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Messages - Glen Koehler

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1
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: Today at 01:15:47 AM »
"When will the Arctic see its first ice-free summer?"
  Nice review by Daisy Dunne at Carbon Brief.
https://interactive.carbonbrief.org/when-will-the-arctic-see-its-first-ice-free-summer/#

2
Arctic sea ice / Re: "Stupid" Questions :o
« on: December 07, 2019, 06:00:04 PM »
Edited quotes
I see that you have all been having a lot of fun debunking my claims. And perhaps they needed debunking, who knows.
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So global warming. Yes, it's a disaster. No, we are not going to stop it. So how much of a disaster is it going to be?
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The only true threat to global civlisation would be a large and consistent disruption in food production. And I'm not seeing anybody predicting such an outcome (although it does seem to me to be at least a possibility).
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Another of the papers he links to makes some properly dystopian claims, e.g. that CO2 "... is rapidly heading towards levels last seen some 50 million years ago — in the Eocene — when temperatures were up to 14 °C higher than they were in pre-industrial times."
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Yes I know that end-of-world prophecies are exciting and lot's of people seem to wish for some sort of apocalypse. I don't
binntho - Disagreement is not opprobrium or personal attack.  You are well known in this forum for providing thoughtful opinion and insight.  If some nut job jumped onto the forum and wrote that disrupting the planetary climate would have minor effect on well being, people would just dismiss it and not bother to respond with forceful argument.  It is exactly because you do seem intelligent, informed, and curious that folks weigh in to redirect what I (and I presume others too) see as a colleague who is engaging in delusional thinking.  We argue with you because we care and trust that you have the ability to change your mind.  That requires the same of us.  I submit that the facts do not support your position. 

RE: "No, we are not going to stop it." 
     It is not a yes/no situation.  Significant damage has already been done.  Dorian/Great Barrier Reef/2003 Eur. heat wave, etc etc ad nauseum.  I personally don't see how there is ANY chance of not breeching 1.5 C, so I wish IPCC would stop paying it lip service.  But we still have the ability to halt the destruction, pain, and loss caused at 2C or 3C vs. 4C.  By numerous analyses by people who dedicate their professional lives to understand this stuff, getting to 4C could result in a runaway situation where human action is overwhelmed by natural reinforcing feedback mechanisms.

RE My #3 citation quoting Lenton et al. Nov. 2019 article in Nature --
     The list of authors for that piece includes many widely recognized top-tier experts (published in the 1st or 2nd most respected peer-reviewed journal).  "Trust the experts" has fallen out of favor now that with the internet anybody can "publish" any thought that bubbles up through their brain (self included). 

     But facts and expertise still matter.  I still trust the experts when I have a toothache or when the relevant experts tell me that the global ecosystem on which I and my children are utterly and entirely dependent is being irrevocably altered.  You misunderstand and misrepresent their statement about potential for a runaway temperature increase.  They did not say that human emissions alone would drive CO2 to 2500ppm.  But there are powerful feedbacks that can and have done exactly that.  That scenario is not merely hypothetical, it has happened before and can happen again.  It is an engineering analysis of physical properties, not a prophecy based on philosophy.  To ignore factual warnings by experts is self-destructive.

     Heeding warnings of impending destruction and attempting to avert it by spreading the alarm is not wishing for it.  The scale of response needed to reinvent and replace our energy system on a global scale is daunting and difficult.  To succeed will require unprecedented concerted action across political, ethnic, economic and other boundaries.  Humanity faces a sink or swim crisis. 

RE:  Not finding scientific evidence for climate change impact on agriculture
     All I can say is look again. It's there.  Lots of it.  Reduced crop yields as cropping areas exceed tolerances for plants already near their thermal maximum.  A CO2 fertilization effect that only allows crop plants more vegetative growth if water, temperature stability and other needs that are threatened by climate change are controlled.  And even if that vegetative growth does occur, it largely acts to dilute food nutrient density instead of increasing it.  As for, "we'll just move cropping areas north with the shifting isotherm", it isn't that simple.  The solar radiation supply required for photosynthesis is not moving north, nor are the soil resources farther north the same as current ag production zones.  Add in altered, and more likely more erratic, precipitation patterns and the prospects for simply shifting north become even more challenging.  As for that CO2 fertilization effect, here is some more bad news -- weeds are better adapted to benefit from it than crops.  Weeds already outpace insect and disease pests for crop production losses.

     There may be localized benefits for a few cool ag production areas where water supply is not reduced.  I happen to live and work in one such area.  But even here the cost-benefit ratio is not necessarily positive.  For the planet overall, the studies show net negative impacts that increase with additional warming.  The result  is stalled or reversed productivity when we need the opposite to feed a larger population.  = Supply-Demand Train wreck.

     Any "ism" taken to an extreme becomes destructive.  Capitalism run amok becomes Nazi fascism.  Socialism run amok becomes Animal Farm Big Brother 1984 totalitarian communism.   Religious isms run amok become the Crusades,the Jonestown massacre, or ISIS.  Maybe Humanism run amok becomes a sterile, isolated, solopsistic, empty narcissism, where the feelings and dignity of other creatures has zero value.  Utlimately that could include other people.  I wonder if the shrinking circle of that logic ends up as Meism.  That seems like the definition of hell.  I prefer a world of other beings that can delight, surprise, and teach me expressly because they are different from me, yet we share a common existence.

     Enough of my self-published internet philosophizing.  To bring it all all back to GDP, we could have a glorious world and a massive economic boon by taking the actions needed to prevent climate catastrophe.   I wish the big business interests would pull their heads out of their asses long enough to see that opportunity.   The money we spend on military budgets would probably be enough to pull it off.

3
Arctic sea ice / Re: "Stupid" Questions :o
« on: December 07, 2019, 12:29:07 AM »
     No, "life on Earth" is not at risk.
The cockroaches love this stuff.  They've seen it before.  Millions of years before the first human walked on two legs. Cockroaches just need some warmth, some organic matter to feed on, and a rock to hide under.  So they will be fine.

     It is this complicated set of brittle, tinker toy supply-chain connections that we call "society" that is vulnerable to catastrophic failure.
     It is the "organized (human) global community" that is at stake, i.e. "civilization".  Things like "cities" (esp. the many large coastal ones), "grocery stores", "phones", & "hospitals".

     My guess is that not all humans would die from hunger, increased health risks with broken sanitation and medical services, or war violence by other humans competing for reduced resources. I think there will be survivors.  Some. 
     How many, living how and where, I am less sure about.
     I wouldn't count on one-day Amazon delivery, an internet connection, or an electricity grid.
     "Do it yourself" would evolve from an interesting hobby to a survival skill.

     At least the obesity epidemic is likely to be reduced, if only because there are several billion fewer people to count.

     And if you think this view is pessimistic, ask yourself if you too have considered some dire projection for 2050, 2070, or 2100; did the math in your head; and concluded "Well, i'll be dead by then anyway".  Is "Better dead than alive" not the ultimate pessimism?  What does that view of the future say about our honor, our legacy, and our responsibility to people younger than ourselves?

     Remember/imagine a time when you looked FORWARD to the future with anticipation for all the cool stuff that was/is being invented by truly awesome human ingenuity.  I want to get back to that.  I think/hope (depends on the day) we can get back to that.  We better. 

    Sorry for preaching, but there is nothing more important than this topic.  Nothing.  Because it affects everything.

4
Arctic sea ice / Re: "Stupid" Questions :o
« on: December 07, 2019, 12:21:12 AM »
1. From The brutal logic of climate change
By David Roberts on Dec 6, 2011
https://grist.org/climate-change/2011-12-05-the-brutal-logic-of-climate-change/

Kevin Anderson, former Director, U.K. Tyndall Energy Program.
“...a 4 degrees C future is incompatible with an organized global community,
is likely to be beyond ‘adaptation’,
is devastating to the majority of ecosystems,
and has a high probability of not being stable.”


**************************
2. From:  Turn Down the Heat - Why a 4°C Warmer World Must be Avoided, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics.  2012
http://documents.worldbank.org/curated/en/865571468149107611/pdf/NonAsciiFileName0.pdf

"The 4°C scenarios are devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher malnutrition rates; many dry regions becoming dryer, wet regions wetter; unprecedented heat waves in many regions, especially in the tropics; substantially exacerbated water scarcity in many regions; increased frequency of high-intensity tropical cyclones; and irreversible loss of biodiversity, including coral reef systems. 
     And most importantly, a 4°C world is so different from the current one that it comes with high uncertainty and new risks that threaten our ability to anticipate and plan for future adaptation needs."

"It would be so dramatically different from today’s world that it is hard to describe accurately; much relies on complex projections and interpretations."

"We are well aware of the uncertainty that surrounds these scenarios and we know that different scholars and studies sometimes disagree on the degree of risk."

"Finding ways to avoid that scenario is vital for the health and welfare of communities around the world. While every region of the world will be affected, the poor and most vulnerable would be hit hardest.  A 4°C world can, and must, be avoided.

"Warming would not stop there. Because of the slow response of  the  climate  system,  the  greenhouse  gas  emissions  and  concentrations  that  would  lead  to  warming  of  4°C  by  2100  would  actually commit the world to much higher warming, exceeding 6°C or more, in the long term, ..."

********************
3.  From Climate tipping points — too risky to bet against
Timothy M. Lenton, Johan Rockström, Owen Gaffney, Stefan Rahmstorf, Katherine Richardson,
Will Steffen & Hans Joachim Schellnhuber, Nature.  27 November 2019
https://www.nature.com/articles/d41586-019-03595-0

"We argue that cascading effects might be common. Research last year analysed 30 types of regime shift spanning physical climate and ecological systems, from collapse of the West Antarctic ice sheet to a switch from rainforest to savanna. This indicated that exceeding tipping points in one system can increase the risk of crossing them in others. Such links were found for 45% of possible interactions.

In our view, examples are starting to be observed. For example, Arctic sea-ice loss is amplifying regional warming, and Arctic warming and Greenland melting are driving an influx of fresh water into the North Atlantic. This could have contributed to a 15% slowdown since the mid-twentieth century of the Atlantic Meridional Overturning Circulation (AMOC), a key part of global heat and salt transport by the ocean. Rapid melting of the Greenland ice sheet and further slowdown of the AMOC could destabilize the West African monsoon, triggering drought in Africa’s Sahel region. A slowdown in the AMOC could also dry the Amazon, disrupt the East Asian monsoon and cause heat to build up in the Southern Ocean, which could accelerate Antarctic ice loss."

 "...the Earth system has been unstable across multiple timescales before, under relatively weak forcing caused by changes in Earth’s orbit. Now we are strongly forcing the system, with atmospheric CO2 concentration and global temperature increasing at rates that are an order of magnitude higher than those during the most recent deglaciation."

Atmospheric CO2 "... is rapidly heading towards levels last seen some 50 million years ago — in the Eocene — when temperatures were up to 14 °C higher than they were in pre-industrial times."

"If damaging tipping cascades can occur and a global tipping point cannot be ruled out, then this is an existential threat to civilization. No amount of economic cost–benefit analysis is going to help us. We need to change our approach to the climate problem.
     Act now
In our view, the evidence from tipping points alone suggests that we are in a state of planetary emergency: both the risk and urgency of the situation are acute "

5
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 06, 2019, 01:10:47 AM »
Remember, all those MTs of CO2 are actually CO2e. We may emit that much sooner than you might think.
Agreed Tom. Though I am often not sure if people actually mean CO2e when they throw out cumulative emissions values.  But unless they specify CO2e one has to assume they mean what they say, i.e. CO2. 

Thus, as you point out, the real situation with CO2e increasing even faster makes the siutation... more worser?  Climate change trajectories are so bad they require new language. 

6
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 06, 2019, 01:03:08 AM »
As usual, I come to the conclusion that by far the best explanation of the behaviour of arctic ice, when it melts and how fast it melts, is found by looking at the changes in temperature ... etc."

Moving on to Notz and Stroeve 2018, it says
    "The sensitivity of Arctic sea ice as described by the linear relationship between global-mean temperature and Arctic sea-ice coverage has been found to remain constant in model simulations across a wide spectrum of temperature trajectories.  In particular, the linearity holds in all CMIP5 models until summer sea ice vanishes in individual simulations. Hence, the observed sensitivity can be extrapolated to directly estimate the response of the Arctic sea-ice cover to future warming."

After describing some complications, they go on to say:
     "Despite these uncertainties, the different estimates result in a relatively narrow range of additional warming above present that is required to obtain a near-ice free Arctic Ocean during summer, defined as the total sea-ice coverage dropping below 1 million km2."

Then they discuss specific temperatures, and variation around those, from which I derived a median estimate of 1.68 +/- 0.25C (95% CI) above the (inferred) 1850-1900 NASA GISS global average land and ocean surface temperature.  (inferred because GISSTemp doesn't start until 1880. Details to translate to 1850-1900 equivalent are trivial and don't affect the stated value).
And for those of you keeping score at home --- as of 2019 the running 5-year average GISSTemp is at +1.15 C.  In earlier post, I used observed recent GISSTemp trends compared to the 1.68 +/- 0.25C to make the year estimates for when Sept gets below 1M km2 Extent.

The 1.7C estimate fits with their statement:
     "As soon as the global-mean temperature has risen by slightly below 2 ◦C, the Arctic Ocean is expected to be on average nearly ice-free during September."

and slightly out of context, but still relevant:
     "A possible modification of these estimates might be caused by the future evolution of anthropogenic aerosols, as they are expected to become less abundant over the next few
decades. "   

     "... in climate-model simulations the expected aerosol reduction causes additional ice loss..."

    "This would imply that the estimates given here are too conservative."

And finally, they remind us that:
     "While the observed linear relationship between sea-ice coverage and global-mean temperature allows one to estimate the long-term average future evolution of the pan-Arctic ice cover, the evolution of the real ice cover will show substantial year-to-year variability because of internal variability."

-----------------
So it seems to me that binntho and crandles are both right!

7
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 06, 2019, 12:38:18 AM »
       Mining S&N 2018 again - these excerpts about the timing of Atlantification line up well with the discussion of possible mechanisms the 2001-2007 steep slope decline:

    "Another large pulse of warm water occurred in the 2000s, peaking in 2007..."
 
     "This ocean warming largely explains the observed Barents Sea winter ice variability and provides a useful predictor for the annual mean sea-ice cover in the Barents Sea.  The Barents Sea region has also been identified as key for explaining model differences between oceanic and atmospheric pathways of energy transfer to the central Arctic Ocean…” 

    "The Atlantification of the eastern Eurasian Basin may therefore provide an additional factor
behind sea ice reductions in that region, perhaps on the same order of magnitude as atmospheric thermodynamic forcing."
(citations removed)

-------------------
      And relevant to Crandles' invocation of the role of Beaufort Gyre decline in the 2001-2007 steep slope episode:

    "Over the last two decades, the amount of freshwater in the Arctic has increased. This is particularly evident in the Beaufort Gyre, which has accumulated an extra 5000 km3 of freshwater in the 2000s compared to the 1980s and 1990s..."

   "The large Eurasian and North American rivers input warm freshwater (on average 15 °C)..."

   "Peak discharge occurs in June and this water is immediately available to melt ice, helping to break up the fast ice. River discharge also adds a large amount of chromophoric dissolved organic matter, which absorbs sunlight at short wavelengths, further warming the surface layers of the ocean and increasing ice melt. On the other hand, increased ice melt and freshwater input increases summer stratification, allowing for more heat to be trapped in the upper ocean, which in turn delays ice formation in autumn."  (citations removed)

8
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 06, 2019, 12:31:56 AM »
Correction
   N&S 2018 correlation of ASI Extent with cumulative CO2 emissions puts the cumulative chance of 1st Aug. and Sept. as 'largely ice free' (which from my guesswork seems to line up with ca. < 2M km2 Extent, details later) at >50% chance by 2033, and regularly (individual year chance > 50%) by 2036.
     Finally, N&S 2018 give correlation of CO2 with July - October being "largely ice free" (which as above, I interpret as ca. < 2M km2 Extent).  For that I used observed emissions through 2019, and Intl Energy Agency emissions trend forecast of 1.1% continued emissions growth out to 2040, then reducing subsequent global emissions as per the observed US and EU combined downward trend since their recent peak.  With those CO2 assumptions, the cumulative 50% chance for a 1st July-Oct  that is "largely ice free" is by 2045, and regularly (individual year chance > 50%) by 2048. 
   -- Rereading Strove and Notz 2018 (which is a 19-page textbook on Arctic sea ice situation as of Sept. 2018, and serves as a background info for the more applied Notz and Stroeve 2018 companion article), I find this statement:
"Extrapolating the linear relationships into the future, we find that the Arctic Ocean completely loses its ice cover (emphasis mine) throughout August and September for an additional roughly 800 ± 300 Gt of anthropogenic CO2 emissions. For an additional 1400 ± 300 Gt of anthropogenic CO2 emissions, we estimate the Arctic to become sea-ice free from July throughout October ..."

    Those are the CO2-ASI correlations I used for that prior post, and it seems I was far too lukewarmist in my interpretation of what was meant by "largely ice free" in the companion Notz and Stroeve article.  Thus, instead of those projected dates being when Aug-Sept, or July-Oct could get below 2M km2 Extent, they may actually be estimates for when those months can have virtually Zero Extent.   Ouch.  I keep thinking climate projections can't get worse, then they do.

     But just to keep things confusing, I settled on the meaning of Aug-Sept being "largely ice free" as < 2M km2 Extent because the extrapolated dates for N&S Aug-Sept "largely ice free" almost match the N&S extrapolated dates for Sept. <1M km2, and the fact that Aug Extent runs about 0.8M km2 higher than Sept Extent.  So my original interpretation still makes more sense to me, but hard to argue against statement by same two authors writing about the same topic at the same time.  So take your pick, and 'Caveat emptor'.  Either way, it doesn't give the Arctic sea ice much time.

   What remains the same is that the timing depends upon the future emissions trend.  The CO2 regime I used assumes that global emissions do not peak until 2040 (as per 2019 IEA estimate).  Unfortunately, that seems to be a plausible scenario.  As suggested by S&N and N&S papers, that emission scenario obliterates ASI in Aug-Sept by the mid 2030s, and for July-Oct by the late 2040s.  That is not a good prospect for human civilization.  But it does not have to be that way.
 

9
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 05, 2019, 03:07:48 AM »
    With Arctic albedo already increasing radiative forcing by about 25% of the GHG influence (forget the source, could look it up if somebody really needs it), consider how much MORE albedo impact would arise from July being "largely ice free".  Remember, if July (a high solar gain month in it's own right) has hugely reduced Extent by 2048, then June must also have much lower Extent than at present. Wide expanses of open Arctic Ocean in June and July = Albedo nightmare.

    That makes 2050 look like end of the line for a planet any of us would recognize.  If Jennifer Francis et al. are even half-right about weather impacts of Arctic warming and ASI decline at 2010-2019 levels, the effects by 2040-50 would be off the charts.

    I believe that with collective human ingenuity just about anything is possible.  But the performance to date for human wisdom with regard to climate management does not make for an optimistic outlook.  By the ASI situation alone (ignoring the many other vectors), it looks like human civilization could be in dire straits by, or well before, 2050 unless things start changing radically and soon.  So let's stop using 2100 as the benchmark and focus on how humans can get past 2050.

10
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 05, 2019, 02:18:38 AM »
1.
Does the following image help show a high MYI level then a low level?

http://nsidc.org/arcticseaicenews/files/1999/11/Figure5-1-350x443.png

Crandles' theory makes sense to me.  But I would change "The 2-3 year ice is pretty steady til 2002, then downwards every year til 2008.... etc." to "The 2+ year old ice...". 
     It is the combination of decline in the 2-3, , 3-4 and 4+ age categories (esp. the 4+ year ice) that causes the steep slope ca. 2001-2007. 

     The transition of the Beaufort gyre from a nursery to a melting zone seems to fit as a qualitative transitional event that gave rise to the observed trends. 

2.
Looks like the CAA's ability to block ice export from the Arctic Ocean is reducing. Maybe one of those small things with large consequences?
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085116?af=R
The Dynamic Response of Sea Ice to Warming in the Canadian Arctic Archipelago

This seems like another qualitative change that could accelerate the end game for late summer ASI decline.  Adding another doorway for ice export can't be good for retaining ice.


3.
    The remaining area is also not really sticking to Greenland for safety as we had hoped for a long time so what is left might get really floaty at some point. Or just disintegrate and die in place.
 
A-Team used to say "we could have a total late summer blow out any year now". (I'm paraphrasing).  I agree.  One summer, any summer, the remaining ice will be thin and fragile enough to become a completely shattered, mobile mess by season's end.

See ice thickness on gerontocrat's last graph over in the PIOMAS thread at https://forum.arctic-sea-ice.net/index.php/topic,119.msg239492.html#msg239492

Not sure where I saw it, but somebody (Notz and Strove 2018?)  suggested that once thickness gets below 0.5 to 0.8m, flash melt under the right conditions becomes possible.  Looking at the thickness trend, the combination of trend + high melt conditions could bring Sept. Extent below 1M km2 as early as mid 2020s. 

4.  Independent of above, Notz and Strove 2018 article gives info to correlate Sept. Extent with Global avg. temperature.  That points to cumulative probability of the 1st Sept with < 1M km2 exceeding 50% by 2035, and regularly (each individual year chance >50%) by 2037. 
(My dates, not theirs, details later.)

   N&S 2018 correlation of ASI Extent with cumulative CO2 emissions puts the cumulative chance of 1st Aug. and Sept. as 'largely ice free' (which from my guesswork seems to line up with ca. < 2M km2 Extent, details later) at >50% chance by 2033, and regularly (individual year chance > 50%) by 2036.

   Finally, N&S 2018 give correlation of CO2 with July - October being "largely ice free" (which as above, I interpret as ca. < 2M km2 Extent).  For that I used observed emissions through 2019, and Intl Energy Agency emissions trend forecast of 1.1% continued emissions growth out to 2040, then reducing subsequent global emissions as per the observed US and EU combined downward trend since their recent peak.  With those CO2 assumptions, the cumulative 50% chance for a 1st July-Oct  that is "largely ice free" is by 2045, and regularly (individual year chance > 50%) by 2048. 

 


11
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 19, 2019, 06:09:27 PM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.
Wow, uniquorn - you've done some great images in the past, but this one sets a new standard.  Really great work.  Thanks.

12
Arctic sea ice / Re: Global sea ice area and extent data
« on: November 15, 2019, 11:15:37 PM »
I compared the actual JAXA extent data with the averages from 1980s to 2010s.
Arctic sea ice extent of 2019 is 4 days behind schedule if compared with the 2010s average. In the Antarctic 2019 is ahead by 7 days, which sums up to 11 days of difference.
These differences are bigger in comparison with earlier decades:
2019 vs 2000s: 15 days Arctic, 8 days Antarctic = 23 days
2019 vs 1990s: 25 days Arctic, 8 days Antarctic = 33 days
2019 vs 1980s: 29 days Arctic, 9 days Antarctic = 38 days
This is a difference of more than a month!

    That is an interesting way to capture the trend Stephan.  Perhaps we can compare the invidual decadal rates by subtracting each one from the previous decade.  (I think but not sure this is kosher.)
     Thus 1990s vs. 1980s:    5 more days
             2000s vs. 1990s:  10 more days
            2010s vs. 2000s:   23 more days
            2020s vs. 2010s:   46 more?? more days (since there a doubling for each previous step)
     Just a wild guess.  There may be constraints on continued growth at a doubling every decade.

The Arctic-only version:
            1990s vs. 1980s:    4 more days
             2000s vs. 1990s:  10 more days
            2010s vs. 2000s:   15 more days
            2020s vs. 2010s:   20 more??  (since each prior step added about 5 days)

The Antarctic-only version:
            1990s vs. 1980s:    1 more day
             2000s vs. 1990s:   0 more days
            2010s vs. 2000s:    8 more days
            2020s vs. 2010s:    8 more??  (since previous step added 8 days)

     At first glance, you might think that the big difference in the Arctic vs. Antarctic trends shows a problem with using this method.  But I think it reflects an actual characteristic of the data.  In the 1980s and 1990s, the Antarctic sea ice was not showing a trend from global warming. 

     I'm surprised that the Antarctic 2010s vs 2000s even showed an increase because I thought it was only in the last few years that Antarctic sea ice Extent was declining.  (or am I completely misunderstanding the dates Stephan is citing for Antarctic sea ice?)

     That possible rapid acceleration for the Arctic looks worrisome.  Good thing we have smart and wise political leadership at the helm to steer us through what could be a time of difficult choices and profound but necessary changes to reduce the harm.
      What... we don't have that?   Uh oh. 


13
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 15, 2019, 10:03:16 PM »
After looking at graphs of individual seas and making comments on them, this is the quote that seems valid, and  even more so, for many of the individual seas.

Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz

Quote
5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.
[/size]

The summer melt turns from a V shape  into a U shape

     Interesting graphical insight gerontocrat.  Seeing those V curves turn into flat bottomed U shapes is a useful visualization of the concept of individual Arctic seas reaching cumulative losses to the point of having temporary ice extinctions.

      Another insight arises from reading your quoting item 5 about the Arctic as a whole gaining 10 days of melt season per decade (starts 3 days earlier, ends 7 days later per decade).  That trend gives a shorthand way of projecting dates for when additional BOE landmarks will occur.  If that rate continued, then once we have September regularly going below the 1M km2 BOE threshold, then every 3 decades after that, at the 1979-2018 melt season expansion rate, the duration of the BOE period would expand by another 30-days.

      I suppose the added low ice/BOE period would be an additional 9 days before and 21 days after the date of annual minimum.  Seems to me that the low ice period would continue to expand forward and backward from the current mid-Septemberish date for annual minimum at the same ratio as before.  Or will that the ratio change as the ice-free period runs into the darkening days of October vs. the sunny dog days of August?  Why is the observed ratio not not the same on either side of the annual minimum, i.e. why 3 days earlier start but 7 days later finish instead of 5 & 5?

     Correlation of global average surface temperature and cumulative CO2 emissions with Arctic sea ice decline stated in the Notz and Stroeve 2018 article at  .....
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg236344.html#msg236344
   ( Oy, citing my own ASIF posts - all I need now is the ability to Like them and my little bubble of narcissism would be complete.  Maybe we should give Trump a special ASIF member privilege to do that in hopes that it would provide a relief valve for his apparently bottomless need for affirmation, and cut back on his Twitterbation.  By now he must be developing the apocryphal hairy thumbs. 
Double oy - I usually discover later than what I criticize in others is often a reflection of some aspect of myself!  So I am ending this digression right now.)

..... suggest a much faster expansion of melt season for the Arctic as a whole than a new month every 30 years.   I suspect that is because the 3 days earlier - 7 days later per decade trend, being based on the 1979-2018 record, is slower than the rate of melt season advancement more recently.  I'll take a second look at Notz and Stroeve to see what date estimates can be extracted for when BOE for Aug, Oct, and July might be expected based on current trends. 

14
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 15, 2019, 01:12:12 PM »
      Yeah that one kind of stuck out to me too.   But in my haste I didn't think about it long enough to realize that by removing it from its surrounding context it wasn't adding value. I think the larger point was that the transition of the Arctic seas, and the Arctic as a whole, from one mode and system state to a new condition happens gradually for a long time, then all of sudden it's done.  Similar to thin edge ice hanging on for a long time until it seemingly goes poof. 

       But you are right, the statement standing alone just looks dumb due to my editing, not the author's original intent.  I have taken it out since by itself it doesn't add value.   

         My editing glitches aside, the Stroeve and Notz, and the Notz and Stroeve 2018 papers together serve as a good comprehensive and fairly up to date (changes every day!) primer to the ASI story.  It addressed a lot of the questions I had in an understandable plain language way, and the authors are recognized experts in that arena.  Both articles are free online with open access (no paywall). 

15
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 14, 2019, 11:58:16 PM »
One more time, same source article:
Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz
2018 Environ. Res. Lett.13 103001
https://iopscience.iop.org/article/10.1088/1748-9326/aade56

New topics.  As before, I think this use is allowed under source article CC license. 
"Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.  Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI."

Here we go:
-------------------

"A study by Burgard and Notz (2017) has found that CMIP5 models disagree on whether the anomalous heating of the Arctic Ocean, and thus the loss of Arctic sea ice, primarily occurs through changes in vertical heat exchanges with the atmosphere (as is the case in 11 CMIP5 models), primarily through changes in meridional ocean heat flux (as is the case in 11 other CMIP5 models) or through a combination of both (as is the case in 4 CMIP5 models). This suggests that our understanding of how precisely the heat for the observed sea ice melt is provided to the sea ice is still surprisingly limited."

---------
~ (words are quotes but citations removed for clarity) **Focusing first on the atmosphere, changes in the sea-ice cover can occur through dynamical changes that drive ice export, thermodynamical influences , or a combination of both.**
---------

"Williams et al (2016) found winter preconditioning continues to play a large role in September sea ice  variability. In particular, winter ice export out of Fram Strait is strongly correlated to the anomaly of the following September SIE, allowing for the possibility of forecasting sea ice conditions in September several months in advance."

-------
" Ding et al (2017) provides the most recent characterization of the role of atmospheric variability on the observed summer sea ice, showing that trends in atmospheric circulation patterns in summer (i.e. a more anticyclonic circulation pattern) have increased the downwelling longwave radiation towards the surface as a result of a warmer and moister atmosphere. They further suggest that these circulation changes dominate summer ice variability rather than feedbacks from a changing sea ice cover."

--------
"The Atlantification of the eastern Eurasian Basin may therefore provide an additional factor
behind sea ice reductions in that region, perhaps on the same order of magnitude as atmospheric thermodynamic forcing."

(skipping Pacification, they discuss it, but no succinct summary quotes.)

-------
    "The large Eurasian and North American rivers input warm freshwater (on average 15 °C) with a distinct seasonal  cycle along the shallow shelf seas (e.g. Carmack et al 2016). Peak discharge occurs in June and this  water is immediately available to melt ice, helping to break up the fast ice. River discharge also adds a large amount of chromophoric dissolved organic matter, which absorbs sunlight at short wavelengths (Griffin et al 2018), further warming the surface layers of the ocean and increasing ice melt.  On the other hand, increased ice melt and freshwater input increases summer stratification, allowing for more heat to be trapped in the upper ocean, which in turn delays ice formation in autumn."

--------------
"While it is understood that changes happening within the Arctic do not stay there, it is less certain whether current Arctic warming is already driving an increase in storm frequency and extreme weather events across the mid-latitudes, including extreme heat and rainfall events, and more severe winters."

-------
"Conclusions
Through novel analysis and a review of recent studies, we have examined the ongoing ice loss of Arctic sea ice across all seasons. We have established the following key results:

1. With respect to the 1981–2010 reference period, relative ice loss has been more significant during autumn, winter and spring the last two years than during summer (figure 1).

2. The ice cover has not only retreated in its areal extent, it has also become much younger (figure 4) and thinner (figure 5) in recent years. In April 2018, only about 2% of the winter sea-ice cover consisted of sea ice older than 5 years, compared to almost 30% of the April sea-ice cover in 1984.

3. The thinning of the ice cover and the overall warming of the Arctic have increased the likelihood
of rapid ice-loss events during summer in recent years (figure 6). On the other hand, the larger expanses of open water have similarly increased the likelihood of rapid ice-growth events during autumn.

4. The increasing relative loss of winter sea ice is in part related to the fact that more and more regions of the Arctic Ocean completely lose their sea-ice cover during summer (figure 2). This limits the potential for a further acceleration of summer sea ice loss, and causes accelerating sea ice loss during winter.

5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.

6. The recent winter sea ice loss is driven by increased inflow of warm air from the south and an overall warming of the Arctic, which both have substantially reduced the number of freezing
degree days in recent years (figures 8 and 9).

7. The primary cause of the ongoing changes in all months are anthropogenic CO2 emissions, with a clear linear relationship between sea ice loss and cumulative anthropogenic CO2 emissions in all
months (figure 7). The sensitivity ranges from an ice loss per ton of anthropogenic CO2 emissions
of slightly above 1m2 during winter, to more than 3m2 throughout summer."

-------   
 "Extrapolating the linear relationships into the future, we find that the Arctic Ocean completely loses its ice cover throughout August and September for an additional roughly 800 ± 300 Gt of anthropogenic CO2 emissions. For an additional 1400 ± 300 Gt of anthropogenic CO2 emissions, we estimate the Arctic to become sea-ice free from July throughout October (see Notz and Stroeve 2018 for details on these estimates, in particular regarding the uncertainty arising from internal variability).

Given today’s emission rate of about 40 Gt CO2 per year, the time window is closing very rapidly to preserve Arctic sea-ice cover all year round."

16
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 14, 2019, 11:32:42 PM »
      Neven has said he does not like long wordy posts, which this certainly is.  If it violates some ASIF code I am unaware of and it gets snipped, no offense taken.  I wanted to make these excerpts for my own use anyway.

     This post consists of some of the best sentences from the paper cited below.  The whole paper is well worth reading and is written in understandable language.  They do dig into the details of various sensors in the methods section, but you can gloss over that stuff. 

     By the way, if you are not used to reading science journal articles, here is a little secret.  Almost nobody completely understands every sentence.  Sometimes not even the authors.  You learn how to read to get what you can get and when it gets obscure you just move on.  Always good to start with the abstract, then it is fair game to skip to the conclusions, and look at some graphs along the way to decide if you to read the whole thing.  Sorry if this comes across as patronizing.  I just figure a lot of people are not used to professional "science culture", I know I certainly had no clue about it through 7 years of on-again off-again undergrad.  Once you realize it is just people, it becomes less intimidating and more fun.

     As for protocol and rightful use of such extensive quoting, the source article has a license statement that looks favorable. "Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.  Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI."

     These topics arise repeatedly in the forum and Stroeve and Notz do a nice job of laying it on the table.  My guess is that as the paper is over a year old and as they are passengers on this planet too, Stroeve and Notz would approve of using the forum to spread their findings.

Source for all of the excepts below:
Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz
2018 Environ. Res. Lett.13 103001
https://iopscience.iop.org/article/10.1088/1748-9326/aade56

        Placement of "-------" indicates larger than usual amount of text was skipped prior to following quote.  All right, here we go.
--------------------

    “There are two ways in which the climate system can reduce the amount of sea ice within the Arctic Ocean:  first by local melting within the Arctic Ocean, and second by export of sea ice through outward sea ice drift. As outlined in the following sections, a number of studies have found the local melting of sea ice to be by far the main contributor to the observed loss, and we hence need to identify the main driver for increased sea ice melting if we are to identify the main driver for the substantial sea ice loss in recent decades.”
--------------

"4.2. Stability of the ice cover
    In addition to changes in the external forcing and internal variability, a self-amplification of the ongoing ice-loss could in principle have contributed to the rapid ice loss in recent years. Such self-amplification is usually discussed in the context of so-called tipping points or nonlinear threshold, which are often defined as processes in the climate system that show substantial hysteresis in response to changed forcing.

     The best known example for such possible hysteresis behavior is related to the ice-albedo feedback  mechanism: a reduced ice cover in a given summer will cause increased absorption of solar radiation by the ocean, contributing to further reductions in the ice cover.  Such positive feedback loop can cause the irreversible loss of Arctic sea ice in idealized studies based for example on energy-balance models (see review by North 1984), and have hence been suggested to possibly  be relevant also for the real world.

     However, an analysis of the existing observational record and a substantial number of respective modeling studies with complex ESMs all agree that such a ‘tipping point’ does not exist for the loss of Arctic summer sea ice. For example, Notz and Marotzke (2012) found a negative auto-correlation of the year-to-year changes in observed September SIE. Hence, whenever SIE was substantially reduced in a given summer, the next summer usually showed some recovery of the ice cover. This was further supported by Serreze and Stroeve (2015). Such behavior suggests that the sea-ice  cover is at least currently in a stable region of the phase space, as otherwise one would then expect that any year with a really low ice coverage should be followed by a year with an even lower ice coverage, driven by the ice-albedo feedback mechanism. As shown by Tietsche et al (2011), the contrasting behavior of the real ice cover can be explained by compensating negative feedbacks that stabilize the ice cover despite the amplifying ice-albedo feedback. The most important of these stabilizing feedbacks relates to the fact that during winter the ocean very effectively releases heat from those areas that became ice free during summer, thus over-compensating for any extreme ice loss in a preceding summer. Ice that is formed later in the season also carries a thinner snow cover and can hence grow more effectively during winter (e.g., Notz 2009).  Stroeve et al (2018) suggest, however, that this stabilizing feedback mechanism is becoming weaker and weaker as Arctic winters become warmer and warmer.  Increased winter cloud cover after summer sea ice loss as found by Liu et al 2012 also weakens the stabilizing
feedback, as it reduces the loss of heat from the ocean surface."


17
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 14, 2019, 03:22:00 AM »
This situation is getting worse fast

From today
The Arctic's Most Stable Sea Ice Is Vanishing Alarmingly Fast
By Mindy Weisberger
https://www.livescience.com/arctic-ice-refuge-vanishing.html
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL083722

From August 2018.
'Archived' heat has reached deep into the Arctic interior, researchers say
By Yale University.
https://phys.org/news/2018-08-archived-deep-arctic-interior.html
https://advances.sciencemag.org/content/advances/4/8/eaat6773.full.pdf
Thanks to ArcticMelt2 for bringing attention to this one with post at
https://forum.arctic-sea-ice.net/index.php/topic,2888.msg236503.html#msg236503

"The upper ocean in the Canadian Basin has seen a two-fold increase in heat content over the past 30 years, the researchers said. They traced the source to waters hundreds of miles to the south, where reduced sea ice has left the surface ocean more exposed to summer solar warming. In turn, Arctic winds are driving the warmer water north, but below the surface waters.

"This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season," Timmermans said. "Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year." "

The region discussed in the second article abuts the area described in the first article, i.e. the wedge of thickest overwintering that runs from the north coast of Greenland along the northern edge of the CAA. Not a good place to store a reservoir of warm water.


18
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 12, 2019, 04:50:20 PM »
Edited quote
Since the third term is a calculated average (and not a finite measure as the other two) then flipping them around makes no sense.

At least we have identified where we disagree,
I submit that mathematically all are true.
E*T=V
E = V/T
T = V/E

It does not matter to their mathematical relationship which one you solve for, the relation stays the same.  In your examples you solve for T based on set values for E and V, and you get a T that is greater than E.  But that is not an inherent requirement.  It is simply an artifact of the values you set for E and V.  You could set E and V to different values and find that the resulting T is less than E.

For example:  As you found
 If E = 0.99 and V = 0.98
then T = V/E = 0.9898
T decline (=1 - 0.9898) is greater than E (1-0.99).

 But
 If E = 0.9898 and V = 0.98
then T = V/E = 0.99
T decline (=1 - 0.99) is greater less than E (1-0.9898)

It does not matter which is directly measured and which is inferred.  Mathematically they are all equally real.  (And BTW, Thickness IS measured.  Volume is calculated from Extent and Thickness).
But if you want to define E and V and then calculate T, that is fine.  Doing so does not require T to be smaller or larger than E.  All that matters is the relative sizes of the E and V values you choose.  Specifically, if E - V is larger or smaller than 1 - E 

For example, if E = 0.9 and V = 0.85,
T = V/E
T = 0.94
T is larger than E
 E - V = 0.05
1 - E = 0.1
E-V is less than 1-E, so T is greater than E

 if E = 0.95 and V = 0.85,
T = V/E
T = 0.89
T is less than E
E - V = 0.10
1 - E = 0.05
E-V is larger than 1-E, so T is less than E


RE:  Oren.  Close but no cigar.  You are using E + T = V. 
It is  E * T =V.
Multiplication vs. Addition.

Addendum to the end game scenario.  Extent losses are largely due to the loss of thin ice at the edge of the pack.
As the pack shrinks, that edge area becomes an increasing proportion of the total pack area.  Circumference to area ratio gets larger.
 
(This is analogous to the surface to volume ratio that lets insects do things we can't, and also why insects have to be small to do what they do, but I digress)

So, as the percentage of the total ice pack subject to edge area losses gets larger, the percentage rate of Extent losses will increase. 

***Not sure about this next statement.  Math fatigue setting in.***
The straight line trend for Extent losses will begin to curve downward unless it is counteracted by a decline in rate of thickness loss around that edge, which does not seem likely.

*** Then again, the absolute amount edge = Extent loss would not increase, and in fact with smaller absolute edge area, absolute Extent losses would decrease.  But the amount of extent loss would be higher ratio relative to the amount of previous year Extent.  So it may just come down to whether you report Extent losses as absolute number of km2 or % of previous year.  Math fatigue now math exhaustion.  This is becoming a "how many angels fit on the head of a pin discussion".  Who cares.  It does not matter. 

    What matters is that the ASI is nosediving.  Because of albedo and other effects, how the Extent trend will evolve is of interest.  Thanks to Notz and Stroeve and their colleagues, we have insight on how the ASI situation will dramatically evolve over the next 10-30 years.  It is a scary, ominous story.  Maybe if the immediacy of ASI collapse is better understood it will help us make difficult decisions to reduce the damage we are doing to ourselves.




19
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 12, 2019, 06:54:21 AM »
Edited quote
As an example, if extent is falling by 1% per year, and volume by 2%, then thickness falls by very close to, but ever so slightly above, 1%. If extent is at 1% and volume at 3%, thickness clocks in at slightly above 2%.

Try one more cup of coffee and you may reach a level of caffeine induced enlightenment where this becomes obvious. ;D

Using your example, but merely flipping Thickness and Exent:
If Thickness is falling by 1% per year, and volume by 2%, then Extent falls by very close to, but ever so slightly above, 1%.
If Thickness loss is at 1% and volume at 3%, then Extent clocks in at slightly above 2%.

In your example, Thickness loss is always a bit greater than Extent loss.  In my flipped version, Extent loss is always a bit greater than Thickness loss.  You say TomAto, I say ToMAHto! :o

The point being that either the Thickness term or the Extent term can be the larger of the two.  It does not matter.  Either way, when they are both are negative, the resulting product of their multiplication (i.e. Volume) is smaller than either of them individually.  So when Extent trend is negative, AND the Thickness trend is also negative, then the Volume loss has to be more negative than either the Extent or Thickness trend individually.  But as for Extent and Thickness, either one of them could more more negative than the other.

20
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 12, 2019, 06:11:30 AM »
Well if binntho agrees with me, he must be right! 

    But here is another perspective about a possible Extent pause.  I am (almost) sure that if Tamino bit into the Extent numbers he would, as he did with global average surface temperature faux pause, show that there is no statistical justification for the relatively small number of yearly data points in the presumed Extent hiatus period to be called a significant violation of the long term linear trend that is derived from a much larger set of of data points with considerable year to year variability.  (BTW Tamino's wife announced on his blog that he had surgery recently.  Sending him wishes for healing and good health.) 

    But I submit to the jury that even if Extent did have a statistically valid hiatus, it would not matter.  There could be a scenario where Volume losses continue their inexorable decline, yet a prolonged series of years with conditions favorable for greater ice dispersion resulted in Extent value flat-lining for enough years in sequence to pass a statistical test for truly being a hiatus.   

     But so what?  In terms of progressive ice decline, that would not change the underlying fact that Volume losses were still proceeding toward zero.  A hiatus in Exent would only temporarily increase the discordance between the Extent and Volume trends.  The increased difference would have to be compensated for at the end.  The only consequence of an Extent hiatus would be that the Extent trend would have to fall that much farther faster when the zero Volume-Thickness-Extent day of no ice reckoning finally arrived. 

    The 10-30 year lag for the majority of global warming impact from elevated greenhouse gas levels to be expressed means that the warming and ice melt trends for the next 10-30 years have already largely been set by our previous emissions.  The fact that the trend-projected date for the first zero ASI Volume event is now within the next 20 years means that it is probably unavoidable at this point even if we sharply reduced further GHG additions.  Then again, Notz and Stroeve point to an 800 Gt CO2 of additional emissions needed after 2018 for the total GHG load to be enough to result in Volume reaching zero.  So in theory at least, keeping total emissions below that amount could presumably prevent the Volume losses from reaching the zero point. 

     (On the other other hand, --- running out of hands ---, I suspect that even if emissions ceased immediately, with enough time and the slow depletion of existing CO2 from the atmosphere, even the GHG emissions already made thus far, bolstered by some permafrost thaw and other feedbacks, would eventually result in ASI Volume-Thickness-Extent reaching zero.)

     That is a moot point for the real world situation.  It does not seem at all likely that humans will cut emissions sharply enough and soon enough to prevent exceeding the 800 additional Gt CO2 after late 2018 threshold.  And therefore, assuming the Notz and Stroeve relationship between total CO2 emissions and ASI Volume is correct, the Extent trend will meet up with the Volume trend at the zero point.  Which year that happens depends on how fast we move towards that 800 Gt CO2 post 2018 threshold.  This being the end of 2019, we have probably reduced the remaining budget to 760 already. 

     Extent can go where it will prior to the zero day of reckoning, but when the Volume trend reaches the point where there is no ice to spread around, Extent will also be at zero.

   Edited quote
And we already know that volume is falling faster than extent, which means that thickness is falling faster than extent.
    I don't agree with the second part, "... which means that thickness is falling faster than extent. " 
    Yes, we know that Volume is falling faster than Extent.  Because Volume is the product of Extent x Thickness, Volume has to fall faster than Extent unless there is either Thickness gain or zero loss.  But Thickness does not have to fall faster than Extent for Volume loss to be less than Extent loss.  It does not matter which of two (Extent or Thickness loss) is greater, or if they are exactly equal, all that matters is the product of Extent x Thickness, because that is what defines Volume.

   

21
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 11:53:08 PM »
Edited quote
... this short video of ice melting explains why I think it will look basically okay in terms of area and extent right up until it isnt.



Nice.  Exactly!  Watch the footprint of that ice cube as it melts.  The area covered declines at a much slower rate than volume as the thickness declines.  Until the thickness gets so small that continued losses come at the expense of the area covered (Extent).  Then it rapidly declines at the very end as Extent loss (footprint) finally catches up the Volume loss (shrinking ice cube).

22
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 11:17:09 PM »
Conversely, volume cannot be zero, if extent and thickness are not.  Volume, being three-dimensional, will always change faster than thickness (one-dimensional) or extent/area (two-dimensional).  At some point, they must converge.  What is your reasoning to believe that volume is the key metric over the others?

I agree that "At some point, they must converge."  That was the reason for my quest -- (cue Man of La Mancha music): How/when will the Extent trend and Volume trends meet?

I suppose you can frame the same question as "When will the Volume trend flatten out so that it can meet the Extent trend?"  I don't see reason for that to happen.  The linear volume trend looks pretty inexorable.  And while, as gerontoacrat noted, Volume measurement has its problems, Extent is not so pristine either.  A pixel with 16% ice counts as 1, with 14% counts as 0; melt ponds misidentified as open water etc. 

     And even if measured perfectly, Extent in the real world is subject to being altered by wind patterns, compaction vs. dispersal.  That is also why I think 2012, while certainly an important event as we watch the ASI go down the tubes, is overrated.  It was hyuge (new American English spelling, as in 'our politics and planet are hyugely screwed up') Extent event, but a less cataclysmic Volume event, and thus less of an informative marker for progressive ASI decline.  Thus Extent is the more mercurial hare, subject to temporary conditions, while good ole Volume is the sober implacable tortoise plodding its way towards cryospheric Armageddon. 

Maybe it is arbitrary that I start with the presumption that you can't have Extent of ice without any Volume of ice to create it.  But that makes more sense to me than the other way around.  Stuff has to exist before you deal with how it is spread around.

I am more likely to buy into gerontocrat's argument that the Volume measures are more subject to error, so this discordance between the Extent and Volume trends (that I repeat, we all agree have to meet up in the end) could be due to spurious Volume measurements.
.... But not really.  Because it makes perfect sense that what we see (Extent loss) is multiplied by what we can't see (simultaneous Thickness loss) to create Volume losses that are bigger than Extent losses.  In fact, the only way Extent losses could keep up with Volume losses is if there was NO Thickness loss. So of course Extent losses lag behind Volume losses.  How could it be otherwise? 

    And it makes sense to me that Thickness is being affected by the same forces that are depleting Extent and Volume.  And it makes no sense to think that Thickness is not being depleted.  And regardless of what you or I think, hard working scientists and other folks take measurements that show that Thickness is indeed going down.

I defer to the great Juan C. Garcia.  His message tag line points to Volume losses being a more important indicator than Extent because Extent, as you noted, is missing a dimension, the key dimension of concurrent thickness losses. 
"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."

23
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 10:47:18 PM »
I always end up with the observation that nature (mostly) abhors a straight line.

For a long time the linear relationship may look the best, but it most often breaks down eventually. So will it be KK's long-tailed gompertz slow  / minimal decline or will it fall apart with a crash

So I just can't go along with Stroeve et al when linear is pushed out to the end. It just ain't like that.

ps: And 2007 and 2012 pushed the max dip in an annual variation well over 1 million km2 when melting conditions are almost perfect.
pps: Volume divided by extent is not a good measure of thickness at minimum, especially using NSIDC data. This is because the ice is very spread out with lots of open water at minimum, concentration getting as low as 55%. Volume divided by Area is a much better measure at minimum.

I think the poof scenario meets the definition of "fall apart with a crash".
It does not rely on linear trend right to end, in fact it demonstrates why that won't be the case. 

We all agree they have to meet up at the end (i.e. Zero Volume & Extent).  And this is how it happens.  Extent decline can keep up its straight line trend that is slower than volume decline, but only for a while. When thickness gets so thin that it is susceptible to flash melt, that is when the Extent trend curves sharply downward and catches up within a single year.  Thus an Extent crash.

RE ps   I used 10-day Extent losses, but I think you are right (whether you meant to imply that or not) that it would be better to use year to year Extent changes as the indicator to estimate when Extent is low enough to suffer a within-one-year loss large enough to get below the 1M km2 threshold.  Being much larger than the 10-day losses, using the year to year losses strengthens the argument for the potential for a single year to go below the BOE threshold.

RE pps I used PIOMAS September average thickness data.  That's all I have to work with.  That is the minimum monthly average, not the minimum day.  I agree that using annual minimum thickness values from November would be unhelpful because those values are very distorted by expanding area of thin refreezing ice.  But comparing the Sept. average Thickness across years seems like a reasonable way to measure a trend for ice thickness.

24
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 10:37:50 PM »
Edited quote
......I find that extrapolated BOE dates of area and extent move to "earlier times" than last year or two years ago, while the extrapolated BOE dates for volume and thickness remain stable. If this trend continues, the "BOE times" (at least those for July to October) will get closer to each other and solving the "problem" of extent and area values well above zero while volume has already reached zero ?!?  :-\
That part makes sense to me. They have to converge at the end.
So you are sure about the linear July volume trend hitting zero in 2034 (1 year before August, which is also odd), but the July log trend not hitting zero until 2038 (10 years AFTER August)?

25
Arctic sea ice / Re: Latest PIOMAS update (November 2019)
« on: November 11, 2019, 10:27:01 PM »
Not that I remember the math that well, but an X2 curve will ALWAYS give a better fit than a linear X curve.  And an X3 curve will ALWAYS give a better fit than an X2 curve.

 I will always treasure the moment when some new grad students showed results from a class lab experiment with six data points on an XY curve all over the place like a sneeze and got a perfect correlation with a wiggly X5 curve!  Which is what has to happen when you use up every last degree of freedom.

26
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 09:38:00 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen], thickness [Dicke] and area [Fläche] will reach zero.

Volume is king/queen.  Extent and Thickness can't be above zero when Volume is zero.  So when I see the linear trend for Volume hitting zero for JULY in 2034, that is yet another Yikes moment.  Can you double check that?   That would bring major albdeo impact, polar cell/weather disruption, and other global consequences if that trend holds up.   This stuff is just getting too weird.  We don't need to worry about 2100. We've got to get past 2034 first. 

27
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 09:04:51 PM »
Also from Notz and Stroeve 2018
“Also for the future, no substantial self amplification of the summer ice loss is expected. In particular, in all models that participated in CMIP5, the linear relationship between Arctic sea-ice cover and global-mean temperature holds until all sea ice is lost. This behavior already takes into account that in many regions, the ice-free duration during summer is becoming longer and longer, and that the ice cover as a whole is getting thinner. These factors are apparently not sufficient to overcome the stabilizing feedbacks and do not cause an acceleration of the summer sea-ice loss.”

    This seems to put to rest hope for a slowdown in ASI losses due to the final ice being at higher latitude.  Notz and Stroeve discuss and dismiss the opposite potential for reinforcing feedbacks to accelerate the rate of decline.  That does not leave much room for a slow down.
   
Stroeve & Notz papers
To state that the linear relationship between sea ice loss and Arctic Global-mean(?) temperatures will hold until there is no more ice is heroic indeed.

How do they deal with September sea ice loss 1979 to 2019 of around 50% and volume loss of around 75% ? If both continue at the same linear rate then an arithmetical impossibility looms.

     What got me started on all this was the discrepancy between the Extent and Volume trends.  Since Extent has to reach zero at the same time as Volume, my query was how much longer before the Extent curve bends down to a necessary eventual reckoning with zero Volume?  Shared Humanity's comment about ice going poof is worth more than what he supposes is its current market value!  It got me to realize that the Extent curve does NOT have to bend down to meet the Volume trend, at least not until the last day.

     Volume is a product of Extent x Thickness.  We've lost about 76% of Volume (based on PIOMAS Sept. Volume trend for 2019 vs.1979), but only about 42% of Extent (based on NSIDC Sept. Extent trend line for 2019 vs. 1979). 

     The Extent value gets multiplied by the Thickness value to get Volume.  So Extent can keep on floating down at a less steep slope until the point at which Thickness gets so thin that it falls prey to a warming event that takes Thickness down to zero.  That is the "poof" moment when Extent suddenly catches up to Volume, i.e. they both reach zero.   

    Figure 6 in the Strove and Notz, 2018 cited in previous post shows that 10-day Extent losses of 1M km2 have occurred, and that losses of at least 0.5M km2 are not that rare.  Thus, once Extent  gets into the range of less than 2.0M to 1.5 km2, there is a possible and increasingly likely chance of a "poof" event of 0.5 to 1.0km2 scale that takes Extent below the arbitrary 1.0M km2 BOE threshold.  That provides an indicator for how much longer Extent losses can continue at a slower pace than Volume losses before a fluctuation in Thickness creates a first time BOE.   

    The Sept. 2019 NSIDC Exent was 4.32M km2.  As per NSIDC "The linear rate of sea ice decline for September extent from 1979 to 2019 is 82,400 square kilometers per year."

    To reach the 2.0M Extent when a poof Event becomes possible, would require losing another 2.3M km2 of Sept Extent below the 2019 value of 4.3 (which is pretty much on the Trend line).  By this reasoning, at 82k per year losses, losing 2.3M km2 would take another 28 years, i.e. 2047 before Extent in 50% of years would be within plausible range of a poof event. 

    This is later than I had expected, since Notz and Stroeve put the 50% chance of any single year going below 1.0M km2 as 2038.  By 2047, Notz and Strove estimate that >95% of individual years will go below 1M km2.

    Hmmm?  So Extent trend alone does not end up at the expected date for 50% chance of BOE.  That leaves Thickness losses as the missing factor that aligns the NSIDC Extent trend with the Notz and Stroeve BOE dates.  And that makes sense. 

     Stroeve and Notz Fig. 5 show the decline of April ASI Thickness, and they cite the PIOMAS April Thickness trend as -0.28M per decade.  Looking at PIOMAS Sept. thickness linear trend, I get a very similar -0.27M/decade trend.  So by 2038, absent any acceleration or deceleration of Thickness losses, the average Sept. ice Thickness is likely to be near 0.51M.  As Thickness declines from 1.022 (Sept. 2019) to 0.51M, the frequency of 0.5 to 1.0 km2 Extent losses in a 10-day period will certainly increase, and the magnitude of infrequent large scale Extent losses will also increase. 

    That is why extrapolation of the Extent loss curve alone yields BOE dates that are artificially late.  Combine the continued Extent loss curve with an increasing (instead of static) scale for 10-day Extent losses (due to declining Thickness), then you can get dates to fit with the Notz and Stroeve estimate of 2038 for when 50% of years could reach BOE status of <1.0M km2.

     In 20 years, the Extent trend goes to 4.32M - (0.084M x 20) = 2.67M km2.  That is way too high to be taken down to 1.0 km2 by a 10-day Extent loss event if the September Thickness remained at the current ca. 1.02M.  But much more likely when the average September Thickness is down to 0.51M.

   So here we have the most likely poof moment scenario for when ASI goes below 1.0m km2.  Around 2038, with Sept. Extent at ca. 2.7M km2 and Thickness is down to 0.5M, a 10-day event removes enough ice to take Extent below 1.0M km2.  (This scenario also fits well enough with Archimid's April max vs. summer losses crossing trendlines.)

    Of course, this is an event of arbitrary significance.  The ice will begin refreezing and our long march to a hot Earth destiny will continue with ups and downs in ASI.  Deniers will cite the fact that Arctic ice coverage in October increased over September to show that there is nothing to worry about.

    As for thin ice melt acceleration, which is also where this adventure started, I stand corrected and have to yield to more educated minds that reversing the Thorndike curve is not legitimate in terms of thickness alone and thermodynamics.  But as Shared Humanity noted, my gut still says that in a real world setting, younger, saltier, highest-surface-to-volume-ratio, more fractured, dispersed, thinner ice has a higher chance in a rolling ocean exposed to currents to get melted by export or to go poof due to flash melt, and that the chances for rapid Extent loss increases faster than the linear change in thickness.  But now I'm just being stubborn. ;D

     I don't know if this convinces anybody else, and there remains the chance of some bonehead error that makes this all wrong, but thanks to the Stroeve and Notz articles I feel like I have some understanding for how the Extent, Thickness, and Volume trends will evolve over the next 20 years.  The Emperors are well dressed indeed, and I retract my arrogant and ignorant allegations to the contrary. 

     

28
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 11, 2019, 06:52:12 PM »
     Having flaunted my ignorance in public in this thread, I am chagrined and pleased to report that the experts have in fact already spoken.  I just wasn't listening.  "Ask and ye shall find that ye have already received, ye just weren't paying attention!"
     Two excellent September 2018 articles, both online with open access:

Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz
2018 Environ. Res. Lett.13 103001
https://iopscience.iop.org/article/10.1088/1748-9326/aade56

The Trajectory Towards a Seasonally Ice-Free Arctic Ocean. 
Dirk Notz and Julienne Stroeve.
Current Climate Change Reports (2018) 4:407–416
https://doi.org/10.1007/s40641-018-0113-2
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411203/pdf/40641_2018_Article_113.pdf

Excerpts from Notz and Stroeve, 2018.

“…we find that the temperature at which the Arctic first becomes ice free will have a 95% uncertainty range from internal variability of ±0.2 to 0.4◦C. These values are in line with results from large-ensemble model simulations. Combined with the temperature threshold of less than +2◦C for a near ice-free ocean during summer, this then implies low, but above zero chances for a near-ice free Arctic ocean at + 1.5◦C global warming.”

“….the 95% uncertainty range for cumulative future emissions of CO2 leading to an ice free Arctic Ocean during summer becomes 500 to 1100 Gt based on the average value of 800 Gt established above. For a given emission per year, this uncertainty range can be translated to an uncertainty range of the year when the Arctic first becomes ice free.  For today’s emission of about 40 Gt CO2per year, we get an uncertainty range of about 15 years,…”

“Based on this approach, we identify the following statements to be very likely true for the future evolution of the Arctic sea-ice cover.
1. The Arctic sea-ice cover has been and will remain linearly related to global-mean air temperature in all months. Global-mean air temperature can hence be interpreted as the most important control variable on future Arctic sea-ice evolution.

2. The observed linear relationship between Arctic sea-ice coverage and global-mean air temperature suggests Arctic sea-ice coverage to drop below 1 million km2 in more than 50% of all years for a global warming of less than 2◦C compared to pre-industrial levels.

3. The observed linear relationship between Arctic sea-ice coverage and cumulative anthropogenic emissions of CO2 suggests Arctic sea-ice coverage to below 1 million km2 for more than 50% of all years for total future anthropogenic CO2 emissions of less than 800 Gt.

4. From internal variability, September sea-ice coverage can vary by a maximum of ±1 million km2for a given global-mean air temperature.

5. This year-to-year fluctuation can directly be translated into an uncertainty of ±0.2 to 0.4C for the global warming at which the Arctic Ocean loses its summer sea ice for the first time. For CO2 emissions, the uncertainty is about ±300 Gt CO2 emissions. Hence, the Arctic Ocean can be expected to be nearly ice-free in 5% of all years for 500-Gt future CO2 emissions and in 95% of all years for 1100-Gt future CO2 emissions.

6. As the observed linear relationship between Arctic sea-ice coverage and global-mean temperature currently hold for all months, they allow us to estimate the future seasonal cycle directly from the observational record.  This is also true for the observed linear relationship between Arctic sea-ice coverage and cumulative CO2 emissions. 

Based on current emission rates of about 40-Gt CO2 per year, these findings imply a substantial likelihood of an ice-free Arctic Ocean during summer before mid-century.  The time window to prevent the loss of the Arctic summer sea-ice cover hence closes very rapidly.”

**********************
My summary of some take home messages:

    The article was written in September 2018.  At 40 GtCO2 per year, the average estimate of “less than 800” Gt CO2 for 50% chance for any single year going below 1m km2, is 20 years after 2018.  Thus, by September 2038

     Due to uncertainty in the estimate and fluctuations between individual melt years, by 2031 (500/40 = 12.5.  2018 +13 = 2031) there is at least a 5% chance for any single year going below 1m km2 Arctic sea ice cover.  With the single year chance increasing for each subsquent year.
 
     By 2046 (1100/40 = 27.5.  2018 +28 = 2046) (if emissions continue at 40 GtCO2 per year) each individual year would have at least a 95% chance of going below 1m km2.

    The Notz and Stroeve dates based on CO2 emissions also fit with dates derived from the Notz and Stroeve global average temperature - sea ice relationship (e.g. <1M km2 in more than 50% of all years at <+2◦C; 1st year <1M km2 possible at ca. +1.5C) when compared to my projection of NASS GISS global surface temperature anomalies:

Year   Projected NASA GISS vs. 1850-1900
          (Obs, ENSO and solar cycle for 2019; ENSO & solar for 2020; Solar & RCP8.5 emissions after 2020)
2019   1.20
2020   1.16
2021   1.14
2022   1.14
2023   1.19
2024   1.25
2025   1.31
2026   1.37
2027   1.42
2028   1.42
2029   1.43
2030   1.44
2031  1.45
2032   1.46
2033   1.48
2034   1.53
2035   1.59
2036   1.65
2037   1.71
2038   1.77
2039   1.78
2040   1.80
2041   1.82
2042   1.83
2043   1.85
2044   1.87
2045   1.94
2046  2.00



29
Arctic sea ice / Re: Latest PIOMAS update (November 2019)
« on: November 10, 2019, 01:21:08 PM »
bbr - I, and I suspect others, would appreciate it if you would explain in more detail how the land ocean balance creates consequences for civilization.  I thought I knew about the various feedback loops, but this one is new to me.  Thanks for considering this request.

30
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 09, 2019, 08:23:30 PM »
RE Overland, J. E., and M. Wang (2013), When will the summer Arctic be nearly sea ice free?, Geophys. Res. Lett., 40, 2097–2101, doi:10.1002/grl.50316.  https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/grl.50316

     Overland and Wang (O&W) look at 3 methods to project when the Arctic will go below 1m km2 ice extent.  The 3 methods (trend extrapolation, stochasitc events, model estimates) come up with dates of 2020, 2030, and 2040 respectively.  There are strengths and weaknesses for each, though the weaknesses of the model  approach are the most defined (which is to be expected in that multi-model estimates provide the most data upon which to measure performance.  It will be interesting to see how much improvement the new generation of CMIP6 models - which I think will have better ocean-atmosphere coupling and cloud physics -  will provide.)   

    The 2020 estimate based on trend was made right after the unprecedented 2012 Extent losses.  (O&W note that Volume loss in 2012 was not so extreme.  I think we worship at the feet of Extent and 2012 too much, no doubt because that is the measure we have best access to.  That is kind of like the drunk looking for his car keys under the street lamp.  But I digress...)  As I have repeated ad nauseum, the volume trend estimate as shown by Wipneus has Sept. volume reaching zero around 2032, so presumably 1m km2 Extent would occur several years before that.

    So if you update the O&W trend estimate from 2020 to 2030, and as per O&W comments, discount the model estimate of 2040 due to a poor track record, then you have two estimates to consider, 2030 by the stochastic approach, and 2030 by an updated trend extrapolation.  Looks like 2030 is the winner.

    Overland and Wang mention the final ice being at higher latitude could be more resistant to melt, but they also point to the CAA as the last refuge.  The CAA as last refuge factor also shows up in the Zhang animation link given in previous post.  To me it looks like the "high latitude = slower final losses" argument does not fit with the CAA as final refuge prediction.  The projected location for the final ice is not centered around 90N.  It occurs in a band around 75-85N.  The land mass effects of CAA apparently greatly exceeds any latitude effect. 

     We already have open water occurring at above 80N as shown in the Sept. 2019 Extent map at http://nsidc.org/arcticseaicenews/files/2019/10/Figure-1.png.  I don't think the high latitude effect is going to provide much added melt resistance.  And whatever high latitude effect there is seems likely to overwhelmed by continued high GHG emissions, Atlantification / Pacification, mechanical weakness, surface area, dispersal, mobility and export.  And as somebody noted above, in the past the CAB ice volume was replenished from peripheral seas.  As those supply lines diminish, the CAB gets indirectly affected by losses in those lower latitude areas that we already have seen are vulnerable to today's level of Arctic warming, and even moreso with continued warming. 

31
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 09, 2019, 06:46:53 PM »
http://psc.apl.washington.edu/zhang/IDAO/multi.html
Animation of ASI Thickness out to 2050 by Dr. Zhang at Polar Science Center.  Shows first BOE by the 1m km2 definition around 2032 (eyeball estimate) with some recovery years in mid-2030s.  By 2040 September min is essentially a BOE every every year and August almost as low.  By 2046 August is at or near BOE every year.  Still plenty of Extent into July even by 2050.

The page and animations are not dated.  Because they use an older emissions-warming scenario (B2) and start future projections in 2005  I assume they were created before the most recent full IPCC reports in 2013-14 (which used RCP scenarios), and probably been created ca. 2004.  A lot has happened since then.  But the animations are still interesting to watch if only too see what state of the art was at that time.

    The files ran on Windows Media Player when viewed through Google Chrome browser over home wifi.  For unknown reasons I could not view  with Firefox. First time through it had some long pauses.  Playing through 2nd time is smoother.  If you are quick with the mouse you can stop and view any single month as freeze frame.

32
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 08, 2019, 09:54:44 PM »
Ditto that request Tor.
 
RE: 
Gerontocrat, your graphs has gotten me thinking.  What if the open water in the peripheral seas is contributing to larger heat losses, resulting in faster refreeze of the CAB?  Widespread ice cover in the past may have kept more heat bottled up beneath the ice.

Uh oh, another possible Achilles heel.  And maybe that was part of the Chris Reynolds 'Slow Transition' hypothesis that I missed.  I can see how ASI refreeze declines could slow as diminishing ice cover allows more ocean heat to escape to the atmosphere during the winter.  That would stall declines in April Maximum.  But even with a semi-stabilized April max, increasing warming of the summer melt seasons would still progress toward a September minimum reaching the BOE threshold of 1M km2 Extent.

    Just to clarify, my proposition that the final meter would melt out faster is not saying that the Arctic is going to ice free year round anytime soon.  It would apply sequentially to each month as its monthly average thickness got to and below 1 meter.  Thus, September Volume and Extent losses would transition from a straight line trend down to a downward bending curve as average thickness declines.  If that is true, then it should start becoming apparent pretty soon (i.e in next 5 years) because Sept. average thickness is getting close to 1 meter.   

      See the Wipneus average montlhly Volume graph at
https://14adebb0-a-62cb3a1a-s-sites.googlegroups.com/site/arctischepinguin/home/piomas/grf/piomas-trnd2.png?attachauth=ANoY7coD8qak1Y1OxDoPDEijpxlR44NBQbsfo1c5i4-Bk1Zvmt1qUiw2vkca4klldt_5e_ZfGwzmI0esENnfeDW9sXTTdna3Brr9mvGsVbPuI1oD5uyzvq7Z3D8zf2EfMCy9nnbKl45gFjfDbj6kZwFDFybvy9yhahjUNE5xVFrB84O_dzfeIEwDQDZXZVbi5nZDn9-9IBKLLbEeSE4eAnkpqcVVwWYWMVXq9QGC-BVCpuGpLMcrTZJ1srgqcr6Ut-8eYoiJQg0L&attredirects=0

      As shown on the Wipneus graph - August and October volumes only trail September by a few years.   But then there is a big jump to July and November, another big jump to December, and another to January and June.  So those later months would still have large amounts of ice for many years to come even if the fast-final-meter hypothesis is correct.

     The Wipneus graph provides some evidence to evaluate the notion that as a month reaches and goes below 1m average thickness, its losses accelerate.   The graph applies X2 curves to monthly average ASI volumes.  According to my reasoning, September should have the steepest downward curve since it is the closest to crossing the 1 meter average thickness threshold (not that there is a discrete threshold to cross). 

     And lo, the Sept. curve does bend down at a steeper rate than the July or June curves.  (August and October curves have essentially same curvature as September, Nov and Dec curves not posted for 2019 yet).  I measured curvature by comparing the left axis 1975 amount vs. the 2020 right axis amount for September vs. June or July curves.  The Sept curve is farther below June or July in 2020 than it was in 1975, so it is bending downward at a steeper rate. This is hardly a Nobel prize winning observation, but at least it fits with my hypothesis.

     But it is also true that while I am not ready throw in the towel quite yet, the more I think about this, the more I realize I am dabbling in concepts I know too little about to make meaningful conclusions.  There are books and articles to explain things like this.  We don't have to figure it out by ourselves because other people have thought about it in a lot more depth. 

      I read through the recent IPCC Cryosphere report looking for a mechanistic explanation and found surprisingly little exposition on this critically important issue.   If you know of a good summary that addresses how ASI loss trends are likely to evolve in the coming 20 years please share citation or link.  Here is one I read a while back, but need to re-read:
    Overland, J. E., and M. Wang (2013), When will the summer Arctic be nearly sea ice free?, Geophys. Res. Lett., 40, 2097–2101, doi:10.1002/grl.50316.  https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/grl.50316
   
     Even though it is getting a bit dated now, it was written right after the 2012 minimum at which time ASI declines were greatly exceeding expectations.  Thus, awareness was high that the Arctic was not behaving as had been predicted.

    I wonder how many of the experts at NSIDC, NASA etc. read the ASIF.  Maybe professional etiquette prevents them from zooming in and correcting the half baked-theories posted by non-experts like me.  (Some of the folks that do post here give the appearance of being professional ASI scientists.  There is tremendous knowledge embedded in ASIF.  If the experts aren't reading it, they should because they could learn a lot too.)  But just saying "Wrong" isn't enough.  What I would like is for somebody with expertise to provide a summary of how ASI loss dynamics are likely to behave over the coming 10-30 years. 

    Specifically, I would like to read an expert opinion on whether the Wipneus volume straight line trend is expected to continue.  And if not, why not.  Because if it continues, we will reach zero average ASI in September 2032, and rapidly declining Sept. average Extent over the next 10 years as Extent losses catch up to Volume losses.  With August and October not far behind September.  That scenario has consequences for the habitability of our planet.  So it is not simply an intellectual exercise.  We really need to understand this stuff.

    Sorry for another long post.  Just trying to get it down in words.  Guess I wasn't born for Twitter times.

   

33
Arctic sea ice / Re: The 2019/2020 freezing season
« on: November 07, 2019, 09:21:11 PM »
      This might belong in the Stupid Questions thread, but can somebody explain how/why Laptev and ESS had such above average Extent and Area refreeze gains when the GFS temperature forecasts over the past two weeks have shown substantial above average temperature anomalies?

     In addition to the anomalies, some of the absolute temperature values were at or just below 0 C.  And if I remember correctly, not just 2m air temps., but also SST temps. were above normal.  So how does that turn into above average refreezing?

     I realize that those seas were starting from below average ice amount, were bound to catch up and by starting late, caught up faster than normal, and that the lack of ice cover may have allowed greater export of ocean water heat into the atmosphere.  But all of that doesn't seem to be enough to explain how such a burst of new freezing happened. 

     My guess is that the GFS air temperatures at 2 meters above the surface were reading high because of ice formation.  Thus in opposition to my assumption that elevated surface air temperatures would retard ice formation, it was the exact opposite, energy released by ice formation was warming the air.

    Regardless of my confusion based on expecting the opposite to have occurred, what explanation is there for the recent rapid ice accumulation at far above the normal rate?

34
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 07, 2019, 09:01:34 PM »
One more...
RE Oren "The physical behaviors of melting and freezing in the Arctic are different due to the effect of the buffer of the water below the ice."
     That factor is beyond my understanding.  Maybe that is why the experts show such a prolonged persistence of the final ice despite current trends.  Nothing I can say because I don't know nuthin' about it and too lazy/ not enough time to read up on it right now.  It may be the Achilles heel of my thesis.

RE GoSouthYoungins "freezing season near the pole brings a darkness and cold that is hard to comprehend". 
     No doubt it is still wicked cold up there.  But it is only the current vs past relative temperatures that count.  Arctic winter cold is not a new factor, and despite still being very cold, the freezing season, like the melting season, is getting warmer.  The equilibrium level for both seasonal max and min amounts of ASI has to decline with both ends of the Arctic seasonal temperature cycle warming.

35
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 07, 2019, 05:29:18 PM »
I concur.  The freeze chart show the influence of thicker ice insulating the freezing water from the cold air.  FDD (freezing degree days) is pretty much the only input.  Melt, on the other hand, is more directly related to the energy received. 

Melting snow atop of ice is almost totally independent of how thick supporting ice is.
etc...

Maybe the question is: if two floes, side by side have the same snow cover at the beginning of the melting season and have the same salt content, etc., but one floe is 2 m thick while the other is 1 m thick ... etc.

 The melting energy is delivered by solar gain, wind, rain and whatever is happening in the water under the ice.

And RE Oren "Also a lot of the melting is due to direct insolation while the temperature stays near zero."

1.  RE freezing energy out and melting energy back in. 
     I see what you are saying about the solar aspect, but I still suspect that it simply comes down energy in vs. energy out, regardless of how that energy travels in or out.  If so, then the Thorndike curve would work in reverse, giving much faster melt for the final 1 meter of ice.

2.  RE Melting snow on top of ice being independent of ice thickness below. 
    That one I agree with.  What portion of the summer melt season energy input is used up by melting snow on top of the ice?  That's a question, not a comment posing as a question.  I truly have no clue about that.  But even if snow cover uses up a significant portion of the summer melt energy, that would only dilute the effect of the final-meter-melting-faster regime, not counteract it.  Once the snow is melted off, then you still have the issue of whether the remaining ice will melt faster if it is 1 meter vs. 2 meters thick.

3. RE "and have the same salt content". 
     But it seems realistic to assume that 2M thick ice does in fact, on average, have a higher portion of MYI (and thus fresher, and mechanically stronger with fewer voids) that is more resistant to melt, on average, than 1-meter-thick ice.  So it seems that qualitative characteristics of the final 1 meter of ice will indeed be a contributing factor for accelerated final melt.

----------
    As shown on the CAB volume chart, even with an eyeball-drawn straight line trend it reaches zero (2048?) about 16 years after the Wipneus whole Arctic Ocean volume chart.  (Polynomial regression curves get you into trouble when extending beyond data used to define a relationship, And the higher the exponent value, i.e. X2 to X3, the greater the hazard.  Given enough exponents you can make a curve do anything. So I am not moved by the X3 extrapolation curve for the CAB volume data.)  If somebody is willing, it wouldn't take long to add a straight line trend to that chart.  The point being that the CAB volume trend does not demonstrate a high degree of additional resistance to melt.

    Another factor not mentioned earlier -- CAB losses might accelerate as the peripheral seas around the CAB no longer provide an ice wall barricade against melting energy.  Also, even at 90N, the encroaching loss of albedo in the waters surrounding the CAB will contribute to greater and proximate summer solar radiation melting energy getting into the CAB.

    All that said, there is a very strong argument against my rambling associations that I failed to mention -- The experts who actually study this stuff.  They continue to publish estimates showing September ASI extent and volume lasting late into the 21st century.  For example, the recent IPCC cryosphere report. 

     So I can't be too adamant in defending my fast-final-meter-melt thesis because I at least know that I don't know the details.  But lest you think I am humble and wise in saying that, let me exemplify opposite characteristics by stating an unfair and baseless suspicion that the experts may be so engaged, enmeshed and enthralled with their models that they don't see what seems obvious to a simpler minded observer like me - the Arctic sea ice is taking a beating.  That charge may not be entirely baseless in that the earlier expert model predictions greatly overestimated how much ASI would remain by 2019.  I am loathe trod down this path, as it is exactly what the climate change deniers do.  But at least in this case I am basing spurious accusation on some concrete observations.  Maybe sometimes the Emperor does have no clothes.  But let's move on, because the "experts are wrong!" line of argument really is on "thin ice." 

     Even without last-meter volume loss acceleration, there is what is to me the bedrock evidence of the Wipneus straight line volume trend.  It looks like a robust trend and it hits zero, nada, zip, in 2032.  Maybe somebody smarter than me will do the math to show at what volume, and thus roughly what year, we can expect rapid acceleration of Extent losses.   Zero Volume requires 0 Extent, but proportional Extent losses have so far lagged behind Volume losses.  Given that we have already lost ca. 3/4 of the September minimum volume, but only 1/2 of the Sept. minimum Extent, even if Volume loss rate remains stable the Extent loss rate would have to accelerate within the next decade.

     Countervailing forces of increased Arctic warming; more fractured, thinner ice; more storms, polar cell weakening; Atlantification/Pacification of Arctic ocean SST  vs.  higher latitude for the final ice; could result in the Volume loss trend continuing on a straight line trend.  If that happens, or even if Volume losses slowed down a bit, the requirement for % Extent losses to eventually catch up to % Volume losses means that Extent loss acceleration may not be far off, if not underway already.  (Which I acknowledge is a different question than the final-meter melt rate question which is the topic at hand.)  If so, then gerontocrat's CAB open water chart will be an interesting metric to watch in next few years.

PS Tor, sorry for misspelling your name in previous post, now corrected. 

36
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 07, 2019, 12:50:22 AM »
Apologies for taking so long to reply... I'll spare you my usual excuses, though I don't doubt they would impress you with their earnest sincerity and momentous import of the ways I manage to waste time ...

   Here is the reasoning why I proposed that the last 1 meter of ASI from 1m average thickness would melt to 0m faster than from 2m to 1m average thickness:
    -- As we lose the older thicker MYI, the remaining ice has higher percentage of younger, and thus saltier and easier to melt FYI.  Everybody seems to agree on that.

e.g. As interstitial noted at
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg201895.html#msg201895
       Thinner ice, presumably with higher portion of First year Ice...
"has pockets with high salt concentrations in it. Some of the pockets even most may not of frozen solid.
   ...When the temperature climbs above -21C the pockets of high salt concentration melt first. The temperature is still too low to melt the pure ice.
   ... This is how multiyear ice is formed each freeze and thaw cycle of salty water can more and more salts out until it is pure ice with no salts. That makes the multiyear ice fresher and more melt resistant."

   -- But here is the main reason - the Thorndike (1975?) chart showing the differential rate at which ice of different thicknesses increases thickness, that Chris Reynolds posted to explain the Slow Transition hypothesis.  To me it says that unless there is some hysteresis effect, then that curve in reverse shows that thin ice also melts MUCH faster for the same amount of heat input.  For a given amount of heating energy, e.g. melting degree days in summer, more ice is lost per unit of energy in summer by thin vs. thick ice, just as more ice is gained by thinner ice for the same amount of freezing degree days during the winter.

      Here is the Thorndike chart

(And you know its good because it is Neven's account icon!)

     Here is my reversed version, with zoom into the last 2 meters.


     Seems to me that the Thorndike chart, when reversed, shows the amount of ice lost for the same amount of heat added to ice of different thicknesses.  Just as the original chart shows the amount of ice gained for the same amount of heat lost from ice of different thicknesses. 

     Thus, I am using Chris Reynolds' Slow Transition evidence to reach an opposite conclusion.

     This is a simple case of Teslacle's Deviant ("What comes in, must go out") to Fudd's First Law of Opposition ("If you push something hard enough, it will fall over") -- for you Firesign Theatre fans.  Seriously though, as a thermodynamic equation, what works in one direction should work in the reverse unless there is some hysteric effect at work.  (e.g. Teslacle was right!  This could be Vulvaire's Correlate to Teslacle - "What went out, comes back in.")

     Another chart adapted from an ASIF post by Jim Hunt
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg201631.html#msg201631
shows the same phenomenon. I didn't reverse this one, but you can do that in your head.

   
     The only argument against a quicker final meter melt notion is that the because the CAB is at higher latitude, the melting process will stall as the Arctic ice melt reaches the high latitude end game.  And I might buy that idea if humanity was intelligent enough to stop pumping greenhouse gases into the atmosphere at an increasing rate, but not seeing evidence that we will, one can only suppose that warming will continue, and in fact that the rate of warming is increasing.

     I admit that gerontocrat's open water chart (up thread at https://forum.arctic-sea-ice.net/index.php/topic,2348.msg235525.html#msg235525) requires a huge rate increase in CAB September open water to have a BOE anytime soon.

      But the cumulative evidence argues that that is indeed what will happen.  While gerontocrat's CAB volume trend chart shows it reaches zero a few years later (ca. 2040?) than the whole-Arctic Wipneus volume chart (2032), it is not that much later.  That suggests that the CAB does not have enough extra resistance against melt to combat the inexorable warming and Arctic amplification underway. 

   As Tor Bejnar noted at
https://forum.arctic-sea-ice.net/index.php/topic,933.msg113144.html#msg113144
"I have also long considered the 'quick' loss of summer ice in the non-CAB regions over the past 30 years (e.g., the Beaufort going, in August, from 2/5th coverage to none between 2013 and 2016) not to be predictive of how fast CAB ice will be lost.  I think this discussion of bathymetry adds some geophysical creds to Chris's theses.  This doesn't mean, however, that I'm 'now' convinced Chris is right.  I think other issues like CO2-equivalent, mobility and storminess (emphasis added GK) may well 'over' compensate for the bathymetry-related suppression of warm water currents remaining near the ocean surface."

     As Bruce noted at
https://forum.arctic-sea-ice.net/index.php/topic,778.msg32178.html#msg32178
"Chris, I don't see any reason for the rate of summer melt increase to flatline, slow down, or even be linear. As the ice thins, the surface/volume ratio increases, which should increase the rate of melt. The thick MYI held off major assaults in 2017 and 2012, but that ice is nearly gone. What we have now is this "mesh ice" that spreads out as the edges melt (which, though it is a negative feedback (because it keeps more of the ocean covered with ice), is a short-lived one). That spreading increases the surface (both top and bottom) that can melt."

    In a second instance of using Chris Reynolds' evidence to reach an opposite conclusion, I will reinterpret a chart he posted at at https://forum.arctic-sea-ice.net/index.php/topic,933.0.html


   Read his post to see how he uses that to argue for the slow transition.  To me it shows that  September ASI volume hits zero ca. 2027, even earlier than the Wipneus chart.

   As for the hiatus, I think we've beat that to death.  I'll just repeat that 10 yearly data points is simply not long enough to make statistically valid conclusions for data with high interannual variability.  I will go out on a limb and bet that the 2012 minimum volume record has a 50% chance of being replaced in 2020, likely won't last beyond September 2021, and almost certainly won't last  beyond Sept. 2022. 

    That said by the guy who expected the October slow refreeze to continue based on GFS forecast showing continued high Arctic temperature anomalies over the last 10 days, when just the opposite happened.  I guess I was confusing the tail and the dog - my new guess is that the air temp. anomalies were high because the water transitioning to ice was giving off heat to warm the air above it. 



37
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 14, 2019, 10:59:29 PM »
     
     Extrapolating any trend line too far beyond the data used to define it is prone to error, but less so for a straight line trend, and much less so for extending a straight line trend by a single data point.  The Wipenus linear Sept. minimum volume trend graph
https://forum.arctic-sea-ice.net/index.php/topic,119.msg232085.html#msg232085
shows the 95% confidence interval for the 2020 ASI September minimum volume as 2.0 to 5.5 million km3.  The +/- 1 standard deviation range shows that the 2020 minimum volume has a 68% chance of being between 3.0 and 4.5 million km3.

     A downward trend at a consistent absolute rate of about 333,000 km3 per year becomes an increasing percentage of the total as the total shrinks.  Back in 1980, losing 0.3M km3 represented less than 2% of the total.  A 0.3M loss between 2019 and 2020 would be a greater than 8% year to year decline.   

     As we approach 3M then 2M annual volume minimums (not that far off according the trendline at 2022 and 2026, respectively), continued declines would become more visually dramatic.  And the ratio of % Extent loss to % Volume loss has to increase as the zero point nears.  The advantage of ASI as a visual marker for global warming will likely become more prominent in media coverage.  Neven may have to start wearing sunglasses in public.   8)

     As Sept. average ice thickness nears 1 meter that suggests (to me at least) that the final phase of September ASI losses may accelerate despite countervailing issues like the final ice being at higher latitude with shorter summer solar input, deeper bathymetry, sparser winter ice allowing more heat loss from ocean to atmosphere etc.  The resistance of sea ice to melt is NOT linear.  It decreases faster than thickness.  1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 

      Declining ice quality could be another accelerating factor.   The fortress of hard core MYI ice that used to persist along the northern coast of Greenland and the CAA took a serious hit in 2019, (see https://forum.arctic-sea-ice.net/index.php/topic,2839.msg232342.html#msg232342)
And as far as I know, the CAA garlic press ridging did not really occur in 2019.  The qualitative effect that reduced ice quality will have on the melting pattern in 2020 will be morbidly interesting to watch.

     But that is next year.  Right now the developing story of low refreeze and a possible record low April maximum volume is almost as compelling as summer progression to the September minimum.  So thanks to gerontocrat, Juan C. Garcia and others for continuing to post updates.

38
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 14, 2019, 12:52:24 AM »
"It is very likely that there will be at least one sea-ice free Arctic summer out of 10 years for warming at 2 degrees C, with the frequency decreasing to one sea-ice-free Arctic summer every 100 years at 1.5 degrees C”

What's the reasoning behind this and how does it stand against the trends on the ice volume chart?

IPCC is said to be trying to improve their communication skills, but there is still room for improvement. 
RE: "sea-ice free Arctic summer".
   A literal interpretation would be that means zero ASI for every day between June 20 and September 21.
     vs. September average going below 1 million km2 Extent.
     vs.  single day September minimum going below 1 million km2 Extent.
     vs. September as a whole having zero ice.
     vs.  single day September minimum having zero ice.

So which is it?  More precise specification of dates and definition of terms for statements about future ice losses would greatly improve clarity and reduce confusion about what is being said.

Speaking of confusion, this discussion belongs in the "When will the Arctic Go Ice Free" thread, not this one.

39
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 12, 2019, 06:33:47 AM »
All good points philopek, but here is an alternate view:

1) If the 80N+ circle is so much less susceptible to melt then why does that straight line downward trend in ASI volume give such a good fit, with 2019 exactly on target?
https://forum.arctic-sea-ice.net/index.php/topic,119.msg232085.html#msg232085 
        If the remaining most northerly areas are going to decline at a slower rate then that effect bettter kick in soon, because the straight line September minimum volume trend hits zero in 2032, and the August and October volumes only trail September by a few years.  If the 80N+ CAB ice is to be a long term survivor, I would expect that straight line trend to be bending upward by now.  But so far at least, the data do not indicate a rate change in volume decline.
   Similarly, there is no apparent rate change to justify other than a continued straight line trend in the September monthly average volume as charted by Jim Hunt  https://forum.arctic-sea-ice.net/index.php/topic,119.msg232040.html#msg232040

2)  Yes, water temperatures are lower in the icey CAB vs. peripheral seas, but those peripheral sea water temperature anomalies are large and encroaching at an unprecedented rate (as far as I know), e.g. https://forum.arctic-sea-ice.net/index.php/topic,2888.msg232462.html#msg232462
    And with declines in ice coverage of the peripheral seas, the effect of albedo decline to warm surface water during the brief summer edges ever closer to the North Pole.

3)  Observations of jet stream weakening and unusual if not freakish warm fronts crossing the North Pole do not bode well for the future of Arctic thermal isolation.  I confess to not understanding the details of Sark's analysis, e.g.  https://forum.arctic-sea-ice.net/index.php/topic,2692.msg232323.html#msg232323 but his scenario seems include loss of Arctic thermal isolation, and thus even greater polar amplification of warming.  Altered, equable weather patterns could also lead to increased ocean heat transport into the Arctic, which seems to already be happening.  What I understand better is the analysis of Jennifer Francis et al. that Arctic air spillage over my head in eastern North America appears to be increasing.  Which bolsters Sark's view in that if cold air is spilling out of the Arctic, then warmer air from the south must be migrating in to take its place.
     And the Arctic is of course part of the bigger picture.  CO2 & CH4 and other GHG emissions, levels in the atmosphere, and surface warming all continue to increase at essentially the RCP8.5 trajectory.  If the global system temperature was static, then the factors working against melt at 80+N might show up in the ice volume data.  But the global heat reservoir continues to increase, and at an increasing rate.  And the vast majority of that heat ends up in the ocean surface layer, where it can be carried to the high Arctic. 

4) As for average ice age, the Wipneus images at  https://forum.arctic-sea-ice.net/index.php/topic,119.msg232086.html#msg232086
https://forum.arctic-sea-ice.net/index.php/topic,119.msg232040.html#msg232040 show that the CAB ice fortress isn't what it used to be, i.e. it is no longer composed of thick, melt-resistant multi-year ice.  I suspect that the reduction of ice quality and "communal integrity" does not get enough attention.  That may be the factor that tips the balance to overcome lesser insolation at the North Pole. 

     So contrary to a long asymptotic stabilization, I can see just the opposite happening -- an accelerated chaotic ASI system breakdown.  With thinner fractured fresher ice replacing the previous thicker saltier MYI, loss of the Beaufort gyre nursery to replace MYI, currents and wind patterns to which the CAB was previously resistant may be able to cause accelerated CAB pack rotation.  That increased mobility could greatly accelerate export to lower latitude melt zones or out of the Arctic entirely through the Fram Strait.  And now the Nares may be a smaller secondary doorway that also allows greater ice pack mobility. Continued Arctic albedo decline moving northward.  Warm humid air fronts reaching the NP.  Continued Atlantification and Pacification of the Arctic Ocean with escalated SST moving closer to the NP.   

    If this view of the situation is correct, then we could be close to a systemic breakdown of the ASI, or at least a continuation of current trend despite higher latitude for the remaining ice.  We may get insight soon enough - if the the straight-line trend continues, that suggests that the 2012 minimum Sept. volume record has a > 50% chance of being superseded in the next two years.

     There are people much smarter than me who study this for entire careers and their understanding as shown in the IPCC reports etc. does not call for such radical change in the next 13 years. With my superficial understanding, I don't hold too much faith in my own opinion.  I may be spinning a few facts into conceptual storytelling. I really would love to be wrong.

    But I keep coming back to that linear ASI volume graph.  Until I see that trend change, my gut says trust the observations.

     

 

40
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: October 09, 2019, 03:57:32 PM »
     Thanks Stephan.  A zero Arctic sea ice volume date for September, and shortly thereafter for August and October has been on my radar for a long time from the Wipneus and your earlier graphs. 
 
      But zero ASI volume-in-July estimates of 2034 (linear) or 2038 (log) are shocking to even my jaded eyes.  Yikes.  The albedo impact of losing ice coverage in July is much greater than August and very much greater than September.  Actually, the whole situation is shocking, but we just get used to the evolving catastrophic trends as a new abnormal.  If that zero Arctic sea ice estimate in July date is anywhere near accurate then we are in big trouble sooner than previously realized.  Remember, you can't have Extent or Area without Volume, so 0 Vol in 2034/2038 also = 0 Ext. 

     FWIW, the September 2019 IPCC cryosphere report shows Extent becoming asymptotic at about 10% of the 2000 level around 2070. 
https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_FullReport.pdf
     
     Given the length and detail of the IPCC cryosphere report, there is a surprisingly brief discussion of Arctic sea ice trends.  ASIF is a better source than IPCC! (seriously). After a quick search, I found nothing in the IPCC report about ASI volume projections.  Figure 3.3 on page 3-13 is the closest information.  It charts ASI Extent under the RCP scenarios.  In those projections, even the RCP8.5 scenario retains 10% September Extent for 2070-2100. 

      The scientists who donate their hard work to IPCC reports are the experts and I feel like an ungrateful flea telling the dog what to do in critiquing their work.  But my small fevered brain is unable to reconcile the trends charted by Wipneus and Stephan, or that I can see for myself in the data from PIOMAS, with the IPCC statements shown below from page 3-25.  To be blunt, I suspect that the IPCC is under-estimating the severity of the ASI trends.  If that were in fact the case, it would almost certainly be due to the political (in addition to scientific) consensus required before IPCC reports are released.  But let me not digress into conspiracy theory.  Here is the gist of what the IPCC Cryosphere report has to say about the expected future ASI:

      "There is a large spread in the timing of when the Arctic may become ice free in the summer, and for how long during the season (Massonnet et al., 2012; Stroeve et al., 2012a; Overland and Wang, 2013) as a result of natural climate variability (Notz, 2015; Swart et al., 2015b; Screen and Deser, 2019), scenario uncertainty (Stroeve et al., 2012a; Liu et al., 2013), and model uncertainties related to sea ice dynamics (Rampal et al., 2011; Tandon et al., 2018) and thermodynamics (Massonnet et al., 2018). Internal climate variability results in an uncertainty of approximately 20 years in the timing of seasonally ice-free conditions (Notz, 2015; Jahn, 2018), but the clear link between summer sea ice extent and cumulative CO2 emissions provide a basis for when consistent ice-free conditions may be expected. For stabilized global warming of 1.5°C, sea ice in September is likely to be present at end of century with an approximately 1% chance of individual ice-free years (emphasis mine) (Notz and Stroeve, 2016; Sanderson et al., 2017; Jahn, 2018; Sigmond et al., 2018); after 10 years of stabilized warming at a 2°C increase, more frequent occurrence of an ice-free summer Arctic is expected (around 10-35%) (Mahlstein and Knutti, 2012; Jahn et al., 2016; Notz and Stroeve, 2016)."

    They do say elsewhere in the report that CMIP5 models have relatively poor ability to recreate Arctic sea ice behavior.  The new generation of CMIP6 models are coming out and have improved capabilities.  It will be interesting to see what they have to say about ASI projections.  So far the only statements I have seen on output from the few CMIP6 model results being reported is that they (i.e. the multiple new component models of the new CMIP6 set) are consistently showing greater sensitivity of global surface temperature to rising CO2 levels than the CMIP5 estimates. 

       None of this bodes well for the ASI, or for human civilization unless we finally take heed and respond to the crisis with the intensity and commitment it requires.  Make your support for any politician explicitly contingent on their climate policy.  Talk about it even if you annoy people by doing so.  Vote climate as if your life depended on it.  Because it does.

41
Arctic sea ice / Re: The 2019 melting season
« on: September 20, 2019, 08:03:00 PM »
      Nobody is saying the topic of changing weather dynamics is unimportant, just that this thread is narrowly focused on the 2019 melt season, not the bigger picture.  Likewise, the existentially important topic of the possible emergence of altered weather patterns will get more informed discussion by appearing in its own thread.  And as noted above, appearing as the main topic of a thread creates a focused archival record of the conversation on that particular topic.

    If your concern is that fewer people will see it there because we all congregate at the melting thread and that people won't make the effort to see another important topic discussed in a separate thread, all I can say is c'est la vie.  You can't make people care about something.  I think the overwhelming majority of ASIF visitors do care about the climate crisis or they wouldn't be here.  An active thread about weather dynamics would be a good addition.  But not good to hijack the thread focused on watching the ice melt.  Diluting the focus and therefore quality of the melting thread would do more harm than good.

42
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 09, 2019, 11:21:43 PM »
      And since I am pontificating on statistics, here are some take away messages from the recent graphical posts by Oren, binntho, Archimid and El Cid (and thanks to all).

RE binntho's Extent and Area straight line trend
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227604.html#msg227604
     While it certainly looks like a significant downward trend, you can't say the slope is different from zero without doing the stats.  It probably is, but your use of the visual assessment method is no more valid than it is for the folks arguing that the process has stalled because it looks that way in the last 10-13 years (again I am shameless, the same applies to me too, my sinful nature was noted in previous post.  We are all fallen creatures.)

RE Oren's CAB volume trend and thickness graph
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227570.html#msg227570
    That's almost the chart I was hoping for, but it would be even better with a straight line regression trendline, tested for difference from zero, and then extended out 20 years to 2040.  FWIW, if you squint and draw a straight line through the CAB volume trend for Day 243, aka end of melt season, the slope of that line will indicate about 4 million km3 decline from 2000 to 2019, i.e. 19 years.  If that trend continues, then take another 4M km3 over next 19 years and it reaches zero in ca. 2038.  That's only a few years later than the Wipneus straight line projection of sea ice volume trend for the entire Arctic.

    The key characteristic about Oren's chart is that it is limited to ice volume in the CAB.  Thus, it presumably removes possible inflation of losses by peripheral seas that are melting out sooner than the CAB.  What started this phase of the discussion was the notion that future loss rate would decline because the CAB would be more resistant to melting.  I think the Oren chart refutes that. 

     I was surprised how strongly negative the CAB end-of-melt-season (i.e. annual minimum, day 243 data) volume is.  The CAB may look like it's been hanging on, but apparently that is the deceptive Extent curve at work.  The CAB has been rotting out from the inside.  As for the future, the presence of ice in the peripheral seas late into the summer might have reduced past losses in CAB.  Their presence has kept Arctic Ocean albedo high and almost certainly reduced pack rotation and transport out through the Farm Strait (and thanks to Tor for insight on importance of  export losses).  With less protection from ice in those peripheral seas as they melt out earlier in the year, the rate of CAB losses could markedly increase in the future. 

   Archimd's graph shows that CAB volume losses appear to already be increasing https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227455.html#msg227455.

     In addition,  the wider amplitude of the fluctuations in El Cid's graph
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg227470.html#msg227470 gives me a bit of the willies because one of the predictors for a nonlinear chaotic system reaching a tipping point is higher variability.  I may be misapplying that concept because max to min amplitude is not the same as variability between years, but I allow myself my own superstitions.

    But 2038 as the projected zero year for CAB sea ice volume is over a century earlier than binntho's trend extension showing Extent not reaching zero until 2187. How can that be?   Extent is not declining as fast as volume because the remaining volume is being contained in thinner and thinner ice, and thus the Extent does not decline as much as it would if thickness remained constant.  But as the thinnest ice contributing to Extent reaches zero thickness, it stops contributing to the Extent number.  In the end, the Extent curve and the Volume curves have to meet because zero volume provides zero ice for Extent.

    Which brings me back to Oren's thickness graph.  Total conjecture, but my guess is that once average thickness gets below 1 meter we will start to see the end-of-melt-season Extent curve start catching up with its parent Volume curve.  Ice melting comments elsewhere on ASIF point to the much lower melt resistance of thin vs thick ice.  Regardless of my conjecture, the Extent curve HAS to catch up to the Volume curve eventually.

    Stay tuned.  I think there are wild times ahead for ASI in the very near future because it is on the edge of the precipice.  It will be entertaining for those of us who like to watch numerical systems evolve.  Too bad it isn't just a horse race or some other innocuous event, but is instead the loss of a crucial component for meteorological and climatic stability on the only planet in the universe known to host self-aware, so-called "intelligent" life (actually any life, but I think we will soon see that microbes are just about as common as water).  As my brother, a conservative who bought into the climate hoax BS for a while, but who is too smart to stay ignorant, said when he came to see the big picture: "This story does not end well".

   

43
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 09, 2019, 11:12:32 PM »
    Folks - we don't need to go around the wheel again about whether the recent apparent flat lining in annual minimum Extent and Area is real or not. (I don't think anyone is arguing that volume has flat lined).  Yes it looks like the trend has flattened out in recent years, and maybe it has.  The point is that given the degree of inter-annual variability between individual data points (i.e. years), the paucity of data points does not provide support for the assertion of a change in long term trend with any acceptable degree of statistical certainty (i.e. less than 5% or even 20% chance of a Type I false assertion error). 

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

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

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

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

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

   

44
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 08, 2019, 06:53:57 PM »
     Thanks El Cid and Archimid.  What I want to see is annual minimum volume (not loss from max, though that too is interesting) with straight line trend extended out 20 years.  (I know, extending trendlines past data range is fraught with potential error, but less so for straight line and certainly worth looking at.)

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

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

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

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

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

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

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


45
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 08, 2019, 07:21:13 AM »
      FWIW, the Wipneus linear PIOMAS volume trend chart at
https://sites.google.com/site/arctischepinguin/home/piomas
suggests that by 2029 any individual year would have a 50% chance, by 2032 an 84% chance, and by 2036 a 97.5% chance, of going below 1 million km3 by the end of melt season.

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

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

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

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

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

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

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

46
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 09:33:24 PM »
Another look at what I would describe as a new floor which supports a minimum threshold that will prove difficult to breach but looking at ice age instead of volume.

Good discussion.  And nice chart of early March Arctic sea ice portions by age of ice SH.
The chart shows 1st-year ice percentage increased from ca. 38.3% in 1984 to 65.8% in 2018, which summarizes to an average gain of 0.8% per year.  If that rate continued for another 48 years then 1st-year ice would account for nearly 100% of early March Arctic sea ice. 

    My understanding is that in one melt season, about 2 meters of ice thickness is lost.  And that the average thickness of 1st-year ice is also about 2 meters. 

   So... once we get to ca. 100% 1st-year ice at start of the melt season in March, then that ice would be thin enough to all melt out by the end of what is now an average melt season.
 
    Of course, with current and accelerating warming of global average surface temperature, by 2067, i.e. 48 years from now, the typical melt season will be much warmer so the scenario i'm creating here may arrive by 2050.

  There would still be refreezing in winter.  But progressively less on average each year.  So that's another trend to throw into the blender.  With a lower starting volume each year, the year when all, or nearly all, the Arctic sea ice melts out by end of melt season gets even earlier.

   And I end up back with what I consider the simplest and most convincing predictor of when Arctic sea ice annual minimum.  That being the Wipneus graph showing linear trend of annual minimum volume reaching zero around 2030. 
https://14adebb0-a-62cb3a1a-s-sites.googlegroups.com/site/arctischepinguin/home/piomas/grf/piomas-trnd7.png?attachauth=ANoY7co-JT1jjQGvpGxNEvrl0OaSjsV--ZIsZkJxM9mAn3liTvPonGye-SIwYIoMrdz3WhCjzTF-7eO1y4xjVMqo4Mqe6Py4I4KqkaHO97Qm_F7_j-0wn7hmI_ipG2OPbsk-eONQXLct1Ze62owhGmvWbQvdKVz21eBmKeJaoqz_EeC_3JYndbm6NHkkBDxQHAohuZUi9NrYqBUZ105uBQF7giHXXIyLZiC9G_kb1PqxmVgYs8y-q-WkPdR-VoZitgO_CypQuuTS&attredirects=0

     So no need for my layers of speculation and assumptions, just look at the numbers as graphed by Wipneus!  Also interesting to note that 2019 September minimum volume is going to land just about exactly on the linear trend in the Wipneus graph. 

47
Arctic sea ice / Re: Basic questions about melting physics
« on: August 31, 2019, 08:06:09 PM »
  The Arctic sea ice minimum has not decreased recently.  If you refuse to see that from the data, there is nothing more that I can say.

KK - depends on what you mean by "recently."  Given the internal variability of the system, a 7-year or 10-year window (i.e. since 2012, 2008) is too short to draw conclusions.  To protect against cherry picking and our innate human tendency for "pattern matching" where there is none, a longer interval of at least 20 years is required. 

     The 20-year downward trend in annual minimum Arctic sea ice volume appears to be much larger than year-to-year variation, and thus appears to be statistically significant.  Maybe somebody with more time and skill will run the stats on 1998-2018 annual min. volume data.  Moreover, 2019 is likely to end up with less the 4M km3, and thus land right on and thus reinforce the PIOMAS trend shown at
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png

    I think focusing so much on Extent leads us to false conclusions on both the high and low side.  2012 was bad for volume, but not nearly as extreme as it was for Extent.  To a substantial degree, Extent reflects temporary wind and current conditions, not the true status of the Arctic sea ice.  By focusing on Extent we can under-represent the cumulative progressive effects on overall condition of the ice. 

     The ice year this year has looked weaker more fractured than in past years.  A subjective measure to be sure, but not to be fully discounted either.  It will be interesting to see how the MYI numbers look after the 2019 melt season.  My guess is that they took another downward hit such that we are getting very close to only 1st and 2nd year ice that is more vulnerable than the tough old 5- and even 10-year old ice of the recent past.  The final phase of decline in ASI Extent is slowed by the much more rapid regrowth of 1st year ice.  But the flip side of that is that 1st year ice also melts out faster.   In retrospect, the functional loss of the Beaufort Sea ice nursery may be seen as a crucial event marking the beginning of the end of ASI in Aug-Sept.   I suspect with only 1st-year ice to get rid of at the start of future melt seasons, it won't last much beyond July 31.

     That's how it looks to me anyway.  No formal training in Arctic or ice, just a little experience analyzing numbers and interpreting science added to lurking in the ASIF.  Thanks to those who provide interesting info and speculation to ASIF.  Esp. thanks to Neven, Gero, JCG, uniquorn, Alphabet and others. Less gratitude for those who engage in extended ego-defensive debates.  To those folks I say, let others disagree with you and get over it.  Nobody else cares if somebody insults you.  Now you can disagree with me! 

48
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: August 17, 2019, 03:53:39 PM »
Is there anything about 2019 that is exceptional? If I understand, 2012 was exceptional because of a big cyclone in the Arctic (am I right)? Is 2019 just a near "normal" year?

     Seems to me that 2019 stands out for the overall poor quality of the ice (thickness, concentration).  Extent and Area do not necessarily reflect that poor condition  so even though it seems unlikely that 2019 will set new low Extent record, it represents another step down the path of arctic Sea Ice degradation, and all that that implies for the climate system as a whole. 

    One aspect the current situation that stands out to me is that the largest chuck of highest concentration CAB ice is on the Atlantic edge.  Very doubtful it will happen in the dwindling melt season, but a cyclone to export that chunk out of the CAB would make a big dent in the Extent/Area/Volume stats.  Though it probably won't happen, just the fact that it could is ominous.  And that IMO is the ASI headline for 2019 -- the ice is in worse shape and more vulnerable than ever. 
 
   As somebody commented above, this degraded state is occurring at/near minimum of a weak solar cycle.  Our friendly star is remarkably stable but the slight variation in energy received from the sun across solar cycle can nudge annual average global surface temperature up and down by ca. 0.1C.  So with ASI in this shape in 2019, what happens at peak of next cycle (albeit also expected to be relatively weak amplitude cycle relative to past 100 years)?  And of course with GHG emissions roaring along, and 93% of the extra retained energy going into the ocean waters, add that to next solar peak in 5-6 years and 2012's freak low Extent/Volume could start to look like the good old days when there were still millions of km2 MYI sea ice that carried over between years.

   So I guess the 2019 headline could be the beginning of the end for the ASI functioning over the last 12,000 years as a climatic anchor and stabilizer during the Holocene period.  That's the period during which so-called  "wise apes", aka Homo sapiens, learned how to do things like agriculture, science, literature and all the rest.  All just my lurker opinion of course.

     Climate sanity should be a requirement for any policy and politician to even be considered.  As the World Bank put it in back in 2012 (before the last 7 years of sooner/more severe climate study results) - the continuity of an "organized global community" depends on it.  I confess that I find it numerically fascinating to learn about the complex interactions of the ASI as it falls apart.  So a preliminary thanks to Neven, gerontocrat and others for hosting this soiree again this year.  But I don't want to see what "disorganized" global community looks like.  It would be nice if there was no reason to enjoy this forum.     


49
Arctic sea ice / Re: 2019 vs 2012
« on: August 14, 2019, 07:26:01 AM »
Post 2 of 2





The 2019 average index calculated by current melt season anomalies is marked with * and is shaded green.  The projected 2019 minimum Extent, Area, Volume, and Thickness values based on current melt season anomalies appear to less reliable predictors than the 2011-2018 average remaining losses.  The average ratio for based on the 2019 melt season anomaly estimates is included in the table to show relative position, but to avoid assigning two ordinal ranks to a single year, only the 2019 minimums based on 2011-2018 average remaining losses are assigned a rank vs. other years.  Likewise, the color coding for 1st, 2nd, etc. lowest values does not include the 2019 melt season anomaly values.

EDIT -- Dang part 2.  Away from computer and can,t fix right now.  Forgot to edit the yellow shaded 2019 values based on 2011-2018 average remaining losses in table below.  Extent ratio should be 1.14 and Area ratio should 1.17.  COMBINED AVERAGE stayed at 1.08. 


The index value for each year is based on its average of ratios to the minimum value observed in 1979-2019 for each measure, not by the average ordinal ranking.

Observations/Speculation: 
-- 2012 stands alone as the lowest overall with 1st place ordinal rankings for all four measures.  (Technically, 2019 minimum thickness was lower, but only by insignificant margin.) 

-- 2019 is second to lowest, with one 1st, and three 2nd place rankings.  The estimated 2019 minimums for Extent and Area are substantially larger than for 2012.  The 2019 and 2012 minimums for Volume and Thickness are similar.
      The *2019 minimum Extent, Volume, and Thickness estimates based on the current season anomaly are lower than the estimate based on 2011-2018 average losses from latest observation date to minimum.  But the Area estimate is higher.  While 2019 still finishes second to 2012 for the average ratio, the gap is much narrower. 

-- 2016 and 2011 are close to each other for 3nd lowest overall ranking, followed by 2010 and 2017 in a tie for 4th place. 

-- The sequential rankings of 2010 (#5), 2011 (#4), and 2012 (#1) suggest that the 2012 minimum record may have been the culmination of a three year sequence of predisposing bad melt years vs. being entirely due to conditions in 2012. 
 
-- Except for 2007, there is a high degree of congruence between the 2D measures (Extent, Area) and the 3D measures (Volume, Thickness). 

-- Nine of the 10 lowest ranking years have been in the last decade.  All of the top ten ranks, except 2007 at #9, have occurred in 2010-2019.  At rank #12, 2014 is the only year in the most recent decade to not be in the top ten for lowest index overall value. 

50
Arctic sea ice / Re: 2019 vs 2012
« on: August 14, 2019, 07:20:43 AM »
Post 1 of 2
     As per request I added an alternate version of the 2019 projected minimum based on extending the melt season to date anomaly vs. 2011-2018 average.  Thus if 2019 reduction in that measure to date was 5% higher than in 2011-2018, then the remaining projected losses to minimum would also be 5% higher instead of using the 2011-2018 average losses from latest observation date to annual minimum.









FWIW - August  12,  2019 has more ice on the Russian side which is surprising with the persistent high temperatures in coastal Siberia earlier this summer.  But 2019 has less ice in core of what used vto the MYI triangular fortress from norther Greenland  to North Pole and Down to Ellesmere Island.  Even though 2019 does not look to break the 2012 records for Extent and Area, it seems that the condition of the CAB is substantially weaker.  Also the high concentration/low spread CAB ice in 2019 is perched closer to the Fram Strait exit ramp.  I guess too late this year for it to get shuttled out of the Arctic and who knows where that ice will be next June.   But that location seems to be more bad news for ASI.



EDIT -- Dang - forgot to update 2019 projected min Extent and Areas based on 2011-2018 remaining losses in the tables.  Can't fix right now, away from computer.  Values in text section above tables are the correct ones.  The yellow shaded Extent in table should be 3.80 & 114%.  Yellow shaded AREA should 2.60 & 117%.
   Thus, since August 4 Extent got closer to 2012, but Area fell farther behind.


 







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