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Messages - Glen Koehler

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1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 22, 2020, 11:50:23 PM »
     I'll pass those comments along.  Out of my league to make any comment.

2
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 22, 2020, 10:27:48 PM »
Climate reanalyzer does not foresee 2m temperatures dropping too much over the next ten days. Because some colors are dithered (for print!?!), the correspondence with the color bar is poor. Accurate tick marks cannot be put on the color bar because its pixel width is not an integral multiple of degrees. These errors degrade expensively acquired data so need to be fixed.
     The brain and 10 nimble fingers that singlehandedly (correction: 10 fingers = 2 hands) operates Climate Reanalyzer is aware of your critique.  The reason for dithering the color scales is because for the weather forecast animations it reduces file download size by a factor of 6X.  The file sizes are not so large as to matter for folks on an unlimited-data high-speed connection, but for people on a slower (or data-metered) connection (DSL was mentioned as a slower connection, and smartphone internet is an example of a metered connection), the file size does matter. 

    That person also mentioned that for stand-alone images, dithering the color scale may not be necessary so a possible change will be investigated.  Suggestions are well received, just remember that while CR may look like some well-funded institutionalized juggernaut, it really is a part-time operation by one person with a vision, programming skill, and committment who built something nobody else (including well-funded institutionalized juggernauts) had gotten around to doing, and done while juggling multiple other responsibilities and deadlines, including a recurring requirement for periods away from the keyboard to eat, sleep and other aspects of life.

3
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 22, 2020, 05:24:34 PM »
Once the water is back to to freezing, the ice will form at the same sort of rates, but it'll be a few days later than in the past...
I'd say it will be a faster refreeze as the surrounding air and the continents will be much colder by then than during previous refreezes. Late but fast refreeze. We shall see
      The Guardian article mentions a possible ecological impact on nutrient transfer from the delayed Laptev Sea refreeze.  It seems likely that once refreeze begins it will be more rapid than "normal" because it will be occurring at a later date.  That makes me wonder if the rate of Arctic Ocean refreeze has important but little-discussed impacts.  If the ice pack edge advances many more miles per day than normal, how does that affect the microscopic and macroscopic organism communities that interact with the water/ice environment?

       Ice vs. water is a major habitat change, and the rate at which that habitat shift occurs could have consequences.  While I doubt that ice-edge advance is going to be so fast as to outrun the ability of air-breathing marine mammals that need access to open water to relocate, that's an extreme (though I think implausible) example of the kind of scenario that comes to mind.  What seems more likely is some effect on the colonization, population growth rate, and niche partitioning of microflora/fauna on newly formed ice.  For example, it may make a difference to community structure if there only 3 versus 30 days between initial colonization and the date when discriminating environmental conditions occur. 

       The relative timing of such events may have trivial consequences, or it may not.  Small differences over such a large scale can have a large impact, especially in a tightly linked system where each domino affects all the following dominoes.  Even though Extent / Area / Thickness / Volume will probably return to closer to the normal range quickly once refreezing begins, even getting back to a closer match with "normal" values after a late refreeze start and rapid rebound may bring with it subtle but significant qualitative physical, chemical, biological and/or behavioral differences that are not apparent from the quantitative Ex / Ar / Th / Vol measurements. 

       The fact that the Russians could not really test their new ice breaker on a run to the North Pole because the ice was too thin and broken is not an Earth-shaking consequence, but it exemplifies how changes ripple through a system in unforeseen ways.  Everything is connected.  I do not expect obvious or catastrophic impacts, but the potential effects of refreeze timing and rate do seem worth noting.  I wonder if/how Arctic scientists are tracking such potential qualitative impacts.

4
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 09, 2020, 11:32:32 PM »
     Of course adding heat is not going to make the Arctic get colder.  That is not what I said and is not implied by the term negative feedback.  My point was that an energy increase that results in more open water that results in increased LWR that results in increased energy lost from the system will have a negative feedback effect to partially counteract that initial energy addition.  That influence would act to partially revert back to the initial energy state but not go below it. 

     Unless a negative feedback is 100% effective (unlikely if not impossible without some other state change), it will not cause a system to even get all the way back to the initial state.  Adding energy to a system increases the energy in that system.  But a negative feedback acts to make the net gain in energy somewhat less than the initial value plus the added amount.  As the negative feedback acts to bring the system back towards and closer to the intial energy state,  the weaker that negative feedback becomes, so the system can't end up being less energetic than it was initially.  (And now somebody can point out some chemical system etc. where negative feedbacks can indeed overun and go below the initial state, but I can't see how that could possibly apply in a large complex system like the Arctic Ocean.)

     My point was that I think binntho was overreacting to his epiphany from A-Team.  Increased LWR can have some effects on air temperature or water vapor on its way toward space, but some portion of that additional long wave radiation will go into space, thus leaving the Arctic system.  That loss will cause energy loss from the system and, to some degree, that loss will function as a negative feedback on system energy level, i.e. warming.  Sorry if I am being pedantic, but your response so completely missed my point that I feel the need to be as explicit as possible.

5
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 09, 2020, 08:37:18 PM »
<snip> Open water during the polar night *is* the positive feedback, the ultimate cause of Arctic amplification.
   But surely increased Long wave radiation outward from the ocean does result in increase of energy exported out of the system into space.  Not all of it is captured in the atmosphere to contribute to Arctic amplification.  Therefore, to some extent open water ---> increased LWR ---> is to some degree a negative feedback that works to stabilize Arctic energy balance.

    Granted all that LWR does not immediately leave the system, and can cause intermediate effects such as warming the overlying blanket of air and water vapor along the way.  Thus, there are feedbacks within the larger open water --- LWR feedback.  But the net effect of greater LWR emission has to result in more energy leaving the system eventually, and thus to some degree serve as a negative feedback.

6
....but, the plot thickens even if the ice won't.

     There is more to the situation than thickness alone.  Structural integrity, decreasing albedo etc. seem very likely to provide reinforcing feedbacks as ASI declines.  Here's a list of potential positive and negative feedbacks not accounted for in a simple regression trend extrapolation.

Acceleration factors NOT accounted for:
     Higher salinity and lower melt resistance of thinner and thus generally younger ice.
     Increased open water leads to longer wind fetch and increased wave height.
     Reduction of mechanical strength and structural integrity of thinner ice leads to fracturing of contiguous ice into smaller pieces.
     Ice fractured into small floes is more vulnerable to wind and current transport into melting zones of the lower latitude CAA and Beaufort Seas following the typical ice movement, and by export via the Fram Strait into Greenland Sea, and also into the lower latitude peripheral ESS, Laptev, Kara and Barents Seas.  As those seas progressively melt out earlier in the summer, that reduces their physical blockage against ice exports out of the CAB.
     Increased proportion of Arctic Ocean as open water results in albedo decrease and increased solar energy absorption during summer, warming surface water.
     Combination of increased wind and open water increases water column turbulence, increases Ekman pumping, weakens halocline thermal isolation, and warms surface water.
     Fractured ice has higher proportional exposure of lateral surface area to ocean water melting energy.
     Greater portion of open water in fall and winter increases atmospheric humidity and cloud cover,  thus increasing reflection of long wave energy emitted from open water back down resulting in (relatively) warmer Arctic night.
     Warmer Arctic Ocean water in summer is likely to generate more cyclone activity leading to more wind damage and Ekman pumping.
     Warmer Arctic air temperatures decrease gradient with lower latitude air, reduces jet stream strength, and thus reduces Arctic isolation from warm southerly air masses.
     Earlier seasonal melt of snow cover on land surfaces surrounding Arctic Ocean increases terrestrial warming that then warms overlying air masses that carry some of that energy into the Arctic Ocean.
     Warmer Arctic air holds more moisture potentially resulting in more rainfall onto sea ice thus increases energy transfer from atmosphere to ice.  The latent energy per gram in liquid rain is large relative to the energy required to melt a gram of ice.
     Progressively stronger Atlantification and Pacification of Arctic Ocean waters are huge influences promoting loss of Arctic seas ice.

Deceleration factors not accounted for:
     The remaining ice more likely to be located in protected bays and other locations less exposed to melting energy.
     With loss of multiyear ice, Volume losses due to Farm export has declined and may continue to decline.
     Rapid freeze and thickening of thin ice allows rate of winter ice formation to quickly recover from summer losses, thus restoring Extent and Area coverage to maintain albedo for following summer.
      Warming surface water and increased melt strengthens the gradient protecting surface fresh water lens from subsurface heat?
     Greater area of open water in fall and winter accelerates greater ocean water energy loss to atmosphere (but rapid thin ice recovery provides insulation to work against this).
     Greater area of open water in summer increases cloudiness to block incoming solar energy.
     Warmer Arctic air holds more moisture potentially resulting more snow deposition to increase albedo on ice and surrounding land masses.

7
Arctic sea ice / Re: Glossary ... for newbies and others
« on: October 03, 2020, 11:35:49 PM »
   I hear you.  I was just responding to gerontocrat's CAS graphs and trying to clarify "CAS" vs CAB.  But apparently there is no such CAS label, just different definitions for CAB.  So I change that suggestion to a new one -- the glossary should note that CAB has different definitions between NSIDC and others.

8
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: October 03, 2020, 11:28:26 PM »
https://www.forbes.com/sites/jeffmcmahon/2018/01/15/carbon-pollution-has-shoved-the-climate-backward-at-least-12-million-years-harvard-scientist-says/#13f60898963e

"The chance that there will be any permanent ice left in the Arctic after 2022 is essentially zero," Anderson said, with 75 to 80 percent of permanent ice having melted already in the last 35 years.

"Can we lose 75-80 percent of permanent ice and recover? The answer is no."
    +1.  Nice catch glennbuck.  Note that the title of the January 2018 article is "We Have Five Years To Save Ourselves From Climate Change, Harvard Scientist Says"  2.75 down, 2.25 to go?

     Not really anything factually new, but a useful article for the collection because:
1)  Authoritative speaker (ozone, Harvard, award etc.)

2)  Impactful message (climate change is serious business, here are some reasons why (Harvard - your new $10 billion campus is in a future flood zone, bye bye south FL, etc.).

3)  Short and to the point.
             
           But what I really like about it (in a blatant case of confirmation bias) is the way that the article succinctly introduces the moral component and complicity of policy makers. 
          "I don't understand how these people sit down to dinner with their kids," Anderson said, "because they're not stupid people."  That's been my zen koan for over a decade.

          Exactly.  The struggle is not about the facts.  The deniers know the facts better than what they let on.  It is precisely because they DO understand the facts that makes them fearful about what those facts require in response.  It is that psychological and moral interface that we need to address to create the unified broad scale effort that is the only way to get through this adolescent transition for human civilization.  Unless we all pull together in the same direction, this boat isn't going to move.

          Those of us fighting for solutions need to focus less on the factual arguments and more on heartfelt listening to folks repeating distortions cynically supplied to them by people who know better but choose to ignore reality for some mistakenly perceived personal gain.  We need to get to both the heart of the issue and its brain (the scientific and technical stuff).

          Our use of fossil fuels has been like a guy in his late teens and early twenties letting it rip, and then realizing one day that his party hearty lifestyle isn't working for the long run, or even in the short run when he confronts his illusions, delusions, and fears and faces the facts.  I'll stop there, because this is the freezing season thread, not the climate change salvation pulpit.  But thanks for reminding me what really matters about watching the Arctic sea ice not so slowly die. 

9
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 02, 2020, 06:58:04 PM »
It makes me think all that ice is going to 'fall off' (break loose from Greenland/CAA/Alaska) and hit me on the head (as an icicle hanging from an eave might [or worse - refrozen half melted snow that partially slipped over the eave's edge before temporarily refreezing in place] ). 

With Greenland (or Canada) at the bottom, all that landmass will hold the ice up forever...
 :)
     To my eye that orientation highlights the fact that much of the remaining ice is at latitude below 80, so presumably more vulnerable to future melt.

10
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: September 29, 2020, 03:07:10 AM »
Ocean Stratification is Not Good News. Very Not Good.
https://climatecrocks.com/2020/09/28/ocean-stratification-is-not-good-news-very-not-good/

"This seemingly technical finding has profound and troubling implications. The more stable the upper ocean, the less vertical mixing that takes place. This mixing is a primary means by which the ocean buries warming surface waters. So the surface warms up even faster. It’s what we call a “positive feedback”—a vicious cycle."

"Our study suggests that key positive feedbacks (amplifying factors) related to reduced ocean heat might lead to more rapid surface warming in the decades ahead than many of the models predict."

11
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 25, 2020, 09:58:54 PM »
Journal article - The hysteresis of the Antarctic Ice Sheet
Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann
Nature volume 585, pages538–544(2020)
https://www.nature.com/articles/s41586-020-2727-5
    New (to me) term - "Creep instability"   Good fit for the times.

"The Graduate" updated for 2020:
Mr. McGuire:  I want to say one two words to you. Just one two words.

Benjamin:  Yes, sir.

Mr. McGuire:  Are you listening?

Benjamin:  Yes, I am.

Mr. McGuire: Plastics.  Creep Instability.

12
Arctic sea ice / Re: The 2020 melting season
« on: September 24, 2020, 10:07:35 PM »
<snippage>
But we must not forget the third vector of energy infusion - ocean heat. And I would suggest that it is dwarves the others - but is at the same time inefficient in a melting contexts, since most of the heat does not reach the ice.

So can we rank these vectors and their interplay when it comes to melting ice? Even if Insolation would seem to be the favorite, we must remember that it still accounts for only around half the melt (simply because so much of a melting season happens outside of peak insolation).

Most of the rest I suppose is caused by ocean heat. And this is where storms kick in - they act both to give mechanical force to the system, mixing waters and moving the ice, and thus enabling the ocean heat to interact more efficiently with the ice. And secondly, the increased air temperatures and moisture that a storm carries in over the ice has it's origins in that same ocean heat.

So I'd suggest that insolation and ocean heat are the two main drivers of melt each year, with storms playing an important part in bringing the latter to bear on the ice, thus increasing melt at all times other than the during peak insolation.
   The Atlantification paper posted about a week ago stated that in the Laptev Sea study area ocean heat diffusion from incoming warm Atlantic water (now exacerbated by thinning of the cold halocline and increased turbulence), was equal to atmospheric warming as a cause for ice melt.  The ASI is getting hit from all sides.

   Edit -- Found the article:  https://journals.ametsoc.org/jcli/article/33/18/8107/353233/Weakening-of-Cold-Halocline-Layer-Exposes-Sea-Ice

13
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 24, 2020, 09:35:59 PM »
So if we manage to get CO2e past 750 ppm Antarctica melts to the bedrock and the seas rise 70 meters or more?
     70 meters will take a long while, but if 3.3 meters floats your boat that can happen at just  650ppm held steady long enough according to a study published yesterday.
 
      Study out yesterday found that eventually West Antarctic Ice Sheet is drinkable at 2.36C above preindustrial.  IPPC 2014 CO2 and Temp tables for RCP8.5 (closest analog to path we are currently on) put 2.36C at about 650 ppm CO2.  Quick skim of article did not find any timeline should that occur, and they take pain to say their report is NOT a projection or forecast.  Based on Deconto and Pollard 2016 simulation, my guess is that to reach that new equilibrium would take 100 years or more.  Then again, who's to say we would stop at 650ppm CO2 (even less likely for 650 ppm CO2e)?
   
     (Speaking of Dec and Poll 2016, the new paper does NOT account for their proposed ice cliff instability, which apparently is still being debated for validity.  If it does apply, then it seems the new study's melt rates would be underestimates by leaving it out.  On the other hand, the new paper mentions both negative and postive feedbacks that could affect this new disaster scenario.) 

     See animated simulation posted yesterday by Potsdam Institute: 
The Hysteresis of the Antarctic Ice Sheet
Sep 23, 2020


Journal article - The hysteresis of the Antarctic Ice Sheet
Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann
Nature volume 585, pages538–544(2020)
https://www.nature.com/articles/s41586-020-2727-5
    New (to me) term - "Creep instability"   Good fit for the times.

14
Arctic sea ice / Re: The 2020 melting season
« on: September 19, 2020, 11:57:21 PM »
The reference was clear, 2012 vs. 2020 per the attached Hycom images.
   I agree that is what he said.  I was just trying to point out that he was applying the wrong starting year to the often-cited 75% decline in ASI Volume.

15
Arctic sea ice / Re: The 2020 melting season
« on: September 19, 2020, 08:02:18 PM »
     I think OTG reference to 25% of Volume refers to 2020 (or 2012) in comparison to 1978.

16
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 18, 2020, 07:32:10 AM »
Wildfires in Arctic Circle release record amounts of greenhouse gases - BBC News

5 minute video, gives a ground level view of Siberia and some of the folks who live there.

17
Arctic sea ice / Re: The 2020 melting season
« on: September 18, 2020, 06:04:09 AM »
 
Here is a chart and table I prepared earlier this year based on PIOMAS volume data... <snip>
   
     Wow, Oren.  2007 is jaw dropping.  I mean, really.  If any of the experts are lurking around the ASIF this is the time to show your cards.  Calling Drs. Alley, Birkel, Box, Dethloff, Goose, Meier, Notz, Mayewski, Overland, Polyak, Scambos, Serreze, Shuppe, Stroeve, Wadhams, Zhang, and all the rest.  WTF, call Dr. Ruth too.  Sadly, Dr. Konrad Steffen is off-duty. 

      You can weigh in under a pseudonym if association with this scruffy lot is hazardous to your professional reputation.  Dr. A-Team, please report to the operating room!  Patient #2007 lost weight all winter and suffered heavy bleeding all summer!  We need a diagnosis.
     
     Assuming minimum Volume in 2020 will be no higher than 2019, a quick trip to Excel suggests that the Late Summer 2020 melt was ca. 9.02 M km3 which would be a new record, leaving 2012 in the dust (for that period). 

     ...and that the 2020 Summer Total melt would be ca. 19.01 Mkm3, just 0.26M short of 2012.  All that from an impressive GAAC and a short-lived semi-GAC in 2020, but without any lightening strikes like the GAC 2012.

     With the day 266 to 266 framing, 2012 takes a step back, and 2016 a step forward.  But 2007 is revealed to be a Monster Performance.  It was like Tiger Woods at the 1997 Masters Tournament just crushing the competition.  (That was more than golf, it was a great day for humankind at a private club that barred black golfers until 1975, but I digress...)

     I'm going to have to go back and re-read those Friv dipole posts from this summer.  Now I know why Neven, Friv and others get so itchy when it looks like a dipole might set up. 
Maybe we need a new Glossary entry:  Dipole = Atmospheric Ice Eating Monster. 

18
Arctic sea ice / Re: The 2020 melting season
« on: September 17, 2020, 10:31:56 PM »
Actually, I'd say the "flip" happened between 2007 & 2012.  Since then, I think we've just been working through latency in the system.
      The 2012 GAC gets lots of attention, which is justified for a freak event with high (though much of it shortlived) impact.  But I haven't seen as much discussion about the weather patterns that had already defined 2012 as a big melt year well before the GAC 2012. 

      Agreed, 2007 really was the starting gun. The more I've learned the more I've wondered "What the heck happened in 2007?"  ASI watchers must have been freaking out at the time because there were no precedents or early warning as far as I can tell.  It was a killer melt year from which the Arctic has never really recovered.  Discussion of the weather patterns or other factors that made 2007 such a drastic melt year would be appreciated by this reader, and I suspect many other ASIF denizens.
     

19
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 17, 2020, 07:55:37 PM »
     Which led to this:  J.R. Mioduszewski, S. Vavrus, M. Wang, M. Holland, L. Landrum, Past and future interannual variability in Arctic sea ice in coupled climate models, Cryosphere 13 (2019) 113–124, https://doi.org/10.5194/tc-13-113-2019

     Abstract (bolding added and format edited slightly for clarity)

    "The diminishing Arctic sea ice pack has been widely studied, but previous research has mostly focused on time-mean changes in sea ice rather than on short-term variations that also have important physical and societal consequences. In this study we test the hypothesis that future interannual Arctic sea ice area variability will increase by utilizing 40 independent simulations from the Community Earth System Model's Large Ensemble (CESM-LE) for the 1920–2100 period and augment this with simulations from 12 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5).

     Both CESM-LE and CMIP5 models project that ice area variability will indeed grow substantially but not monotonically in every month. There is also a strong seasonal dependence in the magnitude and timing of future variability increases that is robust among CESM ensemble members.

     The variability generally correlates with the average ice retreat rate, before there is an eventual disappearance in both terms as the ice pack becomes seasonal in summer and autumn by late century. The peak in variability correlates best with the total area of ice between 0.2 and 0.6 m monthly thickness, indicating that substantial future thinning of the ice pack is required before variability maximizes. Within this range, the most favorable thickness for high areal variability depends on the season, especially whether ice growth or ice retreat processes dominate.

     Our findings suggest that thermodynamic melting (top, bottom, lateral) and growth (frazil, congelation) processes are more important than dynamical mechanisms, namely ice export and ridging, in controlling ice area variability."

     Graphic below is mean ice area from CESM model ensemble.  Of course this paper was written way back in 2018  8).  I think the Wipneus linear Volume trend projection for zero September minimum ASI by 2032 is a better predictor than the climate models which have been routinely late in their Arctic sea ice decline estimates.  No volume = no area.  But that's for another thread!

20
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 17, 2020, 07:53:33 PM »
    Nice catch Juan.
    Some pithy quotes of particular interest to ASIF. 
     
     SIT = Sea Ice Thickness
    "Declines in SIT are particularly relevant for transpolar shipping, as the measure is a chief determinant of the type of polar class (PC) vessel required in ice-covered waters.  Like sea ice  extent, SIT has been declining: at the North Pole, while average SIT was ~4 m between 1958–1976, by 2011–2017, it dropped to <1 m. "

        CAO = Central Arctic Ocean
       "Commercial shipping will  require robust forecasts meeting more stringent criteria, such  as  the IPCC’s definition of “nearly ice-free conditions” when sea ice extent dips below 1 million km2 for at least five consecutive years, or seasonal benchmarks of 90 days or more of operational accessibility in the CAO.  In the near term, making such forecasts may prove challenging since sea ice variability is projected to grow substantially even as its total amount declines.  Nevertheless, in the  long term – i.e. by mid-century and more certainly by 2100 – ice-free summers are ex-pected to occur regularly, promising greater predictability for shipping lines."

      "The CAO may be ice-free in summer as soon as the 2040s, setting in motion the seasonal opening of the TSR.  Even if this sea change does not immediately reconfigure global shipping networks, already perceptible increases in the region’s economic activity suggest that preparations are in order."

     "...[T]he environmental and socioeconomic impacts of the TSR will be more acute at local rather than regional or global scales. While the shipping route promises new avenues for economic development, it may jeopardize the health of coastal ecosystems and vitality of subsistence activities.  Although the CAO is uninhabited, thousands of people live in communities along the Bering Strait, in Svalbard, and in northeast Ice-land where transshipment ports may be constructed and where large vessels could one day dock.  Particularly along the Bering Strait, com-mercial shipping threatens subsistence whaling, sealing, and fishing.  Empowering Indigenous and local communities to exercise stakeholder rights and participate in maritime policy forums for Arctic shipping while minimizing the industry’s negative impacts – and, if possible, finding a  way  that  development of the TSR could provide tangible benefits – is crucial."

     "Yet regardless of the ultimate extent of the TSR’s commercialization, the moment at which the Arctic becomes ice-free will mark a profound turning point in human and environmental history.  As warming and melting accelerate, regions like the Arctic that “had for centuries dramatized the fragility of human life have, in a few short decades, been refigured as representing the earth’s profound vulnerability to collective human agency”.  The increasing accessibility of the TSR epitomizes the  ambivalence of changes to the Arctic in the Anthropocene.  While the opening of a truly trans-Arctic shipping route is a symbol of mankind’s greater freedom of navigation, it also presents a stark reminder of the social and environ-mental costs of this freedom, the conditions that have given rise to it, and the sudden transience of a long-frozen region."

21
Arctic sea ice / Re: The 2020 melting season
« on: September 17, 2020, 07:07:48 PM »
AMSR2: Some recent days of 2020 compared to 2012
Rough overlay of 2012 vs 2020 using awi amsr2 v103, aug20-sep15 (am/pm)

gimp grain extract, the years were slightly different sizes so there is a small scaling error
     Nice graphic uniquorn.
     FWIW - Perhaps the difference between 2020 and 2012 can be summarized as:
                 
      Where 2020 had ice at minimum beyond the 2012 extent, that 2020 ice was thin, fractured, "low quality" (in terms of melt resistance).  Though I suppose the same could be said about the reverse, i.e. where 2012 had ice but 2020 didn't, that peripheral ice in 2012 was hardly pristine.
               
      And where both years had ice in the CAB, a good chunk of the 2020 CAB ice is in a weakened state, whereas in 2012 the central CAB was still pretty much the continuous, thicker (than 2020) ice pack of the pre-21st century Arctic which is no more.
               

22
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: September 17, 2020, 06:56:02 PM »
Whoops - corrected.
       Huh?  I'm still confused (not unusual in my case. Try it, you get used to it after a while).
     
       Here is the supposedly corrected statement at
https://forum.arctic-sea-ice.net/index.php/topic,2975.msg286733.html#msg286733
 
"Average remaining melt (of the last 10 years) would produce a maximum in Sept 2020 of 13.48 million km2, 0.40 million km2 below the March 2017 minimum maximum of 13.88 million km2."

       I think the correct correction would be:
      "Average remaining melt freeze (of the last 10 years) would produce a maximum in Sept 2020 March 2021 of 13.48 million km2, 0.40 million km2 below the March 2017 minimum maximum of 13.88 million km2."

      Is this right, or is there need to correct my correction of the correction?

      We nitpick because we care.  You only hurt the ones you love.  Ditto thanks to all the data providers for what has been a wild ride of a melting season.  I don't think Friv has even been so thrilled as he was this July.  At least somebody's happy!  And thanks to Oren we got through it with minimal umbrage and personal insults about our pet theories!

      I think there is truth in be cause's tag line:
"2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021"

      And I would add "+ 1 = 2022".  Seriously, the bus could be leaving the station.  The trend has been for changes to occur sooner not later than expected.  When's the last time you saw a climate change story about how things are evolving slower or less drastically than anticipated?   For those of you in the U.S., and everybody everywhere for your own elections, please vote and tell everybody you know to vote for climate rationality.  This infection has to be healed or it will kill us. (Sorry, I couldn't resist... I haven't had a good climate scream for awhile.) 

      Getting back to ASIF business, the path ahead for the coming freeze season, and especially the 2021 melt season, look to be "interesting" (in the Chinese curse sense of "May you live in interesting times", which we certainly are).   

23
Arctic sea ice / Re: The 2020 melting season
« on: September 08, 2020, 07:46:29 AM »
September 2-6.

2019.
     1. The Severnaya Zemlya ice pack lives!   :P   

     2. We all assume that there must be extra heat in the Arctic Ocean water due to high pressure -> clear skyies -> high insolation that dominated this summer.  But do we have any metric that tracks the amount of energy in the Arctic Ocean water?  GFS and DMI show 2M air temperature but that is not reflecting supposed extra heat in the water remaining from this summer.

24
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 08, 2020, 07:03:23 AM »
https://forum.arctic-sea-ice.net/index.php/topic,119.msg285372.html#msg285372
Monthly update from the Polar Science Center:
Quote
August 2020 Monthly Update
<snip>
 Ice thickness anomalies for August 2020 relative to 2011-2018 (Fig 6) continue the pattern that has emerged over the winter, spring and shows relatively thin ice along the Russian Coast and thicker than normal in the Eastern Beaufort and the along the Canadian Archipelago.
    How does PIOMAS see thicker than normal ice on the north coast of Ellesmere when the AMSR2 shows a lack of land fast ice at same location for August 2020?  One of them has to be wrong.

https://forum.arctic-sea-ice.net/index.php/topic,2839.msg285417.html#msg285417
amsr2-uhh, jul21-sep6

25
Arctic sea ice / Re: MOSAiC news
« on: September 08, 2020, 06:47:21 AM »
     The year dates on the salinity graphic seem to be reversed.  It looks like reverse Atlantification from the first image (2019) to the second (2020).  For example, north of FJF goes from mostly red in 2019 to mostly yellow in 2020.

26
Arctic sea ice / Re: The 2020 melting season
« on: September 06, 2020, 02:22:00 AM »
In my curiosity of when the minimum might be, and if it might be later, I did a simple linear regression of the NSIDC 5 Day Extent numbers.

It showed a trend towards the minimum occurring later in the year BUT it appears to be mostly driven by there being less early minimums than there being any later minimums.  The lack of insolation seems to put a pretty firm cap on how late the minimum can be.

I would hazard to guess this will remain true until a BOE occurs.  Also, given a standard deviation of almost 5 days this doesn't help much at all (ugh, weather :P).
    Thanks for doing that Burnrate.  While the variability in the minimum date trend does not allow a precise prediction, it does  suggest that with high solar insolation this summer and thus melt momentum, the presumed date for minimum of September 16 (Julian day 259) has a good chance of being delayed by 1-6 days to Julian day 260-264 (Sept. 16-20).  If so that would might narrow the shortfall from the 2012 minimum records, though those extra days would be in the flattening part of the curve(s) for each metric and the gaps to 2012 appear to be too large for any of the 2020 values to go below 2012. 

    Even without new record(s), it is remarkable enough that 2020 is close to matching 2012 given the lack of a once-in-century intensity August storm like 2012 had.  Granted, 2020 had it's own unusally strong melt conditions.  The trend seems to be that about 10 years of global warming progression will be enough to make what were freakishly low minima in 2012 the annual norm (and continuing to head downward) by 2020-2022.

    And while 2020 probably won't go below 2012 for any of the standard metrics (Volume, Area, Thickness, Extent), a less quantitative assessment indicates that the Arctic sea ice has never been in a more vulnerable state.  The shift of the center of mass of the pack to the south and west from the CAA-Greenland-North Pole triangle towards the CAA is not an encouraging sign for longevity.  Then again, that shift may be "corrected" over the winter freeze season.     

27
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 07:23:54 PM »
    Thanks Oren, your explanatoin makes sense to me, and restores peaceful harmony to my cognitive dissonance, at least the part of it due to Arctic sea ice Area stats.

28
Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 04:45:48 PM »
     I had the same question about CAB area increasing.  Understandable that concentration ratio increases as Extent declines and Area remains the same.  But sea surface temperature in the CAB does not look low enough to begin refreezing, so why would Area be increasing?  Given the difficulty in consistently estimating Area (which is why NSIDC, JAXA, and others use the less precise Extent, because while less informative than Area, the daily change in estimating Extent is less and thus gives more consistent values to compare across time periods), I wonder if the recent increase in Area is a measurement anomaly not a real increase.

29
Arctic sea ice / Re: The 2020 melting season
« on: August 30, 2020, 03:34:51 PM »
<snip>
That retreat north of Severnaya Zemlya is really spectacular, wow. And it's not over yet. Today and tomorrow there's a peak pressure gradient of 42 hPa, but according to ECMWF it will be 44 hPa at 120 hrs. The direction of the winds will shift a bit, but overall the ice pack should continue to get pushed towards the Pole.

This could easily become the highlight of this melting season! In many ways it's worse than 2012. And no GAC.
      My vote for MVP of the 2020 melt season is the degradation of the CAA-Greenland-NP triangle.  What used to be the stronghold of MYI has been (almost) reduced to a rubble field.  Capped off by the Polarstern photos at the North Pole.  They went to see Santa Claus and (almost) nobody was home.  This has consequences.
      Another sentimental vote for that plucky ice hugging Severnaya Zemlya that refuses to die despite being bathed in warm water for weeks on end.  Will it survive the rest of melt season?

30
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: August 30, 2020, 03:12:28 PM »
   Thanks Gerontocrat not only for the data but for the concise narrative summaries that provide context and meaning to the numbers.  But I have a question.  In previous message (https://forum.arctic-sea-ice.net/index.php/topic,2975.msg283986.html#msg283986 with remaining melt at the 10 year average, the 2020 minimum JAXA Extent table value is 3.70.  The chart in message above shows that by following the 10 year average melt, the 2020 minimum JAXA Extent bottoms out at about 3.775.  Such a small difference does not change the future of human civilization on the planet, but it just makes me wonder why the chart value does not match the table value.

31
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: August 26, 2020, 04:42:04 PM »
<snip>I've taken the monthly JAXA extent averages for September and the following March, detrended them and plotted against each other, with Sept values on the x axis and March on y.

Below are two very ugly graphs, there seems to be a correlation and it is stronger since the turn of the century. So does this mean that there is a slightly bigger change of a larger maximum following a low minimum?
     Walrus was correct that I addressed the wrong issue in my previous post.  Perhaps a saving grace in my misdirected response is that regardless of the Sept. minimum's influence on the following March maximum, it really does not matter in the big picture because that March max has essentially no correlation with the NEXT Sept minimum.  But whether Sept affects the following March is of interest for understanding ice dynamics even if there is no long term effect, so pointing out the lack of long-term effect is really just to make me feel a bit less useless.

     Face-saving aside, I feel compelled to point out that with an R2 of 7% from a small number of data points the conclusion that there is a trend to discuss is a Hail Mary pass (if binntho can use an obscure scientific term, I can use one from American football) based on statistical noise.  In other words, that slope is almost certainly very far short of statistical signficance.  (binntho your graphing software probably either gave you a direct measure of significance or the variance needed to calculate it.  Sharing it would be informative.)
   
     Moreover, the visually imagined "trend" is highly leveraged by two data points on the extreme ends of the X axis.  Take either one of those points out and there is almost nothing trendy left (not that there is much in the complete set of data points anyway).  Take both out and what's left is the a classic example of random distribution.  There are procedures to identify and justify removal of overly leveraged data points.  I doubt either of those two points is egregious enough to meet those criteria, so this comment is reverse cherry picking.  But it's not nit picking.  Just because a trend line from a small set of data points has a slope does not mean that it indicates anything real.  Noise is more real than signal in such cases.  At least until one shows a numerical test of significance.  The human eye is really great at seeing things that are not there (e.g. the face on Mars etc.) 

      As for the orginal question, I think that for now we can conclude that we don't know, and won't know until we have 20 mores year of data.  At which point the Arctic will be so different that we will have to throw out the first 20 years of data and start over.

32
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: August 25, 2020, 12:32:38 AM »
<snip> This has been discussed before, and I did some work on JAXA extent data looking at deviations from the linear trend of each years maxima and minima.

My conclusion was that there was no discernible link beyween the two.
    Walt Meier, NSIDC/NASA found the same thing.  March had no predictive power for September when you remove long-term trend.  You'd think there would some relation from an unusually high or low March starting point with subsequent September minimum, but his chart (posted months ago in the "When Will the Arctic Go Ice Free" thread) showed virtually zero correlation.  Just goes to show you how strong an influence the single-season melt weather is.  That said, this does not obviate the importance of the long term trend.  As each year carries us farther into the Alice in Wonderland rabbit hole of the new Arctic, the amount of ice will on average become less and less (as if anybody on ASIF didn't know that already, duh).

33
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 12:32:47 AM »
<snip>
Wow what a pic from Polarstern. Makes me think, who knows, a worse year things align it could lead to an ice-free CAB much sooner than 2030.
What would have happened with a central GAC about now...
    A strong storm at 90N would have created a whole new meaning for "pole hole".  The more I think about that Polarstern image, the more shocking it is.  There have been open water reports at 90N in previous years, but the Polarstern reports about weak ice and open water views on their trip to the North Pole indicates damage to the ice pack over a large area, not just a localized weak spot. 
 
    The Polarstern at North Pole image suggests that 2020 seems to have taken another big step towards ASI destruction.  It should be on the cover of the next IPPC report.  I understand it must be fun to reach that iconic spot on the globe, but given the destruction in the photo background which those folks understand more than anybody else, I wish they had taken a second photo of them all looking at the ice in horror. 

34
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 12:25:44 AM »
Rod - thank you for posting that very disturbing image from the North Pile. Simply amazing. This is not your grandfather's Arctic anymore.
UCMiami - maybe not a scientist but excellent post.
Marcel g I agree, if this rotten ice survives it will be by the skin of its teeth. And it still needs to hold on for several tough weeks.
Glen K thanks for the data, I am betting melt ends later now than it used to, especially bottom melt. Surely also starts sooner, for the same latitude. This is not your grandfather's Arctic anymore.
     I can see why you would think that top and/or bottom melt would end later now given the continuing trend of global (and doubly so) Arctic warming.  But that raises a question:  If that's true, why don't we see later dates for September minimum?

35
Arctic sea ice / Re: MOSAiC news
« on: August 20, 2020, 12:15:41 AM »
    +1 Ditto, thanks for addressing the thickness question A-Team.

     I just looked at a bunch of August 18-19 images for thickness and concentration (HYCOMM, Bremen, Hamburg, NSIDC etc.).  Many of the images have a pole hole so not exact value for 90N, but the collection overall shows rather striking difference between what is suggested by the various concentration and thickness images and what is shown in the North Pole photo by MOSAIC and their description of ice conditions during the trip to 90N.  The NSIDC sea ice concentration map appears to most closely match the MOSAIC ground truthing observations.

     UCMiami's comments about new ASI conditions creating a need to recalibrate or reinterpret established ASI observation methods seems spot on.
  <snip>   I feel that the last fifteen years have truly changed the nature of arctic sea ice, but a lot of the systems and analysis was established as 'fact' before that change really manifested and to some degree it has yet to adjust.

<snip> "...measures (Piomas and others) are grounded in a 'solid pack' view of arctic ice and I believe struggle to deal with the 'real world' condition of the pack where 'thick ice' is actually a patchwork of loose flows held together by new and thin ice. Images from Polarstern seem to make this abundantly clear."

36
Arctic sea ice / Re: The 2020 melting season
« on: August 19, 2020, 10:47:02 PM »
      The chart gave me info I did not know about those relationships and timings.  Yes every year is different and trend means that 2020 is different from 2005, but my guess is that the information about seasonal offset between top and bottom melt, and even the approximate dates for start, peak, and end dates for top and bottom melt is probably still reasonably accurate for 2020. 

37
Arctic sea ice / Re: The 2020 melting season
« on: August 19, 2020, 08:28:18 PM »
Surface melting peaks in July and usually ends in mid-August. By contrast, bottom melting peaks in August and often continues into September or October (Figure 4a).
https://nsidc.org/arcticseaicenews/2019/09/summers-not-over-until-bottom-melt-ends/

       Chart from link posted above is useful for assessing remaining melt season prospects.
Light blue bars are bottom melt.  Dark blue line is top melt.

      "Surface melting peaks in July and usually ends in mid-August. By contrast, bottom melting peaks in August and often continues into September or October (Figure 4a)."

     "Figure 4a. This 2005 to 2006 time series from the Beaufort Sea shows ice thickness (red line), growth rate (blue bars with negative values), bottom melt (blue bars with positive values), and surface melt (dark blue line with points). Both surface and bottom melt started on June 10. Surface melt peaked on August 1, and peak bottom melt was two weeks later on August 15. Surface melting ended on August 24, while bottom melting continued until October 24.
Credit: Don Perovich"

38
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: August 12, 2020, 09:00:48 PM »
Wdmn, the phase change itself needs energy.
Link >> http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/thermo/phase.html

     Sorry, no facts to add to the question, but here some perspectives for those of us who don't work with ice physics every day. 

      It always shocks me when reminded that the heat exchange between frozen vs. melted ice is 80% of the heat energy change required to change water temperature from 0C to 100C.

      That huge energy budget to melt ice has been a defense mechanism for preserving the Arctic sea ice.  Consider the 75+% ice volume losses since 1979, the amount of heat input that required is huge.  As the Arctic loses that defensive wall (the ice phase transition energy requirement), the continued energy input into a decreasing portion of ice and an increasing portion of open water means that things will soon be getting even stranger even faster.

      All of us on ASIF are interested in seeing the volume minimum this year.  We don't get daily updates and images for volume like we do for extent and area, so volume gets a lot less discussion.  But it really is the key number (with a respectful nod to Area as the factor that directly affects albedo).   The 2020 minimum volume will almost certainly be closer to the 2012 record low than either extent or area.

       Thickness is also difficult to measure and visualize.  But it also deserves more respect.  Lots of discussion recently about slow down in extent and area trends, with simultaneous comments about how terrible the ice looks.  It is too bad we don't have regular reports and images about qualitative measures of ice condition like thickness, mechanical strength, continuity etc. Concentration is a qualitative measure of ice pack condition, but it is highly variable and apparently is difficult to accurately measure because of sensor errors caused by water on the ice surface and water vapor in the air.

       One of the key things I've learned this year is to mentally blur the dark areas on the much appreciated and repeatedly viewed AMSR2, U. Bremen, U. Hamburg, and Hycom animations posted by ArticMelt, Blumenkraft, Born from the Void, and others.  I think it was a great idea somebody had on the 2020 Melt Season thread to create  5-day average values for such images as a way to smudge some of the spurious readings and highlight what are the more likely true indications of low-concentration and softening ice

       The 2020 story seems to continue the narrative from 2019  -- continued decline but no replacement of the 2012 record-low quantitative measurements, with progressive rot in the qualitative impressions of ice condition.  Continuation of that trend leads to a point where ice thickness and qualitative melt resistance, exacerbated by increased forces of albedo, ice mobility, fracturing (and thus surface area and lateral melt by contact with ocean water as noted by JD Allen) reach a tipping point at which the right conditions create a major "Poof Event" where huge number of extent and area km2 disappear in a short time period. 

       The math backs up this theoretical scenario.  At some point the flatter Extent decline curve has to catchup to the steeper Volume decline curve.  The closer to the end point at which that occurs, the more radically steep the change in Extnet curve has to be.  I thought that Exent would begin that catch up process by now, but I've been wrong about that so far.  Thickness going below 1 meter could be a key tipping point for that Extent decline acceleration to occur.  We are very close to reaching that tipping point. 
       
       Of course, it isn't a smooth incremental process.  What happens in the real world depends on the chaotic vagaries of the weather.  And the early 2020 melt season seems to have been a doozy among those vagaries.  The rot evident in the former MYI bastion of the Ellesmere - Greenland - North Pole triangle is notable as both a qualitative and quantitative highlight of 2020 so far.   

       In earlier years, for a total melt season to reach "Poof Event" intensity would have required prolonged, extreme and unusual conditions.  But with each year of progressive qualitative decline (i.e. ice pack rot), the conditions required for a severe melting event to occur become less extreme and less far beyond the normal range, and thus more likely to occur.  That is exacerbated by the fact that as the Arctic continues to warm, the "normal range" for the amount of energy in melting events increases, thus making the required intensity for a catastrophic "Poof Event" even more likely to occur.

      As for 2020, it ain't over til the fat lady sings.  The amount of low-resistance ice hovering just over the 15% concentration threshold to be counted as a 100% extent pixel could still result in some dramatic drop days.  IMHO, those values, while interesting to watch, are the daily news that is more noise than signal.  The signal is the qualitative decline in ASI overall and the increasingly dire setup for a knockout punch. 

      I didn't mean for this reply to get so long.  Oren, if this is the wrong thread for a sermon, please relocate as needed.  Here is some more positive news - Tesla Inc.'s Battery Day, scheduled for Sept. 22, could bring big news to help us dig out of this mess.  Getting back to doom and gloom, it will be interesting to see what adjectives Friv has saved up for the first big Poof Event.

39
Arctic sea ice / Re: What's new in the Arctic ?
« on: August 01, 2020, 09:45:05 PM »
    Interesting graphic from article posted above showing which sampling locations provided best reduction in variability for predicting Arctic sea ice volume.  They conclude that predictive skill increases with number of sample locations up to six, but predictive skill improvement by adding locations 7-10 was minimal.

Figure 8.  Optimal observing framework, as suggested by the ensemble of model outputs, for sampling predictor variables in order to statistically reconstruct and/or predict the pan-Arctic SIV anomaly. The numbers indicate the first up to the 10th best observing locations in respective order. The hatched area around each location (same colour code) represents their respective region of influence. The selection of points respects the hierarchy of the regions of influence in a way that the second point can not be placed within the region of influence no. 1 (shades of red), the third point can not be placed within the regions of influence nos. 1 and 2 (shades of red and purple), and so on.

40
Arctic sea ice / Re: The 2020 melting season
« on: July 27, 2020, 10:14:11 PM »
    It would be interesting if an ASIF consenus for <3.5M km2 (with not a small chance of <3) (if there is any such consenus) is more accurate than almost all these offical expert estimates which cluster near or above 4M km2.  At this point I'd put my money on ASIF.
There are different metrics. September mean extent above 4M is quite possible. At least more likely than below 3M. This year has great potential to surprise but also some obstacles.
    Guilty as charged for conflating Sept avg with Sept min.  Still, those SIPN estimates look high.  but the truth will soon be known!

41
Arctic sea ice / Re: The 2020 melting season
« on: July 27, 2020, 09:05:17 PM »
Sea Ice Prediction Network for September outlook.
https://www.arcus.org/sipn/sea-ice-outlook/2020/july
    It would be interesting if an ASIF consenus for <3.5M km2 (with not a small chance of <3) (if there is any such consenus) is more accurate than almost all these offical expert estimates which cluster near or above 4M km2.  At this point I'd put my money on ASIF.

42
Arctic sea ice / Re: The 2020 melting season
« on: July 27, 2020, 05:54:35 PM »
Side by side of July 26th in 2012 and 2020.
It's really interesting how you can see the outlines of 2012's end result in the concentration map already at this point in time. I wonder if we're already starting to see the outline for 2020? I could imagine most of the ice in the Beaufort, Chukchi and ESS disappearing and the year ending with a similar outline to 2012.
    That is an interesting way to reduce all the complexity for a look at what might be ahead.  If that is what happens, and 2020 has similar Extent outline as 2012, then I think a key difference would be that the 2020 remnants would have much weaker ice in the core CAA-Greenland-North Pole triangle that used to be the ice fortress.  That area used to be MYI, but that is gone and the ice in the triangle continues to be assaulted by the inexorable advance of melting forces.  If the 2020 minimum follows its current pattern, then 2020 Volume will be lower compared to 2012 even if their respective Extent values are similar. 

    FWIW - in Gow and Tucker 1991 review of polar ice dynamics they report that Arctic melt pond prevalence peaks at ~60% in early summer and declines to 30% and below as summer progresses.  I suspect that has an impact on accuracy and intrepretation of the Bremen/AMSR2/HYCOM/NSIDC ASI concentration charts, i.e. late-July and August concentration readings should be more accurate than those in June.  If the low concentration areas in the CAA-GL-NP triangle in the July 26 images posted above by JCG and glennbuck are reliable, then we are already seeing one of the major outcomes of 2020 -  a reduction of ice concentration/thickness/volume/quality in the CAA-GL-NP triangle.  In addtion, that is almost exactly the area getting exposed to clear sky and warm temperatures right now, so more damage is likely to occur in that area before the end of the 2020 melt season.





43
     Where are the instructions on how to post images to forum server?

44
Arctic sea ice / Re: The 2020 melting season
« on: July 26, 2020, 03:23:45 AM »
      After looking at the GFS July 25 18Z forecast, two things jump out that no one has commented on that may be significant. 
 
1.  It looks like the low pressure on the Pacific side and the moderate but not trivial high pressure on the Atlantic side is creating a sustained reversed-Arctic transport wind field moving already fractured ice toward the Laptev Sea where the high surface temperature is an ice killing zone.  The wind speeds are not that high, mostly below 15 knots, but they are persistent.  I don't know how much ice and how far the ice will actually move, but it could be one more negative influence to bleed out CAB ice.   If signficant, the Laptev bite may not have to reach the North Pole ice, that ice may come out to meet the Laptev bite halfway.




2.  Some of the surface heat in the CAA - Greenland - North Pole triangle is from a 2.5 day period of clear sky extending right up to the pole.  Looking at the surface insolation chart, even late July is still close enough to solstice for that to be another significant dagger into the heart of the CAB.  Thus, energy that does not even show up as changing the temperature will be going into melting ice. The triangle used to be home to some of the thickest toughest multiyear ice.  The ice that remains there this September could be a remnant Extent with none of those other qualitative characteristics.   


Pale, light blue = clear sky over ice.  Dark blue = clear sky over water. 
Green - rain, "Aqua-blue" = snow.

    With only 6 years as an Arctic voyeur, I don't know enough to be apocalyptic, but FWIW in addition to what we are hearing from the old hands on deck, add one more "Holy Cow, I've never seen anything like 2020".  After all the melt season conditioning this year, if these forecasts verify the cumulative effect of the different Arctic regional weather events looks to be in the same league as the GAC2012. 

    No, the low pressure system is not as intense or as long lasting as GAC2012, but this Arctic-wide scenario has someting going on just about everywhere: cyclone in the already fractured Beaufort, unprecedented subsurface heat in the Beaufort, roasting top down heat in the CAA, clear sky and heat in the heart of the CAB triangle, extensive and intensive heat across the entire Atlantic front.  All this happening to ice that has been softened up by May melt pond set up, and extended periods of heat and clear sky in June and July.  So the widespread melt pressure is going onto ice with far below normal resistance.

     Thus the cumulative effect looks equally as significant as the GAC2012.  If I'm wrong, let me know.  That's how I learn.   

45
Arctic sea ice / Re: The 2020 melting season
« on: July 24, 2020, 01:56:47 AM »
     The GFS pressure and surface temp forecast for July 26 18Z to July 29 18Z looks like three days of heavy damage to the Beaufort.  Nothing like GAC2012 but pressure consistently in 980s for most of those three days with relatvely warm temps.  I don't have the actual wind speeds but the tightness of the pressure isoclines suggest it will be a-blowin'.
https://climatereanalyzer.org/wx/fcst/?mdl_id=gfs&dm_id=arc-lea&wm_id=t2anom#gfs.arc-lea.t2anom

   At the same time the temperature forecast for the CAA - northern Greenland - North Pole triangle also looks bad, and also along the entire Atlantic front.

    If this forecast verifies I don't see that slow down that's been talked about actually showing up.
I don't have the meteorological expertise to be too declarative about any of this, but the sheer persistence and scale of melt pressure, on top of what must be residual heat in the water from the abnormally clear sky in July, suggests that 2020 is not slowing down and that the ice is taking a beating that will push it well below 2012.






46
Welcome back binntho. Excellent post.
+1 :)

47
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 07:00:41 AM »

      While some allowance must be made for possible sensor misinterpretation, the July 21 NSIDC ASI concentration map makes the Beaufort look like a fortress ready to fall.

48
     Does anybody care to disabuse me of my conjecture that there is a nonlinear relationship between ice thickness and melt resistance - with decrease in melt resistance curving down faster than the linear % decline in thickness - due to qualitative differences in thinner vs. thicker ice?

     The fact that ice accumulation is radically nonlinear with increasing thickness is accepted as established fact, e.g. the curve published by Thorndike 1975
.

     Earlier this year I pitched the idea that the reverse is true for melting, with 1 meter thick ice melting at twice the rate of 2 meter ice (0.8 cm/day vs. 0.4 in the example shown):  .

     Those who actually understand the physics of ice melt shot down that theory, explaining that the energy flows involved in summer melt are not simply the reverse of winter freeze.  Correction which I gratefully accept, .... but

     ....even if a straight reversal of the thickness-freeze rate curve to estimate thickness-melt rate curve is too simplistic to be valid, that still leaves open the possibility, and (in my mind at least) the near certainty that the melt rate vs. thickness ratio is not a stricltly linear 1:1 ratio.  I have no idea what it would be, but it I'm almost certain that the melt rate for 1 meter vs. 2 meter thick ice has to be greater than 1:1.  And that ratio has to be even greater for 0.9, 0.8, 0.7 etc. meter thick ice vs 2 meter ice. 

      It is well documented and accepted that the chemical and structural characteristics of Arctic sea ice varies with thickness.  Those qualitative differences have to make some difference to the melt rate. 

      This is not merely an academic question.  An accelerating melt rate with declining thickness would have major consequence for acceleration of Extent and Volume losses as average thickness continues to decline as shown on the chart posted by gerontocrat at https://forum.arctic-sea-ice.net/index.php/topic,119.msg275579.html#msg275579  (A chart which I nominate for the ASI Graphical Hall of Fame).

      Which leads to a vision of the near future of the ASI showing accelerated melt to the same weather conditions and energy inputs of previous years, and even more so as continued cumulative global warming, exacerbated by Arctic amplification, increases energy inputs into melt seasons and reduces winter refreeze potential (and greater potential for Arctic cyclones, and jet stream weakening to allow warm air mass incursions, etc.). 

      If so, the drop from 4 million km2 September Extent to 3 million could occur in a shorter time frame than the observed trend for the drop from 5 million to 4 million.  And with average ice thickness in late summer approaching 1 meter, a nonlinear melt response for thinner ice would  accelerate even more for the drop from 3 million to 2 million km2, and even more than that for the drop from 2 million to 1 million km2. 

    (I suspect that dropping below 1 million km2 would complicate things because that final ice has resistance due to protection within bays etc. that would compensate for a thin ice melting effect).

      By extrapolation, the linear Extent decline trend reaches zero decades later than the Volume trend.  But of course that is impossible, because when there is no Volume, there is no ice left to create Exent.  So the Extent trend has to eventually start accelerating to curve downward to catch up with Volume by the date when they both reach zero.  I think that thin ice melt acceleration will be a major contributing factor (along with mobiillty for export, fracturing, surface area and possible others), that will cause that to happen.

     Is there a fallacy in this line of thinking?  What alternative mechanism accounts for the  required unification of Extent and Volume as they approach zero.  Binntho I'm talking to you!  This is right up your alley and I haven't seen you post for a while.

    One more conjecture.  I think that as the average thickness in the High Arctic Seas, as shown in gerontocrat's graph, is approaching 1 meter in September, the accelerated thin ice melt effect, which might have been relatively inconsequential until now, will become an increasingly important influence.  As a result, there will be "Extent goes poof" events of increasing scale and frequency over the next 10 years, resulting in a BOE by the early 2030s if not before.

49
Arctic sea ice / Re: The 2020 melting season
« on: July 20, 2020, 06:23:34 PM »
Here's the year-to-year comparison of the ASI (from AMSR2) maps for 19 July.
This year is unprecedented for the amount of ice cover lost by this date on the Russian side.

     The 2020 heat anomaly and high pressure systems so far this melt year are causing historically low-for-date Extent, with hard to understand not-1st place low Area loss (but I'm not trying to reignite that discussion), and low but not 1st place PIOMAS volume.  Given the conditions, even with the high Extent and Volume at start of season, I am surprised the ice is not in worse shape than it is.

     Looking at the deep purple areas of highest concentration and most likely to survive ice in the link posted by slow wing, July 19, 2020 looks surprisingly strong with a larger area of deep purple  high concentratoin ice than all but 3 of the 15 years displayed at
https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0719

     The years with more deep purple being 2005, 2009, and 2017.   With 2020 showing LESS deep purple than 2006, 2007, 2008, 2010, 2011, 2012, 2014, 2015, 2016, and 2018.
 
      Expanding the comparison to deep + light purple gives a less dramatic comparison, but still does not make 2020 stand out like it seems it should.

     How can that be?  I am probably giving too much importance to an eyeball area estimate of deep purple, but this is one the main images we use to track Arctic ice status.  One unaccounted for factor is remaining melt momentum.  My guess is that 2020 at this point has more energy in the system and thinner, more vulnerable ice than prior years, thus greater losses in store for remainder of melt season than most earlier years (2012 excepted).  I also suspect that thickness losses are a hidden weakness in the 2020 ice.

     I think the High Arctic thickness graph posted by gerontocrat at https://forum.arctic-sea-ice.net/index.php/topic,119.msg275579.html#msg275579 says a lot about the trajectory of ASI decline in recent years.

     Compare the thickness for the 2000s vs. 2010s and now 2020.  I think that the effect of the 0.6 meter (25%) thickness reduction between 2000s and 2020 has more importance than the ratio implies.  That would be because there are important qualitative differences between 2.4 meter and 1.8 meter average ice thickness.  The thicker ice is older, has lower salinity and higher density, and thus higer "melt resistance".  If so, then the 25% reduction in thickness could represent a 33% (just to have a number) decrease in melt resistance. 

     (2017 is an exception somewhat, but it was coming off of high melt year in 2016 followed by an extremely warm winter.  By my theory then, 2017 with its thin ice should have been another near record low September Extent and Volume.  2017 ended up above the straight-line trend for Extent, and just below the trend for Volume.  But the thickness factor does not have to overwhelm melt season weather -- which 2017 apparently lacked -- in order to be true as an important influence).

     If this conjecture is correct, then adding the qualitative effect of thicness reduction to the already low Extent/Area/Volume values puts 2020 even lower compared to all prior years.

     I'll go farther out on a limb to propose that there is a break point around 2 meters ice thickness.  That is about the amount that can freeze in one winter or melt out in a melt season.  I have to wonder if going below 2 meters thickness initiates a nonlinear accelerated reduction in melt resistance.  It certainly reflects the shfit from MYI to FYI which we all agree has been one of the big story lines since 2007.  And speaking of 2007, I think that it, not 2012, is the epic year that should get more attention in terms of understanding the effects of melt season weather and the modern progession of ASI decline.  No disrespect to 2012, but 2007 was a knockout punch that came out of nowhere.  The MYI ice loss that year set the stage for all that has happened since.

50
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 11:35:16 PM »
Anyone who knows what the most intensive Arctic cyclone in July is? Have there been any cases below 970 hpa in July?
I've seen them appear in forecasts ; I remember noting once that there were several in a forecast on gfs .. 2017 or 18. They didn't materialize . b.c.
     be cause's caution about forecast verification is duly noted, but if that beast actually occurs (965?!) we are into twilight zone strangness for ASI.

    I think the answer to Lord Vader's question must be 'not since accurate modern monitoring began'.  There has only been a total of 3 below 970 in August since 1979, and August is a much bigger cyclone month than July.  Those three events were in 2012 (all time lowest at 966.4, 1995 at 966.9 in 2nd place, 1991 at 969.2 in 3rd place, and 4th place also in 1991 at 970.5.
(A younger and less temperate Friv must have been freaking out in 1991!)

      The frequncies in graph are from a population of 1618 August Arctic cyclones.  Graph title is "Frequency distribution of August (1979–2012) Arctic cyclone properties for (a) central pressure".  It is from The great Arctic cyclone of August 2012 by Ian Simmonds and Irina Rudeva.  GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L23709, doi:10.1029/2012GL054259, 2012. 
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL054259


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