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jdallen

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Re: The 2020 melting season
« Reply #2400 on: July 08, 2020, 06:33:51 AM »
Phoenix, you are being intentionally obtuse.

When FOW calls someone out, you know things are bad! He is the nicest guy on the planet. 😂😂😂
FOoW also knows Arctic climate better than most of us would dream of.

He's pointing out very explicitly you (Phoenix) are drilling down further into a dry hole, and gently telling you that you really don't understand the atmospheric dynamics of heat exchange which are currently taking place.

I've tried to do a bit of the same, but you do not appear to be listening.

To be succinct, again, the heat exchange to ice from atmosphere this time of year by way of direct thermal transfer is measured in 10s of watts per square meter, whereas insolation is providing 350-400.  A drop of a degree or so at 2 meters or the surface is not material.  The "250kilo gorilla" is still pounding away at the ice.

To use a somewhat different metaphor, talking about air temperature dropping and reducing heat transfer is like getting excited about someone no longer throwing gravel at you.

Meanwhile someone else is *still* shooting at you with a high calibre handgun.  The reduction in gravel is not going to make a lot of difference in how badly you'll be shot up.
 
« Last Edit: July 08, 2020, 09:58:39 AM by jdallen »
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oren

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Re: The 2020 melting season
« Reply #2401 on: July 08, 2020, 06:59:26 AM »
Nearly the whole gray ice pack is basking in the glorious sun under a cloudless sky, except on the Siberian sector, July 7th 2020. Click to enlarge.

Rod

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Re: The 2020 melting season
« Reply #2402 on: July 08, 2020, 07:07:41 AM »
Phoenix, you are being intentionally obtuse.

When FOW calls someone out, you know things are bad! He is the nicest guy on the planet. 😂😂😂
FOoW also knows Arctic climate better than most of us would dream of.

He's pointing out very explicitly you are drilling down further into a dry hole, and gently telling you that you really don't understand the atmospheric dynamics of heat exchange which are currently taking place.

I've tried to do a bit of the same, but you do not appear to be listening.

To be succinct, again, the heat exchange to ice from atmosphere this time of year by way of direct thermal transfer is measured in 10s of watts per square meter, whereas insolation is providing 350-400.  A drop of a degree or so at 2 meters or the surface is not material.  The "250kilo gorilla" is still pounding away at the ice.

To use a somewhat different metaphor, talking about air temperature dropping and reducing heat transfer is like getting excited about someone no longer throwing gravel at you.

Meanwhile someone else is *still* shooting at you with a high calibre handgun.  The reduction in gravel is not going to make a lot of difference in how badly you'll be shot up.

Just an FYI to the ASIF. When he says “you” he does not mean me. He means Phoenix. I don’t want you guys pissed off at me! I sent him a DM and said the way he quoted the discussion was confusing.

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Re: The 2020 melting season
« Reply #2403 on: July 08, 2020, 07:19:22 AM »
Jaxa has almost another double century.

I expect a slowdown because the Beaufort and Chuchcki without some compaction will need more time to start melting out insitu.

Never the less 2020 is almost 300k km2 below the next closest year.

Pretty cool

MODIS shows a huge area of clear skies and it's expanding.

With brutal fog around the ridge where brutally warm low level heat is being injected.

The dark red is everywhere.  Remarkable!!


FWIW..I blocked Phoenix a little while back because he is disingenuous. And there is no time for that.


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VeliAlbertKallio

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Re: The 2020 melting season
« Reply #2404 on: July 08, 2020, 08:11:59 AM »
Not only melting (aqua blue) on sea ice, but signs of its softening are clear on 8th July 2020. It tells me that some ice has started to honeycomb to become "rotten ice" and opens leads easily:
https://worldview.earthdata.nasa.gov/?v=-931807.9036340355,300518.162858593,-563167.9036340355,514790.162858593&p=arctic
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Re: The 2020 melting season
« Reply #2405 on: July 08, 2020, 08:41:43 AM »
<Don't discuss other posters even if they discuss you. Discuss the ice, no repetitions though. You are under unofficial moderation as far as I am concerned. O>
« Last Edit: July 08, 2020, 08:47:36 AM by oren »

be cause

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Re: The 2020 melting season
« Reply #2406 on: July 08, 2020, 09:22:48 AM »
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 
 (phew)

jdallen

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Re: The 2020 melting season
« Reply #2407 on: July 08, 2020, 09:55:44 AM »
Just an FYI to the ASIF. When he says “you” he does not mean me. He means Phoenix. I don’t want you guys pissed off at me! I sent him a DM and said the way he quoted the discussion was confusing.
Sorry Rod.  You are correct.  I was referring to Phoenix.
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jdallen

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Re: The 2020 melting season
« Reply #2408 on: July 08, 2020, 10:14:41 AM »
[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

July 7th, 2020:
     8,001,159 km2, a century drop of -179,077 km2.
     2020 is the lowest on record.
     Highlighted 2020 & the 4 years with a daily lowest min in Sept. (2012, 2019, 2016 & 2007).
     In the graph are today's 10 lowest years.
     Source: https://ads.nipr.ac.jp/vishop/#/extent

I would have to think a slowdown is coming.

This is ridiculous.
Neither GFS nor ECMWF are showing any sign of that high letting up for two weeks.

With near certainty, we will have it (and the sun) for the next 5 days.

It's been like this for nearly 5 already.  There are places where we could see a full meter of top melt as a result of this weather.   Even half that is really bad for this ice, and that's almost a certainty.
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Phoenix

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Re: The 2020 melting season
« Reply #2409 on: July 08, 2020, 10:15:41 AM »
To be succinct, again, the heat exchange to ice from atmosphere this time of year by way of direct thermal transfer is measured in 10s of watts per square meter, whereas insolation is providing 350-400.  A drop of a degree or so at 2 meters or the surface is not material. 

The potential in the Arctic at this time of year under ice free conditions is 450-500 W/m2 per day.

According to Nico Sun, the CAB runs at about 20% of potential solar input at this time of year, so in a typical early July day, it's receiving about 100 W / m2.

https://cryospherecomputing.tk/awp-region.html

Does heat matter? I think so. You indicate tens of W / m2. That would be less than insolation, but still material.
« Last Edit: July 08, 2020, 11:14:41 AM by oren »

MrGreeny

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Re: The 2020 melting season
« Reply #2410 on: July 08, 2020, 10:18:50 AM »
I've been watching this for the past week and wow extent is dropping like a fly.

For the last several days July 2020's extent loss was 917,659km2 and managed to reach lowest on record by a long shot.

And I must say... the fun is just beginning.
 
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oren

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Re: The 2020 melting season
« Reply #2411 on: July 08, 2020, 11:29:39 AM »
The potential in the Arctic at this time of year under ice free conditions is 450-500 W/m2 per day.

According to Nico Sun, the CAB runs at about 20% of potential solar input at this time of year, so in a typical early July day, it's receiving about 100 W / m2.

https://cryospherecomputing.tk/awp-region.html

Does heat matter? I think so. You indicate tens of W / m2. That would be less than insolation, but still material.
You are bluffing your way through this argument, and badly. You cannot quote Nico Sun without understanding what it is he is really calculating. I have now gone and refreshed my failing memory, and it turns out he is assuming an albedo of 80% for ice and snow, and 85% for ice and snow in the High Arctic. For open water he is assuming 0% albedo. This is why he is showing ~20%-25% of potential solar input for the CAB: 15% of the CAB sea ice area, plus 100% of the (total CAB surface minus CAB sea ice area). However we are currently in a situation where the CAB is made up of gray ice full of extensive melt ponds and hardly any snow, with an albedo which is probably 50%-60% and certainly not 85%. So in a typical July day it is probably receiving double your number at about 200 W/m2.
In addition, his assumption is that the weather (cloudy/sunny), which he ignores, averages out. However a stuck weather pattern generating clear skies over the CAB in early July does not necessarily average out and thus the generated anomaly is not necessarily comparable.
I would of course appreciate input from those who can estimate these numbers better, this is just a back of the envelope exercise.

Michael Hauber

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Re: The 2020 melting season
« Reply #2412 on: July 08, 2020, 12:14:32 PM »
Some improvement in the forecast for EC, via Tropical tidbits, Using Z00 18/July Forecast.  While a high dominates throughout it does weaken a little from 1033 to 1024.  More significantly IMO an upper level low moves in over Beaufort region, shown by much lower 500hp thickness.  And the thickness over the high pressure system drops.  This signifies cooler air aloft, which is not guaranteed to translate to cooler conditions at the surface.  However it makes it less likely that their is sinking air, which is a significant source of warming, and helps clear the clouds.  It is likely that cloud cover will increase through the forecast period if this forecast holds, particularly over the Beuafort sea.  Upper cool air also moves into the Laptev corner, however this is matched by a surface low so as well as cooler cloudier conditions there is more wind, with a bit of a dipole happening, and wind driven transport out into the Atlantic.  Its not a huge improvement, say backing off from on target to badly beat 2012 if recent conditions continues (which was always unlikely) to 50/50 chance to beat 2012 IMO.

00 Hours vs 144 Hour forecast:




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gandul

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Re: The 2020 melting season
« Reply #2413 on: July 08, 2020, 12:36:11 PM »
You mean July 14, much closer in time.

ajouis

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Re: The 2020 melting season
« Reply #2414 on: July 08, 2020, 01:31:10 PM »
A picture is worth a thousand words, preconditioning of the ice is getting bad, the lack of beige picture is to be expected at this time of year but the amount of wetness detected in many areas close to the pole is very high, on par with 2012 everywhere apart from Beaufort and slightly better than 2016. We are not lacking momentum for the later season, let's if the train stops before the terminus this time or goes into uncharted territory.
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Greenbelt

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Re: The 2020 melting season
« Reply #2415 on: July 08, 2020, 02:25:18 PM »
If I'm doing it right, this is a comparison of the same approx area I posted yesterday, this time from today's Worldview vs. June 28 of this year. Still true color mode.  I know there is some ice drift, so it's possible we're not comparing exactly the same ice. But I'm wondering how the large intact-looking blobs seem to meld toward the honeycomb pattern in just over a week's time.
https://worldview.earthdata.nasa.gov/?v=-890112,329216,-539904,533504&p=arctic&t1=2020-06-28-T11%3A50%3A34Z&l1=Reference_Labels(hidden),Reference_Features(hidden),Coastlines,VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor&ca=false

Pagophilus

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Re: The 2020 melting season
« Reply #2416 on: July 08, 2020, 05:43:21 PM »
Three views of the Atlantic side of the ice cap from Worldview, today.  All have had their contrast highly tweaked in Photoshop.  First view is general, from the pole to FJL.  Second and third views are 'closeups' of this image, the second nearer the margin of the ice, the third including the pole itself.

Note that there are fine, ribbony clouds, rather like crinkle crepe fabric, over parts of these images. 
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Pagophilus

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Re: The 2020 melting season
« Reply #2417 on: July 08, 2020, 06:03:09 PM »
NSIDC Comparison tool, Arctic Ice Extent.  7 July 2020 vs same day in 2012 and in 2016.

IMO, 2020 stands out even more strongly now in terms of the comparatively massive ice losses on the Siberian side, and the relatively slower loss of ice from the Beaufort. 
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Greenbelt

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Re: The 2020 melting season
« Reply #2418 on: July 08, 2020, 06:20:22 PM »
In addition to maintaining the big high at about 1030mb for another week, the GFS op also seems toward another southerly wind event with warm Siberian air carried northward toward the pole and eventually the Fram.

FishOutofWater

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Re: The 2020 melting season
« Reply #2419 on: July 08, 2020, 06:20:53 PM »
The past 3 days have been as destructive to the ice as any three days I have watched including the GAC. The creation of extensive melt ponds across the ice of the high Arctic has happened and the transmissivity of the ice to visible radiation has been increased by the weather. Cooler temperatures will not undo that.

The GAC was destructive because it persisted for about 10 days and mixed up warmer saltier water from below. However, there was one benefit to sea ice of the GAC. The ocean lost heat to the atmosphere. This high pressure over the pole in the beginning of July is adding heat to the central Arctic ocean at an extraordinary rate. The anticyclonic spin of the ice pack under the high is also pulling warm water into the Arctic from both the Atlantic subarctic seas and the Bering strait. As long as the high pressure keeps on spinning the warm water will keep on getting pulled in and the ice will melt at an above average rate.

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Re: The 2020 melting season
« Reply #2420 on: July 08, 2020, 06:48:33 PM »
12Z GFS run now minimizes the troughing over the Beaufort and Alaska, with the LP skirting around the high, and not displacing it significantly. The HP weakens slightly to under 1030mb from d5-d6, but then re-strengthens and re-centers closer to Beaufort side of CAB where it stays above 1030mb through at least d10. For what its worth, similar forecast from the 12Z GEM run. Cold air does seem to sneak in from Beaufort to Bering as with previous runs, but also with pronounced Siberian WAA just afterwards as mentioned below.

Looking forward to seeing how the Euro 12Z compares!
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blumenkraft

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Re: The 2020 melting season
« Reply #2421 on: July 08, 2020, 07:02:18 PM »
GAAC

Great Arctic Anti Cyclone

Has it occurred before?

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Re: The 2020 melting season
« Reply #2422 on: July 08, 2020, 07:16:30 PM »
The past 3 days have been as destructive to the ice as any three days I have watched including the GAC. The creation of extensive melt ponds across the ice of the high Arctic has happened and the transmissivity of the ice to visible radiation has been increased by the weather. Cooler temperatures will not undo that.

The GAC was destructive because it persisted for about 10 days and mixed up warmer saltier water from below. However, there was one benefit to sea ice of the GAC. The ocean lost heat to the atmosphere. This high pressure over the pole in the beginning of July is adding heat to the central Arctic ocean at an extraordinary rate. The anticyclonic spin of the ice pack under the high is also pulling warm water into the Arctic from both the Atlantic subarctic seas and the Bering strait. As long as the high pressure keeps on spinning the warm water will keep on getting pulled in and the ice will melt at an above average rate.

Widespread melt pond draining is already occurring on the Laptev side of the CAB. Wouldn't be surprised to see area losses slow down a bit due to that -- at least until the rot is more advanced. If this ridge holds for another week or so, in-situ open water fraction will start increasing pretty quickly.

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Re: The 2020 melting season
« Reply #2423 on: July 08, 2020, 07:28:14 PM »
Pagophilus,

Can you compare this year to 2019?  The total ice extent has been tracking quite closely between the two years for almost a month now.

Juan C. García

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Re: The 2020 melting season
« Reply #2424 on: July 08, 2020, 07:44:54 PM »
GAAC

Great Arctic Anti Cyclone

Has it occurred before?
I would bet that it has happened before. But it is worse with the actual ice conditions.
The problem now is that a GAAC can kill a large part of the ice. An a GAC will do the same job. Both are terrible: the ice is vulnerable either way.
The 2020 timing can also be very bad. A GAAC in the begginning of July is very bad, a GAC later will be worst.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

GoSouthYoungins

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Re: The 2020 melting season
« Reply #2425 on: July 08, 2020, 07:45:56 PM »
The GAAC couldn't be more perfect. It's like someone sketched it out.
big time oops

Frivolousz21

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Re: The 2020 melting season
« Reply #2426 on: July 08, 2020, 07:51:19 PM »
12Z GFS run now minimizes the troughing over the Beaufort and Alaska, with the LP skirting around the high, and not displacing it significantly. The HP weakens slightly to under 1030mb from d5-d6, but then re-strengthens and re-centers closer to Beaufort side of CAB where it stays above 1030mb through at least d10. For what its worth, similar forecast from the 12Z GEM run. Cold air does seem to sneak in from Beaufort to Bering as with previous runs, but also with pronounced Siberian WAA just afterwards as mentioned below.

Looking forward to seeing how the Euro 12Z compares!

That's incredible.  Just stunning.  I can't believe we are having this kind of melt season.  One for the ages.

Can't wait to see cryosat thickness in late September/early October.

The thing now that would seal the deal would be a transition to a traditional dipole anomaly to clear out the Pacific side.
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dnem

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Re: The 2020 melting season
« Reply #2427 on: July 08, 2020, 07:54:54 PM »

That's incredible.  Just stunning.  I can't believe we are having this kind of melt season.  One for the ages.

Had to happen sooner or later.

Juan C. García

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Re: The 2020 melting season
« Reply #2428 on: July 08, 2020, 07:56:24 PM »
And I still think that the lack of airplane aerosols is worsening the impact of the GAAC.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Pagophilus

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Re: The 2020 melting season
« Reply #2429 on: July 08, 2020, 08:11:32 PM »
Pagophilus,

Can you compare this year to 2019?  The total ice extent has been tracking quite closely between the two years for almost a month now.

Gladly, Walrus, but it must be for July 6 in both years, so that will be good enough I hope.  The same differences persist with 2020 to my eye.  Huge extent loss on the Siberian side for this year, and less ice loss in the Beaufort/Alaskan side of the Chukchi.  Everything else seems to be a case of a bit more there, a bit less here -- on the Atlantic side, the peripheral seas etc.  I have not done a thorough check, but this year seems qualitatively different to all the others on the record in terms of this extreme early loss of ice in the Laptev, ESS, Kara and Chukchi seas combined.

So the 2019 and 2020 extents may be tracking fairly closely, but the patterns of distribution are different.
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Greenbelt

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Re: The 2020 melting season
« Reply #2430 on: July 08, 2020, 08:35:02 PM »
And there is it -- ECMWF has shifted to be almost identical to GFS in position and strength of GAAC through Day 6 and Day 7.  I need to go take a walk...

romett1

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Re: The 2020 melting season
« Reply #2431 on: July 08, 2020, 08:36:32 PM »
3-day average 10m wind speed forecast (GFS) - today's forecast vs Tuesday's forecast. Area north to Svalbard to watch, also area around Franz Josef Land.

pearscot

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Re: The 2020 melting season
« Reply #2432 on: July 08, 2020, 08:57:12 PM »
As far as I know, and please correct me if I'm wrong, but in some ways these long-term weather setups, such as the aforementioned GAH (Great Arctic High, or whatever we are referring to it as) almost become a self fulfilling prophecy. What I mean by that is once a strong high is established, the ground/water/surface heat, thus maintaining the weather pattern and/or making it stronger.

Such is the case right now with a substantial heat dome established over much of the lower 48 in the U.S., which is projected to remain until the 3rd week of July.

I'm not trying to claim things I can't prove, but based on the weather alone and what has occurred in the CAA, the high that has existed over the central arctic has been in place for some time now. I'm amazed at the almost overnight destruction of ice in the CAA and temperatures STILL remain around 40-60f+ north of Greenland and many of the Queen Elizabeth Islands. The weather has been quite static there and with the weakening/shredded jet stream, both substantial high and low systems are more likely to move very slowly/remain in place.

The forecast discussion for the Northern Slope of Alaska really speaks to this point with the discussion starting with:
Quote
"Upper Levels and Analysis...
I am going to sound like a broken record on this final midnight
shift, but the upper air pattern continues to be dominated by the
same upper level features."
pls!

KenB

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Re: The 2020 melting season
« Reply #2433 on: July 08, 2020, 09:09:15 PM »
Pearscot:  see also « Reply #2377 on: July 07, 2020, 10:38:30 PM » in this thread for another possible reason for things being so "stable." 
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uniquorn

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Re: The 2020 melting season
« Reply #2434 on: July 08, 2020, 09:24:57 PM »
update on buoy drift using iabp data for whoi itp buoys, apr-jul7

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Re: The 2020 melting season
« Reply #2435 on: July 08, 2020, 09:39:02 PM »
GFS/EURO both in excellent agreement now that the awful pattern will continue through at least mid July. Close to the worst case scenario given the preconditioning and melting momentum already in place. It will take some sort of pattern reversal miracle at the end of a July/August to save a ton of ice this season... which seems unlikely.

This was always going to happen again at some point. The deck is very loaded, and even the “good” melt seasons don’t accomplish nearly enough... another big step down is on the way.

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Re: The 2020 melting season
« Reply #2436 on: July 08, 2020, 09:58:01 PM »
Quite worrying

Was looking at ice during Winter freeze up and thought God that ice is going to have to freeze lots to avoid catastrophe next Summer. And it did. But look now.

We are in unchartered waters now folks. And remember the fairly solid predictions of Summer Ice Free Arctic by 2030. Well it looks like it's going to be close. Certainly by 2040.

And what will climate be like then? Warmer? Wetter? Volatile? All the aforementioned.

Goodbye any benign weather.

igs

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Re: The 2020 melting season
« Reply #2437 on: July 08, 2020, 09:58:31 PM »
And I still think that the lack of airplane aerosols is worsening the impact of the GAAC.


I (normally) quietly agree with that. For me it was obvious the first week of widespread lockdowns.


Only that the topic usually leads to back and forth arguments which is why I usually keep it for me.

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Re: The 2020 melting season
« Reply #2438 on: July 08, 2020, 10:04:59 PM »
GFS/EURO both in excellent agreement now that the awful pattern will continue through at least mid July. Close to the worst case scenario given the preconditioning and melting momentum already in place. It will take some sort of pattern reversal miracle at the end of a July/August to save a ton of ice this season... which seems unlikely.

This was always going to happen again at some point. The deck is very loaded, and even the “good” melt seasons don’t accomplish nearly enough... another big step down is on the way.


If this pattern will change in August it will be even worse due to heavy storms and long stretches of wave building to assault the remaining relatively thin and fragmented ice in most of the CAB.


I think the key will be in CAA. If it melts more or less out in big parts then we're in for a worst case in numbers, else it could be anything between 2012 and 2019 on the lower end of that range.


IMO the gears are already put in place. It's almost unthinkable that after such a heat there won't be many and/or strong storms and even if that happens in early August it will fall on "fertile earth" means primed fuses.

jdallen

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Re: The 2020 melting season
« Reply #2439 on: July 08, 2020, 10:12:37 PM »
<snippage>

The weather has been quite static there and with the weakening/shredded jet stream, both substantial high and low systems are more likely to move very slowly/remain in place.

The forecast discussion for the Northern Slope of Alaska really speaks to this point with the discussion starting with:
Quote
"Upper Levels and Analysis...
I am going to sound like a broken record on this final midnight
shift, but the upper air pattern continues to be dominated by the
same upper level features."

We've got recent similar phenomena that are reflective of this.  An example is the "RRR" - Ridiculously Resilient Ridge - which set up of the NW coast of N. America which lasted pretty much for years and plunged California into a devastating drought.

The procession of Rosby waves is slowing (or they are simply disintegrating) as the northern hemisphere circulatory cells break down.  I think the WAH/WAAC is a side effect of this.
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Aluminium

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Re: The 2020 melting season
« Reply #2440 on: July 08, 2020, 10:24:53 PM »
Changes from June 15.

Laptev ... -64%
Hudson ... -58%
Baffin ... -46%
CAA ... -45%
Kara ... -44%
ESS ... -41%
Chukchi ... -34%
Barents ... -34%
Greenland ... -21%
CAB ... -15%
Beaufort ... -14%
This is changes in volume for 15 days. With 75% of this pace, all seas below -40% easily can melt out by August 1.

There was a powerful WAA started at June 16.



Now we have a GAAC.

Yossarian80

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Re: The 2020 melting season
« Reply #2441 on: July 08, 2020, 10:52:39 PM »
And what will climate be like then? Warmer? Wetter? Volatile? All the aforementioned.

Warmer/wetter overall for sure... but not so volatile except for perhaps tropical weather. Rapidly warming arctic means less north/south temperature gradient. So weaker mid-latitude storms/cyclones, and wavier, more persistent/stuck patterns (resulting in more droughts/floods in specific locations). Not so interesting, which saddens me since I enjoy interesting weather.

If this pattern will change in August it will be even worse due to heavy storms and long stretches of wave building to assault the remaining relatively thin and fragmented ice in most of the CAB.

For sure... a strong HP centered over the ice is awful now due to clear skies, but as the sun angle gets lower a dipole anomaly and/or strong cyclones turns into the worse scenario. I do think the dice are loaded for stronger cyclones to form near the ice edge towards the end of modern day melt seasons, as hot temperatures reach the relatively colder water/ice edge more easily these days. This baroclinicity is a great recipe for stronger arctic storms later in the season, an unfortunate feedback that can rapidly destroy fragile ice.

Michael Hauber

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Re: The 2020 melting season
« Reply #2442 on: July 08, 2020, 10:54:27 PM »
GAAC

Great Arctic Anti Cyclone

Has it occurred before?

2007, 2010 and 2011 had some pretty fierce high pressure set ups.  Not sure whether current is bigger/longer or not.  2007 smashed the record at the time, and even after the last few years with 10 years of warming we still can't convincingly beat 2007's melt (we've beat it by small amounts which to me deserve to be called about equal).  And 2007 had to deal with an Arctic with a much larger amount of thicker and resilient multi-year ice.  2010 had a stunning drop in PIOMAS volume early in the season - I remember commenting at the time that if the anomaly dropped as far in the next month as the month just gone we'd be looking at nearly ice free conditions, however conditions turned cloudy and melt stalled big time.  2010 and 2011 combined may have had a lot to do with pre-conditioning for the record year in 2012 that we still haven't got close to.
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Phoenix

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Re: The 2020 melting season
« Reply #2443 on: July 08, 2020, 10:54:52 PM »
There was a powerful WAA started at June 16.

During that period of powerful WAA from 6/16 - 6/21, the Arctic lost an extra ~ 100 km3 / day according to daily PIOMAS volume records shared by Gerontocrat in the PIOMAS thread.

<The Siberian sector, where the WAA was, lost 20-30 extra km3/day on 6/16-6/18. O>

Edit: there was WAA in several different regions over those 4 days within the CAB. Nullschool has the history.... (yes there is evidence to support that heat can cause significant ice loss)

https://earth.nullschool.net/#2020/06/20/0600Z/wind/surface/level/overlay=temp/orthographic=-116.61,84.75,584/loc=-84.720,83.300
« Last Edit: July 09, 2020, 06:33:01 AM by Phoenix »

BornFromTheVoid

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Re: The 2020 melting season
« Reply #2444 on: July 08, 2020, 10:57:50 PM »
The graph below is a projection of the 2020 NSIDC daily sea ice extent, based on the daily losses since 2000, with the oldest years being lighter grey lines and most recent being darker gray. The years with the lowest minima are coloured. It also includes the date and value of all previous daily minima in circles.
Based on the projections it appears almost certain now that we'll finish in the bottom 6, but will still require and one of the largest losses on record to beat 2012. This is, of course, ignoring the conditioning of the pack, low volume and the continued forecast for high pressure.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

gandul

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Re: The 2020 melting season
« Reply #2445 on: July 08, 2020, 11:06:53 PM »
GAAC

Great Arctic Anti Cyclone

Has it occurred before?

2007, 2010 and 2011 had some pretty fierce high pressure set ups.  Not sure whether current is bigger/longer or not.  2007 smashed the record at the time, and even after the last few years with 10 years of warming we still can't convincingly beat 2007's melt (we've beat it by small amounts which to me deserve to be called about equal).  And 2007 had to deal with an Arctic with a much larger amount of thicker and resilient multi-year ice.  2010 had a stunning drop in PIOMAS volume early in the season - I remember commenting at the time that if the anomaly dropped as far in the next month as the month just gone we'd be looking at nearly ice free conditions, however conditions turned cloudy and melt stalled big time.  2010 and 2011 combined may have had a lot to do with pre-conditioning for the record year in 2012 that we still haven't got close to.
That's a great post, thanks.
However I think this qualifies as a GAAC or a GAH.

The Euro has worsened a lot, looks like this high keeps getting energized

Michael Hauber

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Re: The 2020 melting season
« Reply #2446 on: July 08, 2020, 11:10:21 PM »
Just went back and had a look at 2010 daily records via ESRL

In 2010 the high pressure ran for most of the second half of June - roughly 2 weeks, exceeded 1030 on a couple occasions, consistently peaking at least mid 1020s and covered a good 3/4 of the Arctic for the entire period.  Centered more towards the Beaufort.
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pearscot

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Re: The 2020 melting season
« Reply #2447 on: July 08, 2020, 11:26:40 PM »
<snippage>

The weather has been quite static there and with the weakening/shredded jet stream, both substantial high and low systems are more likely to move very slowly/remain in place.

The forecast discussion for the Northern Slope of Alaska really speaks to this point with the discussion starting with:
Quote
"Upper Levels and Analysis...
I am going to sound like a broken record on this final midnight
shift, but the upper air pattern continues to be dominated by the
same upper level features."

We've got recent similar phenomena that are reflective of this.  An example is the "RRR" - Ridiculously Resilient Ridge - which set up of the NW coast of N. America which lasted pretty much for years and plunged California into a devastating drought.

The procession of Rosby waves is slowing (or they are simply disintegrating) as the northern hemisphere circulatory cells break down.  I think the WAH/WAAC is a side effect of this.

YES! This is exactly what I was alluding to and I think the high pressure over the arctic is reminiscent of the RRR insofar as it is has remained far longer than I originally thought it would have. I don't want to sound like I think this high pressure will remain for the rest of the season, but I do however feel like its sustained existence makes it less likely to be disrupted by weaker lows which may have normally gone into the central pack.

Either way, the results have been shocking. The daily changes to the ice are remarkable.
pls!

gandul

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Re: The 2020 melting season
« Reply #2448 on: July 09, 2020, 12:07:30 AM »
For the record, Michael Hauber, I was not being sarcastic when I said yours was an outstanding post.

The current high is quite extraordinary anyway, especially for a person that has been following this since late summer 2012.

This is going toward 10 days of high pressure peak hovering around 1035 hPa, being maintained by heat injections from persistent lower latitude ridges, especially from Siberia.

Yes, 2019 was the only year so skewed to sustained Arctic ridge since 2012.

pearscot

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Re: The 2020 melting season
« Reply #2449 on: July 09, 2020, 12:20:23 AM »
Just look at how warm it still is above Greenland/CAA!! Feel free to check anything you would like, but the images were taken from yesterday 7/7/2020. I did not see anything resembling this strong of melt until August of last year. This map is ghetto, but it's a working concept...I just wanted to try to show current temps combined with how it's affecting the ice right now.
pls!