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Messages - Glen Koehler

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101
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

102
       RE June 17 pressure system forecast at http://204.197.0.55/MEmodel/ArcticSnowCover18Z2020-06-17.png

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?

103
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
http://204.197.0.55/MEmodel/ArcticSnowCover18Z2020-06-12.png


      Poof!  June 17, 18Z
http://204.197.0.55/MEmodel/ArcticSnowCover18Z2020-06-17.png

 
      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). 

104
Arctic sea ice / Re: The 2020 melting season
« on: June 13, 2020, 02:56:59 AM »
        GFS cloud cover forecasts.  Granted these are 9 and 10 day forecasts, but the near-term forecast images show almost as much clear sky.  I just wanted to see what it looked like at peak solstice insolation.  Light blue is clear sky over ice.

         2 hours past solstice hour June 21 at 0Z
http://204.197.0.55/MEmodel/ArcticClouds0Z2020-06-21.png
           Lots of clear sky and insolation over much of the Pacific side and ca. 33% of the entire Arctic Ocean (eyeball estimate).

42 hours later June 22 at 18Z
http://204.197.0.55/MEmodel/ArcticClouds18Z2020-06-22.png
           Even larger area of clear sky, covering ca. 60% of Arctic Ocean.


105
      From NSIDC September 2012 seasonal summary:
http://nsidc.org/arcticseaicenews/2012/10/poles-apart-a-record-breaking-summer-and-winter/

      'Weather conditions prevailing over the summer of 2012 were quite different from those in 2007.  The summer of 2007 featured unusually high sea level pressure centered north of the Beaufort Sea and Greenland, and unusually low pressure along northern Eurasia, bringing in warm southerly winds along the shores of the East Siberian and Chukchi seas (3 to 5 degrees Celsius, or 5 to 9 degrees Fahrenheit above normal), favoring strong ice melt in these sectors and pushing the ice away from the coast, leaving open water.  The pressure pattern also favored the transport of ice out of the Arctic Ocean and into the North Atlantic through Fram Strait.

     In contrast, the summer of 2012 saw unusually low pressure along the Eurasian coastal seas and extending eastward into the Beaufort sea, most prominently over the East Siberian Sea, with unusually high pressure centered over Greenland and the northern North Atlantic. Air temperatures for summer 2012 were above average over most of the Arctic Ocean (1 to 3 degrees Celsius, or 2 to 5 degrees Fahrenheit), most prominently over the Beaufort Sea, where, because of the pressure pattern, winds were anomalously from the south.

     Melt began two to three weeks earlier than average in the Barents and Kara seas, leading to earlier retreat of sea ice in the region; however, air temperatures remained below average during summer in this region. This points to the impact the continued loss of old, thick ice is having on the ability of the sea ice cover to survive summer melt. Other than the August storm, the pressure pattern in 2012 does not appear to have been as favorable in promoting ice loss as was the case in 2007, and yet a new record low occurred."

(Siberia on left side, Greenland on right, Bering Strait at the bottom)

106
     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?
       

107
Arctic sea ice / Re: MOSAiC news
« on: June 11, 2020, 03:49:24 PM »
   Thanks uniquorn.  The May 15 Fram export event shows as a very brief pulse, but what was going on from mid-March though ca. April 5?  The buoys were moving fast for several weeks.  I don't remember any dramatic weather at that time.

108
Hi FG - My guess (and that is all it is) is that aerosol reduction could also cause increased radiation losses out to space during the winter as the aerosols can also add to the insulating effect of the atmosphere, thus fewer particles = less insulation = more winter heat loss. 

      During the 24 hour nights of polar winter there is no counteracting cooling effect of aerosol particles reflecting incoming shortwave radiation.  So the cooling effect, which dominates during summer is not active during winter.

      But I don't pretend to understand the details of these interactions, just thought I'd take a shot it since you asked.  It would be great to get an answer from somebody who studies this stuff.
 

109
     Inside Climate News article on aerosol drop impact on Arctic sea ice
https://insideclimatenews.org/news/08062020/sulfate-emissions-coronavirus-arctic-heatwaves

     "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. "

110
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. 
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.t2
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.prcp-tcld-topo (light blue = clear sky above ice)
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.pwtr

111
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.

112
Arctic sea ice / Re: The 2020 melting season
« on: June 08, 2020, 04:59:24 PM »
http://ocean.dmi.dk/arctic/meant80n.uk.php
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.   

113
Arctic sea ice / Re: Latest PIOMAS update (June 2020)
« on: June 07, 2020, 10:12:21 PM »
Another one. This is a forecast for June 30 based on the melting rate in 2019. June 30 is blue, May 31 is red.
    Both versions are great.  I like the second that shows May 31 vs June 30 best.  Also agree that animation would be a nice addition (and more work no doubt!).  Whether comparative or not, animated or not, having some form of these bubble graphs at monthly intervals (or at mid-month if there is a PIOMAS update) would be an informative benchmark for tracking seasonal progression.  Thanks for introducing these.

    Maybe 5 or 10-year average melt rate instead of 2019?

    WOW - both Kara and Laptev GONE by June 30!

114
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.

115
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 https://climatecrocks.com/2020/05/28/new-video-breaking-bad-news-in-florida-keys/
 
       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, https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.prcp-tcld-topo) 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.

116
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.

117
Arctic sea ice / Re: MOSAiC news
« on: May 28, 2020, 02:38:55 AM »
   I hope somebody is tabulating these direct observations of surface melt with readings from satellite sensors to help calibrate interpretation of signals to distinguish between air moisture vs. surface melt vs. melt ponds vs. open water.  That would add to the knowledge being gained by having the MOSAIC folks present at the scene of the crime during melt season.

118
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.

119
Arctic sea ice / Re: Glossary ... for newbies and others
« on: May 24, 2020, 08:26:02 PM »
CR = Climate Reanalyzer

120
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.  https://forum.arctic-sea-ice.net/index.php/topic,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 https://imgur.com/a/O82kzZZ

        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” https://nsidc.org/arcticseaicenews/2020/03/

121
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?

122
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.

123
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.  https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL058956

     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 "

124
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. 

125
      Yes, temperatures in the GFS forecast are for 2M.

      FWIW - I've bee working on an algorithm to translate forecast 2M temps into temperatures closer to the surface for agricultural short-crop frost prediction.  The near to ground temperatures are much more dynamic - lower at night, higher during the day, about the same during mid-morning and early evening.  The extremity of variation depends on cloud cover, wind, relative humidity.  Winds over about 7mph (12 km/h) are enough to mix up the vertical air profile enough to overcome temperature stratification.  High cloud cover returns radiant heat to the ground at night, thus keeping near-ground temp closer to 2M temp.  High RH and moisture in the air also works against temperature stratification by height.  The most extreme differences are zero wind and clear skies.

     Of course, the ocean and ice environment is completely different than crops in soil.  I have no idea how much of this is relatable to temperature profiles in the Arctic Ocean and over the ASI.  But some of the same principles may apply.

126
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!

127
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: May 20, 2020, 03:19:01 AM »
<snip>
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).

128
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
https://forum.arctic-sea-ice.net/index.php/topic,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.

129
      What are useful criteria to interpret the impact of high and low pressure systems on the Arctic Sea Ice? 

       I think Neven said last year that pressure over 1033 hPa was a threshold for strong effect from high pressure. 

      I don't have an equivalent value for low pressure other than that the Great Arctic Cyclone in August 2012 was unprecedented for reaching 966 hPa for an extended period over a large area.

      So I am proposing 1030 or higher on the high side as a threshold for major impact and 980 or lower on the low side.  I suspect it may not be as simple as fixed threshold levels, esp. for the low-pressure impact.  The proximity and difference between adjacent low and high-pressure systems could be the determining factor in wind speed and effect on the ice.  But a rule of thumb for interpreting high and low-pressure readings would be useful.

130
Arctic sea ice / Re: Nullschool Forecasts
« on: May 19, 2020, 05:57:26 PM »
   For the Kara Sea, in addition to warm surface temperatures in the current GFS forecast (which are easier to see in Climate Renanalyzer), it seems like the winds (which are easier to see in Nullschool) will also contribute to ice losses over the next 5 days.

131
Arctic sea ice / Re: The 2020 melting season
« on: May 19, 2020, 12:45:38 AM »
We are really close to the 2.5 months when Arctic basin surface temps remain around 0-2C all summer.
Melting really goes nuts and you reach full 24 hour periods of 1-2C and sun.

    FWIW - An unscientific "blow up the graph, add lines and eyeball it" estimate has the DMI >80N daily mean temperature at >= 0C for an average of 68 days from June 10 to August 17. 
    Using a saltwater ice melt threshold of >= -1.8C, the over-threshold season lengthens to 89 days from May 31 to August 27.

132
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. https://insideclimatenews.org/news/16052020/arctic-coronavirus-climate-science-mosaic-research 
    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."  "


133
Arctic sea ice / Re: The 2020 melting season
« on: May 18, 2020, 03:15:03 AM »
Ice drift map. We have the whole ice pack rotating clockwise.
     Recent paper by Walt Meier et al found 10% per decade increase in ASI motion.  The May 8-16 ice drift map seems like it will contribute to that trend, though I don't have any info on what the average ice drift at this time of year looks like.  There are some long arrows in that image. 

    The recent high winds pretty well cleaned out the ice that was around Svalbard and FJL.  When the 2020 melt season story is written that seems like a major event to include.  Not as dramatic as the GAC of 2012, but the ice that was removed was one the remaining reservoirs of relatively thick ice.

    A highly mobile pack would be a major contributing factor for a wipeout melt season.  Too early to know season-long prospects of course.   The Arctic wide GFS forecast does not look as bad for the ice as last week.  The Kara is still in for some heat, and Mid-May has been one heck of a start. 

134
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.
   

135
Arctic sea ice / Re: The 2020 melting season
« on: May 16, 2020, 05:06:53 PM »
<snip> That's quite a big hole appearing North & West of Svalbard - the first significant damage to ice North of 80.
    And some of that area had large positive ice thickness anomalies before the May 10-13 winds pushing out through the Fram Strait. 

    NSIDC vs. AMSR2 image shading:   The NSIDC shows low concentration at some of the same areas as AMSR2, but the light gray shading for the AMSR2 affects many more areas in addition.  The impression of widespread ice damage across much of the CAB in the AMSR2 image is not replicated in the NSIDC image.  That may be due to differences between NSIDC and AMRSR2 in choice of color thresholds for graphing.  Or maybe NSIDC has a way to filter out misleading signals due to atmospheric moisture. 

     My tentative conclusion is that the very dark areas fringing open water in the B&W AMSR2 image are representing low ice concentration, but that the wispy grayish areas over much of the CAB could be due to high air moisture.  And that the NSIDC graphic is more restricted to showing sea ice concentration.  The Kara Sea already looks pretty beat up in both of them.

136
Arctic sea ice / Re: The 2020 melting season
« on: May 16, 2020, 02:56:49 PM »
<snip>  "now we are seeing Swisscheesification of the entire Arctic ..."

      Question 1:  Do those dark areas really indicate low concentration ice or does the sensor get fooled by moisture in the air column between surface and satellite?  I am not proposing, just asking.  Others have suggested that is the case.  If so, note that at the far end of the 10-day GFS there is an incursion of moist air over the central CAB https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.pwtr.  I was told by a climate scientist last year that such incursions were unusual, and that they contribute to localized warming, but take that as a second-hand anecdote from a less than perfect memory.

--------------------------
<snip> Watch this map.
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.snowd-mslp

... and we actually are not fortunate this is hitting early.  In fact in ways, I think it is worse.  All that disappearing snow on the pack is turning into sub-surface or surface melt ponds.

What's happening right now is we've extended the melt season about 4 weeks, from early June into early May.

Hunch:  The 30cm line on May 20th may be a harbinger of our end of season extent this year.

     Question 2:  That is an interesting concept for a long-range predictor for September sea ice Extent.  Is there historical analysis supporting that or something like it? 

     Which raises Question 3:  In addition to waiting for each new GFS or EURO model run, are there any publically available multi-week or seasonal weather forecasts for the Arctic basin with useful skill?  NOAA produces seasonal temp. and precip forecasts for the US that have useful skill out to several months for temp., and out to several weeks - 1 month for precip.  These are not weather forecasts for what will happen on this or that day, but trends for the period as a whole.  Having a skillful multi-week temperature or pressure forecast for the Arctic basin would be very interesting.

------------------------

     GFS vs. EURO  The differences between GFS and EURO are not that great, that's not me talking, it's Marshall Sheperd former president of American Met. Society, and him quoting the director of the EURO model.
https://www.forbes.com/sites/marshallshepherd/2019/02/14/euro-vs-gfs-weather-model-wars-take-a-new-turn-in-march/#7c3625286c2b

       Look at the forecast correlation stats and you see that the EURO does do better overall, but that is not always the case, and in general the scores are within a few percentage points.  GFS is pretty darned good so let's stop insulting it and by doing so dragging on the people who provide it.  And there is considerable investment in new computers, data systems, modeling physics, human and other resources underway that bodes well for continued progress with the FV3-GFS platform that went online last June. 

     Of course, the EURO is not standing still either.  Shepherd points out that the different met centers from around the world work closely together to help each other.  That's the kind of cooperative competition we need to pull out of our global tailspin. 

      The number of satellite, doppler radar, and other technological developments in the past decade is amazing.  If you need some good news, check out the COSMIC program.
  It seems that the original COSMIC  readings include the Arctic.  Great to see a much-improved COSMIC-2 for the lower latitudes.  Now we need a COSMIC-3 covering the polar regions.  (Outside my wheelhouse, but I think that is possible)  It's a matter of priorities not resources.  Understanding and preserving a climate that supports human civilization should be a top priority.  Pay for knowledge now or pay for damages later.


137
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: https://www.washingtonpost.com/news/energy-environment/wp/2016/11/30/he-created-a-beloved-blog-about-the-melting-arctic-but-it-got-harder-and-harder-to-write/

     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 https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.snowd-mslp.

    The Kara is already running below previous years (https://forum.arctic-sea-ice.net/index.php/topic,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.

138
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: May 11, 2020, 11:59:27 PM »
    Paul is referring to a since-deleted post of mine just above his where I spoke about the thickest ice being on the edge of an impending Fram Strait drainage event.  Then I took the post down, which left his post hanging in mid-air with nothing to refer to.  So here I am back again to correct my attempted correction. 

    I was wrong and Paul is correct that the PIOMAS and Cryosat images show thickness anomalies, not thickness.  That said, the locations with the greatest positive thickness anomalies of > +1 meter are likely to be thick enough to affect Fram export volume if they do indeed get moved out.  What actually happens will presumably show up in the next Wipneus Fram export graph that covers the days this week with observed and forecast high winds.  That's if the wind forecast proves accurate, which seems likely since the strong winds shooting down the Fram still appear in the current forecast update through the end of May 11, all of May 12 and into late May 13 UTC time.

139
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 https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.snowd-mslp
    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.
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.aprcp

140
Arctic sea ice / Re: The 2020 melting season
« on: May 11, 2020, 01:14:23 AM »
    Climate Reanalyzer GFS
https://climatereanalyzer.org/wx/fcst/#gfs.arc-lea.t2anom
and Earth Nullschool https://earth.nullschool.net/#2020/05/14/0600Z/wind/surface/level/orthographic=-59.54,45.21,332
show
   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.   

141
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...

142
Arctic sea ice / Re: What's new in the Arctic ?
« on: May 09, 2020, 01:53:44 AM »

143
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, https://doi.org/10.5194/tc-14-1519-2020, 2020.
https://www.the-cryosphere.net/14/1519/2020/
 
   "...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.

 

144
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: May 07, 2020, 08:17:25 PM »
     PIOMAS vs. JAXA AMSR2 thickness (vs. Bremen, NSIDC, ASCAT concentration.)
    In cleaning up the previous message I accidentally replaced the PIOMAS link.  Too much time gone by so now I can't edit that message anymore, but for the historical record here is the correct link to the message showing PIOMAS thickness.  Sorry for my dyslexic typing.
https://forum.arctic-sea-ice.net/index.php/topic,119.msg262853.html#msg262853

     Today's Arctic image of the day (Thanks Espen - btw it looks like they left that door open again!) at https://forum.arctic-sea-ice.net/index.php/topic,416.msg263212.html#msg263212 shows what looks like 100% ice cover at Utqiagvik on May 7. 

     The May 7 Bremen ice concentration map suggest less than 100% cover along most (but not all) of the coast looking west or north from Utqiagvik https://seaice.uni-bremen.de/data/amsr2/today/Arctic_AMSR2_nic.png.  But the Bremen map also shows a thin sightline of 100% ice cover if looking southwest, and it is not very clear in the photo whether there is solid ice or open water offshore. 

     This reminds me of the more definitive photo from the deck of the Polarstern in my earlier post showing solid ice cover even though the sea ice concentration maps for that location on that day indicated concentration well below 100%. 

      My point is not to whine that the ice concentration maps don't match this or that photo, I understand that perfection is impossible.  And I'm old enough in years and young enough at heart to be amazed and appreciative that we get to see any of this stuff (and gloomy enough to brood that good and evil seem to be in a dead heat race towards unwelcome consequences for our actions.  We are just learning the understand the Earth as we trash it.)   

      But I would like to understand what the sea ice concentration maps are measuring and representing.  In at least the Polarstern case, the photo indicates that the sea ice concentration imagery can overestimate the percentage of open water and underestimate the continuity of solid ice cover.  I suspect that at this time of year sensors may interpret superficial surface melt on sea ice as open ocean water.  ASIF posts in other threads have said that is the case for false readings of early melt pond activity, and other posts have noted that moisture in the air can fool sensor readings of ice cover.  Insight on interpreting sea ice concentration images welcomed.

145
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? 

146
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: May 05, 2020, 10:50:47 PM »
<snip> concentration in this instance is a measurement of surface area and does not correlate to thickness or volume.

      Thanks interstitial.  Agreed, but it seems to me that where the average ice thickness is 2-3 meters, there would have to be very nearly 100% concentration.  While cracks, leads, and polynyas are certainly possible in 2-3m thick ice, my guess is that there would be only limited expanse of open water adjacent to such thick ice.  So it surprises me to see the same areas categorized as both 2-3 meters thick and far below 100% concentration on essentially the same date. 

      Maybe having thick ice and <100% concentration at the same location is totally congruent.  I'm just a liquid water landlubber trying to make sense of these images. Are these various observations realistic, or is the apparent conflict between thickness and concentration due to different interpretations of readings by different sensors? 

      The variation between estimated thickness by different methods seems to be greater than the variation between different concentration estimates.  Which makes sense because Extent and Area are more directly observable from satellites than thickness.

      For thickness, my guess is that PIOMAS is the most reliable - even though JAXA and alternate version of AMSR2 thickness agree with each other more than either matches PIOMAS.  My preference for concentration is Bremen AMSR2 false-color, or the Bremen animation.  At least those are the easiest for me to interpret. (But I sure do like that ASCAT animation showing drift motion!)  Based on recent comments made on other ASIF threads, I suspect that what looks like open water on the grayscale AMSR2 can be moisture in the air.  The NSIDC concentration image is aesthetically pleasing but more difficult to translate into concentration %.

     My other not-so-subtle point was that images that include the interpretive legend are more useful than images without the legend.

147
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: May 05, 2020, 04:17:06 PM »
     PIOMAS vs. JAXA AMSR2 thickness (vs. Bremen, NSIDC, ASCAT concentration.)
      There seems to significant variation in the different representations of ASI thickness for last week of April among different observation methods.  To my eye, PIOMAS stands out from the rest in that it makes the condition of the ASI look much stronger than the others.  I don't know if the PIOMAS May 1 ice thickness map is a representation of May 1 or the entire month of May.  If the entire month, that would explain some of the difference.

     Not only do the thickness maps vary, but it seems strange to see 2-3 meter thick ice in some images at the same location of well below 100% concentration in other images. 

    Here is a gallery of recent ASIF postings of images showing ASI thickness and concentration

   https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262447.html#msg262447
   PIOMAS false color thickness May 1

   https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262455.html#msg262455
   and https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262475.html#msg262475
JAXA AMSR2 false color thickness April 30  (missing legend)
   Legend at https://ads.nipr.ac.jp/vishop/#/monitor


Concentration
--------
https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262447.html#msg262447
   NSIDC concentration and Bremen false color conc., both April 30, both missing legends.
   NSIDC legend at https://nsidc.org/data/seaice_index/images/n_conc_hires.png
   Bremen legend at https://seaice.uni-bremen.de/sea-ice-concentration/amsre-amsr2/

   https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262582.html#msg262582
ASCAT Oct. 7, 2019 to May 2, 2020.  Missing legend.
   Inscrutable legend at https://manati.star.nesdis.noaa.gov/datasets/ASCATData.php
  You have to use pull-down list for ice images to see the legend.

   https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262507.html#msg262507
   Bremen conc. gray scale, April 26-May 1.  Missing legend.
   Legend at https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261731.html#msg261731
and https://seaice.uni-bremen.de/sea-ice-concentration/amsre-amsr2/


https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262460.html#msg262460
   Bremen conc. false color animation April 20-30.

https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262432.html#msg262432
   Bremen false color conc. with Polarstern location May 1

https://forum.arctic-sea-ice.net/index.php/topic,3017.msg262472.html#msg262472
   Polarstern photo from bridge April 28


----------------------

   Many more with interpretive legends at http://greatwhitecon.info/resources/arctic-sea-ice-graphs/


148
Arctic sea ice / Re: The 2020 melting season
« on: April 27, 2020, 02:50:58 AM »
April 20-25.
2019.
      Thanks as always Aluminium.  One of the best synoptic views.  Is there a scale to interpret what the different levels of gray to black shading tell us about the condition of the ice?

149
Arctic sea ice / Re: Basic questions about melting physics
« on: April 22, 2020, 03:25:54 AM »
If you really want to learn more about sea ice formation Tor in post 32 linked to an excellent but long and technical read about ice formation and different types of ice. Physical and dynamic properties of sea ice.
https://apps.dtic.mil/dtic/tr/fulltext/u2/a256303.pdf
      Thanks interstitial!  Gow and Tucker 1991 is a classic document, the kind of comprehensive review I love.  I have only skimmed it so far, but already see numerous nuggets that address a variety of questions that have recently been discussed on various ASIF threads, including BOE estimates, land-fast ice ridging, FYI vs MYI, Fram export, and my question about the effect of thinning on melt sensitivity.

      Published in 1991 and based on many observations in the 1980s, reading what these scientists saw in their field studies is haunting.  Peter Wadhams' work is cited 14 times for 10 different papers in the review.  On 7 of those papers he was lead author.  Wadhams has been criticized lately for overstating the imminence of Arctic degradation.  Looking through this wonderful review I felt an emotional attachment to him, and understand his perspective better. 

      The Arctic those folks studied is becoming a distant memory.  They describe the characteristics of thick MYI that could hardly be found anymore.  One especially evocative statement is about what kind of change in the system would be required to melt out the Arctic, and that such a thing could only happen if atmospheric CO2 levels went to unprecedented levels.  And 29 years later, their extreme scenario is our current world.  No wonder Wadhams is freaked out.  If we knew as much about it as he does and had his historical perspective, we'd be more freaked out too. 

      That is one of the unique qualities of climate change.  With most of the scientific issues with which I become familiar professionally or personally, the more you learn, the more complexity, gray areas and nuance you discover.   So your opinion becomes less definitive.  That is why scientists so often speak in qualified terms, sometimes to the frustration of people who just want a simple yes/no black/white answer.  With climate change, for me at least, (but I think most other people who dig into it), the more you learn the more alarmed you get.  Sometimes to the point that you look around and wonder how life can go on looking so "normal" (at least until COVID-19 hit) when the planet is on fire. 

     God bless Peter Wadhams  Even if his BOE predictions were a bit early, when you see the depth of knowledge that he, Gow, Tucker and that generation of scientists developed back when the tools were much less powerful than today, you can better understand why seeing what has happened to the Arctic over the past 30 years would cause them to be alarmed.


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Arctic sea ice / Re: Basic questions about melting physics
« on: April 21, 2020, 12:18:34 AM »
     The Lebedev formula translates cumulative FDD into ice thickness, and yes, through the 0.58 exponential term represents the declining increase in ice thickness as FDD accumulate.  As shown in the Chris Reyolds posts, that formula can be used to estimate the difference in ice thickness additions between two cumulative FDD values.
   
     But what about the reverse process?  Is there a melting DD equivalent?  It seems likely that someone has measured that relationship.  A direct physical approach would be to measure ice thinning effects on blocks of sea ice of different thicknesses kept in a controlled setting and exposed to different temperature regimes. 

     A large scale field-based empirical approach might be possible by correlating Arctic seasonal temperature observations with subsequent reductions in Extent, Thickness, and Volume.  In addition to air and/or sea temperature, I suspect that such a study would need to also account for other factors such as cloud cover/solar radiation and wind, and also for the timing of those melting factor inputs on melt pond formation and surface changes to albedo. 

     This question seems so fundamental to understanding Arctic sea ice behavior that it must have been tackled by multiple research projects.  Most of my exposure to Arctic research is from what shows up in climate blogs, lay press articles, and on ASIF.  Minimal effort literature searching has not found anything to address this question, and that's all the time I have available at present. 

     What I am looking for is research relevant to melting DD vs. ice loss, and in particular to the effect of sea ice thickness on subsequent rate of thickness decline in response to melting DD.  The assumption that thinner ice melts faster than thick ice is often stated, and it makes sense due to salinity, structural weakness, surface/volume ratio, etc.  But how much faster does thin ice lose thickness to the same melting energy than thicker ice exposed to the same melting conditions? 

      The Thorndike 1975 ice thickness vs. thickness growth rate curve addresses that question for the winter ice thickening season.  I've been told that simply reversing that curve to get the response for ice thinning in the melt season is not valid.  So what is the melting season equivalent for the Thorndike 1975 ice thickness - thickness accumulation curve?

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