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Messages - Glen Koehler

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1
Arctic sea ice / Re: What's new in the Arctic ?
« on: October 27, 2020, 11:43:42 PM »
    Huh?  They say
 "....the Arctic could become ice-free in summer for the first time within the 21st century. Projections with CMIP-5 (Coupled Model Intercomparison Project Phase 5) models show that this could be the case as early as 2030 to 2050 for higher emission scenarios such as RCP8.5 (Representative Concentration Pathway). Some GCMs (global circulation models) show an ice-free Arctic for the first time within this century also for the moderate emission scenarios at a warming of 1.7 °C above pre-industrial. Furthermore, observations reveal that the Arctic summer sea ice declines faster than expected in experiments from GCMs."

     Which is accurate when the term "ice-free in summer" refers to < 1M km2 ASI Extent at September summer minimum.

     Then they are vague about what ASI Extent or Area they plugged into their model.  But in Figure 1a the caption says "Regional warming for the whole Earth if Arctic summer sea ice (ASSI) in June, July and August, mountain glaciers (MG), Greenland Ice Sheet (GIS) and West Antarctic Ice Sheet (WAIS) vanish at a global mean temperature of 1.5 °C above pre-industrial.   (bolding added by me).

     ALL ASI vanishing in June July and August (as in zero Extent-Area-Thickness-Volume) during peak solar input is an entirely different scenario than reaching ASI > 1M km2 Extent for a couple of days in September before refreeze resumes.

     So which is it?  <1M km2 ASI Extent or Area at September minimum, or ASI vanishing to give zero km2 ASI for June 1 - August 31?   Based on the Fig. 1A caption, it seems to be the latter, which renders that first paragraph completely out of context with their simulation and egregiously misleading.   

      Before noticing the aforementioned oddity, my hackles got raised by Figure 4.  It is one of the most easily misinterpreted, and therefore poorly designed, data graphics I have ever seen.  The X axis on a chart implies that X values cause the Y axis values as a response.  But that is not really what is happening in Fig. 4.  A reader could all too easily look at that chart and think it says that at 2.5C above preindustrial global mean temperature (GMT) we should expect 4M km2 summer ASI Area.

    At https://forum.arctic-sea-ice.net/index.php/topic,2975.msg286961.html#msg286961 our friend gerontocrat made it back safely from his foray into the COVID-19 infested streets to buy booze to let us know that on September 18 ASI Area reached 2,631,888 KM2. 

     2020 is coming in hotter than expected, with a good chance of beating out 2016 as the warmest year in the modern record (disturbing that given solar minimum AND piddling ENSO signal, 2020 should have come in well below 2016 despite 4 more years of incremental warming since 2016, but that's for another rant.)  2020 is nowhere near +2.5C > preindustrial GMT, yet September minimum ASI Area is already well below 4M km2 (and has been for a while). 

     Fig 4. exacerbates the confusion by showing a labeled 1979-2006 average ASI summer minimum sea ice area range of ca. 5.75M - 6.25M km2.

     I think what Fig. 4 is trying to say is that IF ASI vanished in context of GMT at +2.5C, we should expect about 0.10 C additional warming due to the increased Arctic albedo (shown on the right axis).  Whereas, if ASI vanishes for June - July - August  when GMT is at +1.5C, then we should expect an additional 0.18 C of albedo induced warming from that cause.

     So what the heck is the left Y axis referring to?  I tried to help them out by guessing, "Oh, they mean average ASI Area for June-July-August at those GMT values.  Thus about 6.8M km2 average ASI Area for June-July-August at 1.0C.  Conveniently, glennbuck had posted just the chart I needed just below the gero post at https://forum.arctic-sea-ice.net/index.php/topic,2975.msg286915.html#msg286915.  Yes, that fits.

     But then why does the label in Fig 1A say "Minimum Arctic sea ice area (observations) average 1979-2006"?  Those values are the June-August average, not the average of the summer minima.  And what does it add to this chart except confusion?

     Correct me if I'm wrong.  Maybe I'm too dumb or tired to understand what they are saying.  But I think it is the other way around.  It is the authors' responsibility to communicate clearly, a task at which this article fails, and worse than that it very easily leads to gross misrepresentation to, and misunderstanding by, the reader.

     The ASI situation is truly bad and getting worse.  But the entire 3 month period of June-July-August is not going to be ice-free in the 2030-2050 time frame. 

      Conversely, summer minimum ASI Area is already well below 4M km2 at our present +1.1C, so there is no way that September minimum ASI Area at +2.5C GMT will be near 4M km2.  There won't be ANY September ASI Area at 2.5C GMT over preindustrial. 

     At least the fallacies balance each other.  But leading the reader to counteracting fallacies is not good enough, in fact it's a mess.




2
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 02:46:11 AM »
      The Panoply map is very interesting.  What are typical cooling rates for November, December, and January?  In other words, what does a current temperature of 273-275K in most of the ESS and Laptev, and much of the Kara, suggest for when those waters are likely to freeze?
      Here is CR temperature anomaly map for same day.  It is an apples vs oranges comparison because Panoply and CR  are not representing temperature at the same depth in addition to using different data sources.     

3
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.

4
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.

5
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.

7
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.

8
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.

9
Arctic sea ice / Re: Glossary ... for newbies and others
« on: October 09, 2020, 08:25:56 PM »
   If the ASIF glossary is not limited to acronyms, even though gerontocrat restates the list in his updates, glossary definitions for
Central Arctic Seas (= Chukchi, Beaufort, CAA, East Siberian Sea, Central Arctic Basin, Laptev Sea, Kara Sea)
vs.
Peripheral Arctic Seas (=Okhotsk, Bering, Hudson Bay Baffin  Bay, Gulf of St. Lawernce, Greenland Sea, Barents Sea)
  would be useful to have in the glossary because that is where people are likely to go first when they encounter those terms and are looking for clarification.

    Also worth noting in definition of the CAB that even though the Lincoln Sea is labeled as a separate entity (e.g. NSIDC map), for Extent/Area/Volume stats it is counted as part of the CAB.

10
Arctic sea ice / Re: Latest PIOMAS update (Oktober)
« on: October 06, 2020, 07:50:45 AM »
    I really like the day 266 to 266 Min to Min accounting vs. calendar year.  It shows how the impact of winter 2006-2007 created a fundamental reset in the ASI that persists to this day.  It also gives deserved "credit" to the 2015-2016 winter, when the 2M temperature anomaly maps on Climate Reanalyzer were blood red for weeks on end.  And it shows why 2020 felt like such a wild ride of a melt season (-7.4 vs. -6.8 for 2012). 

11
      Third and final chapter...
       Looking at those lists makes me wonder if it I wasn't right the first time.  (I used to tell my kids "I've never made mistake.  I thought I did one time, but it turned out later I was wrong about that.").

       Here's what I think will happen.  Some August in the next 10-12 years, that pile of heat buried just below the surface in the Beaufort Sea, and/or a similar heat bomb in the Laptev, ESS or Kara, will break through the halocline/thermocline and melt the ice so fast that even Friv won't see it coming.  That will lead to the first September BOE. 

       Subsequent years will show some rebound, but just as the system changed in 2007, the Arctic will never be the same.  A year or two or three later will be another September BOE, and from then on September BOE will be a regular thing.  And August BOE (which matters a LOT more in terms of albedo) will only be a couple of years behind September.  July BOE will take 10-15 years longer than August, but as August declines toward 1M km2, July is accumulating increasing open water exposed solar energy absorption.  There is nothing magic about 1M km2.  The earlier in the summer each km2 of reflective ice becomes dark open water means that km2 of water is exposed to more direct sunlight for a longer time, thus allowing more energy to enter the system.   

12
....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.

13
  From the "When will the Arctic Go Ice Free?" thread.  But my reply is more about ice physics so put it here.
Not sure that thinking about volume as being decreased is the right approach. 

To first order, so ignoring pesky complicating factors like winds and currents moving ice around, isn't maximum ice area a measure of how much space gets cold enough, and maximum ice thickness a measure of the amount of heat loss in that area? The slow decline in area says that it still gets cold enough to create ice in much the same area, but the relatively rapid decline in ice thickness says that nonetheless there is a lot more heat in the system so less ice can be made. Both are likely to keep heading as they are and volume just is the result of combining the two.

     I agree that Volume is a function of Area and Thickness, so your logic makes sense to me.  But what I think gerontocrat was getting at was that as the ice thins, qualitative changes occur to increase the melt rate for the same degree of melting energy.

     I also began promoting that argument last year.  While I still think it is true, I have to partially recant my previous contention that once Arctic sea ice gets below 2 meters the melt rate should increase rapidly due qualitative changes in the ice.  The door shut on that when I read Maycut and Rothrock 2004: "While summer melting of undeformed ice is nearly independent of thickness, winter ice growth rates depend inversely on thickness." 
     Changes in the thickness distribution of Arctic sea ice between 1958–1970 and 1993–1997
     Y. Yu  G. A. Maykut  D. A. Rothrock. 2004
https://doi-org.wv-o-ursus-proxy02.ursus.maine.edu/10.1029/2003JC00198

     The winter ice growth part of that conclusion is demonstrated in the first chart below from
Thorndike, A. S., D. A. Rothrock, G. A. Maykut, and R. Colony.  1975.  The thickness distribution of sea ice. J. Geophys. Res., 80, 4501–4513.  Abstract at:  https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JC080i033p04501.  (Good luck finding the PDF.  I gave up.  You'd think that a seminal paper like that would be easy to find.)

     Zhang and Rothrock 2001 provide some data on the effect of ASI thickness on summer melt rate.  That rate increase is much smaller than I had expected.  It does not have an appreciable impact until thickness is below 1 meter, and even at 0.5 meter the rate is only about 25% faster than the rate for 2 meter thick ice.
     Jinlun Zhang and Drew Rothrock.  2001. A Thickness and Enthalpy Distribution Sea-Ice Model.  J. Phys. Oceanogr. 31 (10): 2986–3001.
https://doi.org/10.1175/1520-0485(2001)031<2986:ATAEDS>2.0.CO;2

     The second chart below shows the source of the data for my derivative 3rd chart, which shows the degree of melt acceleration due to thinning ice.  Along the X axis are different average ice thicknesses (thicker on the left) from the PIOMAS data.  The melt rate is from polynomial regression of data points from the solid line in the Zhang and Rothrock chart.  The vertical axis is the estimate cm of melt per day in June-August. 

     But what really shifted my view was reading Goosse et al. 2009.  It is a wonderful article that explains a lot about ice melting behavior.  Paradoxically (to me at least) they explain why thick ice loses more from year to year than thin ice.
     Increased variability of the Arctic summer ice extent in a warmer climate
     H. Goosse  O. Arzel  C. M. Bitz  A. de Montety  M. Vancoppenolle.  2009
     https://doi.org/10.1029/2009GL040546

14
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.

15
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. 

16
Arctic sea ice / Re: Glossary ... for newbies and others
« on: October 03, 2020, 07:24:47 PM »
CAS = Central Arctic Sea.  Used by NSIDC.  Which gerontocrat tells us is 3.2 km2 less than the CAB.  JAXA uses CAB right?

17
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: October 02, 2020, 07:15:13 PM »
The next step in my evolution is learning more about salinity. But I don't know how the read Uniquorn's graphs... I'm unable to visualize it...

Isn't there a way to turn the Mercator 2D images into a 3D graphical presentation? They have salinity at all levels, so isn't it possible to use that data to create something like this?


    That would make a lovely live-feed wallscreen animation for NSIDC headquarters.

18
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.

19
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."

20
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 27, 2020, 10:25:54 PM »
  BTV - Could do a version of the bar chart to show change from Sept Minimum to Minimum? 
That would visualize the stats posted by Oren showing what an absolute beast 2007 was.
I think this is what you're after.
      Thanks BFTV, uber Nice!  That is even more informative than I expected.  I was looking to see a visual representation of the strong melt year from Sept 2006 to Sept 2007 - which the chart definitely demonstrates.  But it shows a lot more than that.  One bonus is seeing just how dynamic Arctic sea ice change is from year to year.

      The chart highlights some other major change years: 1990, 1993, and of course our favorite 2012.  On the other side of the coin, it shows 2013 as a large rebound year.

      Going out on a limb, I think the chart reflects the fact that 2007 was a "deep" melt year  ::) , whereas 2012 was kind of a superficial melt year in that much of the melt was due to the release of subsurface ocean heat by the GAC 2012 that caused late summer melt, but the loss of that heat also contributed to the large rebound in 2013. 

      Pushing my ignorance one more step, I think that the chart shows that 2019, while a 2nd place (at the time) finisher to 2012, was more a "deep" melt year, i.e. the real deal, not some flash in the pan caused by a temporary cyclone stirring up the waters. 

      And finally, I expect that 2020 was another "deep" melt year.  Yes the July cyclone in the Beaufort was a significant nudge, but it was not the driving factor behind the total melt, and did not release that heat bomb that lies at depth in the Beaufort Sea.  When that heat eventually is released, it will be an ice Armageddon -- for a while at least.  Such an event would likely be followed by a rebound year just like 2013 followed 2012.  Then again, with the ASI getting weaker from year to year, such a body blow could push it over the edge into a new equlibrium from which it cannot recover even with relatively mild melt weather in the subsequent year(s).
     
      If we look at each year as the first of a two-year pair to factor in the reboud effect, then 2007 really stands out as not only the biggest melt year, but a big melt year without a recovery the following year.  While 2019 was an intermediate melt year, it is one of only three (the others being 1997-1998, and 2007-2008) with two melt years in succession.  Both members of the 2019-2020 pair were stronger than the 1997-1998 pair.  (Worth noting that 97-98 was strong El Nino.  As was 2015-2016, which had back to back loss years, but much weaker.)

      I suspct that in addtion to the summer weather, the strong 2020 melt in the Laptev (and possibly ESS and Kara as well) this year may reflect the weakening of the thermocline due to Atlantification. If so, it is likely to be a persistent feature from now on, not a single year anomaly.

      And ominously, what drove the damage to the CAA-Greenland-North Pole triangle this year, including the north Greenland megacrack?  If it was purely a weather issue (which seems very possible) then it is less likely recur next year, though with continued warming such a weather scenario (or one with similar impact) also becomes increasing likely.  If the melting in the triangle was due to ocean forces, such as suspected for the Laptev, then it would be more likely to be a regular feature going forward.  I can't even guess at that question.  But the assault on the Atlantic-side ice edge during August and September 2020 has me suspecting that Atlantification contributed at least partically to the 2020 triangle melt.

      All just guesswork.  Interested in hearing what other folks think.  I just wish this very interesting intellecual exercise was about something other than the disruption of the planetary climate we all depend on.  I feel guilty enjoying watching the process unfold (and not the only one with those feelings I'm sure).  I tell myself it is important to stay informed.  Which is true.  But a part of me just likes watching math unfold regardless of the horrendous implications.

     I don't think the public really gets it that our entire civilization is built with reliance upon expectation of climatic norms for both levels and variaiblity around those norms, and upon dependable weather patterns like monsoons and other systems that drive agriculture and other endeavors.  I hope that ASIF, besides being fun to watch and enjoyable as my first and only on-line community, serves a purpose at raising awarenss.  When you vote, just remember: Creep Instability

21
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 27, 2020, 04:52:39 AM »
  BTV - Could you do a version of the bar chart to show change from Sept Minimum to Minimum? 
That would visualize the stats posted by Oren showing what an absolute beast 2007 was.

22
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 26, 2020, 07:19:23 PM »
   One of your best graphics BTV, and that's saying something.

23
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.

24
Arctic sea ice / Re: The 2020 melting season
« on: September 24, 2020, 10:24:12 PM »
Thanks Vox.  ;D A week ago turns into > a month ago pretty fast these days.

25
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

26
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.

27
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.

28
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.

29
Arctic sea ice / Re: Changing Arctic Ocean Currents
« on: September 18, 2020, 11:08:44 AM »
I've never really been convinced that the AMOC was slowing or weakening.  The system as a whole is very variable and changes cyclically, but the waters north of the GIS gap and south of Labrador have both been unusually warm for several years, indicating that the Greenland cold spot is an unrelated phenomena and that the conveyance of oceanic heat to the far north is continuing unabated.

The much hyped putative driver behind a percieved slow-down doesn't really exist in geologically modern times: No glacier is big enough, close enough, and melting fast enough, or draining suffiiciently into the Arctic to cause a fresh-water induced slowdown - which is a popular theory to explain big swings in the AMOC in the geological past.

And a quick google on "amoc strengthening" finds plenty of evidence to support Hefaistos' post, including this one in Science Direct from 2016: There is no real evidence for a diminishing trend of the Atlantic meridional overturning circulation

here is another interesting paper, On freshwater fluxes and the Atlantic meridional overturning circulation. From the Abstract:

Quote
While the role of freshwater forcing in the AMOC has received much attention, this question remains unresolved ... Our results robustly suggest that for the equilibrium state of the modern ocean, freshwater fluxes strengthen the AMOC

Recent research is pointing to a link between the Indian Ocean and the AMOC, with a warmer
IO causing a stronger AMOC. There are plenty of papers to be found online, including this one:

PC23A-03 - The Strengthening of the Atlantic Ocean Meridional Overturning Circulation Caused by Enhanced Indian Ocean Warming, from the Abstract:

Quote
Here, we describe how a salient feature of anthropogenic climate change – enhanced warming of the tropical Indian ocean (TIO) – can strengthen the Atlantic meridional overturning circulation (AMOC) by modulating salinity distribution in the Atlantic
     Here is what Stefan Rahmstorf (who wrote the oft-quoted paper about a 15% AMOC slowdown, and who probably eats AMOC Sverdrup data for breakfast every morning) said about it on September 17 at http://www.realclimate.org/?comments_popup=18180#comment-626528

New studies confirm weakening of the Gulf Stream circulation (AMOC)
     "[T]here is growing evidence that another climate forecast is already coming true: the Gulf Stream system in the Atlantic is apparently weakening, with consequences for Europe too."

 "The Intergovernmental Panel on Climate Change (IPCC) stated for the first time a year ago in the Summary for Policy Makers of its Special Report on the Oceans:
   “Observations, both in situ (2004–2017) and based on sea surface temperature reconstructions, indicate that the Atlantic Meridional Overturning Circulation (AMOC) has weakened relative to 1850–1900.”  "

"Two new studies now provide further independent evidence of this weakening."

1. "The result: the Florida current has weakened significantly since 1909 and in the last twenty years has probably been as weak as never before. Piecuch’s calculations also show that the resulting reduction of heat transport is sufficient to explain the ‘cold blob’ in the northern Atlantic."

2. "Model simulations show that a weakening of the AMOC leads to an accumulation of salt in the subtropical South Atlantic." 
"This is exactly what the measured data show, in accordance with computer simulations. The authors speak of a “salinity fingerprint” of the weakening Atlantic circulation."

"In addition to these oceanographic measurements, a number of studies with sediment data indicate that the Gulf Stream circulation is now weaker than it has been for at least a millennium."

"[T]he latest generation (CMIP6) of climate models shows one thing: if we continue to heat up our planet, the AMOC will weaken further – by 34 to 45% by 2100. This could bring us dangerously close to the tipping point at which the flow becomes unstable.

This article appeared originally in German in Der Spiegel: Das Golfstromsystem macht schlapp"



30
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.

31
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. 

32
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.
     

33
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!

34
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."

35
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.
               

36
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).   

37
Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 09:27:20 PM »
The Polarstern from above on "Sunday morning", via the MOSAiC Twitter feed:
& no Lat / Long, date / time printed on the image..

Isn't anybody taught the basics of record keeping anymore?

Even the most junior Cop knows that without the chain of evidence the data cannot be relied upon.

Bloody amateurs.
     Assuming the date on photo is date it was taken, the Mosaic tracking website has the Polarstern location on Sept 6 2020 at 88.45N 115.3E

38
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.

39
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

40
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.

41
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.     

42
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.

43
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.

44
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?

45
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.

46
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.

47
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).

48
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. 

49
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?

50
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."

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