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Quantum

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Re: The 2017 melting season
« Reply #3600 on: August 06, 2017, 05:05:24 PM »
It's colder than July :)
But it doesn't hurt to remember that melting temperature for FYI ranges between -1.5°C and -1.8°C
Isn't that the freezing temperature, not the melting temperature? Since the ice expels salt I would have thought it was much closer to 0C and that subzero temperatures would almost stop top melt entirely. Lateral and bottom melt of course will of course continue.

Fairbanksnchill

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Re: The 2017 melting season
« Reply #3601 on: August 06, 2017, 05:49:46 PM »
Bruce Molnia, A USGS physical scientist, touches on the different characteristics of ice at different temperatures here.  If the arctic sea reached -40 C then it would require 25% more energy to melt cold ice vs warm ice (just under freezing).

The math would be 2.05 j/g/k x 40 degrees k delta + 333.55 j/g/k (Heat of Fusion).
Warm ice would only require the heat of Fusion to melt.

Entropy dictates that the ice would spread out as much as it could based upon forces applied to it. (e.g. piles of sand spread out due to gravity or wind blows leaves around on your yard)

In 2012 the Beauford sea had open ocean buttressing 2m thick ice according to hycomm and now it's ~.5 meters.  According to this forums source measurements on extent and volume the average sea ice thickness is 1.04 meters.  Energy can either melt 1 km² of 5 meter thick ice or 5 km² of 1 meter thick ice.  I don't mean to prognosticate, but if I witnessed a vast reduction in extent I would not be surprised.

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Re: The 2017 melting season
« Reply #3602 on: August 06, 2017, 06:30:29 PM »
It's colder than July :)
But it doesn't hurt to remember that melting temperature for FYI ranges between -1.5°C and -1.8°C
Isn't that the freezing temperature, not the melting temperature? Since the ice expels salt I would have thought it was much closer to 0C and that subzero temperatures would almost stop top melt entirely. Lateral and bottom melt of course will of course continue.
That is why he said first year ice, which is in its first year, not necessarily a whole year old yet. It takes a while for the salt to work it's way out of the newly frozen ice.
Of course, for the ice overall, it is probably more important to look at water temps, and by that I mean those just below the surface, and maybe even deeper with the water being disturbed by storms.

Thomas Barlow

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Re: The 2017 melting season
« Reply #3603 on: August 06, 2017, 08:01:09 PM »
Is it true to say that it was around Aug. 7th-8th that 2012 started to go way off track? What caused it? A storm? A series of storms? Persistent heat?
Any documentation or observations of what caused it?

http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

cesium62

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Re: The 2017 melting season
« Reply #3604 on: August 06, 2017, 08:21:55 PM »
Is it true to say that it was around Aug. 7th-8th that 2012 started to go way off track? What caused it? A storm? A series of storms? Persistent heat?
Any documentation or observations of what caused it?

http://www.huffingtonpost.com/2013/02/03/arctic-cyclone-2012-august-sea-ice_n_2611336.html

The Great Arctic Cyclone of August 2012” arose in Siberia on Aug. 2 and crossed the Arctic Ocean to Canada, lasting an unusually long 13 days. The cyclone hit a pressure minimum of 966 millibars on Aug. 6, the lowest ever recorded for an Arctic storm. The stronger the pressure gradient, or difference in pressure, the stronger the winds associated with a storm.

Since the storm, which was equal in strength to a hurricane, tore across the Arctic, scientists have wondered whether its winds and waves were a guilty party in the disappearing Arctic sea ice.


Sterks

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Re: The 2017 melting season
« Reply #3605 on: August 06, 2017, 08:32:07 PM »
It's colder than July :)
But it doesn't hurt to remember that melting temperature for FYI ranges between -1.5°C and -1.8°C
Isn't that the freezing temperature, not the melting temperature? Since the ice expels salt I would have thought it was much closer to 0C and that subzero temperatures would almost stop top melt entirely. Lateral and bottom melt of course will of course continue.
You are right, a melting temperature is probably not proper for a material that no longer is homogeneous. However the FYI has its amount in salt almost intact in high concentration in the brine. Let's say that it requires lower overall heat than MYI, rather than a singular lower temperature, to melt out, since the brine melts first, at much lower temperature.

If the ice survives, I believe the brine pockets are gradually re-filled with water with lower concentration of salt, making it more resistant next year.

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Re: The 2017 melting season
« Reply #3606 on: August 06, 2017, 09:02:37 PM »
The Great Arctic Cyclone of August 2012 arose in Siberia on Aug. 2


Not forgetting to mention that the storm in question was originally christened over on the Arctic Sea Ice Blog.

Other suggestions were Fred, Craig or Pat!
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charles_oil

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Re: The 2017 melting season
« Reply #3607 on: August 06, 2017, 09:08:28 PM »

1900 GMT - CNN international just now starting a programme which promises a big segment on climate change & melting icecaps....


May appear later on:  http://edition.cnn.com/CNN/Programs/fareed.zakaria.gps/


Apologies for OT post.

bbr2314

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Re: The 2017 melting season
« Reply #3608 on: August 06, 2017, 09:12:41 PM »
It seems that NHEM snowcover may soon begin its autumnal ascendance; by D10 the GFS and CMC have extensive falls over Alaska, The Yukon, and Northeastern Siberia. These probably won't endure for too long, but a definite sign that things are starting to cool off...



However reliable the Canadian snowcover maps are, the graphs are showing extent remaining well above normal (relatively speaking).




Sterks

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Re: The 2017 melting season
« Reply #3609 on: August 06, 2017, 09:38:07 PM »
We got spoiled by last year series of storms. Now a persistent storm, that will hit for third or fourth time on the weakest area of the pack, with 985 - 976 - 976 -982 - 982 - 982 hPa evolution daily, week-long , got to show something remarkable, but obviously doesn't call as much attention. It is like comparing slow erosion to a landslide.
In my opinion it can provide the last impetus to maintain steady extent losses throughout entire August

CraigsIsland

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Re: The 2017 melting season
« Reply #3610 on: August 07, 2017, 12:06:37 AM »
The Great Arctic Cyclone of August 2012 arose in Siberia on Aug. 2


Not forgetting to mention that the storm in question was originally christened over on the Arctic Sea Ice Blog.

Other suggestions were Fred, Craig or Pat!


Thankfully not Craig.

Am named in Craig in real-life and all Craig's really do not want that honor.

greatdying2

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Re: The 2017 melting season
« Reply #3611 on: August 07, 2017, 03:33:30 AM »
As mentioned by others, but bears repeating: the forecast over the next (and past) few days is bad, especially on the Russian and Pacific sides. E.g. The images attached are for +3 days from now.

It looks increasingly likely to me that the Pacific side will undergo continued rapid retreat this week, and possibly the Laptev bite will join it. On the other hand, the weather seems nice Atlantic side (which still has to worry about currents however).
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greatdying2

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Re: The 2017 melting season
« Reply #3612 on: August 07, 2017, 04:01:20 AM »
The attached 2 animations may help you get a better sense of how the melt season has proceeded over the last 2 weeks. The first shows the original Bremen NIC concentration images (cropped). The second shows a filtered version, where each pixel is set to the latest concentration less than 90% (i.e. not purple) over 5 days (current day plus preceding 4 days).

WARNING: While the filter may remove some high concentration (purple) atmospheric artifacts from the original, thus making it easier than in the unfiltered version to see what may be happening for instance on the Pacific side, it also may introduce false low concentration artifacts. Interpret accordingly.
« Last Edit: August 07, 2017, 04:27:37 AM by greatdying2 »
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

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Re: The 2017 melting season
« Reply #3613 on: August 07, 2017, 04:13:38 AM »
P.S. For easy reference, here is the key for the colour codes.

(Note that red, orange, and yellow represent concentrations from 90% to 70%.)
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

numerobis

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Re: The 2017 melting season
« Reply #3614 on: August 07, 2017, 05:31:33 AM »
It's colder than July :)
But it doesn't hurt to remember that melting temperature for FYI ranges between -1.5°C and -1.8°C
Isn't that the freezing temperature, not the melting temperature? Since the ice expels salt I would have thought it was much closer to 0C and that subzero temperatures would almost stop top melt entirely. Lateral and bottom melt of course will of course continue.
You are right, a melting temperature is probably not proper for a material that no longer is homogeneous. However the FYI has its amount in salt almost intact in high concentration in the brine. Let's say that it requires lower overall heat than MYI, rather than a singular lower temperature, to melt out, since the brine melts first, at much lower temperature.

If the ice survives, I believe the brine pockets are gradually re-filled with water with lower concentration of salt, making it more resistant next year.

My taste buds are quite certain that FYI that's come ashore is not nearly so salty as sea water.

It's also quite porous for the most part (except for the occasional layer of solid blue ice). That would fit with your conception of brine pockets.

romett1

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Re: The 2017 melting season
« Reply #3615 on: August 07, 2017, 07:22:01 AM »
As mentioned by others, but bears repeating: the forecast over the next (and past) few days is bad, especially on the Russian and Pacific sides.

Just small update - Aug 6 vs Jul 30. Images: ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/

greatdying2

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Re: The 2017 melting season
« Reply #3616 on: August 07, 2017, 08:19:36 AM »
Just small update - Aug 6 vs Jul 30. Images: ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/

Thanks. Yes -- as expected, today (Aug. 6) looks like another big drop, and more to come...
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Neven

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Re: The 2017 melting season
« Reply #3617 on: August 07, 2017, 09:41:16 AM »
The current ECMWF forecast is looking more like it. It's still not a GAC, but the pressure is pretty low and it stays low for a couple of days, which should stir the weak ice on the Pacific side of the Arctic some more. Of course, we have to wait and see how accurate the forecast is, but it's been pointing to this for a couple of days now:
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Rob Dekker

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Re: The 2017 melting season
« Reply #3618 on: August 07, 2017, 10:14:41 AM »
The attached 2 animations may help you get a better sense of how the melt season has proceeded over the last 2 weeks. The first shows the original Bremen NIC concentration images (cropped). The second shows a filtered version, where each pixel is set to the latest concentration less than 90% (i.e. not purple) over 5 days (current day plus preceding 4 days).

Thank you greatdying2, that is a very useful animation. You can really see the low concentration ice proceed deeper into the CAB, and there is not as much noise as the original AMSR2 images.
One note : You mention ''latest concentration", but I assume you mean "lowest concentration", is that right ?
And one question : You chose 5 days for your filter while previously you chose 3 days (the LAMB).
What made you change that filter period ?

greatdying2

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Re: The 2017 melting season
« Reply #3619 on: August 07, 2017, 10:29:09 AM »
Thanks Rob. Latest is correct, not lowest -- but it's the latest value less than 90% (the latest non-purple value). The first version used lowest (minimum), but I have been playing with different and hopefully improved algorithms. This is also why the period used for these is 5 days rather than 3 (for now) -- it works better with the median filter (not shown here), and I wanted to compare apples to apples. For more details, please see this thread:
http://forum.arctic-sea-ice.net/index.php/topic,2131.0.html
« Last Edit: August 07, 2017, 10:35:52 AM by greatdying2 »
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Jim Hunt

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Re: The 2017 melting season
« Reply #3620 on: August 07, 2017, 11:25:38 AM »
It's still not a GAC, but the pressure is pretty low and it stays low for a couple of days, which should stir the weak ice on the Pacific side of the Arctic some more.


As I just pointed out over on the ASIB, assuming the forecast verifies and unlike GAC 2012, this sequence of cyclones are positioned to drive significant swells directly at the Chukchi/Beaufort MIZ:

http://GreatWhiteCon.info/2017/08/facts-about-the-arctic-in-august-2017/#Aug-7

The effects?



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JayW

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Re: The 2017 melting season
« Reply #3621 on: August 07, 2017, 11:58:23 AM »
I'll try again

80 hour loop. August 3-6

Not sure why the gif won't run, I'll use another method.


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Re: The 2017 melting season
« Reply #3622 on: August 07, 2017, 12:10:41 PM »
I'll try again

80 hour loop. August 3-6

Not sure why the gif won't run, I'll use another method.

working well (gif running) no problem, thanks
« Last Edit: August 07, 2017, 03:04:31 PM by magnamentis »
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F.Tnioli

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Re: The 2017 melting season
« Reply #3623 on: August 07, 2017, 01:12:41 PM »
It's colder than July :)

And September will be colder than August.
September would _normally_ be colder than August, i'd say. But i doubt there is a 100% lifetime guarantee about that.

Pi26

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Re: The 2017 melting season
« Reply #3624 on: August 07, 2017, 03:11:27 PM »
Much more fast ice around Greenland mobilizes.
Images from 7th and 3rd August.

« Last Edit: August 07, 2017, 03:16:29 PM by Pi26 »

Often Distant

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Re: The 2017 melting season
« Reply #3625 on: August 07, 2017, 03:25:34 PM »
Crikey. Here comes a cannonball the season has been dodging?

oren

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Re: The 2017 melting season
« Reply #3626 on: August 07, 2017, 05:00:13 PM »
80 hour loop. August 3-6
JayW, thanks for these. Looking closely I can imagine seeing both the drak spongelike ice get much darker, losing concentration, while also being compacted towards the pack. So the extent loss is mostly from movement plus some melt, while the area loss happens deep behind the front lines, with more spongelike ice capable of going poof in the coming days.

F.Tnioli

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Re: The 2017 melting season
« Reply #3627 on: August 07, 2017, 05:05:24 PM »
80 hour loop. August 3-6
JayW, thanks for these. Looking closely I can imagine seeing both the drak spongelike ice get much darker, losing concentration, while also being compacted towards the pack. So the extent loss is mostly from movement plus some melt, while the area loss happens deep behind the front lines, with more spongelike ice capable of going poof in the coming days.
"Spongelike ice", eh. I and few others call that "ice soup", though. IMHO better way to put it: "ice" still suggests there is solid, rigid structure, if full of holes; "soup" is free from such a notion.

Capable of going poof - that's the story of this season. It would be most outstanding if such a mode would indeed be maintained through the remainder of the season, thus making 2017 the most "dodgy" season we ever had so far. In the sense of how long, and much, it "could poof".

greatdying2

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Re: The 2017 melting season
« Reply #3628 on: August 07, 2017, 09:41:07 PM »
Tomorrow, the latest storm will pass over the arm of higher concentration and probably thicker ice near the ESS. It will be interesting to see in the following days whether it will do much measurable damage.

(NB: The attached Bremen map has been filtered by using for each pixel the latest concentration under 90% (not purple) over 5 days ending on the date labelled. See: http://forum.arctic-sea-ice.net/index.php/topic,2131.0.html)
« Last Edit: August 07, 2017, 10:00:30 PM by greatdying2 »
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Re: The 2017 melting season
« Reply #3629 on: August 07, 2017, 09:55:11 PM »
Then for the following 2 days, the storm moves on to the Chukchi and Beaufort, where it almost certainly will do easily measurable damage, and a lot of it.

What will the storm do after 3 days...?
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Pi26

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Re: The 2017 melting season
« Reply #3630 on: August 07, 2017, 10:54:55 PM »
What will the storm do after 3 days...?

This world only will do whatever a world must do, after humans did what humans must do. 😎

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Re: The 2017 melting season
« Reply #3631 on: August 08, 2017, 12:16:20 AM »
Speaking of thickness, here is the PIOMAS modelled thickness from April, and how much it is off by based on Cyrosat measurements.

Together, this does seem to support an arm of thicker ice in the CAB next to the ESS.

http://forum.arctic-sea-ice.net/index.php/topic,119.msg112164.html#msg112164
http://forum.arctic-sea-ice.net/index.php/topic,8.msg124238.html#msg124238
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Thomas Barlow

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Re: The 2017 melting season
« Reply #3632 on: August 08, 2017, 12:17:54 AM »
Comparing this week 2016 (middle), to mid Sept. 2016 shrink, and looking at the thickness, and to 2012 and 2017 this week, I'd say 2017 looks vulnerable with over a month to go.

Ninebelowzero

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Re: The 2017 melting season
« Reply #3633 on: August 08, 2017, 12:57:11 AM »
Interesting sequence Thomas.

The thing that catches the eye about the 2017 plot is a 'channel' of thinner ice running from the Fram strait towards the Beaufort sea.

What is it?

slow wing

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Re: The 2017 melting season
« Reply #3634 on: August 08, 2017, 01:31:24 AM »
Interesting sequence Thomas.

The thing that catches the eye about the 2017 plot is a 'channel' of thinner ice running from the Fram strait towards the Beaufort sea.

What is it?
If I recall correctly, it was a band of ice that piled up against the coast and then was blown out to sea.

A-Team

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Re: The 2017 melting season
« Reply #3635 on: August 08, 2017, 01:36:10 AM »
2017 plot has a 'channel' of thinner ice running from the Fram strait towards the Beaufort sea. What is it?

Tracking that channel feature back to the 15 Sep 16 minimum (see up-forum), it appears to be a finger of first year ice, ie open water on that date that subsequently froze over the winter. This interpretation would likely be supported by NSIDC's sea ice age product (if they were to update that in a timely manner). Because of the late weak freeze season, presumably very little FYI will survive into the fall, so it's critical to track where it is today.

However the Hycom FYI finger has no support (no corresponding visible feature) in AMSR2 concentration map, Piomas ice thickness models, or Sentinel-1AB cloud-free mosaics. That's a non-fatal concern as those products have problems of their own as seen in the Piomas error map below.

Hycom can persist in its interpretation for now but it is on a collision course with reality if the finger continues to thin as it has for many months now (the animation runs to 14 Aug 17) because there is no mistaking open water.

« Last Edit: August 08, 2017, 02:22:56 AM by A-Team »

slow wing

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Re: The 2017 melting season
« Reply #3636 on: August 08, 2017, 02:54:03 AM »
A-Team, I was thinking the 'Beaufort Finger' was this feature?
« Last Edit: August 08, 2017, 03:01:31 AM by slow wing »

A-Team

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Re: The 2017 melting season
« Reply #3637 on: August 08, 2017, 04:22:52 AM »
thinking Beaufort Finger' was this feature?

In that case (which overlooks NBZ's mention of Fram), you are quite right in that that piece of MYI  broke off the thick CAA ice and swung around in the half-Gyre that we have had in recent years.

Once upon a time, ice circled (and thickened) in the Beaufort Gyre for years and years, leading to a pronounced dome of lower salinity (see Proshutinsky papers on Ekman pumping that Fish has been citing: http://www.whoi.edu/page.do?pid=66578 for an update).

Looking once again at that all-time great animation of Tschudi's sea ice age data by the climate.gov team over the last 26 years, one wonders how the textbook Beaufort Gyre story retains any traction in the new Arctic.

From my perspective, the current drama unfolding on the Chukchi/Beaufort is mostly just the windy specifics of the expected demise of the weak FYI ice there, whereas more noteworthy export of SYI has been taking place across the Svalbard-FJL-SZ maginot line.

It's not easy to translate wind forecasts or reanalysis products (ie pressure gradients) into quantitative ice movement, the problem being it depends on directional surface friction (eg pressure ridges and ice edges). This roughness determines the effectiveness of coupling (momentum transfer) and we know next to nothing about what's currently down there (satellites mostly view radially, flattening) nor new effects from more pervasive younger ice.

So other than waves induced by wind over long fetches open water directed straight on to the ice edge, well-covered by JimH, we might just as well skip the persistent weather pattern -- even though it is causative -- and just directly track the ice going into the Barents.

The idea here is not so much that the bathymetric break to the north of Svalbard-FJL-SZ will end up ice-free again as it is that so much ice has been pushed out to the Barents this year.

The animation below shows the last three weeks. Here, as in a June post, there's been a cloud removal process applied to affected passive radar sea ice concentration scenes (which active radar like S-1AB does not need).

GreatD has started a whole forum on these enhancements. It's worth noting the commonsensical choices are already provided as menu items at ImageJ and Gimp. The one below (underneath as-is) isn't striving so much to recovered masked concentration values as it is seeking persistent feature visualization and their motion. The upper ten percent of ice concentrations are not resolvable visually so the whites have been replaced by a tan color.

The second product shows where it makes a difference to let a darker pixel from the previous day over-ride the current day's. Posters positing that clouds darken could perhaps make their case with Saldo's S-1AB 3-day mosaics (which are greatly under-utilized on these forums).
« Last Edit: August 08, 2017, 04:33:21 AM by A-Team »

greatdying2

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Re: The 2017 melting season
« Reply #3638 on: August 08, 2017, 05:07:25 AM »
A-team, those are terrific visualizations. On the first one, is there supposed to be a difference between the top and bottom panels? The second one, showing daily deltas, really does a good job illustrating the amount of ice being melted on the Atlantic side even as more keeps getting exported.
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Re: The 2017 melting season
« Reply #3639 on: August 08, 2017, 05:21:48 AM »
The waves forecast for the next few days from windy tv on the Pacific and Siberian side. The rapid retreat of the ice should continue on that side. On the Atlantic bulwark breezes turn to push the ice inwards. Luckily no storms on that side, for now

Edit - click the the forecast gif to animate

The northern route is open now, only a bit of slush to delay a yacht around Vilkitsky strait
« Last Edit: August 08, 2017, 12:56:57 PM by subgeometer »

meddoc

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Re: The 2017 melting season
« Reply #3640 on: August 08, 2017, 07:41:57 AM »

Tracking that channel feature back to the 15 Sep 16 minimum (see up-forum), it appears to be a finger of first year ice, ie open water on that date that subsequently froze over the winter. This interpretation would likely be supported by NSIDC's sea ice age product (if they were to update that in a timely manner). Because of the late weak freeze season, presumably very little FYI will survive into the fall, so it's critical to track where it is today.

However the Hycom FYI finger has no support (no corresponding visible feature) in AMSR2 concentration map, Piomas ice thickness models, or Sentinel-1AB cloud-free mosaics. That's a non-fatal concern as those products have as seen in the Piomas error map below.

Hycom can persist in its interpretation for now but it is on a collision course with reality if the finger continues to thin as it has for many months now (the animation runs to 14 Aug 17) because there is no mistaking open water.


I guess Hycom is best at interpreting Trends, not to give someone absolute Numbers about the Ice's State.
Something it does do pretty well, though.

greatdying2

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Re: The 2017 melting season
« Reply #3641 on: August 08, 2017, 07:56:58 AM »
Bremen NIC, 7 days ending August 7th, filtered.

More extent loss today on Pacific and a little in the Laptev bite.

(NB: The attached Bremen map has been filtered by using for each pixel the latest concentration under 90% (not purple) over 5 days ending on the date labelled. See: http://forum.arctic-sea-ice.net/index.php/topic,2131.0.html)
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

deconstruct

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Re: The 2017 melting season
« Reply #3642 on: August 08, 2017, 09:03:58 AM »
Comparison of the forecast from GFS and ECMWF vor the next 4 days (09th to 12th Aug 2017).
Both are in good agreement, even on the last day (96h forecast time).

I think that we will see quite some damage from that storm, especially since the ice underneath is already vulnerable and the pressure gradient towards the high on the Siberian side is strong (50+ hPa over a small distance.

romett1

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Re: The 2017 melting season
« Reply #3643 on: August 08, 2017, 09:44:36 AM »

I think that we will see quite some damage from that storm, especially since the ice underneath is already vulnerable

Just small update again - Aug 7 vs Jul 30. Images: ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/


Rob Dekker

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Re: The 2017 melting season
« Reply #3644 on: August 08, 2017, 10:47:52 AM »
The one below (underneath as-is) isn't striving so much to recovered masked concentration values as it is seeking persistent feature visualization and their motion. The upper ten percent of ice concentrations are not resolvable visually so the whites have been replaced by a tan color.

That "tan color" feature is very noisy, and certainly not "persistent". Since it is related to the upper ten percent, which is not indicative of ice melt, I'd suggest you replace it with the immediately below 90% bracket which is white. That should stabilize the image and be more gentle on the eyes.

slow wing

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Re: The 2017 melting season
« Reply #3645 on: August 08, 2017, 12:03:44 PM »
At tropicaltidbits.com, NAVGEM as well has the storm strengthening - down to 973 hPa in the 48h prediction.

With weaker ice than in 2012, we may well be looking at storm damage to the ice comparable to that from the 2012 GAC (Great Arctic Cyclone).

From memory, Neven records the GAC as bottoming out at 966 hPa and lasting 13 days. For comparison, NAVGEM records the current storm as having already dropped to 985 hPa at 12z back on 5 August, waxing and waning through the present and still at 986 hPa at their final, 180h prediction, 10 days later at 12z on 15 August.

While that final prediction is expected to be too far out to be reliable, the point is that the NAVGEM predictions show no sign of the storm dying out in the foreseeable future.

So for how much of August will it rotate around the Arctic Basin, sometimes weaker, sometimes stronger, but bringing significant winds all the while to potentially damage the ice pack?

Jim Hunt

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Re: The 2017 melting season
« Reply #3646 on: August 08, 2017, 12:56:52 PM »
So other than waves induced by wind over long fetches open water directed straight on to the ice edge, well-covered by JimH, we might just as well skip the persistent weather pattern.


Welcome back A-Team, and thanks for your kind words. On that theme here's Wipneus' latest AMSR2 delta map, amongst other things:

http://GreatWhiteCon.info/2017/08/facts-about-the-arctic-in-august-2017/#comment-222692

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subgeometer

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Re: The 2017 melting season
« Reply #3647 on: August 08, 2017, 01:03:15 PM »
The PAC has been pretty persistent so far and may yet deepen in into a GAC, as the sun lowers. It seems to have a production line of lows on a track to feed it

F.Tnioli

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Re: The 2017 melting season
« Reply #3648 on: August 08, 2017, 03:34:23 PM »
And it has lots and lots of open water all around periphery seas, and last i heard, plenty extra moisture in the air is never good to diminish storms. We had a discussion in this topic like a month or so ago about possibility for a late season GAC-like event to make a big difference in terms of September (/October??) minimum, back then there were no practical signs of such. And i said, back then, that it's "just a possibility". Now i start to feel a bit of a prophet... In a saddening way.

Thomas Barlow

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Re: The 2017 melting season
« Reply #3649 on: August 08, 2017, 04:51:08 PM »
Interesting sequence Thomas.
The thing that catches the eye about the 2017 plot is a 'channel' of thinner ice running from the Fram strait towards the Beaufort sea.
What is it?
That channel is evident here, but not as continuous: