Support the Arctic Sea Ice Forum and Blog

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Glen Koehler

Pages: 1 2 [3] 4 5 ... 9
101
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?

102
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."

103
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. 

104
Arctic sea ice / Re: MOSAiC news
« on: August 19, 2020, 08:48:21 PM »
    Great picture.  Looks like a mix of melt ponds and open water.  Correct?  Any estimate of thickness of the ice in the picture? (it looks very thin, ca. 0.25 meter?). 

105
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"

106
From https://nsidc.org/arcticseaicenews/2020/8/
  NSIDC update August 18 2020

     "Note how the projections have seesawed up and down from June through mid-August. This is a result of the changes in the extent loss rates from one period to the next; it highlights how strongly weather conditions affect the ice loss through the summer, as well as the influence of thickness on how fast ice is melted away."   (emphasis added)

      I suspect that relationship will be a key factor resulting in accelerated melt rates in coming years.  It would be very interesting to see a chart that helps quantify the influence of thickness on ice melt rate.  Surely such a chart must exist somewhere, but I have not seen it.  If anyone has an image or link please post it.  Thanks in advance for anyone who can do so.

107
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.

108
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: August 12, 2020, 09:23:51 AM »
Ode to the Beaufort Sea, the CAB & the permafrost, and I hope not the U.S. electorate
    William Butler Yeats - (though he did not know that was the topic or the title when he wrote it)

"Turning and turning in the widening gyre   
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;

Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere   
The ceremony of innocence is drowned;

The best lack all conviction, while the worst   
Are full of passionate intensity."

109
Arctic sea ice / Re: The 2020 melting season
« on: August 02, 2020, 02:05:35 AM »
Direct solar isolation  melt we have observed:
75-80N: as late as August  20th.
70-75N: end of August.
   Here is another version showing where we are at relative to insolation.  This one based on the Surface insolation graph posted by Tealight.

110
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.

111
Arctic sea ice / Re: Arctic Image of the Day
« on: August 01, 2020, 05:01:23 PM »
    Thanks for posting that Miki.  It is both gorgeous and exemplifies many of the mathematical patterns in nature.

112
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!

113
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.

114
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.





115
Glen, that is pretty straight forward. Just click the 'Attachment and other options' below the input window. There you can choose a file from your computer to upload.
   Thanks bk, good info.  ;D I completely missed the "Attachments and other options" line.  After being on the forum for years and even after reading your post I could not find it, and was looking for it among all the buttons above the input box.  Missing the obvious seems to be one of my strength areas.

116
     Where are the instructions on how to post images to forum server?

117
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.   

118
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 24, 2020, 07:10:45 PM »
I attach two of my graphs from which I calculate my BOE number.
      Thanks Stephan.  Can you repost those charts with X year axis going out to 2075 instead of ending at 2025?

     BOE in September is our big marker only because it is the first one up to bat.  But also interesting to see the trend lines for Extent and Volume levels for August, July, June etc. out to 2075.  The decline in ice coverage in those months has a much greater effect on solar radiation absorbtion and is much more important for planetary energy budget.

     Your chart indicates about a 20 lag between June vs. July. If we think 2020 is dramatic, imagine the impact of having the ice in its current condition coinciding with June 21 summer solstice.

119
     Summary of the Thin ice accleration hypothesis -- Absent some qualitative effect that makes thinner ice HARDER to melt (which does not seem to be the case at all), even without any effect of qualitative differences for thinner ice that reduce melt resistance, it seems irrefutable that 1M km2 of 1-meter thick ice (thus 1M CUBIC meters of ice) will melt out faster than 1M km2 of 2-meter thick ice (2M cubic meters) simply because there is only half as much ice to melt. 

    As Thickness declines and approaches 1 meter in late summer (and as average albedo declines with Extent losses) the rate of Extent losses will likely increase between now and 2030.  I don't even want to be right about this, because it is kind of sickening to think about the consequences.  But my rational mind also wanted an explanation for how the Extent and Volume trends will, as they arithmetically must, meet by the time September ice approaches extinction.

120
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.






121
Today I was looking at some areas where floes are moving pretty rapidly, e.g., the Nares Strait.  Here, rapidly means maybe a slow walk, say 0.5 - 1.0 km/hr.  But it got me wondering, with chunks of ice floating around, running into each other and scraping past, and so on...is it noisy?  Seems like it could be quite loud.  Maybe someone who's actually been around this kind of activity can fill me in on what it sounds like?  Thanks!
     Different setting but same idea.... I once happened to be next to local river when the winter ice jam broke on warm April afternoon and the sound was impressive.  Grind... crash...thud...groan... crack!

122
Not at all.  We are talking about a trend line, not an absolute value.  The volume trend line has already lessened over the past several years.
http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/
    I see nothing in the link to PIOMAS update about the trend line slope for Volume becoming less negative.  What it does say is "Sea ice volume is an important climate indicator. It depends on both ice thickness and extent."  In order for Volume trend to change, antecedent values in Thickness and/or Extent must change in the same direction.

    I don't understand the relevance of your distinction between trend and absolute value.

    You are free to consider the Extent linear trend estimate (2072) instead of the Volume linear trend estimate (2032) as the better estimator for when September ASI for both measures will approach zero  (see https://forum.arctic-sea-ice.net/index.php/topic,2348.msg273488.html#msg273488).  But you won't have much company in thinking that.
 
     As much as I can guarantee anything, I guarantee you that the date for Extent going below 1M km2 is better predicted by the Volume trend line on Wipneus chart as 2030 =+/- 6 years,

123
     The only way for Volume loss trend to decline relative to Extent is for Thickness to increase.  With the net energy balance of the Arctic system already above equilibrium to maintain the current seasonal ice levels, compounded by increasing energy inputs from GHG emissions that not only continue to load the system, but still doing so at any increasing rate, I see virtually no chance for Thickness levels to increase, or for the Volume rate of decline to lessen.

124
Welcome back binntho. Excellent post.
+1 :)

125
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.

126
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 03:07:44 AM »
Do you expect a 2nd place, MH?
1st-highly unlikely
2nd- good chance but weather will need a spell of favourable melt conditions at some stage
3rd or lower - quite possible if weather stays favourable for ice retention.

      Given gerontocrat's summary below, I think that "good chance" for 2nd (i.e. 3.96M km2 JAXA Extent) is a very, very good chance:
<snip> In every year from 2007 to 2019 remaining melt results in an extent below 3.96 million km2, which was the 2nd lowest extent in 2019.

     But the ice does not care what we say about it.  It will tell us exactly how much it will melt over the next few weeks. 
     This poem comes to mind:

   Ice asks no questions, 
      presents no arguments,
         reads no newspapers,
           listens to no debates.
     
    It is not burdened by ideology,
       and carries no political baggage
           as it changes from solid to liquid.

    It just melts.

                                 ~ Henry Pollack
------------------
   
  But of course, we like to guess at the future. 
     Here are some measures of our predictive ability:

      Improved Volume prediction accuracy as melt season observations become available.
R-square reduction in variability derived from R values posted by Stephan at https://imgur.com/a/O82kzZZ

      Linear model estimate for 2020 September average PIOMAS Volume before any 2020 observations:
 3.9M km3 (1.2 – 6.6), (95% of cases expected to fall within 1.2 – 6.6M km3, i.e.  +/- 2.7M km3).
   
      With MARCH observation as predictor, confidence interval (CI) reduction for September average Volume estimate: 4%.  Width of 95% CI with March observation: +/- 2.6M km3.
      With APRIL Volume observation, confidence interval reduction: 7%.  Width of 95% CI with April observation: +/- 2.5M km3.
      With MAY Volume observation, confidence interval reduction: 32%.  Width of 95% CI with May observation: +/- 1.9M km3.
      With JUNE Volume observation, confidence interval reduction: 63%.  Width of 95% CI with June observation: +/- 1.0M km3.
      With JULY Volume observation, confidence interval reduction: 83%.  Width of 95% CI with July observation: +/- 0.5M km3.
      With AUGUST Volume observation, conf. interval reduction: 94%.  Width of 95% CI with August observation: +/- 0.2M km3.

      The same approach for Extent shows the R2 reduction by having observations at the end of March, April and May is insignificant.  Estimate error reduction only reaches 22% by the end of June, and 56% at the end of July.

127
Arctic sea ice / Re: The 2020 melting season
« on: July 22, 2020, 03:24:39 AM »
Made a table of 2020 extrapolations with some particular dates set as sort of "mile markers" for a quick reference to how the ice is doing. I think these three options bound outcomes pretty well.
   Thanks Killian.  Those are very interesting comparative extrapolations.  I find them more informative than the debate about the degree of compaction.  The fact that your extrapolation from 5 low melt years stills ends up at 3.6 M km2 is remarkable and well below the straight line trend, and rougly 8-10 years ahead of where 2020 "should" be on that trend line (eyeball estimate).

    Taking 2012 out of the "Worst case" scenario yields an estimate similar to the "Bad case" scenario at ca. 3.4-3.5.  That reinforces a final estimate of around 3.5.  That would still leave 2012 in 1st place, but not by much. 

      I wonder how warm water melt momentum in 2020 is still unexpressed in the real time measurements.  And with warmer water the chance of cyclone is also lurking in the wings.  Putting those pieces together suggest that 2020 is heading for a near miss 2nd place without any additional anomalously strong melt weather between now and minimum, and may even replace 2012 without any dramatic melt weather, due to momentum.
     
      While another GAC 2012 is unlikely, if there is a strong storm, then it looks like 2020 has a very good chance of going below 2012.  As other ASIF posters have noted, regardless of the record, the ice condition looks terrible and already has one thinking about what kind of setup 2020 is creating for 2021.  The 2019 + 2 = 2021 tag line used by ASIF member be cause is looking prophetic. 

       But that's next year.  The end game for this year looks to be dramatic and historically significant.  We will have numbers soon.
 

128
     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.

129
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.

130
Arctic sea ice / Re: The 2020 melting season
« on: July 19, 2020, 05:49:21 PM »
   Climate Reanalyzer got stuck by a power blip yesterday.  Some of the Arctic forecast animations are already updated to July 19, the rest will be back online in few hours by 1800 UTC July 19.  The updated pressure forecast no longer shows a sub-990 low pressure system.

131
Arctic sea ice / Re: Glossary ... for newbies and others
« on: July 19, 2020, 04:30:42 PM »
Thanks for the correction - Conterminous United States (the lower 48)

National Weather Service - Table of Commonly Used Acronyms and Abbreviations
https://www.weather.gov/mdl/about_acronyms

132
Arctic sea ice / Re: Glossary ... for newbies and others
« on: July 19, 2020, 04:03:05 AM »
CONUS - Continental U.S.  Frequently used acronym in meteorology.

133
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 19, 2020, 03:35:48 AM »
Vox_mundi posted a Navy Arctic Roadmap https://forum.arctic-sea-ice.net/index.php/topic,3183.msg275158.html#msg275158
   That document has an interesting graphic showing projected of ASI Extent in 2030 vs 2012. 
    A rough eyeball comparison of the area for their 2030 area suggests that it is about 30% of the 2012 area. 
    Given that 2012 JAXA & NSIDC Exent minimums were 3.18 and 3.41 million km2, respectively, the 2030 Navy projection at ~30% of 2012, is a pretty close fit to what a 1 million km2 September minimum BOE event would look like.

     When that happens, it will be a headline for a day, and the ice will begin winter increase shortly thereafter, and humanity will go back to ignoring planetray climate disruption.  Or perhaps we will be wiser by then.  A lot can happen in 10 years.  It certainly will for the Arctic ice.  The question is whether human response will evolve accordingly.  Vote Climate as if your life depended on it.  Annoy your famiy and friends by harping on it.  They will love you for it later.


134
Arctic sea ice / Re: Shift in timing of ice minimum over the years
« on: July 19, 2020, 02:24:30 AM »
   Previoius chart is solar radiation at top of atmosphere.  Tealight posted a chart of insolation at surface.  The low sun angle in the Arctic increases the amount of atmosphere through which solar radiation must pass which reduces the level reaching the surface.  Chart posted by Tealight shows values for latitude in 10 degree increments so you don't have to guess where 80N falls between 60 and 90.
    Based on comment in 2020 Melt thread by GoSouthYoungins
https://forum.arctic-sea-ice.net/index.php/topic,3017.msg274806.html#msg274806
that insolation driven melt essentially ends in last week of August (which I have not verified from other sources, but seems reasonable) I added estimated dates for start and end of insolation melt season.  Residual melt from warm water melt would account for the remainder of melt season until September minimum.
    Caveat:  I don't know any of this stuff, just making back of the envelope estimates.  Corrections encouraged.


135
Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 05:23:22 PM »
mercator 0m (ocean) temperature with amsr2uhh overlaid at 80% transparency. amsr2 0% concentration has been set to fully transparent. jun1-jul17
    Up thread I asked if pack ice disconnecting from continental and large island shores might lead to increase in ASI pack rotation.  Near the end of uniquorn's animation, just as the periperhal ice detaches from shorelines, the whole pack starts rotating.  Example of cause and effect, or just selective observation of a random correlation?
 
    The animation also shows active export from Lincoln Sea via the Nares Strait, which seems especially significant as it could be reducing what little is left of MYI.       

136
Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 06:29:53 AM »
<snip>  Many of the great weather forecasters here on ASIF have already mentioned this, but a head Met at an agency in the UK seems to agree.
    James Peacock is a great meteorologist who follows sea ice closely. He watches the ASIF, and might even have an account here.
    Today he posted what might be some scary news for the ice if it comes true. His model runs support what others have said that we might see a strong low over the Beaufort in about a week. Since the Beaufort is the last remaining hold out for the ice, that will be bad if it happens. It will churn up warm water and cause mechanical breakup of existing floes.
   Peacock - "...like putting the sea ice into a washing machine...'
     ... and set to warm rinse cycle.

GFS has pressure going down to 984 not a cataclysmic 965, and the storm lasting about two days, but still bad news for the ice...
 
GFS surface temp forecast for July 24



GFS cumulative precip forecast for July 17-24


137
Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 05:59:44 AM »
NSIDC July 16 update
https://nsidc.org/arcticseaicenews/2020/07/siberian-downward-slide/
"Through the first half of July 2020, sea ice extent declined by an average of 146,000 square kilometers (56,400 square miles) per day, considerably faster than the 1981 to 2010 average rate of 85,900 square kilometers (33,200 square miles) per day."

"Air temperatures at the 925 mb level (about 2,500 feet above sea level), as averaged over the first half of July, were unusually high over the central Arctic Ocean—up to 10 degrees Celsius (18 degrees Fahrenheit)"


138
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: July 18, 2020, 12:44:19 AM »
Just a reminder, to really damage the ice a bomb cyclone not only needs low pressure, it has to be relatively long-lived and positioned so as to create long fetches. Right now I’m more concerned about the low earlier in the forecast bringing excessive heat and moisture from Siberia.
I agree 100%.
Phoenix - was telling us that worth a post?  I don't mind your willingness to poke at consensus understanding (as long as you stick to facts and don't cherry pick)... and my kvetching about your post is equally off-topic. 
   I'm just asking for a bit more discretion in sharing your musings.

139
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


140
Arctic sea ice / Re: Latest PIOMAS update (July 2020)
« on: July 16, 2020, 07:21:51 AM »
   Even though it is a short range of dates comparison between, it is surprising to see the 2007 value lower than the others (except for 2014). 

   2007 was a true blow-out year, especially for MYI ice reduction, from which the Arctic has never really recovered.  It would stand out above 2012 except the freakish GAC that pushed 2012 into new territory. 

    As for 2020, if this year's May and June melt pond conditioning and the current July roast-a-dome don't produce a 1400 km3 drop, it seems like that could only be because there is less ice to melt.

141
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 07:08:21 AM »
     It looks like soon all the ice abutting continental coasts and major islands will be melted out.
How much difference does that make to Arctic-wide ice pack rotation? 
Does that free up the pack to rotate faster with consequences for transport into Barents, Fram Strait,  ESS, and Laptev melting zones, with possible addition of Ekman uplift of warmer subsurface water?

142
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 06:56:04 AM »
Meanwhile, the Beaufort is dragging its feet and is almost highest in the AMSR2 record..
     The July 22 HYCOM thickness forecast posted by Milwen at
https://forum.arctic-sea-ice.net/index.php/topic,3017.msg274198.html#msg274198
and the HYCOM concentration forecast posted by OfftheGrid at
https://forum.arctic-sea-ice.net/index.php/topic,3017.msg274287.html#msg274287
both indicate that the Beaufort is unlikely to serve as a defensive wall for much longer, as it is beginning its own period of rapid retreat.




143
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: July 16, 2020, 12:51:36 AM »
Let's not get bogged too much in definitions.
    At the cost of adding one more distracting message, I feel compelled to congratulate and thank Oren for superb moderator service during what is turning out to be quite a rodeo this year as the ASI appears to enter the next phase.  You've handled the usual food fights, occassional personality disorders, and the inevitable cases of topic drift with a diplomatic and effective aplomb.

144
Arctic sea ice / Re: The 2020 melting season
« on: July 15, 2020, 09:02:20 PM »
Also HYCOM 7 day forecast. Whole CAA is basically gone.  :o
  ...plus ice retreat along north coast of Greenland.

145
Arctic sea ice / Re: Albedo-Warming Potential
« on: July 08, 2020, 08:07:41 PM »
Thanks Comradez, that provides a much better understanding of the AWP situation.  I was looking at the AWP graph as actual energy input.  Clear vs cloudy sky cover radically changes that interpretation.

146
Arctic sea ice / Re: Temperatures at Eureka, Nunavut, Canada
« on: June 29, 2020, 04:24:22 PM »
    My speculations were for non-professional weather stations.  NOAA or Env. Can. ownership and the photos indicate professional-grade weather stations with technical support, so far less likely to have issues with low-quality sensors, improper placement etc. that not infrequently occur at non-professional stations.

147
Arctic sea ice / Re: Temperatures at Eureka, Nunavut, Canada
« on: June 29, 2020, 02:56:01 AM »
could be be an elevation difference?
They are both down as 10m. Still showing a difference of 7 C beteeen the 2 stations.
       Alternate possibility.  May sound too simple to be true, but it wouldn't be the first time to have incorrect readings from improperly operated weather sensors.  If one of the sensors is missing a radiation shield or does not have an aspiration fan to move ambient air across the sensor, then it can report much higher temperatures than a properly protected sensor.  Or if the sensor is placed near a building, pavement, or (God forbid, but it happens) on a roof, it will give falsely high warnings during sunlight hours.  Did the two sensors agree until direct sunlight returned?

      And there is always the possibility of a sensor for which everything was done right, i.e. properly shielded, aspirated, located and calibrated --- but then it just goes bad.  Temperature sensors are robust, but anything can break.
     When did temperature readings from the two stations begin to diverge?  An abrupt change in readings for one of the sensors could indicate equipment malfunction.

148
That's an interesting diagram, oren!  The one thing that isn't intuitive for me, though, is why the initial longwave energy emitted from the surface is 110 units.  Where does that come from? 
      Way outside my lane and just my understanding, but in case it's useful:  It is counterintuitive to see 110 emitted when only 89 were supplied, and thus a -29 deficit.  Everything has to balance in the end, so who makes up for those -29?  My guess is that shortwave energy that reaches the surface, is absorbed and converted to longwave (infrared), and then reemitted upward from the surface, makes up that difference. 

      That means that the Earth receives more shortwave than it emits, and emits more longwave than it receives.  The net energy has to balance, but within the total energy budget, energy from one wavelength bucket can translate into energy in another wavelength bucket, i.e. from shortwave to longwave. 

      A black tar road receives a lot of downward shortwave and a lesser amount of downward longwave radiation.  The shortwave is absorbed and converted to longwave, and the tar road emits a lot of longwave back up (the road gets hot in the sunshine).

      My objection to Walrus' statements is not so much about the unsupported statements about a specific mechanism that this discussion has evolved into, but conflating the "warmest temperatures of the year" to overall cooling, and using the comparison of 1986-2015 vs 1900--1960 observations to conclude that the current change is towards cooling, esp. when the projections looking forward show increased warming for all measures, including for warmest day of the year. 

      The original question was about why a specific location would be warming less than the rest of the planet.  The Tamino article addresses that very question with his usual superb skill, including a discussion of and links to recent peer-reviewed studies for anybody who wants to go into it at depth.  I assume that if Walrus' hypothesis had any credence, then the articles that investigated the southeastern U.S. "warmhole" would have included discussion of that as a factor, and that it would have thus shown up in Tamino's summary of the findings of those studies.  But it does not appear in that discussion, which is not surprising because if it were true it would apply everywhere and would not be a localized regional influence.

       I have not confirmed that assumption and not interested enough to do so.  But if somebody wants to, that would one way to close the book on Walrus' hypothesis.

149
     Thanks binntho.  A simple "Like" wasn't enough gratitude for your taking the time to stand up for fact-based evidence. 
      Nobody needs to get their feelings hurt.  Some ideas are correct and hold up, some not.  You don't know until you ask a question or propose an answer.  That is core to the scientific method.  It can't answer every question but it is the best method we have, esp. for addressing objective, physical questions.  Tamino provides the definitive discussion of the "warmhole" question.  I hope the Stupid Questions thread can move on. 

150
     My statement about a "minority of U.S." was with respect to and true for the summer temperatures graphic, it was not referring to the warmest days graphic.   

      RE "The warmest temperatures of the past two decades in the U.S. are below those of the first two decades of the 20th century.  That precedes the dust bowl!"
     Not true.  The comparison for the warmest days image is 1986-2016 vs 1901-1960.  Thus the comparison to earlier years includes all of the dust bowl years. 

     The reason for my objections to your argument is your assumption that "just because the warmest temperatures are not increasing."   Yes they have increased if the reference point is warmest temperatures of the day, i.e. average daily max.  Only looking at the extreme warmest day of the year leads to a distorted impression.  That is why folks are giving you grief about this. 
   
      And by putting it in the present tense you imply that those warmest day of the year temperatures are not increasing at present.  But you have not shown data to support that. The data you cite are observations over two extended periods, not the current rate of change.  To the contrary, the trend forecast estimates that the warmest temperature of the year will be higher in the future. 

      Neither of us have shown data about the current rate of change for warmest temperature of the year.  I am saying that a) we need a comparison of more recent data to evaluate that question and b) that the warmest temperature of the year is not the real story anyway, and focusing on that narrow measure obscures the larger issue.  Your stance seems to be that past observations for warmest temperature of the year represent their current rate of change, which they do not.  And that the warmest temperature of the year deserves more attention than broader measures, with which I simply disagree.

Pages: 1 2 [3] 4 5 ... 9