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Messages - Glen Koehler

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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.

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!

Arctic sea ice / Re: The 2020 melting season
« on: July 27, 2020, 09:05:17 PM »
Sea Ice Prediction Network for September outlook.
    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.

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.

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

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.   

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'.

   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.

Welcome back binntho. Excellent post.
+1 :)

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.

     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,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.

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

     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,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.

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.

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.

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?

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.

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.

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.

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 20, 2020, 04:53:59 PM »
     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. 

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 19, 2020, 05:37:28 PM »
     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.

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 19, 2020, 04:32:17 PM »
<snip> The data supports the hypothesis.
     Only in a narrow cherry-picking view.  Your narrow focus on the extreme events in one region is misplaced. 

     The observed summer-only temperature observations show only slightly cooler in a minority of U.S. (note: even the light peach-colored areas in the Southeast were warmer, only the areas in blue were cooler relative to earlier in the century)

     Moreover, the narrow focus on the warmest days of the year is temporary.  All areas are expected to show higher temperatures on the warmest days of the year going forward.

    The focus on observed extreme high temps in one region misses that point that AGW is making the planet hotter in ways that are not good for human civilization and most other existing species. 

    A wider view that does not focus on the exceptional case is more accurate.  Here are the observed regional U.S. changes in max and min daily temperatures.  All the regions show increase for both daily average Max and Min temperatures.

      And that slightly wider view is still narrowly focused on one country.  The global picture is even more compelling.

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 19, 2020, 04:21:06 PM »
What's causing Arctic amplification?

      Thanks KiwiGriff.  Your post deserves more prominence than the "Stupid Questions" thread. 
       It speaks to the centrality of the ASI to the future habitability of our planet... sooner than most people realize.  What happens when we start hitting BOE in September, then BOE in August and October a couple of years later?  With July (with near peak insolation) next up on the stove.  And before each month reaches BOE, EVERY month trends toward more open water and lower albedo. 

      IMHO we are very close to even more dramatic ASI loss acceleration.  That in turn poses major risk of systemic shifts in the weather patterns that we depend upon for agriculture and everything else.  By soon I mean that 2030 is looking bad.  Even that is an understatement given that we have already lost >75% of the September ASI volume, so 2020 is already bad.  But the situation is likely to get much worse in the next 10 years unless we act forcefully in the right direction.  I hope we all vote and act as if we are in a planetary crisis, because we are.

Arctic sea ice / Re: The 2020 melting season
« on: June 19, 2020, 03:48:56 PM »
June 14-18.2019.
The CAA is simply swamped with melt water.
Nares also
As we reach peak insolation...

Source: www-grida-no—graphicslib

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 13, 2020, 04:04:55 AM »
       RE June 17 pressure system forecast at

Questions for those with meteorological knowledge: 
      What keeps those multiple adjacent low pressure systems on the Russian side from converging into one big low pressure system? 
      Or the multiple high pressure systems on the North American /GIS side from converging into one big high pressure system? 
      If either set did converge, would the intensity of the resulting combined system be more or less intense? 
      And if both the Russian/low and North American/high groups consolidated, would that create a Titanic dipole?

Arctic sea ice / Re: The 2020 melting season
« on: June 13, 2020, 03:29:05 AM »
      Alternate views of GFS snow depth forecast:  June 12, 18Z

      Poof!  June 17, 18Z

      The June 17 image also shows good view of dipole.  The positioning looks conducive for clear sky over Pacific side and some ice movement away from the ESS and Laptev Sea into the CAB.  But neither the high pressure or the low pressure system are very strong so wind speed where they meet should not be very strong, thus fairly wide spacing between isobar lines.  (My attempt to interpret the image for those even less familiar with pressure maps than me.  Caveat: I am not a meteorologist, I just play one on the internet). 

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 11, 2020, 04:07:58 PM »
     I do not have a clear understanding of why a dipole weather pattern over the Arctic is so influential for ice melt.  Here are my guesses:

     1.  High pressure system over the Pacific side of the Arctic creates clear skies and thus higher insolation and thus greater direct exposure of ice surface to solar radiation and thus greater surface melt.

     2.  High pressure over Arctic results in downward moving air mass with warming temperatures reaching the surface.

     3.  Low pressure system paired with high pressure system creates a wind tunnel where the two systems meet.  When oriented to create a strong Pacific to Atlantic wind field, this pulls ice away from the Pacific side and into the Atlantic side where it is closer to export out of the Arctic.
Ice already on the Atlantic side is pushed toward exit via the Barents Sea and out the Fram Strait into rapid melt zones?

      4.  Strong wind field disrupts (what is left) of the Beaufort Gyre nursery for growth of multi-year ice. 

      5.  A strong coherent wind field caused by a dipole creates more Ekman pumping, reduces thermocline layering, and brings heat from deeper levels to the surface?

      6.  Strong winds in any direction move the ice around more, creates more wave action, increases fracturing, and thus more surface area exposed to melt through direct contact with sea water?

      7.  Dipole pattern brings in large volume of warmer air from the lower latitudes into the Arctic, displacing normally colder Arctic air mass?

      8.  Dipole pattern also brings in large volume of moist air that has higher heat carrying capacity?

     These are questions, not statements.  Which of them are accurate?

     Inside Climate News article on aerosol drop impact on Arctic sea ice

     "Overall, this winter wasn't particularly warm, but now that's flipped around in the last month and we're really seeing the effects," says Mark Serreze, director of the National Snow and Ice Data Center (NSIDC). "Big holes are opening up along the Siberian coast where it's been the warmest."

     "This Central Arctic heatwave may not be a one-off event only occurring in spring 2020, researchers suggest. Rather, if levels of global industrial air pollutants continue to fall due to the Covid-19 pandemic, the current Arctic warmth could be a bellwether of what's to come later this summer when sea ice melt annually kicks into high gear."

     "Indeed, in a 2017 study, scientists posited that the sulfate aerosols released due to human activity masked the decline in Arctic sea ice in the mid-20th century, before the Clean Air Act went into effect, and actually led to periods of ice growth."

     "Using earth system computer modeling, his simulations showed that sulfate aerosol reductions in Europe since 1980 could potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic received approximately 0.3 watts per meter squared of energy, warming by 0.9 degrees Fahrenheit on average as Europe's sulfur emissions declined."

     " "We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and the Arctic climate are inherently linked," his 2016 Nature Geoscience study stated. "

Arctic sea ice / Re: The 2020 melting season
« on: June 09, 2020, 07:58:15 PM »
      Based on Climate Reanalyzer graphs of GFS, the Beaufort Sea ice is in for a rough week with surface temps, clear skies and precipitable water incursions all pointing towards accelerated melt. (light blue = clear sky above ice)

Arctic sea ice / Re: Latest PIOMAS update (June 2020)
« on: June 09, 2020, 02:44:37 PM »
    Thanks Uniquorn.  I think the animated 2010-2020 thickness map is the single best tracking tool we have.  I hope you keep doing them.  The timings were perfect for watching repeatedly.

Arctic sea ice / Re: The 2020 melting season
« on: June 08, 2020, 04:59:24 PM »
The DMI 80N shows the temp curve remaining below 0C. We seem to dodge the bullet of a prolonged peak on the front end.
   DMI 80+N temp chart is observations not forecast.  And a biased one at that.  Moreover, during melt season the surface temperature is essentially capped near the freeze/thaw point as energy goes into melting ice not raising air temperature.  Thus even during a strong period of melt those temps will stay near freezing as long as there is still widespread ice to melt.

925 mb temp anomalies for May 1- June 5 in the selected years 2012, 2016, 2019, 2020. 

     Thanks JayW - the 2020 anomaly is stronger than what I expected.  As Niall cautioned, I don't know how closely the 925hPa correlates with surface impact, but seeing the big dark blob of red for 2020 really makes me wonder about the current preconditioning state of the ice, and what that suggests is coming, as igs noted upthread about a potential cliff. 

     I agree that qualitative condition deserves more attention.  I suppose thickness and concentration serve as qualitative metrics.  But thickness is intermittent and concentration is about relative measures of surface coverage not the physical state of the ice.  I'm wondering if there are other qualitative measures, such as a measure of ice continuity and pack integrity.  Perhaps an index that goes from 1 for completely solid continuous ice to near 0 for completely fractured rubble.  Is there anything like that?  I also haven't seen a melt pond roundup for May yet.   

Arctic sea ice / Re: Arctic energy balance
« on: June 03, 2020, 02:24:42 AM »
Thanks Freegrass.  That Total Precipitable Water video explains a lot of ecosystem/habitat variation around the planet.  In particular the grasslands of central and northern Asia, and why the polar regions are considered deserts despite being dominated by water ice.  It also demonstrates better known moisture habitat relationships like the Amazon and central African rain forests.  And finally it demonstrates the intermittent and somewhat random, but over time, reliable variation between wet and dry that supports agricultural regions in the mid-latitudes.

Arctic sea ice / Re: The 2020 melting season
« on: May 29, 2020, 12:54:02 AM »
Again, on the topic of the Kara sea. Here's a zoom in. 24./26./28.05.
       Thanks for those superb and highly informative images blumenkraft.  Am I correct that the reported Extent and Area values for that location on those three days is likely to show virtually no change?  Yet the change is dramatic when ice quality and thickness is considered.  That is the monster hiding under the bed for ASI loss.  It doesn't change much for a long time as it absorbs energy and rots out .... and then it falls prey to some intermittent melting event.

        A similar point (albeit in a far distant context) about smooth model projection tractories vs. the bumpy ups and downs of what actually happens is made in a short video by Peter Sinclair
       That may seem off-topic, but my point is that the same principle applies to Arctic melt and is becoming increasingly relevant as 2020 early season conditioning softens up the ice for a potential sucker punch later.  Because of the ways we measure/perceive changes, they don't make an impression until a threshold is exceeded and then change seems to erupt suddenly.  But it was building all along.

       Loss of MYI was strike 1 of 'below the surface' change.  Thickness decline leading to structural weakness, fracturing and increased mobility is strike 2.  Strike 3 is when the rot is no longer hidden.

       As Juan Garcia's tag line says, Extent losses mask the other dimension of Thickness loss which is not as intuitively apparent to our visually based monitoring.  Thus, an entire dimension of ASI decline is essentially hidden, and accumulates with less notice.  Then another GAC (or current forecast for large areas of clear sky within 24-->10 days before solstice, comes around and Wham!, a whole lot of built-up change potential suddenly becomes manifest, appearing as a dramatic new event even to folks who have been watching all along. 

       I'm preaching to the choir of course, and not revealing anything new to the people who come here.  But those pictures compelled me to comment on ice condition as an under-appreciated dimension, and as the defining characteristic of the 2020 melt season so far.  Call me Chicken-Little, but that ice looks dangerous.  And the records indicate that reaching that condition in May is anomalously early for the Kara Sea.

       All of which is a long-winded way of saying what A-Team (I think) once said.... one of these days... the ice will go "poof."  The nature of complex, interactive, chaotic systems is to not see change coming until it suddenly happens.

Arctic sea ice / Re: Nullschool Forecasts
« on: May 28, 2020, 05:32:25 AM »
       FG - I'm not asking for a seminar, or an explanation of the reasoning for your alarm, just the name of the thing that grabbed your attention.  Is it the wind?  The temperature?  Particular locations? Precipitable water?  Is it a strong low-pressure system near the Bering Strait?  Or high pressure dominating the CAB?

       Since the image clips don't show the scale legend to allow interpreting what the colors mean, and since most of us won't bother to go over to NullSchool to find the legend bar, the colors in the images are intriguing but not quantitatively informative.  If you are referring to temperature in a certain region, use your text message to tell us how high they are such that they grabbed your eye.

       If you just say "Oh My God!" with no text to identify what it is you are referring too, and post an image without a legend, it may not be clear to us what has your attention or what the image is representing. 

       Yes, we can watch the clip and get some sense of it, especially if we are used to NullSchool images.  So it's not that the images are useless without some explanation and a legend.  But if you are going to the trouble to make a clip, why not gift wrap it just a little bit to make it more meaningful? 

       When this is all in the history books, and your great grandchildren are looking back at what their 'Oompah' did during the great meltdown of 202?, make them proud.  Until then, thanks for your efforts.  I enjoy the freshness of your wonder and curiosity, and have learned from your queries.  Like you, I am a non-expert tuning into this drama, and just trying to figure out what's going on.  Even though it is a horror show when you consider the larger implications, it is a fascinating process to watch.

Arctic sea ice / Re: The 2020 melting season
« on: May 24, 2020, 09:14:14 PM »
Slater's model has picked up the current preconditioning  and thinks it is favourable for strong melting way into July.
It predicts 7.34 m km² for July 13th, currently nosediving ...

   Wow, if that forecast verifies, then 2020 would be 600K and 8% below the previous records for July 13 Extent in 2019, 2016, 2012. 

    It is useful to have Phoenix provide a skeptical check on habitual ASIF catastrophism (as in "this year is the big one!"), but it is also true that 2020 has come out of the gate strong, and that the current Extent and Volume numbers do not yet reflect the preconditioning that has occurred.  In addition, the current GFS forecast shows surface temperature for most of the Arctic Ocean above 0C from May 29 - June 3, combined with substantial areas of clear sky and what seems to be high amounts of precipitable water along the Atlantic front and north of Greenland (but I lack the historical perspective to interpret the precipitable water forecast).   

    I worship at the church of the long term linear trend, which has the 2012 volume record remaining intact for 2020 but then a ca. 50% chance of falling in 2021, and increasing each year thereafter.  For Extent, the trend estimate shows the 2012 record being safe for 5-10 years.  While it is far too early to say anything definitive about 2020, considering the recent conditioning, the current GFS forecast, that scary albedo graph posted by Sublime_Rime, and the Slater model forecast (which has been pretty accurate in recent years), 2020 seems to have a greater than 50% chance of going below the 2012 volume record.  The Extent record from 2012 was due to a freak event (the GAC) that is unlikely to be repeated in 2020, so is less likely to be surpassed.  But that is less important anyway, as I also worship at the church of Volume vs Extent with the Rev. Juan C. Garcia.

Arctic sea ice / Re: The 2020 melting season
« on: May 24, 2020, 03:07:34 AM »
       A while back Stephan calculated the R values for Volume and Extent at the end of each month to the following September minimum.  Accepting a few assumptions (that seem reasonable), squaring those values gives the R2, a measure of the percent of interannual variation that can be explained by knowing those values, and thus reducing the width of the confidence interval for estimating the subsequent September minimum.,2348.msg257955.html#msg257955

Improved Volume prediction accuracy as melt season observations become available. 
R-square reduction in variability derived from R values posted by Stephan at

        Linear model estimate for 2020 September average Volume before any 2020 observations:  3.9M (1.2 – 6.6) km3, (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.

      Those values indicate that until we have the end of May, and really the end of June, volume observations, prior observations don't give us much foresight about the September volume minimum.  Which in turn suggests that melt season conditions (temperature, cloudiness, and storms) that take effect in June, July, and August are the primary determinants for the September volume minimum.  (Some of those conditions, such as melt pond formation, may have been established earlier, but do not manifest as changes in volume until after May 31).  Thus, about 68% of the variation in September minimum Volume becomes apparent after May 31 (100% minus 32% = 68%).

     The same approach for Extent shows the R2 at the end of March, April and May at insignificant level, only reaching 22% by the end of June, and 56% at the end of July.  Thus, changes that manifest in July and August account for 78% of the variation in September minimum Extent (100% minus 22% = 78%).   

      An expert analysis by Walt Meier and NSIDC concluded  “Plotting the de-trended maximum versus minimum extent (Figure 2) shows a near-random distribution.”  “The seasonal maximum extent and the September minimum extent are not correlated...“  "because summer weather conditions strongly shape the September minimum.”

Figure 2. This plot compares de-trended maximum extent (x-axis) with minimum extent (y-axis). The yearly values shown are calculated by subtracting the linear trend value for that year from the total extent.  Credit: W. Meier, NSIDC.  From “Maximum extent is not predictive of minimum extent”

Arctic sea ice / Re: The 2020 melting season
« on: May 24, 2020, 02:45:30 AM »
      FWIW - Useful to clarify the question and frame of reference.  Phoenix puts more emphasis on conditions that affect the ice in the CAB and along the northern edge of the CAA that is considered likely to be the last to succumb to September melt.  Other folks generally refer to conditions for the Arctic overall. 

       So another question within the discussion is to what degree is the "last to go in September" ice isolated vs connected to conditions in the larger Arctic system.  For example, if the Kara Sea gets roasted early this year, as appears to be the case, how much does that affect the overall ASI September minimum?

Arctic sea ice / Re: Freeform season chatter and light commentary
« on: May 23, 2020, 01:01:53 AM »
      Good to see those neighbors keeping a six-foot distance between them as they reconnect after a long winter.

Arctic sea ice / Re: The 2020 melting season
« on: May 23, 2020, 12:33:55 AM »
Stopped being lazy and checked and the low was heavily influenced that year because of the Mackenzie.

     I haven't given much attention to the effect of river discharge on the Arctic sea ice.  While the warm outflow of a big river seemed important for impact on the ice near the river delta, it seemed too small to matter much to the big picture, e.g. heat content of the entire Arctic Ocean, or even to the entire Beaufort Sea.  But these statements from the paper linked by Error refute that:
     "The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean"

     "...the volume of the total discharge over the 3 week period is equivalent to a layer thickness of 0.19 m of warm waters across the entire open water area of 316,000 km2"
     (ed.  The area of the Beaufort Sea is 178,000 km2)

      "The warmest waters were observed near the coast of the Mackenzie Delta, e.g., 13°C at 147 km, 10°C at 287 km, 8°C at 350 km, and 2°C as far as 456 km from the Mackenzie River mouth"

     "The Mackenzie River has an enormous watershed of 1.8 million km2 with the southern extent reaching to 52.2oN. This watershed is primarily within the continental climate regime, and the heat can be intense in summer when the maximum temperature may reach 32°C around latitude 53°N (e.g., Edmonton, Alberta, Canada). Fresh and warm Mackenzie waters reside in the surface layer with the attendant high thermal capacity thus contributing excessive heat to melt sea ice, most effectively when the sea ice cover has been fragmented "

     "In addition to the Mackenzie, there are a number of other large rivers that discharge into the Arctic Ocean. Notable are the Yukon, Ob, Yenisei, Lena, and Kolyma Rivers, each with its immense watershed under a continental climate regime providing massive discharge of warm waters into the Arctic Ocean or a peripheral sea to melt sea ice in spring and summer. "

     "This massive discharge carries an enormous heating power of 1.0 × 1019 J/yr for each 1°C of the warm river waters above freezing, equivalent to 2.5 gigaton of trinitrotoluene (TNT) per °C per year. "

     "In the summer melt season, warm river waters, for which the temperatures can be higher than 10°C, contribute directly to melting sea ice. In the fall season around the time of sea ice freezeup, surface waters cool while the halocline stratification insulates the surface from the deeper seawater, allowing more sea ice to grow. At the same time in the fall, rivers also start to freezeup, drastically reducing the river discharge. Thus, to be an effective insulator, the stratification needs to be persistent to maintain the surface layer consisting of a large mass of fresh river waters that already discharged into the Arctic Ocean earlier in the summer. Such maintenance of the stratification requires calm‐ocean conditions without significant mixing throughout the summer to fall freezeup. In summer 2012, the violent storm significantly enhanced ocean mixing that transported ocean heat upward and further contributed to sea ice melt "

Arctic sea ice / Re: Nullschool Forecasts
« on: May 21, 2020, 03:14:14 PM »
      FG  and others - when you comment on a benign or threatening forecast, please specify what it is you are referring to.  Otherwise, I may not be able to see what you are seeing, and I suspect neither do a lot of other people.  Sorry to nag, but this has happened a lot lately by various posters - noting something extreme or of supposed importance without specifying what it is. 

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: May 20, 2020, 11:45:52 PM »
      Thanks, that's a good paper.   A lot to digest.  They focus on summer and early fall.  It seems like more open water in fall and winter would also lead to greater heat loss, thus functioning as a negative feedback.  But also that a higher cloud cover would work against that by reflecting more longwave radiation back down.  Lots of counterbalancing forces in a complex system. 

       Reminds me of my son describing the existence of "deterministically chaotic" systems today.  It seemed like a contradiction in terms to me, but as he explained it a system can be both deterministic AND chaotic, which means that it is unpredictable until you calculate each step between here and there.  Maybe the Arctic melt works like that.  We won't know until we get there!

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: May 20, 2020, 03:19:01 AM »
This means SOLAR ALTITUDE just isn't high enough until the first week of June to overcome albedo.

This means we well have to see background temps warm likely another 2-4C around the ice in May and snow cover to vanish at least a week earlier than the current earliest before we see ice volume sustainably go lower than it already has.

This means a total melt out isn't likely until 2035-2040 or later

      I get the main point, even though the details within the reasoning are beyond my skill set.  And the basic point makes intuitive sense.  But I am truly asking, not arguing:
     Does your analysis fully account for the fact that the rules of ice melt are changing as thick MYI ice has been replaced by thinner saltier FYI, and even the FYI is getting thinner from year to year? 

     My gut (and linear regression of the Sept. volume trend, which I beat to death upthread) tells me that there is an exponential iterative process unfolding by which weaker ice begets more open water, lower albedo earlier in the season, warmer weather patterns, more storms, longer wind fetch, more ice mobility leading to export.  All of which leads to acceleration of ice loss. 

     Of course, my gut hunches aren't analysis, and are subject to overlooking major counter-arguments like the Chris Reynolds long slow decline scenario.  But I don't buy into that theory (no need to get sidetracked by why in this message).  I have a harder time discounting Notz and Stroeve 2018, who have PhDs in this stuff, swim in the data 365 days a year, and write deep articles about it that come up with the same 2035-2040 timeline as you stated or even later. 

     But I'm still wondering if the seasonal procession of solar angle (the one thing still operating normally in this topsy-turvy world) is enough to rule the system for a relatively incremental orderly dissembling of the ASI, when the stuff that the sun is shining on is changing so rapidly from year to year.  Rapid evolution in the receiving end of the solar energy <--> ice melt equation leads me to think that one or more abrupt, chaotic, or nonlinear qualitative process(es) will emerge and take over before many more years of weakening of the ice. 

      In other words, I see the "ice" hitting the fan by 2025-2030 with the next big warm anomaly and high Arctic storm activity year.  My scenario has 2035 beyond the far end of a plausible 1st BOE date, whereas the 2035-2040 estimate keeps it out of reach until at least 2035, and probably later.  I hope I'm wrong.

     Either way, at some point in the not too distant future, humanity will slap our foreheads in a collective Homer Simpson "D'oh" (as if we weren't warned and didn't see it coming).

Arctic sea ice / Re: The 2020 melting season
« on: May 19, 2020, 11:12:09 PM »
RE long-term arctic sea ice volume deviation chart,2975.msg264869.html#msg264869

     Thanks Stephan.  I don't have the foresight to make Sept. predictions, but I'd bet dollars to doughnuts that the upside anomaly in the current chart will fall back a lot closer to the long-term trend line when the May 2020 volume data are included.

Arctic sea ice / Re: The 2020 melting season
« on: May 18, 2020, 07:11:03 PM »
    Excerpts from:  The Largest Arctic Science Expedition in History Finds Itself on Increasingly Thin Ice.  By Michael Kodas. May 17, 2020 in Inside Climate News. 
    The statements below from a great article about the MOSAiC expedition give insight to the current state of the ASI and the 2020 melt season to date.  The article appears to have been written when the May 11-15 weather was in the forecast, but had not happened yet, so the effects of that weather were not known.  The May 11-15 "clear-sky / warm-up / Fram-flush" almost certainly exacerbated the conditions described in the article.

     " Even before the expedition had finished setting up its camps and instruments in November, the ice started cracking. Then, a storm sent huge rifts through the floe and knocked out the power system for several days. Cracks revealing open water repeatedly isolated Met City, sometimes forcing researchers to walk for more than an hour around the fissure to reach the site, a few hundred yards from the ship.

     "We just didn't know that we were going to face this much cracking," Shupe told me. "It really did take us by surprise, even though we knew the ice was thin, we knew the Arctic was different, it still snuck out ahead of us somehow." "

     " An unusual weather pattern, which included the opening this spring of the largest ozone hole ever measured above the Arctic, produced winds that pushed MOSAiC's ice floe across the pole much faster than the expedition's organizers expected.

     "We have this kind of flow regime in the Arctic right now that's been really static," Shupe said. "It's stuck where it is and it's blowing us across the Arctic faster than anticipated, faster than any of the past 12 years that we used in our analysis to figure out where we would go." "

     "Maybe the ice would slow down or even reverse direction, as it had early in the expedition, he thought. Colder weather might freeze some of the leads of open water that had fractured MOSAiC's floe. Maybe the ice would stabilize. But, increasingly, Shupe was having to come to terms with the fact that the ice floe he had hoped would be the expedition's home for a full year was unlikely to survive the summer.

     "I went into it ready to be surprised, and it still got out ahead of me," he told me. "How fragile the ice has been. I knew it was gonna be thin, but it's still thinner and more fragile than I thought it would be."  "

Arctic sea ice / Re: The 2020 melting season
« on: May 18, 2020, 02:55:53 AM »
RE AMSR2 image:
The "dark areas" are of course also much more prominent than usual, or so we seem to think, but I think I've learned the lesson some time ago not to take those too literally. Althogh one does wonder if some sort of Bluecheesefication is underway as well?

    There may be something to "Bluecheeseification".  If the wispy gray-dark areas over the CAB in the AMSR2 image are in fact indicating high moisture content in the air, that does not necessarily make it disconnected from the ice condition.  Because where did that moisture come from? 

    My first guess was that it's just part of the weather system, some air masses more moisture than others.  If so, then the air moisture would be a misleading signal not connected to the condition of the ice.  But now I'm wondering if perhaps those darj areas are showing higher air moisture caused by surface melt or lower concentration ice with more openings to allow communication of CAB water to the air above it.  Total speculation of course.  But it fits with the Bluecheeseification idea.

Arctic sea ice / Re: The 2020 melting season
« on: May 16, 2020, 01:47:20 AM »
    Ditto ArcticMelt2, thanks for the WAPost article and also those ice thickness images.  They could have spiced it up with some ASIF quotes from the Fabulous Friv.  It is a credit to the ASIF that the experts quoted in the article didn't add to what has already been noted in greater detail in the forum.  Good to see a major US press outlet paying attention to news that matters vs the latest ramblings of the mad King.  Actually, the WAPost climate team led by Chris Mooney is among the best of all the major newspapers/magazines.  Mooney even did a story about Neven and the ASIF back in 2016:

     Comparing the 2012, 2019 & 2020 sea ice thickness images, the one strength 2020 had was the thick ice near the Fram Strait.  That is the very ice that was presumably pummeled by the warmth, sun, and WIND this week.   2012 and 2019 each had a long arm that may have impeded Arctic-wide rotation.  2020 lacks that structural brace.  I don't know if Arctic-wide ice translocation is affected by the distribution of thick ice at that scale.  The significance of that pattern could just be a visual figment of my imagination.  (Or as Pete Walker said: a "Fig Newton of my immaculation") 

     The last 7 days of the current GFS shows Kara Sea temps consistently above 0C.  Not much clear sky & direct sun in that forecast, but the clouds bring some rain (too warm for snow) to deliver additional thermal energy to the surface.  All of which leads to forecast zero snow cover in the Kara by May 24

    The Kara is already running below previous years (,2975.600.html#lastPost thanks to Gerontocrat).  Putting that together with the forecast suggests that by June 1 the Kara could be in unprecedented condition.

    The Barents Sea hardly seems to matter since any ice in it is doomed anyway.  But FWIW, Earth Nullschool shows continued low-pressure system winds scouring it out for another day or two.  Does it make much difference to clear the lanes for more export out of the CAB?  Erosion of the ice on the CAB - Barents border can't help.  At least the great Fram Flush of early 2020 has ended. 

     Following up on Freegrass's tiptoe through the tulips of DMI images, looking at the DMI temperature graph for every year since 1958 shows that this early-mid May warmup has no real match in previous years. 

     It seems like every year the ASIF gets all heated about impending ice doom.  2020 so far is providing some hard numbers in that direction.  Yes, it is still early, but as wiser watchers have noted, it is the early momentum that sets the stage for the rest of the melt season.  True enough that a basin-scale clear-sky event would be worse if it happened 2-3 weeks from now and closer to the solar max.  Then again, decreasing albedo well BEFORE the solar max increases the impact of reduced reflection of solar radiation. And having a clear-sky event early does not preclude having another one later.

Arctic sea ice / Re: The 2020 melting season
« on: May 11, 2020, 01:29:27 AM »
... and add this to the pile
    Check out the forecast change in snow depth at
    I suppose that happens every May and I don't have the experience to say how the current forecast compares to the normal rate of snow depth decline, but it looks like a big drop over a 10 day period.

    It will be interesting to how this multifaceted weather assault will affect the Extent and Area stats over the coming week.  It also looks like conditions that promote melt pond development which Neven and others have pointed to as a factor that influences that the longer-term melt season.  And it makes me wonder whether the MOSAIC experiments that were left in place will still be there when the Polarstern gets back.

    PS The cumulative precip forecast supports the "clear sky under the high-pressure system" interpretation mentioned previously.

Arctic sea ice / Re: The 2020 melting season
« on: May 11, 2020, 01:14:23 AM »
    Climate Reanalyzer GFS
and Earth Nullschool,45.21,332
   a) Strong positive temperature anomalies for next week over most of the Arctic Ocean (ArcOc)

   b) Surface temperatures warm enough to advance ice melt over large areas of ArcOc

   c) A persistent high-pressure system over the ArcOc for the next week or more, resulting in what I interpret to be large areas of clear sky -- during mid-May with solar shortwave radiation within 6 weeks of annual max, thus beginning of the 3-month period of highest solar gain.  (The color scheme is subtle but if I remember correctly, the CR creator told me the light blue indicates clear skies over ice.)

   d) A persistent low-pressure system east of NE Greenland that creates a strong windfield on May 10-13 for increased Fram export.

     Any one of these four would be noteworthy on their own.  The combination seems remarkable.   

Arctic sea ice / Re: The 2020 melting season
« on: May 09, 2020, 07:14:24 PM »
So, it sure looks like someone's lying: either those who said "no meltponds there", or whomever said "after mid-April melt ponds confused the sensors".
Ditto I hope you keep participating, but Oren was correctly moderating.  Now let's get back to the weather and ice...

Arctic sea ice / Re: What's new in the Arctic ?
« on: May 09, 2020, 01:53:44 AM »

Arctic sea ice / Re: What's new in the Arctic ?
« on: May 09, 2020, 01:51:58 AM »
Tschudi, M. A., Meier, W. N., and Stewart, J. S.: An enhancement to sea ice motion and age products at the National Snow and Ice Data Center (NSIDC), The Cryosphere, 14, 1519–1536,, 2020.
   "...Overall, ice speed increased in Version 4 over Version 3 by 0.5 to 2.0 cm s−1 over most of the time series. Version 4 shows a higher positive trend for the Arctic of 0.21 cm s−1 per decade compared to 0.13 cm s−1 per decade for Version 3 (ed. note:  Thus the new estimate of acceleration in sea ice motion is about 10% per decade).

      The new version of ice age estimates indicates more older ice than Version 3, especially earlier in the record, but similar trends toward less multiyear ice.

     Changes in sea ice motion and age derived from the product show a significant shift in the Arctic ice cover, from a pack with a high concentration of older ice to a sea ice cover dominated by first-year ice, which is more susceptible to summer melt. We also observe an increase in the speed of the ice over the time series ≥ 30 years, which has been shown in other studies and is anticipated with the annual decrease in sea ice extent.


Arctic sea ice / Re: PIOMAS vs CryoSat
« on: May 05, 2020, 11:08:51 PM »
    Thanks uniquorn.  I found that, but I could not deciper what the o-like symbol (which to me means sigma & 1 standard deviation), represents on that scale.  -5 to -30 what? 

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