in 2003-2007 to blow a gasket in the ASI?  Yes, there were some warm summers, but there have been warmer summers since then with less drastic impact on the PIOMAS volume.  My first guess was that the cause was crossing a threshold for enough ice thinning and fracturing to increase mobility, combined with favorable drift/wind patterns (and some warm sunny summers), to create systemic change causing gigatons of MYI to flush out through the Fram.

     Which led to:
Spreen, G., de Steur, L., Divine, D.,Gerland, S., Hansen, E., & Kwok, R.(2020). Arctic sea ice volume export through Fram Strait from 1992 to 2014. Journal of Geophysical Research:Oceans, 125, e2019JC016039. https://doi.org/10.1029/2019JC016039

     I don't see a massive Fram flush in 2003-2007 to explain the big volume losses.  But it does show less Fram losses starting in 2009.  So that's at least a partial explanation for the slowdown in volume losses in the recent decade.  Spreen et al. noted that reduction in Fram export correlated with CAB volume, which aligns with what Kassy said at the beginning.

     My latest and final guess is that conditions reached a threshold for rapid melt of MYI in 2003-2007.  This all reminds me of the great 1998-2013 global warming 'faux pause' exploited by the climate change deniers esp. in 2010-2013, and that even had climate scientists scratching their heads for a while.  Of course, the heat was still there, it was just that a larger portion was being partitioned in the ocean.  And eventually the pendulum swung back with surface temperature blow-outs and new record highs in 2014, then 2015, then 2016.  I suspect that ASI may show a similar same pattern of a temporary slow down period followed a step-change acceleration.  And ASI conditions in late 2020 seemed to indicate a system with internal weaknesses close to another breaking point.

     I will stop guessing and polluting the Forum by flaunting my ignorance in public for now and do more reading.  Stroeve and friends wrote a post mortem about 2007 which I need to revisit.  The Arctic is complex, interesting, and not given to simple explanations.
« Last Edit: January 28, 2021, 06:59:08 AM by Glen Koehler »

crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1834 on: January 28, 2021, 01:40:46 AM »
You may want to read the slow transition thread
https://forum.arctic-sea-ice.net/index.php/topic,933.msg32299.html#msg32299

Quick summary:

The trigger for rapid loss:

MYI used to make it around the Beaufort gyre which gave the MYI time often lasting 10 years, time to be compressed and thicken.

Chukchi to Laptev started melting out each year so MYI didn't make it around the gyre. The area of 3+year MYI collapsed ensuring Chukchi to Laptev melts out each year.

Why doesn't it encroach further and further; Why does it slow down?

Basically when the thick MYI is down to a new much lower minimal level the period of rapid loss is over.

Thermodynamic growth of ice in winter. The thicker the ice the more insulation there is so heat is lost only slowly. Less heat loss=less ice formation. So there is a limit of around 2m of ice through thermodynamics (compression, slabbing and ridging obviously make some thicker). Whereas with very little ice thickness then the ice grows rapidly over winter.

Consequently when and where there is thick MYI losing its thickness down to 2m in summer, this ice is gone and it doesn't grow back. If instead we have 1.5m FYI then this all melts out but it  regrows back quickly in winter. This means much less net change from one year to the next.

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1835 on: January 28, 2021, 02:04:32 AM »
     Thanks crandles.  I had read through the entire long slow decline thread a couple of years ago during another crusade to understand ice thickness trends, and got the gist of the thin vs. thick ice thermodynamic winter recovery mechanism.  But your excellent summary makes it very clear and adds context about the Chukchi and Laptev seas changing from ice nursery to killing zones as the main cause of the MYI demise.  I think it would be useful to cross-post it there as an epilogue capstone to that vaunted thread.
« Last Edit: January 28, 2021, 02:02:03 PM by Glen Koehler »

kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1836 on: January 28, 2021, 03:38:23 PM »
Quote
Why doesn't it encroach further and further; Why does it slow down?

Basically when the thick MYI is down to a new much lower minimal level the period of rapid loss is over.

Thermodynamic growth of ice in winter. The thicker the ice the more insulation there is so heat is lost only slowly. Less heat loss=less ice formation. So there is a limit of around 2m of ice through thermodynamics (compression, slabbing and ridging obviously make some thicker). Whereas with very little ice thickness then the ice grows rapidly over winter.

Consequently when and where there is thick MYI losing its thickness down to 2m in summer, this ice is gone and it doesn't grow back. If instead we have 1.5m FYI then this all melts out but it  regrows back quickly in winter. This means much less net change from one year to the next.

But it is important to remember that this is only a temporary situation. We have more and more open water in summer, more mobile ice. This over time interferes with the buildup of thick ice.

Early open waters can lead to mixing up heat and i suspect that this process can provoke areas with year round open waters.

And of course the very atmosphere over the now cracked up ice is changing from Arctic desert to some state with more water vapour year around so some day we are going to get a steady drizzle over ice.

The statistics are just an abstraction of a whole bunch of underlying physical processes.
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1837 on: January 28, 2021, 04:17:46 PM »
Quote
Why doesn't it encroach further and further; Why does it slow down?

Basically when the thick MYI is down to a new much lower minimal level the period of rapid loss is over.

Thermodynamic growth of ice in winter. The thicker the ice the more insulation there is so heat is lost only slowly. Less heat loss=less ice formation. So there is a limit of around 2m of ice through thermodynamics (compression, slabbing and ridging obviously make some thicker). Whereas with very little ice thickness then the ice grows rapidly over winter.

Consequently when and where there is thick MYI losing its thickness down to 2m in summer, this ice is gone and it doesn't grow back. If instead we have 1.5m FYI then this all melts out but it  regrows back quickly in winter. This means much less net change from one year to the next.

But it is important to remember that this is only a temporary situation. We have more and more open water in summer, more mobile ice. This over time interferes with the buildup of thick ice.

Early open waters can lead to mixing up heat and i suspect that this process can provoke areas with year round open waters.

And of course the very atmosphere over the now cracked up ice is changing from Arctic desert to some state with more water vapour year around so some day we are going to get a steady drizzle over ice.

The statistics are just an abstraction of a whole bunch of underlying physical processes.

yes just an abstraction of a whole bunch of underlying physical processes.

We try to pick out what we think important by way of changes but certainly can be wrong or introduce bias.

>more and more open water in summer
>atmosphere over cracked up ice ... some day we are going to get a steady drizzle

What make you think these are not gradual processes slowly encroaching further into the Arctic applying throughout the period of record and into the future, and instead are going to pick up in importance in some future period to cause a noticeable acceleration in ice loss?

The models don't seem to suggest that. Yes models are simplistic, not including all effects, but the modellers try to pick out what is important. You could be right and these experts wrong about what is important but generally in such a situation I would generally prefer to back the experts especially when there are lots of models independently produced and they all tend to do the same thing. 

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1838 on: January 28, 2021, 08:19:01 PM »
Quote
Why doesn't it encroach further and further; Why does it slow down?

Basically when the thick MYI is down to a new much lower minimal level the period of rapid loss is over.

Thermodynamic growth of ice in winter. The thicker the ice the more insulation there is so heat is lost only slowly. Less heat loss=less ice formation. So there is a limit of around 2m of ice through thermodynamics (compression, slabbing and ridging obviously make some thicker). Whereas with very little ice thickness then the ice grows rapidly over winter.

Consequently when and where there is thick MYI losing its thickness down to 2m in summer, this ice is gone and it doesn't grow back. If instead we have 1.5m FYI then this all melts out but it  regrows back quickly in winter. This means much less net change from one year to the next.

But it is important to remember that this is only a temporary situation. We have more and more open water in summer, more mobile ice. This over time interferes with the buildup of thick ice.

Early open waters can lead to mixing up heat and i suspect that this process can provoke areas with year round open waters.

And of course the very atmosphere over the now cracked up ice is changing from Arctic desert to some state with more water vapour year around so some day we are going to get a steady drizzle over ice.

The statistics are just an abstraction of a whole bunch of underlying physical processes.

Why do you believe that the current situation is only temporary?  The recent trend from Tamino is longer lived that the steep drop.  The statistics favor the most recent trend.

kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1839 on: January 29, 2021, 12:08:09 AM »
Quote
>more and more open water in summer
>atmosphere over cracked up ice ... some day we are going to get a steady drizzle

What make you think these are not gradual processes slowly encroaching further into the Arctic applying throughout the period of record and into the future, and instead are going to pick up in importance in some future period to cause a noticeable acceleration in ice loss?

One is physics.

Open water. If a large stretch of water opens up earlier in the year it will soak up more heat during the summer which will make it harder to freeze when next winter comes. Then there is also a chance of storms mixing up heat from below which increases with the time we have open water during summer.

This is an accelerating process because it further hinders the overall growth of ice and in the HCO it it is the most plausible mechanism for the quick climate flips.

We can also turn the argument around.

Why would you expect this current system to be stable? If we just went through an event which flushed out the big ice then why on earth would that same process fail to flush out much thinner ice in the long term?
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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1840 on: January 29, 2021, 12:18:35 AM »
Quote
>more and more open water in summer
>atmosphere over cracked up ice ... some day we are going to get a steady drizzle

What make you think these are not gradual processes slowly encroaching further into the Arctic applying throughout the period of record and into the future, and instead are going to pick up in importance in some future period to cause a noticeable acceleration in ice loss?

One is physics.

Open water. If a large stretch of water opens up earlier in the year it will soak up more heat during the summer which will make it harder to freeze when next winter comes. Then there is also a chance of storms mixing up heat from below which increases with the time we have open water during summer.

This is an accelerating process because it further hinders the overall growth of ice and in the HCO it it is the most plausible mechanism for the quick climate flips.

We can also turn the argument around.

Why would you expect this current system to be stable? If we just went through an event which flushed out the big ice then why on earth would that same process fail to flush out much thinner ice in the long term?

For one, the current system has existed longer than the period of rapid melting. 

With regards to physics, the current system has more poleward ice than the preceding system.  The amount of melt may be approaching a similar amount of freeze during the winter.  It is entirely possible that we just transitioned into a new equilibrium.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1841 on: January 29, 2021, 09:20:40 AM »
Quote
It is entirely possible that we just transitioned into a new equilibrium.
Then pray tell how come both volume and extent records continue to be broken every year, for long stretches of time? That it doesn't happen in September, yet, does not mean the system is stable.

Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1842 on: January 29, 2021, 10:33:35 AM »
Quote
It is entirely possible that we just transitioned into a new equilibrium.

It is obvious that we transitioned into a new equilibrium. What is needed to know is if there are other states of equilibrium between now and ice-free. My bet is that there are a few more states of "equilibrium" and each one will bring its own set of surprises for the rest of the world. Mostly very bad surprises with a few good ones.

Because we are afraid to look we won't know until they happen.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

KiwiGriff

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Re: When will the Arctic Go Ice Free?
« Reply #1843 on: January 29, 2021, 02:12:50 PM »
Quote
If you don't think my shape is justified then see tamino:
https://tamino.wordpress.com/2015/10/01/arctic-sea-ice-2/

Yes lets
Arctic Sea Ice: More than Just the Minimum
Posted on October 16, 2018
https://tamino.wordpress.com/2018/10/16/arctic-sea-ice-more-than-just-the-minimum/



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We have data for each day over nearly 40 years, we have annual averages for 39 years, and both yearly maxima and minima for 40 years. But for some reason, some people (as in, most climate deniers) only want to talk about 12 minima. Why do you think that is?


Here are the yearly maximum values:


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There’s definitely no improvement since 2000. It appears to have followed the pre-existing trend pretty closely, and note that the two lowest values are in the last two years, the four lowest values are in the last four years.


Here are the yearly average values


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Again, no improvement, no recovery. The two lowest values are in the last two years, the three lowest values in the last three years. It’s not better than it would have been if it had followed the pre-existing trend; it’s worse.



In short tamino points out in a later post there is...
No hiatus in ice loss unless you only focus on just one metric the yearly minimum.

In my view.
It is a faux pause like the one from 1998 in global temperatures.
Looking at a few outlaying data points like the extreme lows in 2007 and 2012  is looking at the  noise in yearly weather not the long term trend that is  climate change.
Global Warming is ongoing.
Sooner or later the minimum loss will again reflect the ongoing ice loss year around.
Animals can be driven crazy by placing too many in too small a pen. Homo sapiens is the only animal that voluntarily does this to himself.
Notebooks of Lazarus Long.
Robert Heinlein.

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1844 on: January 29, 2021, 03:04:25 PM »
If you regard the 2012 and 2016 Arctic sea ice mimima as outliers, as is justified by reference to standard statistical methodology, the hiatus  / slow down etc disappears.

Instead, those years give an indication of how far below the current long-term trend a summer sea ice mimimum can go.

Mind you, my speculation that belongs to me is that the linear trend in extent and volume will continue until volume is insufficient to prevent a major break up of the ice in the central Arctic Ocean.

Perhaps the summer '20 advance of the Atlantic Front ice edge to well north of 85, and the late fall state of the ice twixt Greenland and the North Pole as reported by Mosaic are signs of the shambles to come.

So without any models to back me up I say with total unwavering confidence the 1 million KM2 extent will happen (at least for a few days) before or at September 2030. (And my story is just as good as yours - so there!)

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The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1845 on: January 29, 2021, 03:24:07 PM »
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It is entirely possible that we just transitioned into a new equilibrium.
Then pray tell how come both volume and extent records continue to be broken every year, for long stretches of time? That it doesn't happen in September, yet, does not mean the system is stable.

I do not have the data readily available for volume, but I do for extent.  Records are not continuing to be broken.  A new record low extent maximum was last set in 2017.  In fact, the 2020 maximum was higher than the 21st century average maximum.  A new record low minimum was last set in 2012.  The average annual average extent hit a new record low in 2016. 

Perhaps it is not a new equilibrium, but approaching a new one. Melting has decreased during all seasons since the high melts centered around 2005.

Maybe someone else has updated volume data (compared to the Tamino graph).

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1846 on: January 29, 2021, 07:49:32 PM »
Record low maximum and record low minimum are not the only records there are. This year Arctic sea ice extent was lowest on record in July for a very long stretch and by a huge margin, though I don't have that chart readily available. I can supply a chart of daily records for total volume (PIOMAS). 2020 was lowest on record for 25 days, and 2nd lowest for 86 more days. In a stable system this would not be happening. The 2012 Sept low outlier serves as the Monster El Nino of Arctic sea ice, enabling all sorts of false hiatuses to be bandied about.

Note: no year before 2011 holds any daily record low, even 4th lowest.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1847 on: January 29, 2021, 08:21:01 PM »
A quick download from JAXA and some Excel meddling have produced the following chart for daily extent records. This year having spent more than half the year in record lowest or 2nd lowest territory does not support the equilibrium theory. Sorry.

Click to enlarge.

The Walrus

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Re: When will the Arctic Go Ice Free?
« Reply #1848 on: January 29, 2021, 08:38:15 PM »
Record low maximum and record low minimum are not the only records there are. This year Arctic sea ice extent was lowest on record in July for a very long stretch and by a huge margin, though I don't have that chart readily available. I can supply a chart of daily records for total volume (PIOMAS). 2020 was lowest on record for 25 days, and 2nd lowest for 86 more days. In a stable system this would not be happening. The 2012 Sept low outlier serves as the Monster El Nino of Arctic sea ice, enabling all sorts of false hiatuses to be bandied about.

Note: no year before 2011 holds any daily record low, even 4th lowest.

Since the ice was in a dramatic decline, no year before 2011 would be expected to hold any daily new lows.  2017 set the most new lows, by far, and was double any other year for the top two slots.  Hence the dramatic drops in 2012 and 2017 precluded any prior years from reaching the top four spots. 

In a stable system, the distribution of new lows would be evenly distributed throughout the number of data points.  Over the past five years, that is roughly the case, with 2017 and 2018 being the high and low years (for records).  Last year was below average for new records lows, but rather average in the other top spots.  Which is what would be expected in a stable system.  If the system has truly entered a new stable environment, then 2021 would behave similarly, with slightly fewer records due to a sixth year added to the system data points.

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Re: When will the Arctic Go Ice Free?
« Reply #1849 on: January 29, 2021, 10:03:37 PM »
You can not just use extent or volume or area, you must check how they dance together.

If you look at those long term Arctic ice movies you see a sort of skeleton and all the ice goes towards Greenland. As volume declines and most of it is near Greenland anyway we might run out of  ice in the CAB/Siberia CAB/Atlantic area early which would open up the areas for mixing up bottom heat. Mix up enough and you can make it through the winter.

I am convinced that this is the mechanism which explains the quick (within a decade) climate flips in the HCO so we will see something similar happen but with more heat buried below and much more heat from the rest of the system. I think the bet is rather safe.

Just aside

Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.