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Author Topic: The 2020/2021 freezing season  (Read 94750 times)

A-Team

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Re: The 2020/2021 freezing season
« Reply #550 on: October 26, 2020, 12:27:57 AM »
Quote
the original C2S palette is quite unreadable
The auto-archive has been created by L Kaleschke of AWI who sometimes posts here and on twitter. The files are updated daily using the updated Smos and whatever Cryo swaths that have come in. The day to day differences are small but can be visualized either by differencing the pngs or by visualizing the (perfectly done) netCDF in Panoply.

The combining algorithm parts are complex and have been under intensive development for years. Kaleschke spent four months on the Polarstern; one of the main objectives there was to synch plane and satellite overflights with myriad ice cores to improve products such as this and AMSR2. This can't be said about Piomas.

The first quickie below is contoured for major and minor scale ticks. Note the lat lon graticule is gone and the image is in 'Greenland down' orientation. The second emphasizes the thicker ice, there is very little thicker than a 1.0m this early in the freeze season and only a tiny bit near the 2.56m maximum. The third displays thickness isopleths.

No script is needed for the volume calc in an equal area pixel projection like lambert azimuthal. It's a menu item in ImageJ. It takes another click or two in Excel to graph the distribution of ice thickness (which is likely normal about the mean but skewed against thicker ice without notable kurtosis).

The main .nc files here are a great opportunity to learn about graphical display and analysis of netCDF data using painless Panoply.

https://www.giss.nasa.gov/tools/panoply/download/   easy stable netCDF menu-driven tool
https://imagej.nih.gov/ij/download.html  free scientific graphics tool

ftp://ftp.awi.de/sea_ice/product/cryosat2_smos/v203/nh/LATEST/  home folder

ftp://ftp.awi.de/sea_ice/product/cryosat2_smos/v203/nh/LATEST/W_XX-ESA,SMOS_CS2,NH_25KM_EASE2_20201017_20201023_o_v203_01_l4sit.png

ftp://ftp.awi.de/sea_ice/product/cryosat2_smos/v203/nh/LATEST/W_XX-ESA,SMOS_CS2,NH_25KM_EASE2_20201017_20201023_o_v203_01_l4sit.nc
« Last Edit: October 26, 2020, 01:07:46 PM by A-Team »

jdallen

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Re: The 2020/2021 freezing season
« Reply #551 on: October 26, 2020, 02:10:51 AM »
Quote
the original C2S palette is quite unreadable
<snip>
The quickie below is contoured for major and minor scale ticks. Note the lat lon graticule is gone and it is in 'Greenland down' orientation. The second emphasizes the very thickest ice, there is a tiny bit at 2.56m.
<snip>
This may be the most depressing image I've ever seen on these forums.

It suggests all the land fast ice is gone, for practical purposes.

It suggests all of the 3m+ ice is gone, similarly.

The pack is completely unhinged and at the full mercy of the weather.
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FishOutofWater

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Re: The 2020/2021 freezing season
« Reply #552 on: October 26, 2020, 03:09:18 AM »
Gandul, there are many papers that discuss the Atlantic water layer and the increasing Atlantification of the Eurasian side of the Arctic. Google is your friend and I have given references to some articles in the past. The high salinity water in the Mercator model along the continental shelf margin in the Laptev sea has no other possible source than the north Atlantic if that high salinity water actually exists. The Coriolis effect tends to turn water to the right in the northern hemisphere except when there is a sea surface height gradient or pressure gradient in the opposite direction. There's no Pacific water layer in the Laptev sea and the Siberian shelf water has fresh water from the Siberian rivers.

I don't understand physical oceanography very well, but this is very simple geochemistry. High salinity is a dead give away that the water is of Atlantic origin.

The enhanced heat loss this fall and winter will cause an increase in mixing which will likely decrease stratification in the Laptev sea. All other variables held constant this will increase Atlantification and the sinking of saline water to mid ocean levels along the Laptev shelf margin. Of course, large scale shifts in the winds and weather could cause something else to happen.

jdallen

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Re: The 2020/2021 freezing season
« Reply #553 on: October 26, 2020, 06:30:54 AM »
I don't understand physical oceanography very well, but this is very simple geochemistry. High salinity is a dead give away that the water is of Atlantic origin.
Salinity is a key indicator, along with the documented invasion of Atlantic fauna and algae northwards and eastwards out of the Norwegian sea.

It is happening now, probably has been for over a decade.  I don't think it's theoretical any more.
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Aluminium

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Re: The 2020/2021 freezing season
« Reply #554 on: October 26, 2020, 07:41:31 AM »
October 21-25.

2019.

aslan

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Re: The 2020/2021 freezing season
« Reply #555 on: October 26, 2020, 08:22:03 AM »
Temperature on Kotelny Island finally falls below -10°C. Winter is coming.

Not wanting to sound disparaging, but -10°C at Kotel'nyj at this time of year is barely the normal high, and temperatures are already back to -2°C :

http://ogimet.com/cgi-bin/gsynres?ind=21432&decoded=yes&ndays=20&ano=2020&mes=10&day=26&hora=12

Of course it is cooling. Even with all the warming possible, October is bound to be a month of rapid decline of the temperatures in  the NH. But anomalies are still extreme and the seasonal cooling not so strong. Even though we are not going to see a repeat of the month of Septemebr, with monthly mean temperatures higher than the preceding records by many °C over millions of square kms ; October is still going to book new records. As of now for exemple, mean temp' at Kotel'Nyj is -2.8°C and the record is -3.2°C in 2018. We will need more than one or two "mornings"(ok, Tn  ;D ) at -10°C for not breaking the record.

idunno

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Re: The 2020/2021 freezing season
« Reply #556 on: October 26, 2020, 08:50:08 AM »
Hi all,

Its been some time, and I havent been regularly following...

When I was often contributing here, I'd argue that the summer minima were not the most serious indicator, and that a failure of the refreeze, which raises the SST from -30C or thereabouts (ice) to -1.8C (water) would have a much more dramatic effect on the atmosphere. That seems to be afoot.

I am well out of my depth with data-handling and graphing, but I'd like to throw out there that the most useful graph that could be produced in the current extraordinary conditions would be one showing the total ice extent area as an average over the preceeding 365 days, on any particular day for which we have data.

Perhaps it may be more practical to pick the first day of each month. Either way, I'm fairly sure that the lowest reading would be the last one, and this would hold the record only until the next one becomes available.

I think this might be helpful for the general public, for them to appreciate the current dire state of affairs.

(If this has been graphed already, please excuse my current state of ignorance)

cheers,

idunno

oren

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Re: The 2020/2021 freezing season
« Reply #557 on: October 26, 2020, 09:14:24 AM »
idunno, this has already been covered, please check this thread
https://forum.arctic-sea-ice.net/index.php/topic,2909.0.html
Our "old faithful" Gerontocrat is updating the chart frequently, based on data from the most recent 365 days. The record is still held by March-April 2017, but we may have a good chance of breaking it.

Sepp

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Re: The 2020/2021 freezing season
« Reply #558 on: October 26, 2020, 09:22:52 AM »
I look forward to seeing your results!

These are the results of your script (I did not have time, to use the other approach suggested by A-Team):

Arctic on 20201022 - Volume = 4627.1 km³, Uncertainty = 715.0 km³
With 15.0% threshold - Area = 4508628.4 km², Extent = 5413750.0 km²
Arctic on 20201023 - Volume = 4636.8 km³, Uncertainty = 713.3 km³
With 15.0% threshold - Area = 4572533.6 km², Extent = 5473125.0 km²

So this would give 400 to 500 km³ less than Piomas Mid October numbers. Actually quite closer than I expected.

oren

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Re: The 2020/2021 freezing season
« Reply #559 on: October 26, 2020, 09:52:57 AM »
Thanks Sepp. Do you know what was the difference with PIOMAS in April, before C2S stopped providing data?

aslan

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Re: The 2020/2021 freezing season
« Reply #560 on: October 26, 2020, 10:29:55 AM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.

Sepp

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Re: The 2020/2021 freezing season
« Reply #561 on: October 26, 2020, 10:45:03 AM »
Thanks Sepp. Do you know what was the difference with PIOMAS in April, before C2S stopped providing data?

According to figure 10 on the PIOMAS site it was roughly around 5000 km³ or 20 percent below the PIOMAS value, while currently its only around ten percent. But the dates do not match exactly, so those values are a bit ambigous, I think and even with this slow freezing, the difference of one week might be quite significant. I’d expect PIOMAS releases their own comparison chart with the final October report. Those numbers might give a better picture than mine.
« Last Edit: October 26, 2020, 11:11:00 AM by Sepp »

Pagophilus

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Re: The 2020/2021 freezing season
« Reply #562 on: October 26, 2020, 11:22:43 AM »
NSIDC comparison tool.  Oct 24 2020 ice extent vs Oct 24 2019, 2016, 2012.

SimonF92

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Re: The 2020/2021 freezing season
« Reply #563 on: October 26, 2020, 11:38:35 AM »
NSIDC comparison tool.  Oct 24 2020 ice extent vs Oct 24 2019, 2016, 2012.

Very nice. A clear demonstration.
Bunch of small python Arctic Apps:
https://github.com/SimonF92/Arctic

Freegrass

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Re: The 2020/2021 freezing season
« Reply #564 on: October 26, 2020, 12:48:38 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Wind + Temp @ 850hPa
Wind @ 250hPa
Large GiFS!
Now let's pray...

If the science don't fit our beliefs, we pray to God and cuddle up in our own delusional fantasy where everything makes sense again...

Pavel

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Re: The 2020/2021 freezing season
« Reply #565 on: October 26, 2020, 12:57:05 PM »
Well, at least there is no strong heat advection to the high Arctic. But this pattern was the entire last freezing season and has resulted the low snow cover in Eurasia by the end of winter and abnormal Siberian heat in spring

Aluminium

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Re: The 2020/2021 freezing season
« Reply #566 on: October 26, 2020, 02:00:19 PM »
This winter I would not be surprised to see heat advection from the Arctic.

Shared Humanity

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Re: The 2020/2021 freezing season
« Reply #567 on: October 26, 2020, 03:00:05 PM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.

Hard for ice to form in seas with 4 meter waves. How deep does the mixing of water occur in such seas?

Général de GuerreLasse

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Re: The 2020/2021 freezing season
« Reply #568 on: October 26, 2020, 03:09:30 PM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.

Hard for ice to form in seas with 4 meter waves. How deep does the mixing of water occur in such seas?

The average wave period does not seem high to me, except in the Barents Sea. It may not be enough to mix the water in depth? I am not a specialist.
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aslan

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Re: The 2020/2021 freezing season
« Reply #569 on: October 26, 2020, 03:28:54 PM »
This is Arctic. Even though on its own a wave period of 10 seconds is not extraordinary (in the Pacific, period of 20 seconds are possible...), it is not the way it must work. For the depth of the mixing, I don't know and I am not sure there can be an answer. It depends on different factors, and especially the stratification of ocean. During the storm of 2012, mixing occurs over a depth of about 10 to 30 meters : https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/grl.50190. And during a storm in October 2015, it was about the same idea : https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2018JC013764
But it is really hard to give some numbers. It depends a lot on the stratification of the ocean. Either way, even though it does not sound a lot, wave period of 10 seconds and mixing depth of 30 meters are really significant in the Arctic.

P.S. : Worth to read also :https://reader.elsevier.com/reader/sd/pii/S1463500316300622?token=DFCB8444FB3423422C3C831531FD0FB4704E87BCAFBCCEF5681DA1C00B8EDCDAE777B94E618EBCD0F4333143CEB831D5

(but there is also the question of the reduced stratification of the atmosphere which should promote higher wind speed at surface, no matter the change in the pressure field. I am not aware of anay studies about this subject)
« Last Edit: October 26, 2020, 03:42:36 PM by aslan »

aslan

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Re: The 2020/2021 freezing season
« Reply #570 on: October 26, 2020, 04:47:55 PM »
Quick and dirty sorry, but about the storm of tomorrow, to illustrate again. Map is wind speed (orange and yellow) at 500m (about 925 hPa), wind at same height (I hope...), theta (potential temperature) in black, surface temperature at -2°C in blue for an approximate ice edge, vertical velocity at 925 hPa (max threshold at -10 Pa/s) in gray and convective rainfall in transparence. And when I say convective rainfall, yeah I really meant that models are forecasting CBs all over the Arctic in the coming day. Next step, a subtropical storm in the Arctic.... This said. If we follow the wind, we hit a wall of theta which is the inversion over sea ice. There is surface based CAPE north to Kotel'Nyj (For central Arctic in late October, this qualify as a "holy mother of Einstein, what the f*** is going on" level on the crazyometer). This layer of unstable air is forced to rise over the ridge of theta, bringing mid level CBs over ice pack. We are swimming in a pool of craziness. This advection can be followed on soundings as the theta at the top of the inversion is the same that theta at surface north of Kotel'Nyj. We really have an isentropic lift forced by the temperature inversion over the pack, forcing ascents and instability... And on top of that, we can see that LLJ can't descend to surface over ice pack.
Soundings are from south to north (77°N, 81°N, 82°N)
Of course there is also and mostly synoptic scale forcings, etc... but there is really some things going on at the interface between sea ice and ocean, and we are to the point we need a good swath of CBs to cool down the Arctic Ocean. On top of that, in the Arctic night, CBs are powerfull at isolating the surface, radiating a lot of heat toward he surface in longwave (and sea ice is not white in IR...)
« Last Edit: October 26, 2020, 04:53:17 PM by aslan »

aslan

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Re: The 2020/2021 freezing season
« Reply #571 on: October 26, 2020, 04:52:35 PM »
Last sounding

Général de GuerreLasse

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Re: The 2020/2021 freezing season
« Reply #572 on: October 26, 2020, 05:19:59 PM »
This is Arctic. Even though on its own a wave period of 10 seconds is not extraordinary (in the Pacific, period of 20 seconds are possible...), it is not the way it must work. For the depth of the mixing, I don't know and I am not sure there can be an answer. It depends on different factors, and especially the stratification of ocean. During the storm of 2012, mixing occurs over a depth of about 10 to 30 meters : https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/grl.50190. And during a storm in October 2015, it was about the same idea : https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2018JC013764
But it is really hard to give some numbers. It depends a lot on the stratification of the ocean. Either way, even though it does not sound a lot, wave period of 10 seconds and mixing depth of 30 meters are really significant in the Arctic.

P.S. : Worth to read also :https://reader.elsevier.com/reader/sd/pii/S1463500316300622?token=DFCB8444FB3423422C3C831531FD0FB4704E87BCAFBCCEF5681DA1C00B8EDCDAE777B94E618EBCD0F4333143CEB831D5

(but there is also the question of the reduced stratification of the atmosphere which should promote higher wind speed at surface, no matter the change in the pressure field. I am not aware of anay studies about this subject)

A big thank you to you Aslan, the link you have given is exciting. I think I'll have to read and reread it to understand it, but the extract I propose here is enlightening. You were right, I suspected it a little bit  ;D but here I have a good explanation that I will dig.

"The autumn storms that regularly occur in the Beaufort and Chukchi Seas are elevating the sea state now, and will continue so into the future, simply because it is increasingly likely that the storms will occur over larger open water areas that persist longer into autumn. It is yet to be determined if the higher sea states will in turn feed back to the large-scale evolution of the sea ice. The increasing sea state may affect not only the ice cover development, but also wave forcing in the coastal zone. Either way, the increasing sea states may alter air-sea fluxes and associated ecosystem processes. It is possible that the increasing sea state may play an important role in modulating the presumed changes in air-sea fluxes and upper ocean properties that are occurring, and in turn may modulate the response of sea ice to climate change."
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BornFromTheVoid

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Re: The 2020/2021 freezing season
« Reply #573 on: October 26, 2020, 05:50:25 PM »
Here's a side by side comparison of the first 25 days of ice growth this October compared to 2012
(Larger, better quality version on twitter here: https://twitter.com/Icy_Samuel/status/1320764047638302720)

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Milwen

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Re: The 2020/2021 freezing season
« Reply #575 on: October 26, 2020, 09:01:04 PM »
Yes Milwen. This evening's ECMWF op run has substantial warmth flooding the eastern half of the Arctic at the end of the run. Still 10 days away so at the end of the medium range.

Negative Arctic dipole.
« Last Edit: October 26, 2020, 09:12:40 PM by Niall Dollard »

jdallen

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Re: The 2020/2021 freezing season
« Reply #576 on: October 26, 2020, 11:36:04 PM »
Yes Milwen. This evening's ECMWF op run has substantial warmth flooding the eastern half of the Arctic at the end of the run. Still 10 days away so at the end of the medium range.

Negative Arctic dipole.
... and the same level of astounding temperature anomalies we saw in 2016, and to a lesser degree later, except, perhaps, worse.
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uniquorn

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Re: The 2020/2021 freezing season
« Reply #577 on: October 26, 2020, 11:46:04 PM »
cs2smos thickness difference, oct23-25.
Guessing that blue spot must be bathy related.

Gumbercules

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Re: The 2020/2021 freezing season
« Reply #578 on: October 27, 2020, 03:20:08 AM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.

Hard for ice to form in seas with 4 meter waves. How deep does the mixing of water occur in such seas?

The average wave period does not seem high to me, except in the Barents Sea. It may not be enough to mix the water in depth? I am not a specialist.

Wouldn't a lower period result in more mixing? Higher period means lower frequency, longer wavelength wave, so a smoother ocean. Lower period means high frequency, meaning shorter wavelengths, meaning more turbulent ocean.

This is just my initial analysis based on intuition.

A-Team

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Re: The 2020/2021 freezing season
« Reply #579 on: October 27, 2020, 11:53:52 AM »
Quote
bathymetry --> ice thinning spot?
Thousands of meters deep, tectonically quiet, nothing down there for a heat or turbulence source?

Whenever something is measured in physics, there's an obligation to estimate the error. In the Cryo2Smos netCDFs, there is indeed an included Geo2D file that generates the error map. Subtracting two close dates will lead to more combined error. If this error is too high relative to bona fide data differences, interpretation becomes problematic.

The error map seems to have a hot spot at the blue anomaly above. Here it might be worth clicking over to array view and looking at the patch of numbers for the nature of the oddity. It is more likely to originate from the Cryo than from the SMOS.

The ice thickness time series here only will only get to day 4 this afternoon. So the opportunities for limiting subtraction error will improve, from day2-day1, day3-day1 (above), day4-day1 etc and at some point will become relatively negligible in comparison to data differences.

As weeks and months of data become available, sufficiently separated date pairs can determine a ice thickening rate map across the lower Arctic. Note reducing the map to a single volume number loses all these important regional differences.

On the open water side, still 40% of the Arctic surface, the counterpart to the ice thickness netCDF is a high quality daily netCDF for 'foundational' sea surface temperature, the mixed layer at 10m. That archive goes back for many months but here the interest is how fast the water column temperature has been cooling during the freeze season to estimate when it will become cold enough to freeze over. Again a nuanced regional (map) basis is preferable to a single extent number.

There is no single reason that explains the late freeze-up this year. Instead, the observed heat built up in the water column over time has to be apportioned among the various sources and balanced against mechanisms of heat loss. Inputs include global climatic trends and tele-connections, Arctic Amplification, creeping Atlantification, clear skies and summer insolation of open water, Siberian heat waves, mid-latitude moisture intrusions, cyclones, wave mixing, cooling buoyancy induced turbulence and so on. Outputs, mechanisms by which the water column loses heat, have been discussed earlier. Right now, the air is too warm and wind mixing to depth too high but those are acting on a heat state attained via earlier effects.

"The Arctic sea ice is growing very slowly this year. The ocean temperature in the entire mixed layer has to drop below the freezing point because the sea water is salty: when it cools down, the density increases and this leads to [buoyancy-driven] convection as it sinks. The lack of new ice growth is [quite anomalous]. SMOS shows an exceptionally small [advance] area covered with thin ice." Fig 3 Fig 4 https://twitter.com/seaice_de

The main difficulty in using Panoply to make time or difference series is in setting the range to accommodate the earliest and latest dates. If too broad, data will be squeezed into a narrow portion of the color range, losing resolution; too narrow, outlying but differing data will lumped into the end points.

Although Panoply offers over a hundred palettes, it may be best just to use the 255-grayscale where subtraction of pixels means what you want it to mean, subtraction of data values. (Images are spreadsheets.) Then colorize the final product later using one of the thousands of LUTs available in ImageJ, with custom adjustment wherever colors are not visually distinguishable.

The key is looking at product histograms of data value scatter and their asymmetry. The latter can be seen by superimposing a horizontal flip on a fast rocker.
« Last Edit: October 27, 2020, 03:05:35 PM by A-Team »

uniquorn

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Re: The 2020/2021 freezing season
« Reply #580 on: October 27, 2020, 12:13:23 PM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.
Hard for ice to form in seas with 4 meter waves. How deep does the mixing of water occur in such seas?

An essay from Peter Wadhams 2003  How Does Arctic Sea Ice Form and Decay?
Quote
How ice forms in rough water
If the initial ice formation occurs in rough water, for instance at the extreme ice edge in rough seas such as the Greenland or Bering Seas, then the high energy and turbulence in the wave field maintains the new ice as a dense suspension of frazil, rather than forming nilas. This suspension undergoes cyclic compression because of the particle orbits in the wave field, and during the compression phase the crystals can freeze together to form small coherent cakes of slush which grow larger by accretion from the frazil ice and more solid through continued freezing between the crystals. This becomes known as pancake ice because collisions between the cakes pump frazil ice suspension onto the edges of the cakes, then the water drains away to leave a raised rim of ice which gives each cake the appearance of a pancake. At the ice edge the pancakes are only a few cm in diameter, but they gradually grow in diameter and thickness with increasing distance from the ice edge, until they may reach 3-5 m diameter and 50-70 cm thickness. The surrounding frazil continues to grow and supply material to the growing pancakes.

At greater distances inside the ice edge, where the wave field is calmed, the pancakes may begin to freeze together in groups and eventually coalesce to form first large floes, then finally a continuous sheet of first-year ice known as consolidated pancake ice. Such ice has a different bottom morphology from normal sea ice. The pancakes at the time of consolidation are jumbled together and rafted over one another, and freeze together in this way with the frazil acting as "glue". The result is a very rough, jagged bottom, with rafted cakes doubling or tripling the normal ice thickness, and with the edges of pancakes protruding upwards to give a surface topography resembling a "stony field".

This open access article from Nature covers winter storms in much greater detail, describing both positive and negative effects on ice growth.

Winter storms accelerate the demise of sea ice in the Atlantic sector of the Arctic Ocean
Robert M. Graham, Polona Itkin, […]Mats A. Granskog    25 June 2019
Quote
Abstract
A large retreat of sea-ice in the ‘stormy’ Atlantic Sector of the Arctic Ocean has become evident through a series of record minima for the winter maximum sea-ice extent since 2015. Results from the Norwegian young sea ICE (N-ICE2015) expedition, a five-month-long (Jan-Jun) drifting ice station in first and second year pack-ice north of Svalbard, showcase how sea-ice in this region is frequently affected by passing winter storms. Here we synthesise the interdisciplinary N-ICE2015 dataset, including independent observations of the atmosphere, snow, sea-ice, ocean, and ecosystem. We build upon recent results and illustrate the different mechanisms through which winter storms impact the coupled Arctic sea-ice system. These short-lived and episodic synoptic-scale events transport pulses of heat and moisture into the Arctic, which temporarily reduce radiative cooling and henceforth ice growth. Cumulative snowfall from each sequential storm deepens the snow pack and insulates the sea-ice, further inhibiting ice growth throughout the remaining winter season. Strong winds fracture the ice cover, enhance ocean-ice-atmosphere heat fluxes, and make the ice more susceptible to lateral melt. In conclusion, the legacy of Arctic winter storms for sea-ice and the ice-associated ecosystem in the Atlantic Sector lasts far beyond their short lifespan.

<>

Winter storms enhance ocean mixing, heat fluxes, and ice melt
Sea ice dampens energy transfers between the atmosphere and ocean, and therefore the Arctic Ocean is traditionally considered to be energetically ‘quiet’ with weak turbulent mixing58. However, strong winds during the N-ICE2015 winter storms enhanced ice drift speeds54 (Figs 3a and 5a), which increased ocean-ice velocity shear59. These processes were found to generate mixing in the upper ocean, and led to increased transfer of ocean heat towards the ice59,60 (Fig. 5c–e). Observed winter ocean-ice heat fluxes typically more than tripled from 2 W m−2 to 7 W m−2 during storm periods (Fig. 5c, Methods), further impeding ice growth and in several cases initiating bottom melt59,60 (Fig. 3b).

Ocean mixing is particularly important in many regions of the Arctic Ocean because warm water of Atlantic origin is located below cold and fresh Polar Surface Water61. Along the continental slope north of Svalbard, warm Atlantic Water (>2 °C) is found close to the surface (Figs 1, 5e). Vertical mixing thus generates enhanced ocean heat fluxes. The magnitude of this heat flux is dependent on the mixing rate, as well as the depth and temperature of the warm water. During the N-ICE2015 winter drift over the deep Nansen Basin, Modified Atlantic Water (>0 °C) was found at approximately 100 m depth62. Under calm conditions in the deep Nansen Basin, Meyer et al.60 observed ocean heat fluxes at the pycnocline of approximately 3 W m−2 (Fig. S1). However, during storm periods, wind-driven mixing almost doubled the pycnocline heat fluxes to 5.5 W m−2 (Methods, Fig. S4a). These enhanced ocean heat fluxes are relatively small in comparison to changes in the atmospheric surface energy budget during storms37 and were insufficient to induce ice bottom melt, but nevertheless acted to further suppress ice growth (Figs 2e and 5c). Previous work using autonomous buoy measurements have inferred enhanced ice-ocean heat fluxes during winter storms in the Beaufort Sea25. It is therefore expected that these conditions in the Nansen Basin are representative of large areas of the central Arctic Ocean.

Accepted that the water has to be cold enough to form frazil ice.

Thanks for the post above A-team. I'll check out the error anomaly. That area seems already identified as possible out of range results.
« Last Edit: October 27, 2020, 12:38:07 PM by uniquorn »

Freegrass

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Re: The 2020/2021 freezing season
« Reply #581 on: October 27, 2020, 12:30:47 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!
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A-Team

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Re: The 2020/2021 freezing season
« Reply #582 on: October 27, 2020, 03:56:49 PM »
Our parallel efforts with thickening ice and cooling water column netCDFs share the problem of the growing ice pack boundary. The former won't have any earlier time series data (too much water vapor for the satellite) and the latter will start to lose its value (because water temperature is no longer observable under ice and somewhat locked in).

The good news is the areas are complimentary so both can be combined in a single time series animation, perhaps colored separately to avoid confusion. Panoply has a helpful command at the bottom of the Plot menu for saving all current map settings to preferences (new default for next map) but does not have any mechanism for sharing these settings.

I currently have plot size set to 220 so the map will later crop to 500 pxl width; the scale bar will fit under it if set to 25 with tick fortran format %0f with size 6 font. The map is stereographic at -45º 90º with outer edge 65º.

The SST lower range of 271.15 causes the ice pack to be uniquely selectable (black) whereas filled corners picks up some Bering Sea and an upper range of 280 with background 255 gives all of the warm Chukchi a gray even back to Sept 15th (the problem area being off Point Hope).

After saving out png's for two dates (Sept 15h and Oct 23rd in example below), they can be compared in a blinker graphic or better, subtracted and offset by 128 pxls using 'grain extract; in Gimp which allows for the split red loss, blue gain palette called 'unionjack' in ImageJ.

This results in the (tentative) image below that shows the water column down to 10m has indeed  cooled appreciably in the 38 days between the melt minimum and Oct 23rd but not enough for -1.8 freezing. Color-picker clicking on any pixel should light up a single band on the temperature scale as there's been no dithering.

One small area in the Chukchi seems to have warmed and an area by the Lena delta may be blown out (need a smaller offset). If this had been done as array/09.15 - array/10.23 within Panoply, that would have generated a cooling scale of degrees K lost. Offset could probably be controlled with range settings.

Glen K requested a daily velocity map video of cooling rate with year-on-year anomalies. The former is just grain extract on the tile-up but requires making all the dailies; the latter isn't feasible because previous years have too much ice pack.

It would however be practical to go back far earlier in the summer as the files are there; this might give a handle on apportioning heat content gain between insolation, carry-over and Atlantification. Peak heat might only have been reached by mid-August, depending on the region.

Hopefully more forum members will engage with netCDF -- it is the standard data format in climate change and it doesn't get any easier than Panoply.

The final image makes a 'prediction' for the freeze-over date for the Laptev. The image takes a copy of the blue line from 2012, colors it gold and moves it over exactly horizontally until it extends the most recent 2020 date. A dotted green line is then dropped from the intercept down to the calendar date, intercepting it in late November, almost a full month later than the previous record from 2012. Note the Chukchi, ESS and Kara are not included in the analysis: the former will stay partly open into January and the ESS will freeze up somewhat earlier than the Laptev.

Freeze-over could even be a week later if the dire weather forecasts in #570 and #575 come to pass. GFS-nullschool foresees temperatures in the -3.7ºC range mid-day on Nov 1st for the whole open water region, not cold enough to trigger seawater freezing.
« Last Edit: October 27, 2020, 10:49:20 PM by A-Team »

FishOutofWater

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Re: The 2020/2021 freezing season
« Reply #583 on: October 27, 2020, 05:43:55 PM »
Holy shit.

The unprecedented ocean heat on the Siberian shelf has triggered the Siberian shelf clathrate "methane bomb".

https://www.theguardian.com/science/2020/oct/27/sleeping-giant-arctic-methane-deposits-starting-to-release-scientists-find

High levels of the potent greenhouse gas have been detected down to a depth of 350 metres in the Laptev Sea near Russia, prompting concern among researchers that a new climate feedback loop may have been triggered that could accelerate the pace of global heating.

The slope sediments in the Arctic contain a huge quantity of frozen methane and other gases – known as hydrates. Methane has a warming effect 80 times stronger than carbon dioxide over 20 years. The United States Geological Survey has previously listed Arctic hydrate destabilisation as one of four most serious scenarios for abrupt climate change.

The international team onboard the Russian research ship R/V Akademik Keldysh said most of the bubbles were currently dissolving in the water but methane levels at the surface were four to eight times what would normally be expected and this was venting into the atmosphere.

interstitial

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Re: The 2020/2021 freezing season
« Reply #584 on: October 27, 2020, 05:56:12 PM »
Thanks for the analysis/info A-team.


The green line will probably end up a week or two earlier than what you indicated.

vox_mundi

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Re: The 2020/2021 freezing season
« Reply #585 on: October 27, 2020, 06:02:55 PM »
0.2 Degrees C Locked In: Ice Loss Due to Warming Leads to Warming Due to Ice Loss: A Vicious Circle
https://phys.org/news/2020-10-ice-loss-due-vicious-circle.html



The loss of huge ice masses can contribute to the warming that is causing this loss and further risks. A new study now quantifies this feedback by exploring long-term if-then scenarios. If the Arctic summer sea ice were to melt completely, a scenario that is likely to become reality at least temporarily within this century, this could eventually add roughly 0.2 degrees C to global warming. It is, however, not in addition to IPCC projections of future warming, since these already take the relevant mechanisms into account. Still, the scientists have now separated the effects of the ice loss from other effects and quantified it.

The 0.2 degrees C rise is substantial, given that global mean temperature is currently about one degree higher than in pre-industrial times, and governments worldwide have agreed to stop the increase well below two degrees.

"This is not a short-term risk. Earth's ice masses are huge, which makes them very important for our Earth system as a whole—it also means that their response to anthropogenic climate change, especially that of the ice sheets on Greenland and Antarctica, unfolds on longer timescales. But even if some of the changes might take hundreds or thousands of years to manifest, it's possible we trigger them within just a couple of decades," says Ricarda Winkelmann who leads the research group.


a Regional warming for the whole Earth if Arctic summer sea ice (ASSI) in June, July and August, mountain glaciers (MG), Greenland Ice Sheet (GIS) and West Antarctic Ice Sheet (WAIS) vanish at a global mean temperature of 1.5 °C above pre-industrial. b Same as in (a) with an additional zoom-in of the Arctic region if only the Arctic summer sea ice vanishes, which might happen until the end of the century. The light blue line indicates the region of removed Arctic summer sea ice extent, where its concentration in CLIMBER-2 is 15% or higher. In all panels, the average additional warming on top of 1.5 °C is shown in absolute degree.

Nico Wunderling, Matteo Willeit, Jonathan F. Donges, Ricarda Winkelmann (2020): Global warming due to loss of large ice masses and Arctic summer sea ice. Nature Communications,
https://www.nature.com/articles/s41467-020-18934-3
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gerontocrat

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Re: The 2020/2021 freezing season
« Reply #586 on: October 27, 2020, 06:34:29 PM »

The final image makes a 'prediction' for the freeze-over date for the Laptev. The image takes a copy of the blue line from 2012, colors it gold and moves it over exactly horizontally until it extends the most recent 2020 date. A dotted green line is then dropped from the intercept down to the calendar date, intercepting it in late November, almost a full month later than the previous record from 2012.
The assumption is that the Laptev will freeze to maximum almost verically/.

If you look at its neighbour, the Kara, you will see that while this used to be the case in that sea, it no longer is, at least not every year. This tends to show especially in the sea ice area graphs. Sometimes ice growth to maximum is in fits and starts, and sometimes the winter maximum is not 100%.

My speculation is that one year the Laptev is going to go the same way - but in which year?
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Re: The 2020/2021 freezing season
« Reply #587 on: October 27, 2020, 10:40:05 PM »
Some of the data included with CryoSat2-Soil Moisture and Ocean Salinity merged sea ice thickness netCDF (oct18-24).

I currently have plot size set to 220 so the map will later crop to 500 pxl width; the scale bar will fit under it if set to 25 with tick format %0f with size 6 font. The map is stereographic at -45º 90º with outer edge 65º.
Will work towards this set up.
« Last Edit: October 27, 2020, 10:46:04 PM by uniquorn »

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Re: The 2020/2021 freezing season
« Reply #588 on: October 28, 2020, 12:15:25 AM »
Quote
ocean heat on Siberian shelf has triggered the Siberian shelf methane clathrate release
I interpreted this pre-pre-publication presser slightly differently. The map below is an attempt to locate the location of the six monitoring points. Continental slope is where the continental shelf breaks off to the abyss; it is an area of frequent slumping and landslides like its permafrost counterpart on shore.

Kotolny Island is 1630 km from the pole so the 600km offshore could be scaled from there along with the 10x150 km survey area (which might be crosswise to what's shown). The red area is bounded between 100m to 300m depth according to Mercator Ocean so fits the location of sloping shelf break.

Atlantic Waters move as an eastern boundary current topographically steered by bathymetry to circulate the Arctic Basin at its buoyancy-appropriate depth of about 300m. That fits warming of the survey site by Atlantification according to MO's seawater temperature map.

The Guardian article mentions methane clathrate/hydratse which are CH4 guest molecules trapped in water cages. The depth and temperature here seem too high for its stability zone. [fixed]

Semiletov has previously stressed that upwardly migrating free methane gas (not to be confused with clathrate) may be trapped and accumulating under a lid of underwater permafrost left over from the last ice age when the shelf here was subaerial. There's no stability zone limitations for this. Free methane may be what is being released by warming-induced slumping. The methane craters mentioned are further inland on the shelf proper.

It's true that methane is surprisingly soluble in cold seawater -- not all released goes up to the atmosphere. While certain bacteria can metabolize it to carbon dioxide, those are associated more with a bottom mud layer. One micro-molar methane is implausible as a food source in nutrient poor 0ºC surface waters, especially in view of rapid equilibration with low atmospheric methane concentration. Photosynthetic eukaryotic algae in blooms do not assimilate methane; the sequenced genome of Emhux lacks the genes for the unusual enzymes and cofactors involved.

The reporter here should be applauded for not seeking out 'balancing' quotes from the influential CO2 scientific poobahs that see Semiletov's research as going off-message (off their message) with methane as major and worsening greenhouse gas with potentially catastrophic and unstoppable releases ahead. The dog whistle for that is a 100yr time frame; here the far more appropriate 20yr was taken (though some would do instantaneous).

https://www.usgs.gov/center-news/subsea-permafrost-and-associated-methane-hydrate-us-arctic-ocean-margin

"The 60-member team on the Akademik Keldysh believe they are the first to observationally confirm the methane release is already under way across a wide area of the slope about 600km offshore. At six monitoring points over a slope area 150km in length and 10km wide, they saw clouds of bubbles released from sediment.

At one location on the Laptev Sea slope at a depth of about 300 metres they found methane concentrations of up to 1.6 micro-molar, which is 400 times higher than would be expected if the sea and the atmosphere were in equilibrium.

Igor Semiletov, of the Russian Academy of Sciences, who is the chief scientist onboard, said the discharges were “significantly larger” than anything found before. “The discovery of actively releasing shelf slope hydrates is very important and unknown until now,” he said. “This is a new page. Potentially they can have serious climate consequences, but we need more study before we can confirm that.”

The most likely cause of the instability is an intrusion of warm Atlantic currents into the east Arctic. This “Atlantification” is driven by human-induced climate disruption. The latest discovery potentially marks the third source of methane emissions from the region. Semiletov, who has been studying this area for two decades, has previously reported the gas is being released from the shelf of the Arctic – the biggest of any sea.

For the second year in a row, his team have found crater-like pockmarks in the shallower parts of the Laptev Sea and East Siberian Sea that are discharging bubble jets of methane, which is reaching the sea surface at levels tens to hundreds of times higher than normal.  This is similar to the craters and sinkholes reported from inland Siberian tundra earlier this autumn."
« Last Edit: October 28, 2020, 04:31:11 PM by A-Team »

uniquorn

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Re: The 2020/2021 freezing season
« Reply #589 on: October 28, 2020, 12:59:19 AM »
CS2SMOS difference between oct22 and oct25 with average uncertainty of those 2 dates.

Not quite ready to let go of a relationship to bathymetry yet so here is the overlay. It reminds me of something noted in august

added polarview, oct26. Still looks like an active eddy.
« Last Edit: October 28, 2020, 01:51:11 AM by uniquorn »

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Re: The 2020/2021 freezing season
« Reply #590 on: October 28, 2020, 06:23:49 AM »
3-day average wind forecast - Kara, Laptev, ESS, Chukchi all restless. Especially Kara Sea.

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Re: The 2020/2021 freezing season
« Reply #591 on: October 28, 2020, 07:33:20 AM »
October 23-27.

2019.

uniquorn

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Re: The 2020/2021 freezing season
« Reply #592 on: October 28, 2020, 11:29:34 AM »
iabp buoy204760-764 update, surface temperatures, oct11-28

Positive retroaction

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Re: The 2020/2021 freezing season
« Reply #593 on: October 28, 2020, 11:43:53 AM »
hello, I'm starting a little forecast for 7 to 10 days
Thanks again to Uniquorn for the link
If we combine the animation of the extent of the last 7 days, with the salinity and SST at 0 and 30 m, and we look at the forecasts for the next 3 days in air temperature and SST, we deduce

- that kara may be freezing a bit on the south east coast, but not yet in the south west, nor in the central region

- a little frost to come to the west of the new siberian islands, that is to say on the east of laptev

- but more frost seems possible on the eastern half of the ESS, less attacked by the fresh waters of the Chukchi and by the AW
but the rest of the frost seems very difficult, especially on kara of course, but also on the north-east ESS
the winds of these days are likely to bring up the shallow water which was not yet much cooled by the atmosphere and this will increase the SST, especially in kara, with the addition of a southerly flow over Kara
we also note a small hot anomaly which is encrusted slightly in the south west of beaufort, the restant frost of beaufort will be weak and its help on the total extent gain is practically finished, as has been said earlier
That's just my opinion, wait and see :)
all this suggests that if there is a sudden rebound this year, it is not yet for this week
« Last Edit: October 28, 2020, 11:52:16 AM by Positive retroaction »
Sorry, excuse my bad english

BornFromTheVoid

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Re: The 2020/2021 freezing season
« Reply #594 on: October 28, 2020, 12:07:25 PM »
Just looking at the cumulative extent anomaly (vs the 81-10 average) for the Russian Arctic seas, ESS, Laptev and Kara. Already plenty more than any other year's annual total, and likely to see the record breaking anomaly grow over the coming weeks.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Freegrass

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Re: The 2020/2021 freezing season
« Reply #595 on: October 28, 2020, 01:41:03 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Wind + Temp @ 850hPa
Large GiFS!

Nullschool changed their menu and the format. So I have to find a new way to do this...  :-\
« Last Edit: October 28, 2020, 01:52:06 PM by Freegrass »
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Re: The 2020/2021 freezing season
« Reply #596 on: October 28, 2020, 01:55:57 PM »
Just looking at the cumulative extent anomaly (vs the 81-10 average) for the Russian Arctic seas, ESS, Laptev and Kara. Already plenty more than any other year's annual total, and likely to see the record breaking anomaly grow over the coming weeks.

Isn't the scale for the anomaly incorrect, shouldn't be thousands of million km^2.

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Re: The 2020/2021 freezing season
« Reply #597 on: October 28, 2020, 02:02:48 PM »
Wouldn’t that be bigger than a continent?
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Re: The 2020/2021 freezing season
« Reply #598 on: October 28, 2020, 02:12:06 PM »
hello, I'm starting a little forecast for 7 to 10 days
Thanks again to Uniquorn for the link
If we combine the animation of the extent of the last 7 days, with the salinity and SST at 0 and 30 m, and we look at the forecasts for the next 3 days in air temperature and SST, we deduce

- that kara may be freezing a bit on the south east coast, but not yet in the south west, nor in the central region

- a little frost to come to the west of the new siberian islands, that is to say on the east of laptev

- but more frost seems possible on the eastern half of the ESS, less attacked by the fresh waters of the Chukchi and by the AW
but the rest of the frost seems very difficult, especially on kara of course, but also on the north-east ESS
the winds of these days are likely to bring up the shallow water which was not yet much cooled by the atmosphere and this will increase the SST, especially in kara, with the addition of a southerly flow over Kara
we also note a small hot anomaly which is encrusted slightly in the south west of beaufort, the restant frost of beaufort will be weak and its help on the total extent gain is practically finished, as has been said earlier
That's just my opinion, wait and see :)
all this suggests that if there is a sudden rebound this year, it is not yet for this week

I would especially mention the "inability" of the ice edge refreeze at West Beaufort to propagate beyond the shelf break of the Canada basin against Chukchi sea. It looks to me there is a continuous flow of Pacific water from Chukchi sea that is precisely descending there, and as long as this water doesn't stop to flow and descend along the break the ice cannot advance.

In the last frames of today's Aluminium animation it seems the ice is finally advancing, but it is difficult to say.
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Sublime_Rime

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Re: The 2020/2021 freezing season
« Reply #599 on: October 28, 2020, 02:12:52 PM »

The Guardian article does not mention methane clathrate/hydrate which references CH4 guest molecules trapped in water cages. The depth and temperature here seem too high for its stability zone.


Hey A-team, I'm a little confused. Semiletov does mention hydrates in the article via direct quotation: '“The discovery of actively releasing shelf slope hydrates is very important and unknown until now,” he said.'

Also, '"This East Siberian slope methane hydrate system has been perturbed and the process will be ongoing,” said the Swedish scientist Örjan Gustafsson, of Stockholm University, in a satellite call from the vessel.'
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