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jdallen

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Re: The 2020 melting season
« Reply #350 on: April 18, 2020, 07:45:11 AM »
Probably for the first time in about 3 million years, yes.

Not exactly JD:

http://GreatWhiteCon.info/2016/09/santa-extends-his-secret-summer-swimming-pool/
<snerk> 

Well, yes, but I was interpreting the question in context of BoE or near BoE giving us a complete meltout of say, everything within 100KM of the pole.

But, YMMV  ;)
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jdallen

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Re: The 2020 melting season
« Reply #351 on: April 18, 2020, 08:06:08 AM »
The open water may extend to the Pole in Siberian side in September if such pattern will continue. The Laptev/ESS ice is already thin + early surface melting and quick land snow retreat in Siberia

If that happens, would it be the first time the pole melts?
Probably for the first time in about 3 million years, yes.

Possibly, although some have suggested that it may been as recently as 100,000 years ago.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL057188
https://www.independent.co.uk/environment/climate-change/arctic-could-become-ice-free-for-first-time-in-more-than-100000-years-claims-leading-scientist-a7065781.html

Others as recently as 6,000 years ago.

https://www.sciencedirect.com/science/article/pii/S0277379113004162?np=y
https://phys.org/news/2008-10-ice-arctic-ocean-years.html

I've been skeptical of assertions there have been more recent melt outs of the Arctic than during the late Pliocene warm period - which coincidentally corresponds to the last time atmospheric CO2 was this high.

I'm open to the possibility it's happened, but I haven't seen enough yet that's sufficiently definitive to convince me.

Others are welcome to post to that effect and I'll be happy to chew through them.
 
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oren

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Re: The 2020 melting season
« Reply #352 on: April 18, 2020, 09:59:18 AM »
Just a gentle reminder, please continue discussions of the ASI thousands of years ago in a different thread.

El Cid

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Re: The 2020 melting season
« Reply #353 on: April 18, 2020, 05:13:36 PM »
I took a look at Bremen ice pictures for this date for many years and I have not seen so much light purple - maybe expect for 2007 April but then the weakness was in other zones. Now the Beaufort , the ESS and the Laptev seem very very weak. 2020, 2016 and 2007 shown.

I know it is totally weather dependent but I think we will see a record this year

Freegrass

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Re: The 2020 melting season
« Reply #354 on: April 18, 2020, 05:48:14 PM »
I took a look at Bremen ice pictures for this date for many years and I have not seen so much light purple - maybe expect for 2007 April but then the weakness was in other zones. Now the Beaufort , the ESS and the Laptev seem very very weak. 2020, 2016 and 2007 shown.

I know it is totally weather dependent but I think we will see a record this year (so true)
I don't see people using this website much, but I like it because IMHO the data matters less than the evolution of the data. Same data sets show trends, and this site's volume trend is showing a record minimum in volume.

I also like the animation this site provides.

http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-thickness-and-volume/
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Pavel

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Re: The 2020 melting season
« Reply #356 on: April 18, 2020, 07:14:40 PM »

jdallen

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Re: The 2020 melting season
« Reply #357 on: April 18, 2020, 09:20:24 PM »
https://worldview.earthdata.nasa.gov/?v=-171008,-991488,812032,-474880&p=arctic&i=1&l=Graticule,Reference_Labels(hidden),Reference_Features(hidden),Coastlines,VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor,MODIS_Terra_CorrectedReflectance_TrueColor

Look at this crack  :o

While I understand your alarm, *this* crack in particular isn't especially troublesome.  If you go back through the images, you'll see the ice in a similar state at this time most years over the last 15 or so.

Early on looking at Nares and Fram export I was very concerned about it, but while not trivial (at peak, 10-15,000km2 daily export of older ice will never be trivial...), I've seen over time it isn't as definitive in the way other seasonal dimensions are.

The crack is less important than the over-all integrity and thickness of the ice.  I'm less concerned about this region of the Arctic.  I think what will be happening in the other peripheral seas with early melting and melt ponding will be far more crucial to what outcome we have in September.
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Sublime_Rime

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Re: The 2020 melting season
« Reply #358 on: April 18, 2020, 09:21:16 PM »
For more senior posters: To what extent to we expect this pulse of anomalies, averaging 4-5 C above normal, across the Eurasian side of the arctic over the next week to impact preconditioning (or pre-preconditioning)? Is it too early to begin melt-pond formation in earnest? If so, would melting snow atop the ice still reduce albedo, even if re-frozen?

I'd also like to begin tracking meltpond formation more closely in the weeks ahead. Does anyone know of a good resource for quantifying this?
« Last Edit: April 18, 2020, 10:00:48 PM by Sublime_Rime »
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Freegrass

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Re: The 2020 melting season
« Reply #359 on: April 18, 2020, 09:51:59 PM »
To what extent to we expect this pulse of 4-5C anomalies across the Eurasian side of the arctic over the next week to impact preconditioning (or pre-preconditioning)?
I'm sure more senior posters will correct me if I'm wrong, but I think the higher temperatures will only have an impact on the freezing of the ice. This "heatwave" basically ends the freezing season early.

Is there a mathematical formula that calculates the increase of ice volume with temperature?
How much possible volume do we lose with a 20°C temp anomaly? And how does that compare to fram export?
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Pavel

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Re: The 2020 melting season
« Reply #360 on: April 18, 2020, 11:47:03 PM »
If the snow on the ice melts because of heat and moisture and refreezes after that, the albedo drops significantly. It may cause early meltponding, futher albedo drop and volume loss much more than Fram export

Freegrass

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Re: The 2020 melting season
« Reply #361 on: April 19, 2020, 01:04:17 AM »
If the snow on the ice melts because of heat and moisture and refreezes after that, the albedo drops significantly. It may cause early meltponding, futher albedo drop and volume loss much more than Fram export
That makes sense Pavel, but wouldn't snow blow over it again and cover those albedo weaknesses?
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Phoenix

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Re: The 2020 melting season
« Reply #362 on: April 19, 2020, 02:15:38 AM »
For more senior posters: To what extent to we expect this pulse of anomalies, averaging 4-5 C above normal, across the Eurasian side of the arctic over the next week to impact preconditioning (or pre-preconditioning)? Is it too early to begin melt-pond formation in earnest? If so, would melting snow atop the ice still reduce albedo, even if re-frozen?

I'd also like to begin tracking meltpond formation more closely in the weeks ahead. Does anyone know of a good resource for quantifying this?

It might be more informative to share the absolute temperature chart along with the anomaly chart.  If we're at a time of year when the norm is -15C and we have a +5C anomaly, then the anomaly probably won't much a huge impact.

oren

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Re: The 2020 melting season
« Reply #363 on: April 19, 2020, 07:58:16 AM »
It's certainly too early to begin melt ponding in the Arctic Basin. And I can't recall any source that tracks melt ponding quantitatively, though looking at Worldview shows a telltale bluish color when melt ponding is widespread.

wallen

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Re: The 2020 melting season
« Reply #364 on: April 19, 2020, 08:09:30 AM »
It's certainly too early to begin melt ponding in the Arctic Basin. And I can't recall any source that tracks melt ponding quantitatively, though looking at Worldview shows a telltale bluish color when melt ponding is widespread.


With so much multi  directional cracking deep in the CAB, can this impact on the occurrence of melt
ponding ?

jdallen

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Re: The 2020 melting season
« Reply #365 on: April 19, 2020, 09:29:34 AM »
If the snow on the ice melts because of heat and moisture and refreezes after that, the albedo drops significantly. It may cause early meltponding, futher albedo drop and volume loss much more than Fram export
That makes sense Pavel, but wouldn't snow blow over it again and cover those albedo weaknesses?
Temperatures are not yet high enough for surface melt.  The primary effect here is to slow thickening of the ice in the region affected.

At this time of year, when there is melt, it tends to form sub surface (of the snow pack) melt ponds.  This does decrease albedo and increases  heat capture.

Looking at current temps under CR, it's still too cold.

Again looking at CR, the real action will be on the Laptev and Kara in a few days, where temperatures will be high enough for surface melt of the snowpack.  That may provide preconditioning for better melt when we get to May.

The real time to start watching these temperatures, albedo and cloud cover is in a couple of weeks.  That's the point at which insolation kicks up seriously and melt ponds will set the stage for what happens during the rest of the melt season.
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Re: The 2020 melting season
« Reply #366 on: April 19, 2020, 09:34:51 AM »
with so much multi  directional cracking deep in the CAB, can this impact on the occurrence of melt
ponding ?
Mostly its easy to forget the scale. small objects you see may be a kilometer or more across. so not really

Phoenix

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Re: The 2020 melting season
« Reply #367 on: April 19, 2020, 02:54:47 PM »
April 10-16.

2019.

The kind of things one notices while observing their second melt season.

The crack which shows the beginning of the melt in the ESS. It runs from the islands which separate the ESS from the Laptev and meanders through the ESS until it connects with shore.

That initial crack is very similar shape as last year.  I could be wrong, but I'm going to guess it's a similar shape every year.  What is it about that particular piece of real estate that causes that crack to appear there first ?

Niall Dollard

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Re: The 2020 melting season
« Reply #368 on: April 19, 2020, 05:21:27 PM »

  What is it about that particular piece of real estate that causes that crack to appear there first ?

The ESS is a shallow sea. The fast ice stretches out several kms from the Russian coast and then separates from the main pack in the spring.

I havent checked back to see if the break off point is exactly same each year but probably something similar. This year it coincides quite close to the 25m depth line (isobath) looking at this bathymetry map. 

Phoenix

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Re: The 2020 melting season
« Reply #369 on: April 19, 2020, 07:11:35 PM »

  What is it about that particular piece of real estate that causes that crack to appear there first ?

The ESS is a shallow sea. The fast ice stretches out several kms from the Russian coast and then separates from the main pack in the spring.

I havent checked back to see if the break off point is exactly same each year but probably something similar. This year it coincides quite close to the 25m depth line (isobath) looking at this bathymetry map.

Thanks Niall for the detailed bathymetric chart. I see the correlation of the crack to the bathymetry.

I'm trying to get some sense of the process which creates the crack. In that regard, I'm wondering if the fast ice is frozen all the way down to the sea floor? It's shallow there and a frozen continent in winter might have the means to freeze the water beneath.

blumenkraft

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Re: The 2020 melting season
« Reply #370 on: April 19, 2020, 07:50:36 PM »
Without commentary, the Sunday movies.

7-day hindsight mean temperature anomalies
& DMI 80°N 2m Temperature

blumenkraft

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Re: The 2020 melting season
« Reply #371 on: April 19, 2020, 07:51:21 PM »
Fram export/import via SAR

blumenkraft

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Re: The 2020 melting season
« Reply #372 on: April 19, 2020, 07:51:57 PM »
Ice drift map.

blumenkraft

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Re: The 2020 melting season
« Reply #373 on: April 19, 2020, 07:52:29 PM »
Ozone.

VeliAlbertKallio

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Re: The 2020 melting season
« Reply #374 on: April 19, 2020, 07:55:44 PM »
This is just so terrible I started to cry, I knew Professor Sir John Houghton. He just passed away due to UK's terrible coronavirus epidemic.

 :'( FAMOUS BRITISH SCIENTIST AND IPCC 2007 NOBEL PRIZE TAKER DIES OF CORONAVIRUS

https://www.bbc.co.uk/news/uk-wales-52325374  :'( :'( :'( :'( :'( :'( :'( :'( :'( :'( :'(

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oren

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Re: The 2020 melting season
« Reply #375 on: April 19, 2020, 08:48:31 PM »
Ozone.
I prefer that this regular update be posted in a new thread, as it does not affect the current melting season as far as I can tell.

Niall Dollard

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Re: The 2020 melting season
« Reply #376 on: April 19, 2020, 09:34:05 PM »


I'm trying to get some sense of the process which creates the crack. In that regard, I'm wondering if the fast ice is frozen all the way down to the sea floor? It's shallow there and a frozen continent in winter might have the means to freeze the water beneath.

It's not the ESS, but there is a nice schematic of the break up process over at Barrow (Utqiagvik) Alaska on this link.

https://seaice.alaska.edu/gi/observatories/barrow_breakup/

The fast ice there is supported by grounded pressure ridges. But some years the pressure ridges can be unreliable. I imagine it is something similar in ESS, only extended out further ?


Niall Dollard

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Re: The 2020 melting season
« Reply #377 on: April 19, 2020, 09:53:36 PM »
This is just so terrible I started to cry, I knew Professor Sir John Houghton. He just passed away due to UK's terrible coronavirus epidemic.

 :'( FAMOUS BRITISH SCIENTIST AND IPCC 2007 NOBEL PRIZE TAKER DIES OF CORONAVIRUS

https://www.bbc.co.uk/news/uk-wales-52325374  :'( :'( :'( :'( :'( :'( :'( :'( :'( :'( :'(

Yes. It is sad news.

A wonderful tribute to him from his granddaughter on twitter here:

https://twitter.com/hannahmmalcolm/status/1250778555505655808

Phoenix

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Re: The 2020 melting season
« Reply #378 on: April 19, 2020, 10:13:58 PM »


I'm trying to get some sense of the process which creates the crack. In that regard, I'm wondering if the fast ice is frozen all the way down to the sea floor? It's shallow there and a frozen continent in winter might have the means to freeze the water beneath.

It's not the ESS, but there is a nice schematic of the break up process over at Barrow (Utqiagvik) Alaska on this link.

https://seaice.alaska.edu/gi/observatories/barrow_breakup/

The fast ice there is supported by grounded pressure ridges. But some years the pressure ridges can be unreliable. I imagine it is something similar in ESS, only extended out further ?

That's a great link Niall, thank you !!

From the image it appears that the pressure ridge is a barrier to incoming warm current. I confess that I have zero clue as to why an ice ridge would form instead of freezing all the way to the coast. The image shows the ridge extended away from the coast. The area between the ridge and the coast is depicted as surface fast ice over water. Why that section wouldn't freeze all the way to the ocean floor is a mystery.

Anybody? 

oren

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Re: The 2020 melting season
« Reply #379 on: April 19, 2020, 10:42:47 PM »
Ice growth rates are not high enough to freeze all the way to the bottom. During a season new ice can reach maybe 2m, the thicker the ice the slower the growth. But ice floes being stood sideways due to pressure from the pack (and counterforce from the shore) can reach the bottom.

Glen Koehler

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Re: The 2020 melting season
« Reply #380 on: April 20, 2020, 12:12:13 AM »
And I can't recall any source that tracks melt ponding quantitatively, though looking at Worldview shows a telltale bluish color when melt ponding is widespread.
  Neven discussed visual estimates of melt pond prevalence on the ASI blog a few years ago.  It seems like a tool was being developed but never really arrived.

This from: https://neven1.typepad.com/blog/2014/04/more-on-melt-ponds.html#more
-------------------
Neven asks - "How difficult is it to create near real-time melt pond cover fraction data that can be compared to other melting seasons in the 2007-2013 period?"

We may not be that far away. One of the papers currently in discussion at The Cryosphere Discuss is Sea ice melt pond fraction estimation from dual-polarisation C-band SAR – Part 1: In situ observations (R. K. Scharien, J. Landy, and D. G. Barber).
http://www.the-cryosphere-discuss.net/8/805/2014/tcd-8-805-2014.pdf
Posted by: Kevin O'Neill | April 27, 2014 at 01:09
-------------------

And this
https://neven1.typepad.com/blog/2016/07/2016-melting-momentum-part-3.html?cid=6a0133f03a1e37970b01b7c87b7ac1970b#comment-6a0133f03a1e37970b01b7c87b7ac1970b
« Last Edit: April 20, 2020, 12:28:13 AM by Glen Koehler »

Phoenix

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Re: The 2020 melting season
« Reply #381 on: April 20, 2020, 12:13:08 AM »
Ice growth rates are not high enough to freeze all the way to the bottom. During a season new ice can reach maybe 2m, the thicker the ice the slower the growth. But ice floes being stood sideways due to pressure from the pack (and counterforce from the shore) can reach the bottom.

So, what are those ridges in the image that Niall shared ? It looks like a vertical wall of ice from  sea floor to surface.  Is that image misleading ?

Big picture, I'm still trying to understand why the ice begins to melt in that particular place. Any enlightenment appreciated.

Niall Dollard

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Re: The 2020 melting season
« Reply #382 on: April 20, 2020, 01:22:00 AM »
Ice ridges can stick up and down.

Have a look at these recent sonar scans from the MOSAiC expedition.

https://twitter.com/CKatlein/status/1246136156594622465

Re Melt Ponds. NOAA's Physical Science Lab (formerly the ESRL) has a forecast section on melt ponds (under the "Coupled" Menu) As it happens it's showing some activity at present in the northern Kara.

https://psl.noaa.gov/forecasts/seaice/

oren

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Re: The 2020 melting season
« Reply #383 on: April 20, 2020, 02:39:10 AM »
It's useful to read the Wikipedia entry on Pressure Ridges, and another entry about Stamukha.
https://en.wikipedia.org/wiki/Pressure_ridge_(ice)
https://en.wikipedia.org/wiki/Stamukha

Quote
Pressure ridges are the thickest sea ice features and account for about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice.

Quote
One of the largest pressure ridges on record had a sail extending 12 metres (39 ft) above the water surface, and a keel depth of 45 metres (148 ft). The total thickness for a multiyear ridge was reported to be 40 metres (130 ft). On average, total thickness ranges between 5 metres (16 ft) and 30 metres (98 ft), with a mean sail height that remains below 2 metres (6.6 ft).

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Re: The 2020 melting season
« Reply #384 on: April 20, 2020, 03:09:05 AM »
It's useful to read the Wikipedia entry on Pressure Ridges, and another entry about Stamukha.
https://en.wikipedia.org/wiki/Pressure_ridge_(ice)
https://en.wikipedia.org/wiki/Stamukha

Quote
Pressure ridges are the thickest sea ice features and account for about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice.

Quote
One of the largest pressure ridges on record had a sail extending 12 metres (39 ft) above the water surface, and a keel depth of 45 metres (148 ft). The total thickness for a multiyear ridge was reported to be 40 metres (130 ft). On average, total thickness ranges between 5 metres (16 ft) and 30 metres (98 ft), with a mean sail height that remains below 2 metres (6.6 ft).

Interesting. stamukha (the grounded version of ridges) are most often found at depth of 20m which corresponds to Niall's depth chart above. Additionally, stamukha is a Russian word and the crack in question is found on the Russian coast.

So far, the shoe fits !!

So, a good working theory is that the repeating initial crack in the ESS is found at the 20m depth stamukha line.

If I were to imagine how the works in total, you have incoming warm Atlantic water entering the Arctic and Coriolis forces have it hugging the Siberian coast until it hits the stamukha wall and is forced toward the surface which is just a few meters above. Sound reasonable ?

Thanks for the wiki link Oren.

Edit: Alternative / complementary view is that the opening of this crack is also influenced heavily by wind. Looking at Aluminum's most recent post (#339) it seems like the crack was pretty wide a few days ago and then shut down with a change in wind direction.
« Last Edit: April 20, 2020, 03:39:44 AM by Phoenix »

John_The_Elder

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Re: The 2020 melting season
« Reply #385 on: April 20, 2020, 03:10:44 AM »
To what extent to we expect this pulse of 4-5C anomalies across the Eurasian side of the arctic over the next week to impact preconditioning (or pre-preconditioning)?
I'm sure more senior posters will correct me if I'm wrong, but I think the higher temperatures will only have an impact on the freezing of the ice. This "heatwave" basically ends the freezing season early.

Is there a mathematical formula that calculates the increase of ice volume with temperature?
How much possible volume do we lose with a 20°C temp anomaly? And how does that compare to fram export?

There is a formula that calculates the increase of thickness with temperature. Found at https://sites.google.com/site/cryospherecomputing/fdd.

Volume should reach its peak any day now if has not already.
John

oren

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Re: The 2020 melting season
« Reply #386 on: April 20, 2020, 04:39:56 AM »
Which reminds me of the very useful graph of FDDs by Nico Sun. This year was much better than the last few years, as the Arctic was colder during the winter, and volume is not running at a near-record level. Hopefully this will pay off with higher resistance to melting.

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Re: The 2020 melting season
« Reply #387 on: April 20, 2020, 08:23:52 AM »
Ozone.
I prefer that this regular update be posted in a new thread, as it does not affect the current melting season as far as I can tell.
Oren - I see you are listed as Moderator and thus you decide "what goes where". However, consider that the ozone level animations are a kind of proxy for the polar stratospheric circulation, also that the stratospheric ozone in the polar vortex will increase rather dramatically at the onset of a Sudden Stratospheric Warming (SSW). Such events do have relevance in the melting season. For a simple example please see:

]https://ozonewatch.gsfc.nasa.gov/facts/warming_NH.html

Actually it is a bit more complicated than the simple view expressed above, see:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/jgrd.50651
https://arxiv.org/abs/1807.11750

Thus, I think that the ozone measurement animations are relevant to melting, at least in the early part of the melting season.
« Last Edit: April 20, 2020, 08:30:01 AM by guygee »

Aluminium

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Re: The 2020 melting season
« Reply #388 on: April 20, 2020, 10:35:19 AM »
April 14-19.

2019.

oren

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Re: The 2020 melting season
« Reply #389 on: April 20, 2020, 10:53:59 AM »
Thanks for the explanation guygee. Let the ozone remain.

Freegrass

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Re: The 2020 melting season
« Reply #390 on: April 20, 2020, 01:48:20 PM »
Five day forecast Wind @ Surface not looking good for the Barents sea ice.
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Re: The 2020 melting season
« Reply #391 on: April 20, 2020, 02:36:20 PM »
There is a formula that calculates the increase of thickness with temperature. Found at https://sites.google.com/site/cryospherecomputing/fdd.
1) I'm surprised that a formula based solely on temperature would be accurate. 
The chart from Thorndike 1975 shows that the thicker the ice the slower it grows. 
See https://forum.arctic-sea-ice.net/index.php/topic,778.msg32166.html#msg32166

     The Crysopshere Computing background page for the formula does not address the thickness effect specifically, but it does say that the formula is just a rough estimate that ignores other factors:
     "The ice thickness increases at a rate roughly proportional to the square root of the cumulative FDD. Formulas such as this are empirical, meaning they are calculated only with observed data, so they really are simplifications of the ice growth processes. The formulas assume that the ice growth occurs in calm water and is reasonably consistent, and they do not take into account sea ice motion, snow cover, and other surface conditions."

     IMO that explanation also implies that the formula is for the initial phase of ice formation, i.e. starting from no ice (= 0 thickness). 


2) Is there a formula, crude or otherwise, for the decrease in ice thickness according to starting thickness and/or temperature? 

     A while back on the "When will the Arctic Go Ice Free?" thread I proposed reversing the Thorndike "thickness effect on subsequent ice thickening" curve to estimate the rate at which thinner ice melts faster than thicker ice.  But that idea was shot down as incorrect.  Apparently, the effect of thickness on more freezing is not reversible to estimate the effect of thickness on melting rate. 

     A query and a minimal search for such a formula found nothing.  It seems like an easy physical experiment to do, and an important clue to how ASI decline will evolve as the average Thickness continues to decline along with Extent and Volume.  Somebody must have calculated that effect.

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Re: The 2020 melting season
« Reply #392 on: April 20, 2020, 03:39:56 PM »
1) I'm surprised that a formula based solely on temperature would be accurate. 
The chart from Thorndike 1975 shows that the thicker the ice the slower it grows. 
See https://forum.arctic-sea-ice.net/index.php/topic,778.msg32166.html#msg32166
Thank you Glen! This link you posted provided an answer to my question how much possible volume we would lose with a 20°C temp anomaly. Probably not much, except for places with thin ice.

Quote
Say you increased the length of the freeze season, you'd get only small increase in thermodynamic thickening because by 1.5m and above the rate of ice growth is small. This is because as the ice thickens it better insulates ocean (warmer) from the colder atmosphere. So for anything over 1.5m thickness, shorten the freeze season even by as much as a month and you get very little impact on thermodynamic thickness
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Re: The 2020 melting season
« Reply #393 on: April 20, 2020, 03:53:55 PM »
Glen Koehler,
I think that the formula given by John_The_Elder in the previous post: "Thickness (cm) = 1.33 * FDD (°C)0.58", is relative to a starting situation without ice. If at the beginning there is already an ice thickness to use the formula you have to add to the FDD the value that gives the thickness already present (and the influence of the thickness in the formula is given by the exponent 0.58).

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Re: The 2020 melting season
« Reply #394 on: April 20, 2020, 05:20:46 PM »
Glen Koehler,
I think that the formula given by John_The_Elder in the previous post: "Thickness (cm) = 1.33 * FDD (°C)0.58", is relative to a starting situation without ice. If at the beginning there is already an ice thickness to use the formula you have to add to the FDD the value that gives the thickness already present (and the influence of the thickness in the formula is given by the exponent 0.58).
Nico Sun quotes this formula in his webpage for FDD   https://cryospherecomputing.tk/index.html

The source quoted is  "Lebedev - 1938". One wonders what research / testing has been on this formula since 1938.
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Re: The 2020 melting season
« Reply #395 on: April 20, 2020, 05:39:06 PM »
Here's a link to a Chris Reynolds discussion on ice growth calculations, and another to a post in his "Slow Transition" thread about Lebedev and Billelo and related issues.
http://dosbat.blogspot.com/2015/01/the-simplest-model-of-sea-ice-growth.html
https://forum.arctic-sea-ice.net/index.php/topic,933.msg58049.html#msg58049

I would ask that further discussion of this very important issue continue in a different existing thread, or start a new one if needed.
Make a search for Lebedev and Billelo to help in locating a suitable venue.

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Re: The 2020 melting season
« Reply #396 on: April 20, 2020, 09:39:52 PM »

Also:

When insolation < emission, snow is bad as it insulates and prevents heat loss.
When insolation > emission, snow is good as it prevents the ice heating up.


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Re: The 2020 melting season
« Reply #397 on: April 20, 2020, 10:54:16 PM »
They tell me that the highly +ve Arctic Oscillation has had much to do with the strong Polar Vortex and the resulting high Arctic Sea Ice maximum this year, especially almost 100% concentration in the central seas..

So I thought I had better have a look at the forecasts on....

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml

There is a GFS and an Ensemble forecast, 7, 10, & 14 day forecasts. Both products suggest the +ve AO isn't over yet. If so, this could imply continuing cold in the central seas and warmth in the periphery?

Also, both sets of forecasts consistently under-estimated the strength of the +ve index from January to date.
Also, the 7 day forecast is close to reality. The 14 day forecast looks pretty useless to me.

ps:- It is a really good website - even a quick wander around in it taught me quite a lot.
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Re: The 2020 melting season
« Reply #398 on: April 21, 2020, 12:27:39 AM »
I have more satellite data that I have been hoping to present this season but due to my system breakdown and cost of repairs US$1,500, I have not been able to access the images I would have wished to put out this season on some debates. (Difficulty is that the firmware reader of data is incompatible with all PC and MacIntosh so finding people and spares is very hard for me to fix it.)
I can on this debate offer you a few images that I have put on my Curriculum Vitae that can be downloaded from Academia.edu. They are not of best resolutions, nor all of the images available that are highlighting this matter, but every bit will, nevertheless, help.

It is costly to produce images which provide optic side scans and repeat scans (multiplexing) of sea ice as this involves flying satellite constellations repeatedly in different angles and one after another. It is getting ever easier and one day all this is probably routine. Also a Fournier triangulation is avoided to spot visually a target such as a moving warship and to identify which ship or submarine has surfaced from the Arctic sea ice. It is tedious exercise to keep tabs (particularly on nuclear submarines as they are small and can disappear quickly back into ice).

For our discussion here we are interested about the formation of the leads, why and where they form:

Multiplex imaging with satellite cluster produces images of entire Arctic Ocean cloud-free during sunlight season, including the infrared and UV-scanners that identify sources or ships' heat or electric lights, whatever. On CV page 10 you can see how the continuous breakwater pulse propagates within the Arctic Ocean and weakens the sea ice from the estuary onwards. (The large image on the top.) Typically ultimate "C", penultimate "B", and antepenultimate "A" ice floes form from the Russian coast running their weakened seams perpendicularly to Canada where the ultimate "C" typically hits at the Western Last Sea Ice Area (Western - LIA) where the turning process causes opposite stress point, thus segregating the ultimate "C" and penultimate "B". There are two of these, but only one C/B is shown on my CV, both of them would be interest to this discussion.

There are couple other processes on the Arctic Ocean:

Page 8 The antepenultimate "A" facing the Atlantic runs on its own with the alternating zebra patterns of green and white on this image (result of breakwater waves or cells rolling on shallow sea).

The density differentials form the colours here as the river water from Russia moves along and rolls a bit like Swiss roll on its way to deep water near Fram Strait. The high density water is white as sea surface is lower than the ocean median ice surface (the median lines are highlighted on image for clarity), the low density river water is green due to it representing higher than the ocean median ice surface (due to its being less saline, it needs higher water column than saline water to keep ocean surface at equilibrium pressure).

The white colour forms over the dense water where ocean surface is lower than median and fills with drift snow. The green colour forms on the crest that is higher and without the drift snow that accumulates on troughs. The snow accumulation further amplifies the effect anchoring even more snow over the dense, saline rollers.

Because of this constant rolling of Swiss rolls between the ocean floor and its surface (sea ice), there is an overall current which has higher gravity potential and faster forward movement on surface, this then marks the boundary between antepenultimate "A", and penultimate "B" as the B flows slower than A.

These things have also changed over the years as ice in overall has pulverised and not been forming uniform films, but overall show the effect of North Asian rivers discharging onto the Arctic Ocean and forming weak points by supply of warmer water and its mixing and dragging heat out from warmer waters beneath - then maintaining a thinner ice along a narrow channel which presses against Canada (Western Last Sea Ice Area, by splitting the sea ice C/B and B/A, with B/A junction also running at different speed.

The differential movement on p. 8 is shown by 12 perpendicular secondary cracks (highlighted) on the main B/A crossing from Komsomoletski Island to Ellesmere Island.

Page 9 focuses on vortices or breakwater cells that fall into the deep channel, warm up aggressively and surface like cumulus cloud with the centre of pancake elevated with edges bending down and below median and filled by snow. These curving sea ice "spaghetti" edge formations are rare in comparison of the rectangular edge formations caused by breaking ice and re-freezing ice.

The rest of my Curriculum Vitae outside pages 8, 9, 10 are irrelevant to this forum.
https://www.academia.edu/5859691/Curriculum_Vitae_for_Exploration_and_Research

It's useful to read the Wikipedia entry on Pressure Ridges, and another entry about Stamukha.
https://en.wikipedia.org/wiki/Pressure_ridge_(ice)
https://en.wikipedia.org/wiki/Stamukha

Quote
Pressure ridges are the thickest sea ice features and account for about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice.

Quote
One of the largest pressure ridges on record had a sail extending 12 metres (39 ft) above the water surface, and a keel depth of 45 metres (148 ft). The total thickness for a multiyear ridge was reported to be 40 metres (130 ft). On average, total thickness ranges between 5 metres (16 ft) and 30 metres (98 ft), with a mean sail height that remains below 2 metres (6.6 ft).

Interesting. stamukha (the grounded version of ridges) are most often found at depth of 20m which corresponds to Niall's depth chart above. Additionally, stamukha is a Russian word and the crack in question is found on the Russian coast.

So far, the shoe fits !!

So, a good working theory is that the repeating initial crack in the ESS is found at the 20m depth stamukha line.

If I were to imagine how the works in total, you have incoming warm Atlantic water entering the Arctic and Coriolis forces have it hugging the Siberian coast until it hits the stamukha wall and is forced toward the surface which is just a few meters above. Sound reasonable ?

Thanks for the wiki link Oren.

Edit: Alternative / complementary view is that the opening of this crack is also influenced heavily by wind. Looking at Aluminum's most recent post (#339) it seems like the crack was pretty wide a few days ago and then shut down with a change in wind direction.
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Re: The 2020 melting season
« Reply #399 on: April 21, 2020, 12:44:34 AM »
Volume is not running at a near-record level. Hopefully this will pay off with higher resistance to melting.

That rather depends upon which volume metric you choose to look at:

http://GreatWhiteCon.info/2020/03/facts-about-the-arctic-in-april-2020/#Apr-19
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