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igs

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Re: The 2020 melting season
« Reply #4800 on: August 13, 2020, 01:06:40 AM »
F.O.o.W.,

Most weather forecasters are predicting cooler temperatures for northern Alaska over the next fortnight.  Hence, I would side with weatherdude.


Since when does northern Alaska decide over the ate of the ice. Even if at 0C would a storm now destroy the beaufort ice and then from a sea-ice in salty waters perspective temps around 0C means melt and this is the coldest average one will get north of Alaka over the next 5-10 days that are in question.

« Last Edit: August 13, 2020, 05:28:20 AM by oren »

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Re: The 2020 melting season
« Reply #4801 on: August 13, 2020, 01:51:17 AM »
That should make the extent drop a little.
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FishOutofWater

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Re: The 2020 melting season
« Reply #4802 on: August 13, 2020, 02:10:28 AM »
F.O.o.W.,

Most weather forecasters are predicting cooler temperatures for northern Alaska over the next fortnight.  Hence, I would side with weatherdude.


ahh... I forgot, you are the other one, not much of a surprise. Since when doesn northern Alaska decide over the ate of the ice. Even if at 0C would a storm now destroy the beaufort ice and then from a sea-ice in salty waters perspective temps around 0C means melt and this is the coldest average one will get north of Alaka over the next 5-10 days that are in question.

The very thin ice in the Beaufort and Chukchi seas is going to be blasted by warm southerly winds over the next week to ten days. The American and European models are in basic agreement on this. I don't know the details of local forecasting in Alaska but I have been reading weather maps since I was ten years old and temperature forecast maps are about as simple as they get. And, you know, it certainly looks to me like it's going to be warmer than normal on the north slope for the next week. I'm showing both the American and European models because they tell similar stories the ECM at 850 mb and the GFS at the surface. Click figures to animate.

Thanks A-Team for coming back and giving us some excellent observations, analyses and animations.
« Last Edit: August 13, 2020, 05:30:34 AM by FishOutofWater »

The Walrus

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Re: The 2020 melting season
« Reply #4803 on: August 13, 2020, 02:26:08 AM »
F.O.o.W.,

Most weather forecasters are predicting cooler temperatures for northern Alaska over the next fortnight.  Hence, I would side with weatherdude.


ahh... I forgot, you are the other one, not much of a surprise. Since when doesn northern Alaska decide over the ate of the ice. Even if at 0C would a storm now destroy the beaufort ice and then from a sea-ice in salty waters perspective temps around 0C means melt and this is the coldest average one will get north of Alaka over the next 5-10 days that are in question.

Considering that no storm is forecast over the next 10 days, just cool and cloudy days, I would say that is not conducive to enhanced melt.

Paul

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Re: The 2020 melting season
« Reply #4804 on: August 13, 2020, 02:36:58 AM »
I do get the feeling the "classic" dipole could be just around the corner but it's still a little far out for it to be a certainty. Will be interesting what it affects would be if it does develop. In the short term it's a mix of high pressure with a bit of troughing nearer the ESS and a very strong reverse flow through fram so expect more developments in that diffused area to the NE of Greenland. As I keep saying, maybe high pressure is better than low pressure but there is still above average temperature at upper heights and it would not surprise me if the PV is slow to form this year.

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Re: The 2020 melting season
« Reply #4805 on: August 13, 2020, 03:18:24 AM »

Considering that no storm is forecast over the next 10 days, just cool and cloudy days, I would say that is not conducive to enhanced melt.

You didn't say you thought the next few days wouldn't be "conducive to enhanced melt," you said you agreed that the weather was going to be favorable for sea ice retention and be so favorable it would lead to a record early minimum.

VeliAlbertKallio

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Re: The 2020 melting season
« Reply #4806 on: August 13, 2020, 05:15:06 AM »
I think 2020 season's great lessons may be that very high sea ice concentrations probably have a tipping point where lack of leads between the ice floes becomes negative feedback, reducing floe side melting and water overturning near and beneath ice. Ice also reduces ventilation of ocean, it means that heat will take longer to escape during the winter darkness and cold, also enhanced by the growing Lake Snow Effect on the Arctic Ocean (Maurice Ewing - William Donn Effect): open perimeter seas piling up snow onto CAB further preventing heat escape and sea ice thickening under the thick snow.
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Re: The 2020 melting season
« Reply #4807 on: August 13, 2020, 05:44:28 AM »
I have been following with interest the patch of persistent ice in the Kara sea next to Severnaya Zemlya. Intuitively it should have melted a while ago, with the Laptev cleared out and the rest of the Kara too. However it appears that the ice was quite thick, had a lot of cloudy days at the edge of the GAAC, and did not move around much. I would guess that the ice was originally pressured against the islands and strengthened in the process. In addition it is plausible that runoff from the SZ ice caps is making the water fresher and helps protect the sea ice. Nevertheless, my feeling that it's not melting is not substantiated by the reality - it turns out that it's shrinking steadily and has become quite mobile. Another two weeks should see its final demise, before the annual minimum.

The animation begins in early July but skips many cloud-covered images. The AMSR2 animation covers the same period. Click.
« Last Edit: August 13, 2020, 05:56:06 AM by oren »

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Re: The 2020 melting season
« Reply #4808 on: August 13, 2020, 06:07:06 AM »
latest AMSR2 (Aug 12), 3.125 km grid

you may need to click for full resolution

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Re: The 2020 melting season
« Reply #4809 on: August 13, 2020, 06:22:01 AM »
I'm trying to get a good look at the patterns I saw in the lower resolution image. This one is a better look. Same date, from the northwest passage directory. What is with all the lines and arcs?

click for full resolution



Michael Hauber

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Re: The 2020 melting season
« Reply #4810 on: August 13, 2020, 06:23:59 AM »
The ice in the Chukchi region (red circle) is very vulnerable in my opinion.  Ice in the Beaufort (green circle) is quite solid and unlikely to show significant melt until minimum. 

While the forecast at day 7 and beyond looks quite spectacular when looking at winds, SLP or temp anomalies, keep in mind that summer is now waning quickly.  Attached is 850hp temp for day 7 forecast, and the very warm temps (> 4C) capable of causing fast surface melt are quite limited in area (especially compared to previous weeks where 4C spread over large parts of CAB basin).  This area does correspond quite well to the area I think is very vulnerable.

We are now entering the season of bottom melt where surface temps are of less importance.  Not sure how much, and to be honest I find weather at this time of year much harder to decipher.  Except ice transport.

Climate change:  Prepare for the worst, hope for the best, expect the middle.

jdallen

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Re: The 2020 melting season
« Reply #4811 on: August 13, 2020, 07:20:11 AM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...

Juan C & Gerontocrat: seems like good odds that melting rate this month could be record low unless it doesn't speed up soon.
it will  :) :) :) :) :) :)

I'm honestly mystified.  There's heat in the air, there is heat in the water, there's been rainfall, there is still insolation, especially over regions on the Pacific side. 

The ice quality is awful.  I mean *REALLY* awful. We have very little pack in the sense that it existed just a decade ago.  Instead, we have what amount to vast stretches of dirty ice cubes.

But the numbers aren't budging.

I feel like we are missing something critical.

 

But
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pearscot

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Re: The 2020 melting season
« Reply #4812 on: August 13, 2020, 07:28:43 AM »
I'm truly mystified too, but for the time being I'm just focusing on what I can see with Worldview. What I think is going on right now (and when I take the wind into account) is that the ice is really be pushed and dispersed into the warmer peripheral seas so while the sensors may not indicate much melt per se, there is still a lot going on.

My case in point is what's going on above north Greenland. I think it's melting a lot because the large area that is now open did not just transfer thick ice to a place directly adjacent, rather it just keeps thinking in all directions. Same with the Beaufort. I really have no idea how this season ends, but at the end of August I think the north coast of Greenland may have a clear path of water connecting it to the north Atlantic.
pls!

Freegrass

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Re: The 2020 melting season
« Reply #4813 on: August 13, 2020, 07:37:30 AM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!
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El Cid

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Re: The 2020 melting season
« Reply #4814 on: August 13, 2020, 08:16:11 AM »
2016 was when sea temps were generally the highest in the Arctic, so I compared 2020/08/10 to the same date in 2016.

You can see how extremely hot sea temperatures are on the Atlantic-Siberian side. This will have ramificiations in the fall (likely a very slow freezing season), but is also significant now, because the Atlantic side will likely be attacked heavily by bottom melt. The Beaufort-Chukchi region is already disintegrating quickly and then there is the Greenland gap. Because of the above I think 2020 will stll come out first with a big bang at the end

BornFromTheVoid

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Re: The 2020 melting season
« Reply #4815 on: August 13, 2020, 09:43:43 AM »
Impressive growth in that gap to Greenland and the eastern CAA over the last few days.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

BornFromTheVoid

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Re: The 2020 melting season
« Reply #4816 on: August 13, 2020, 10:14:54 AM »
Here's another for ye.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

SimonF92

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Re: The 2020 melting season
« Reply #4817 on: August 13, 2020, 10:34:33 AM »
I'm trying to get a good look at the patterns I saw in the lower resolution image. This one is a better look. Same date, from the northwest passage directory. What is with all the lines and arcs?

click for full resolution

Rain clouds moving over the ice, causing surface water to affect the sensors differently to adjacent drier areas?
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gerrit

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Re: The 2020 melting season
« Reply #4818 on: August 13, 2020, 10:48:01 AM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...


I'm honestly mystified.  There's heat in the air, there is heat in the water, there's been rainfall, there is still insolation, especially over regions on the Pacific side. 

The ice quality is awful.  I mean *REALLY* awful. We have very little pack in the sense that it existed just a decade ago.  Instead, we have what amount to vast stretches of dirty ice cubes.

But the numbers aren't budging.

I feel like we are missing something critical.

I think the missing ingredient is gradient  ;) AKA isobars. Without mixing, there is very little heat transfer into the ice itself. The last month or so has been extremely 'dull'. For some technical background on this, look at https://en.wikipedia.org/wiki/Nusselt_number

G

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Re: The 2020 melting season
« Reply #4819 on: August 13, 2020, 11:06:59 AM »
The last month or so has been extremely 'dull'.

You call this chart from July 28th "extremely dull"?
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Re: The 2020 melting season
« Reply #4820 on: August 13, 2020, 12:45:16 PM »
I followed a link from skeptical science to this new paper. I thought it was relevant to this melting season so I typed in the data below. It is a good read.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL089469
Intensification of Near‐Surface Currents and Shear in the Eastern Arctic Ocean

strengthened upper ocean currents and shear are observed to coincide with weakening stratification. This coupling links the Atlantic Water heat to the sea ice, a consequence of which would be reducing regional sea ice volume.

We propose a new process, the ice/ocean‐heat positive feedback, that can accelerate current sea ice loss and impede the rate of recovery of eastern Arctic sea ice even if large‐scale climate warming conditions relax.


Atlantification, weakening of the halocline spreading into the Kara & Laptev seas (& beyond?)
Resistance to refreeze?
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D-Penguin

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Re: The 2020 melting season
« Reply #4821 on: August 13, 2020, 12:54:52 PM »
Here's another for ye.
A very good graphic showing the current state of progression of the condition of the ice. A side-by -side comparison with 2012 would be interesting.
+1
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Freegrass

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Re: The 2020 melting season
« Reply #4822 on: August 13, 2020, 01:15:24 PM »
Latest Five Day Forecast
Wind @ Surface
Wind + Temp @ 850hPa
Wind @ 250hPa
Large GiFS!

Things are looking a lot more favorable for the ice than it looked a few days ago. Except for the ice in the Greenland sea that is. That ice seems doomed...
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Jim Hunt

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Re: The 2020 melting season
« Reply #4823 on: August 13, 2020, 03:15:57 PM »
The clouds have cleared over the "Laptev Bite" this morning (UTC):

https://GreatWhiteCon.info/2020/08/facts-about-the-arctic-in-august-2020/#Aug-13
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Pmt111500

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Re: The 2020 melting season
« Reply #4824 on: August 13, 2020, 03:46:53 PM »
Some 250k to travel by ice to the NP from Greenland, I think. Still not for everyman, such a trip, though I've heard of couple who done 70 clicks one way in a day by skating on sea ice. That method is not likely to succeed on the Arctic Ocean though, for the ice is of rather poor quality for skating.

FishOutofWater

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Re: The 2020 melting season
« Reply #4825 on: August 13, 2020, 03:50:52 PM »
The Slater model predicted the slowdown in extent loss 50 days ahead of the slowdown. There was a change in the weather about 2 months ago that staved off complete collapse. Of course, there was also the issue of easy to melt thin ice melting out rapidly in the heat of early July leaving the thicker harder to melt multi year ice behind to melt out slowly.

Last winter should have been very good for ice because the polar vortex was strong all winter keeping the cold air pretty well locked up in the Arctic but the weather was not particularly cold despite the strength of the vortex because of the heat that got through the thin ice. However, the lack of a Beaufort high last winter protected the ice on the Canadian side of the pole and made for a much slower start to the melt season in the Beaufort sea.

The long term damage being done this year is the Atlantification of the Siberian side of the Arctic ocean. That warm salty water will be releasing copious amounts of heat throughout the fall and winter months and will cause the polar vortex to be displaced towards Scandinavia affecting NH weather next year. The memory effects of the big melt this July will carry over into next summer.

In many ways the weather is like a casino but ocean heat changes the odds. As the weather transitions towards winter as the days rapidly darken near the pole ocean heat will increase the chances of strong storms near the ice water interface and could still bring some surprises at the end of the melting season. We are well into bottom melt season so the mixing up of ocean heat will be critical to the minimum ice extent. Predicting that minimum will be a matter of luck because we could still get a really strong Arctic cyclone more intense than the one in late July, but no one can predict one now.

blumenkraft

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Re: The 2020 melting season
« Reply #4826 on: August 13, 2020, 04:01:42 PM »
The Slater model ...

Just adding for context.

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Re: The 2020 melting season
« Reply #4827 on: August 13, 2020, 04:09:43 PM »
Juan C & Gerontocrat: seems like good odds that melting rate this month could be record low unless it doesn't speed up soon.

2020 has so far lost 0.53 M km². A little more than a third of the month has passed, and the slope of decrease decreases towards the end of the month. A place in the lower part of the ranking list seems possible.

IMHO we have now entered the phase when Heat Energy balance becomes increasingly critical and we can no longer reference previous years as predictors of even the short-term or medium term condition of the Arctic ice. The 'Puff' event will be sudden and happen at any time from 'now' and is likely to surprise many, particularly those who rely on the past trend of events to predict the future demise of the Arctic ice.
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ArcticMelt2

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Re: The 2020 melting season
« Reply #4828 on: August 13, 2020, 04:43:01 PM »
https://twitter.com/ECCC_CIS/status/1293874963045384192

Quote
#Seaice coverage in the eastern Canadian #arctic is at it’s 3rd lowest level in the last 40 years for the week of August 13th.   Significant ice movement in the archipelago during the last week.


Paul

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Re: The 2020 melting season
« Reply #4829 on: August 13, 2020, 04:56:28 PM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...

Juan C & Gerontocrat: seems like good odds that melting rate this month could be record low unless it doesn't speed up soon.
it will  :) :) :) :) :) :)

I'm honestly mystified.  There's heat in the air, there is heat in the water, there's been rainfall, there is still insolation, especially over regions on the Pacific side. 

The ice quality is awful.  I mean *REALLY* awful. We have very little pack in the sense that it existed just a decade ago.  Instead, we have what amount to vast stretches of dirty ice cubes.

But the numbers aren't budging.

I feel like we are missing something critical.

 

But

Not as mystified as some because the weather patterns has been largely favourable for the ice with the exception of that 2 day deep low since the large anticyclone dominated in July.

I and a few others commented at the time whilst the anticyclone was damaging for extent, it did 2 things. Kept the Beaufort sea cooler where the ice was thicker and secondly it compacted the CAB ice and just for the record I don't believe for a second it made the ice thicker or it helped the ice to 'ridge' as some said it has but it prevented dispersion. Even now, the CAB ice looks fairly compact but it also looks pretty thin looking from above. I mention that having some compaction or high pressure is not fully a bad thing as when you go through the 2nd half of the melt season the compact ice should be more resilient to any open water trying to sneak its way in. We are seeing with the ice on the Chukchi/Beaufort border how open water can easily start to melt the ice once the ice is diffused. This happened in 2016 also hence the theory a disperse pack is more damaging for the longer term in a melt season rather than the shorter term.

Unfortunately because the ESS and Laptev ice areas are essentially ice free and more ice will melt in the Beaufort Sea, Its going to be difficult for the ice to remain above 4 million, confidence on ice finishing above 4 millions has marginally increased though and maybe the next 2 weeks will reveal more on that front. Regardless, we have seen a taster this year what thin ice(which it was in the ESS and Laptev due to the positive AO) and above average temperatures can do to the ice edge pretty rapidly.

Melt season is far from over though and you still can't rule out a record low but I think the slow melt in the Beaufort sea has saved from that happening.

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Re: The 2020 melting season
« Reply #4830 on: August 13, 2020, 05:48:07 PM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...

Juan C & Gerontocrat: seems like good odds that melting rate this month could be record low unless it doesn't speed up soon.
it will  :) :) :) :) :) :)

I'm honestly mystified.  There's heat in the air, there is heat in the water, there's been rainfall, there is still insolation, especially over regions on the Pacific side. 

The ice quality is awful.  I mean *REALLY* awful. We have very little pack in the sense that it existed just a decade ago.  Instead, we have what amount to vast stretches of dirty ice cubes.

But the numbers aren't budging.

I feel like we are missing something critical.

 

But

JD...
Long time (occasional) lurker, first post. I have none of the expertise or certainty that many people posting here exhibit, so I hope my question is sensible - and not a waste of time.

Since the oceans are the primary repository for excess heat (greater volume and larger heat of fusion of water), is it possible that cumulative changes have reached a point where thermal/ saline and other aspects are beginning to shift - changing the ocean currents and consequently, heat distribution?
I wonder that this might cause Arctic heat to be mixed more deeply... and less deep import of heat from the Atlantic. Is it possible for the Arctic to become somewhat thermally stagnant? The central basin would play a huge role in such a case...

In any event, this seems to be one possible explanation for all the heat and the puzzling slowdown in melting. If I am way off, let me know. Always appreciate input and the chance to learn from more informed people.
Rob

Noob warning: I missed one of the questions required to post!

oren

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Re: The 2020 melting season
« Reply #4831 on: August 13, 2020, 07:21:50 PM »
Welcome reikel!

blumenkraft

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Re: The 2020 melting season
« Reply #4832 on: August 13, 2020, 07:27:47 PM »
Noob warning: I missed one of the questions required to post!

Hey, Rob. Nice to meet you.

Wich one? Lena?

igs

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Re: The 2020 melting season
« Reply #4833 on: August 13, 2020, 07:38:17 PM »
IMHO we have now entered the phase when Heat Energy balance becomes increasingly critical and we can no longer reference previous years as predictors of even the short-term or medium term condition of the Arctic ice. The 'Puff' event will be sudden and happen at any time from 'now' and is likely to surprise many, particularly those who rely on the past trend of events to predict the future demise of the Arctic ice.

That's it and so many great post here recently, very useful stuff so it's mostly a great pleasure to read.

That said even if all the current extent would be at 16% (hypothecially) it would still show a slowdown just to end up with zero (hypothetically)

Hope my point is comprehensive, else someone who with better semantics will certainly chime in.

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Re: The 2020 melting season
« Reply #4834 on: August 13, 2020, 07:41:09 PM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...
I'm honestly mystified.  There's heat in the air, there is heat in the water, there's been rainfall, there is still insolation, especially over regions on the Pacific side. 

The ice quality is awful.  I mean *REALLY* awful. We have very little pack in the sense that it existed just a decade ago.  Instead, we have what amount to vast stretches of dirty ice cubes.

But the numbers aren't budging.
There's heat and light, but not much. Temps are barely above freezing and the sun is quite low by now. Dirty ice cubes can last a long time in those circumstance. My example is the Hudson Bay Ice, which took months to melt out in higher temps and greater insolation.

Freegrass

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Re: The 2020 melting season
« Reply #4835 on: August 13, 2020, 07:47:14 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!
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Gizmo

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Re: The 2020 melting season
« Reply #4836 on: August 13, 2020, 08:10:01 PM »
Looks breezy through the Fram over the weekend.  But the wind direction seems like it would tend to move the ice towards northern Greenland and through the straight into the warm Atlantic.  Might we see that patch of rotten ice above Greenland break up further and get hammered?

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Re: The 2020 melting season
« Reply #4837 on: August 13, 2020, 08:20:14 PM »
Could the slowdown of extent loss in regard to Arctic sea ice be related to the net loss of ice in the northern hemisphere. I mean the GIS, glaciers, permafrost, ect... Perhaps there was a sharing of heat absorption among these that balanced out the effects. Just a theory that I am throwing out there to be shot down or whatever. I don't know myself.
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Re: The 2020 melting season
« Reply #4838 on: August 13, 2020, 08:28:08 PM »
Holy mole! I never thought the gap could get so bad this year.

I agree with what was said above regarding the large area of ice just over the 15% threshold. I think we could easily lose over 1M k2 in just 10 days with even mild mixing and surface heat.
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jdallen

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Re: The 2020 melting season
« Reply #4839 on: August 13, 2020, 08:55:54 PM »
The last month or so has been extremely 'dull'.

You call this chart from July 28th "extremely dull"?

*Exactly* the sort of thing I was thinking about.

There is movement.  One presumes there is Ekman pumping of some sort to go along with it.

Are we dealing with a resolution issue?

IIRC, we're looking at 0.5KM2 resolution at best for the pixels for the various products when they are producing these numbers.

If we have vast areas where the ice has shattered into far smaller pieces - generally less than 0.5km2 - I could see where large stretches of ice could have significant melting that wouldn't turn up in our metrics.

For example, in my included bit of detail below:  This is at the CAB/Laptev margin.  Considering the quality of the ice, how much melting is being hidden there in what is basically a sea covered in ice cubes?
« Last Edit: August 13, 2020, 09:01:47 PM by jdallen »
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jdallen

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Re: The 2020 melting season
« Reply #4840 on: August 13, 2020, 09:07:55 PM »
To amplify my thoughts here, consider this image from the Mosaic thread.  This is Polarstern at the end of June in what would certainly show up as 100% concentration.

How much melt is missed because it's below resolution?

https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2906.0;attach=277722;image

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jdallen

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Re: The 2020 melting season
« Reply #4841 on: August 13, 2020, 09:09:21 PM »
Could the slowdown of extent loss in regard to Arctic sea ice be related to the net loss of ice in the northern hemisphere. I mean the GIS, glaciers, permafrost, ect... Perhaps there was a sharing of heat absorption among these that balanced out the effects. Just a theory that I am throwing out there to be shot down or whatever. I don't know myself.

You'd need to provide supporting evidence, which I suspect you'd not find.  Without that, we're just speculating wildly.
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jdallen

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Re: The 2020 melting season
« Reply #4842 on: August 13, 2020, 09:13:43 PM »
From the "numbers" thread - loss of both extent and area is  very low, prompting this exchange...

<snip>
I'm honestly mystified.
<snip>
I feel like we are missing something critical.

JD...
Long time (occasional) lurker, first post. I have none of the expertise or certainty that many people posting here exhibit, so I hope my question is sensible - and not a waste of time.
<snip>
I wonder that this might cause Arctic heat to be mixed more deeply... and less deep import of heat from the Atlantic. Is it possible for the Arctic to become somewhat thermally stagnant? The central basin would play a huge role in such a case...
<snip>
Welcome Reikel.

To answer that we'd need to look at the gradient in temps shown by buoys tracking water column temperatures.

I haven't looked at that thread, but if stagnation was happening, we should see evidence of it there.  To my (admittedly limited) knowledge, there hasn't been any evidence shown to suggest what you're talking about.
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FishOutofWater

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Re: The 2020 melting season
« Reply #4843 on: August 13, 2020, 09:22:14 PM »
The ECMWF continues to forecast much warmer than normal temperatures for Alaska's north slope and the Beaufort sea for the next ten days. Yes, this is normally the time of the year when temperatures in the Beaufort sea start sinking back towards the freezing point of fresh water. However, this mid to late August warmer than normal air temperatures combined with heat in the upper 50m of the water column will continue to melt the ice. Moreover, as the ice blows with the wind some of ice will come in contact with higher salinity water which will enhance melting.

I have reviewed the latest forecast map set and observed that winds may favor closing some of the open areas north of Greenland.  High pressure between Greenland and the pole will probably favor enhancement of the Laptev bite and closure of the gaps between Greenland and the pole. We'll see.

I don't claim to know how this melt season will end up but it's far from over. Winter is coming but we have another month of melting.

Click to see latest ECMWF animation of anomalous warmth forecast over the Beaufort sea.

ArcticMelt2

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Re: The 2020 melting season
« Reply #4844 on: August 13, 2020, 09:33:00 PM »
I don't claim to know how this melt season will end up but it's far from over. Winter is coming but we have another month of melting.

The ice is melting, there is little doubt about it. The holes are getting bigger.

http://ocean.dmi.dk/arctic/icedrift_anim/index.uk.php

ArcticMelt2

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Re: The 2020 melting season
« Reply #4845 on: August 13, 2020, 10:04:39 PM »
The same goes for NSIDC data.

A-Team

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Re: The 2020 melting season
« Reply #4846 on: August 13, 2020, 10:05:37 PM »
Quote
dnem asks: is the 15 Sep 2020 slide in #4796 your actual best guess scenario for that date? What would the extent of that scenario be?
No. It is better to focus on weather that has actually happened and document what that has done to the ice. For example, we do not have a grip on what is causing the unprecedented opening between Ellesmere-Greenland and pole so no have clue what comes tomorrow, much less Sept 15th. Even the better ‘operational’ forecasts like hycom haven’t been able find ice physics that reproduces what we can plainly see happening.

Sept 15 will come soon enough, it’s grossly over-weighted in posts. The melt forum is not really concerned with melt season but rather with loss of the planet’s refrigerator, the darkening solar reflector of high latitude northern hemisphere. Open water having only a tenth the albedo of sea ice, it carves out the lion’s share of growing energy imbalance as it fits increasingly better to seasonal insolation inputs. So it gets a forum.

‘Extent’ isn’t extent but rather a bare number that has forgotten its ice distribution picture. The bizarre opening this summer will go down the rabbit hole of a line graph. Multi-decadal trend lines are a much better use of extent numbers but even there, the x axis intercept has provided a dangerous upper bound to BOE oo far out in the future whereas the end game will likely be vastly faster and different process from the trend.

The 15 Sept scenario in #4796 isn't ‘photoshopping the future’ for the sake of an extent visualization stand-in because there is a physical basis to it: lowered concentration feeds on itself as enhanced lateral melt takes edges and smaller floes down to open water. So nipping away successively at the lowest concentration remaining in the palette does mimic the dominant process creating open water. However there’s no ability to anticipate less-than-boring weather.

This visualization method also works on hycom thickness though the physical basis is different (bottom melt). Because the embedded palette is so complex, it is harder to progressively infill the thinnest ice remaining with open water gray but still doable with lots of back and forth on the color picker radius. Hycom goes out six days on the weather so again a 30 day visualization will be thrown off by weather.

Ascat in late-May can supply surprisingly realistic visualizations based on yet another physical basis, residual brine channel salinity. The grayscale images are whiter on older matured ice and darker on newer FYI and SYI and systematically so. Thus iterated stepping of the contrast slider can incrementally erode higher dielectric ice, mimicking summer melt-off. Ascat does not provide useful images from mid-June to mid-Sept.

Despite the differing physical bases and gimp operations to exploit them, what the three future visualizations have in common is a stepping number. If that’s overdone or underdone, the visualization won’t look much like the actual future, especially if there’s unexpected weather. That departure is of interest in itself. However the images will remain a big step up from bare extent numbers or photoshop artwork.

The first animation below shows major changes are going on every day, just not ones that manifest on the low resolution extent/area forums

The five slides below start with the alarming OsiSaf of 11 Aug 2020, a 48-hour measure of ice pack displacement captured by well-tested AI. The background dark blue is open water; the inner light blue is not quite fully open as it still has vulnerable ice. There’s advantages to simplicity in terms of capturing a good overview; it’s sometimes hard to find a basic take-away from AMSR2 displays with 1% concentration increments that need a hundred colors.

The second slide overlays a reinitialized GFS wind display at 850 hPa in the middle of the OsiSaf date range. This shows winds a couple kms above the surface which again captures the main story without getting into complexities of actual surface air movement. It shows an unremarkable central anti-cyclone surrounded by three even less remarkable small cyclones. A confused jet stream far above has introduced not just surface highs and lows but given angular momentum to them.

The third slide drops the weather pattern onto the ice motion display. It’s a fairly good fit — the ice is moving right along under the anti-cyclone) — considering the 3-hr nullschool dynamic is on a 48-hour OsiSaf summary. The three cyclones are over open water, making waves but not directly moving ice. Persistent winds over long reaches can create swells that greatly damage the ice pack many hundreds of km away if they hit head-on. We have no idea if the next six weeks will bring extreme winds like these.

Air pressure differences per se don’t bring strong cyclonic winds, the gradient between the pattern of highs and lows has to be steep (close isobars). It follows that merely giving the low (970 hPA for the 27 July 2020 event) doesn’t adequately describe the strength, persistence, and ice impacts of the storm.

The fourth slide shifts to where the rubber meets the road: wind power density (WPD) vs frictional resistance of the ice (from pressure ridges, surface roughness and exposed freeboard edges). Wind tunnel data has established that the force exerted on the ice is better fit to the cube of wind speed (rather than speed). That means a mild Arctic zephyr of 5m/s (often seen by the Polarstern) provides 1/8 the push of a brisk 10m/s wind and 1/64 that of a 20m/s gale (rather than the 1/4 expected from assuming a linear relation).

A key feature of WPD in an Arctic cyclone is its strong variation with location and timestamp. Because of the cube, this is exaggerated for WPD relative to plain wind. On this fourth slide, the wind is seen acting very unevenly on the ice, the gold color indicating extreme forces above Ellesmere and Greenland and the blue a far more moderate impulse. Since we have no real idea of the level and distribution of friction across the ice surface, we have no real idea how the ice pack will respond to forces that vary so markedly in magnitude, direction and persistence.

Strong persistent non-cyclonic winds off Siberia brought a most unusual TransPolar Drift in late winter, causing havoc for the Polarstern, putting it months ahead of schedule and prematurely flushing it down the Fram. How does do cyclonic wind gyres differ in ice effect from straight southerlies? A tight radius of curvature means over a short distance through the eye that the wind has reversed direction by 180º. The ice, being pushed in opposite directions, forms a shear zone when cold and thick but more just a jumble of floes when thinner and weakly matrixed. A straight southerly has no curvature but may vary across a transect.

The ice also picks up on the overall cyclonic rotation as seen in this fourth slide. However the torque is not evenly applied. If the ice pack has open leads or polynyas, some of this can be adsorbed by compression or dispersion; if not, by ridging and over-rafting. In summary, though cyclonic events don’t necessarily bring extreme winds (or WPD), the ice pack is stressed in more complex ways. In late summer, on thinning ice, the effects can be dramatic.

The major 27 July 2020 cyclone will have a huge effect on the overall melt season. Even though much of the devastated ice might have melted out anyway just barely before Sept 15th, the early melt wrapping up now has exposed the perimeter of the central older thicker icepack both to enhanced lateral melt and to extreme wind exposure (so far unrealized).

Tigertown

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Re: The 2020 melting season
« Reply #4847 on: August 13, 2020, 10:14:06 PM »
Could the slowdown of extent loss in regard to Arctic sea ice be related to the net loss of ice in the northern hemisphere. I mean the GIS, glaciers, permafrost, ect... Perhaps there was a sharing of heat absorption among these that balanced out the effects. Just a theory that I am throwing out there to be shot down or whatever. I don't know myself.

You'd need to provide supporting evidence, which I suspect you'd not find.  Without that, we're just speculating wildly.
I won't speculate any further on that theory. Even if true, it might be years down the road before anyone could prove it. Anyway, I really expect the numbers to catch up soon. I think you are more on target about the melt being hard to see. I bet volume is dropping steadily, despite the slowdown in extent drop.
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grixm

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Re: The 2020 melting season
« Reply #4848 on: August 13, 2020, 10:27:00 PM »
To amplify my thoughts here, consider this image from the Mosaic thread.  This is Polarstern at the end of June in what would certainly show up as 100% concentration.

It would certainly not show up as 100% concentration. The concentration measurement is perfectly able to pick up small cracks between shattered ice, as well as melt ponds on top. That's because the the signal intensity the satellite sees for a certain area at its minimum resolution, will be naturally averaged out for that whole area, because it's an inherently resolution-less analog sensor. If a pixel only has 50% ice in it, the signal the sensors pick up for that pixel will be 50% strong, regardless of how the ice in the pixel is distributed. One wide crack or many tiny cracks, it doesn't matter.

And attached is the actual concentration data for that date with the Polarstern location highlighted. It shows up as around 85-90% concentration, which looks about right to me based on the photo.

uniquorn

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Re: The 2020 melting season
« Reply #4849 on: August 13, 2020, 10:55:26 PM »
Hudson Bay hasn't quite melted out yet.  https://go.nasa.gov/2PR612A