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F.Tnioli

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Re: The 2019 melting season
« Reply #4400 on: July 23, 2019, 04:12:19 PM »
...
That's a bad comparison
Oh it depends on agenda, though, Friv. In their goal is to create an _impression_ among not-so-bright and not-so-scholarly about the thing being "not so hot", - then their comparison is actually excellent, you know? Using people's common sense of "winter sun is not hot and it's low over horizon", which in fact is a mistake caused by all the heat loss from the athmosphere during every night there in Boston and such places, - quite very smart, you know. ;)

Niall Dollard

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Re: The 2019 melting season
« Reply #4401 on: July 23, 2019, 04:13:25 PM »
I pointed out before there is far more at play than just solar.

According to the ESRL output there is very little top melt expected under the centre of the high.

But that's not saying the dipole is not bad. Of course it is there is a lot more going on. Besides bottom melt will continue for at least two months more. Solar will still be a big factor in the not-so high Arctic. But solar isnt the be all and end all.

Squeezed between the dipole centres will be warm moist winds bringing rain and warm ocean currents attacking the Beaufort/Chukchi/ESS/Laptev edges. That's where a lot of the melt will be occuring. 

F.Tnioli

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Re: The 2019 melting season
« Reply #4402 on: July 23, 2019, 04:31:07 PM »
I pointed out before there is far more at play than just solar.
"Far" more? As in, solar is kinda not so significant thing? Nope, can't concur. The proper way to say this, IMHO, is "there is more at play than just solar" - drop "far" word for good. Then it's quite correct.

...
According to the ESRL output there is very little top melt expected under the centre of the high.
...
If ESRL says "very little top melt" under July sun in so wet (as it is now) Arctic - then i'd doubt ESRL 1st, everything else 2nd. I mean, when else there would be anything higher than "very little top melt" if not in July under open sun? Next time, they'll probably tell there is "very little melt" in the Arctic whole summer. Yeah. Sure.... Not!

...
Solar will still be a big factor in the not-so high Arctic.
...
I don't quite see how "a big factor" and "very little top melt" compute with each other. They just don't, in my book. Assuming that the "high" you mentioned will happen not only "oh-so-high Arctic", of course. So, you can not state both in the same time. But you just did. Care to explain? Thank you very much in advance!

cavitycreep

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Re: The 2019 melting season
« Reply #4403 on: July 23, 2019, 04:34:42 PM »
Sea Ice Concentration, July 8 – July 22

Love you, Friv  ;D

Niall Dollard

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Re: The 2019 melting season
« Reply #4404 on: July 23, 2019, 04:34:54 PM »
From ESRL here's the melt forecast at +126, when the dipole is about at its worst with strong melt running up along the boundary zone between the two pressure centres.


oren

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Re: The 2019 melting season
« Reply #4405 on: July 23, 2019, 04:36:35 PM »
Quote
No this EXPLOSION OF POWER is

BEYOND NUCLEAR FISSION
BEYOND NUCLEAR FUSION
BEYOND SUPERNOVA EXPLOSION

NO THIS IS SOMEWHERE BETWEEN OG BIG BANG AND MULTIVERSE BIG BANG.
And Friv is back!  8)

uniquorn

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Re: The 2019 melting season
« Reply #4406 on: July 23, 2019, 04:38:39 PM »
The ESRL expermiental sea ice pages drill down far more detail. It takes considerable time to tease through and assimilate the wealth of forecasts on that page.
https://www.esrl.noaa.gov/psd/forecasts/seaice/
Thanks for this Niall. Not many posters take the time to go into such detail. Not that I necessarily agree with the esrl forecast :)

F.Tnioli

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Re: The 2019 melting season
« Reply #4407 on: July 23, 2019, 04:41:26 PM »
From ESRL here's the melt forecast at +126, when the dipole is about at its worst with strong melt running up along the boundary zone between the two pressure centres.
I wouldn't be surprised the least to see that strong melt along the boundary, but i'd be indeed hell surprised to see as little melt as they project for the center of that high. So yep, i doubt that particular ESRL forecast like really very much. It's like saying "hey 24/7 sun still high enough for most of its energy to reach the surface - means almost nothing in an Arctic melting season". You know? Really hard to "buy", this sorta thing. Except if there is nearly no ice left there beforehand.

Niall Dollard

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Re: The 2019 melting season
« Reply #4408 on: July 23, 2019, 04:45:04 PM »
They just don't, in my book. Assuming that the "high" you mentioned will happen not only "oh-so-high Arctic", of course. So, you can not state both in the same time. But you just did. Care to explain? Thank you very much in advance!

Not sure what you are referring to with oh so high arctic. The lose term "high Arctic" refers to Arctic area near the pole. Not at all related to the meteorological high pressure.

Now I don't want to get bogged down in semantics and let everyone go back to discussing the melt and where it will happen.

And not derail this thread.  :)

Niall Dollard

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Re: The 2019 melting season
« Reply #4409 on: July 23, 2019, 04:51:04 PM »
So yep, i doubt that particular ESRL forecast like really very much. It's like saying "hey 24/7 sun still high enough for most of its energy to reach the surface - means almost nothing in an Arctic melting season". You know? Really hard to "buy", this sorta thing. Except if there is nearly no ice left there beforehand.

It is but one forecast and of course should not be taken as gospel. Worth reminding everyone that the first word in ESRL is Experimental (lol !)

Bring back the buoys I say and curse Trump for all his cutbacks.

At this time of year it was always a great daily joy to check the O buoy camera to see the condition of the ice first hand.  :(

aslan

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Re: The 2019 melting season
« Reply #4410 on: July 23, 2019, 05:27:20 PM »
Ice is collapsing also north of Greenland. not a surprise given the warmth at Alert and Kap Morris Jesups, but still impressive to see.

https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2019-07-23-T00%3A00%3A00Z&z=3&v=-637043.2969331892,-1342611.7433077618,1329036.703066811,-313491.74330776196

It is important because we usually assume that the last bit of sea ice will be northward of Ellesmere and Greenland. But after all, perhaps it is not going to the case ? Last year also, sea ice quit the Greenland coast. And studies have found evidences of beaches along northern coast of Greenland during Holocene : https://science.sciencemag.org/content/333/6043/747

subgeometer

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Re: The 2019 melting season
« Reply #4411 on: July 23, 2019, 05:32:03 PM »
There's still plenty enough sun the push up the Beaufort and Chukchi SSTs up some more, and quicken  bottom and side melt amidst all that dispersed ice everywhere south of 80 N. Even in the absense of any notable storms, 2012 will have trouble catching this year..

But all that open water and high SSTs make storminess likely though, once the sun really does start to drop in a couple of weeks

RoxTheGeologist

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Re: The 2019 melting season
« Reply #4412 on: July 23, 2019, 06:00:51 PM »
This looks like the Great Arctic Anticyclone with strong winds and waves and clear skies. The sun still be high in the sky. I expect singnificant ice drop in any metrics.

High in the sky ? Under the anticyclone centre area (at 85N) the sun elevation angle will vary between 15 and 25 degrees.

Ok I know the sun does not set but from elevation angle POV, this is something similar to a January 10th afternoon in Boston, Mass.

the insolation is about the same as 30°N  right now. Are you saying that sea ice wouldn't melt under the Floridian Sun?

The only thing saving the ice from soaking up all those Watts is that it's still pretty white over a lot of the CAB, perhaps reflecting 60%. With that amount of sunshine it will darken quickly and as the ice thins the water under the ice absorbs more and more energy. The open ocean is going to soak up 90%.




oren

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Re: The 2019 melting season
« Reply #4413 on: July 23, 2019, 06:05:37 PM »
As the CAA could play a key role in determining the Sept. min, here's a revisit of the last 4 weeks at the Baffin Bay end of the Parry Channel. As can be seen, once the ice is thin enough it converts from stable and sturdy-looking fast ice to a heap of free-floating rubble. The only question is how fast will this process continue, and will it manage to clear the whole channel before the end of the season.

Shared Humanity

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Re: The 2019 melting season
« Reply #4414 on: July 23, 2019, 06:08:11 PM »
As the CAA could play a key role in determining the Sept. min, here's a revisit of the last 4 weeks at the southern end of the Parry Channel. As can be seen, once the ice is thin enough it converts from stable and sturdy-looking fast ice to a heap of free-floating rubble. The only question is how fast will this process continue, and will it manage to clear the whole channel before the end of the season.

The Perry Channel remains closed for traffic this season IMHO. This does not preclude new minimums in extent, area or volume.

binntho

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Re: The 2019 melting season
« Reply #4415 on: July 23, 2019, 06:20:18 PM »
This looks like the Great Arctic Anticyclone with strong winds and waves and clear skies. The sun still be high in the sky. I expect singnificant ice drop in any metrics.

High in the sky ? Under the anticyclone centre area (at 85N) the sun elevation angle will vary between 15 and 25 degrees.

Ok I know the sun does not set but from elevation angle POV, this is something similar to a January 10th afternoon in Boston, Mass.
Insolation at 90 degrees is greater than at the Equator until the first week in August.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

UCMiami

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Re: The 2019 melting season
« Reply #4416 on: July 23, 2019, 06:22:05 PM »
Oren - nice animation. With all the activity in the other seas, people think the CAA should be 'doing something' in June and early July, but the graphs for this sea show it is always the last of the non-CAB seas as far as area and extent to start falling. And it is generally right around mid-July that the melting momentum begins to show. The ice here locked as it is into narrow channels and with only a few 'exits' can't really be exported to another sea and most of it ends up melting in place and that takes quite a bit of time. Those large areas of melt-ponding in June did not reduce ice area, but did reflect serious decreases in ice thickness.

(This is not that different a process to what happens to the large stretches of land fast ice in the ess and laptev. except when they do finally break and melt, they can also be moved out into open water and over washed with waves)

Shared Humanity

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Re: The 2019 melting season
« Reply #4417 on: July 23, 2019, 06:25:27 PM »
Insolation at 90 degrees is greater than at the Equator until the first week in August.

Ought to settle this question.

oren

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Re: The 2019 melting season
« Reply #4418 on: July 23, 2019, 06:55:59 PM »
Another CAA animation, courtesy of Uni Bremen. Baffin melt-out can be seen in the background.
BTW, I am also of the impression that Parry Channel will stay closed this year. The North-western end appears quite sturdy, though surprises can and do happen.
CLICK to animate.

FishOutofWater

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Re: The 2019 melting season
« Reply #4419 on: July 23, 2019, 07:13:15 PM »
The ice in the Parry channel is showing signs of weakening on both ends but the middle of the channel has been cloud covered for days so its condition is hard to assess. However, there is evidence across the CAA that channels are starting to open up so I expect to see the Parry channel open by September.

PIOMAS shows that the ice in the channel was quite thin on July 15. The ice in the channel can get pretty thick in winter because it is surrounded by cold snowy land but in summer the ice is subject to more heat because it is surrounded by warm land. That leads to late melt outs of the channels.
« Last Edit: July 23, 2019, 07:21:18 PM by FishOutofWater »

Ossifrage

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Re: The 2019 melting season
« Reply #4420 on: July 23, 2019, 07:21:02 PM »
It is important because we usually assume that the last bit of sea ice will be northward of Ellesmere and Greenland. But after all, perhaps it is not going to the case ? Last year also, sea ice quit the Greenland coast. And studies have found evidences of beaches along northern coast of Greenland during Holocene : https://science.sciencemag.org/content/333/6043/747

Anthropology had long suggested otherwise. We know that both the Dorset and Thule cultures had a presence up the Nares Strait. For the Thule, that presence continued east along the north coast of Greenland, past Cape Morris Jesup, and at least some distance down the east coast, all aided by the Medieveal Warm Period.

AGW has exceeded the climate forcing of the MWP, so there's no reason to expect that Greenland's north coast will be the final refuge of sea ice. For near-shore ice, that honor will almost certainly go to a section of the CAA, bounded on the east by Axel Heiberg Island and on the west by Eglinton and Prince Patrick (essentially, this comprises the Sverdrup Islands). These areas were never settled by the Arctic indigenous peoples, even during the MWP.

It's probably worth noting that the ice in the Sverdrup Islands functions more like fast ice than like sea ice, even in relatively large open bodies of water like the Prince Gustav Adolf Sea. The transition between that CAA fast ice and the CAB sea ice is what allowed the CAA/CAB crack, in fact. The sea ice has become sufficiently unmoored that Arctic-wide winds have applied torque this season, shearing the sea ice away from the CAA boundary. It's difficult to judge the current condition of the crack in the vicinity of the Sverdrups because the area has been under heavy cloud for awhile now. As of the 20th, there was about 50km of almost completely open water to the north of Brock, and I can almost convince myself there's about that much ice rubble north of Ellef Ringnes on the 22nd, under the cloud deck. At some point, clear skies will out. In any case, the PGAS and adjacent channels seem quite robust again this year, but that crack lowers regional albedo and portends their eventual failure.

The last refuge of actual open sea ice will probably be somewhere north of the Lincoln sea, in a narrow triangle described by the Ward Hunt Ice Shelf - Kap Kane Ice Shelf - North Pole.

bbr2314

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Re: The 2019 melting season
« Reply #4421 on: July 23, 2019, 08:13:03 PM »
It is worth noting that the first snowfalls of the season are now appearing in the medium-long range across elevated areas adjacent to the Arctic.



Perhaps this will help increase the temp gradient vs. the Arctic and encourage a GAC (as was speculated earlier in this thread for different reasons)? Whatever falls should be mostly transient until the end of August, but I wonder if the (possibly) unprecedented amount of open water this year will yield record early snowfalls in nearby high latitude + high elevation land areas, which will worsen the gradient with the Arctic further, advecting heat into the Arctic Ocean, and paradoxically prolong the melt season.

Shared Humanity

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Re: The 2019 melting season
« Reply #4422 on: July 23, 2019, 08:50:01 PM »
Getting an early start on the season this year?  ;)

Alphabet Hotel

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Re: The 2019 melting season
« Reply #4423 on: July 23, 2019, 09:00:05 PM »
Northern CAA ice breaking up. Cornwall Island is in the center. Google Maps says the tiny island directly above it is called Haig-thomas Island.

edmountain

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Re: The 2019 melting season
« Reply #4424 on: July 23, 2019, 09:11:25 PM »
Insolation at 90 degrees is greater than at the Equator until the first week in August.

Ought to settle this question.
Except that the albedo of the underlying surface is in large part a function of the angle of incidence of the solar radiation. This is true not just for water but also for sea ice.


Source: Hudson, 2011 https://doi.org/10.1029/2011JD015804

At 90°N latitude at this time of year the solar zenith angle is about 70° so that all the time is spent in the high-albedo part of the curve. South of 30°N, once the sun rises, almost all daylight hours have a solar zenith angle less than 70° and for much of the day less it's than 40°; at tropical latitudes it can obviously reach 0° at high noon. The end result is a great deal of time is spent in the low-albedo part of the curve.

I have no idea how to quantify this difference. My point is that it's not as simple as calculating the theoretical 24-hour solar insolation based on latitude alone and calling it a day.

bbr2314

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Re: The 2019 melting season
« Reply #4425 on: July 23, 2019, 09:15:30 PM »
You suddenly changed the goalposts from 85N to 90N. I think your argument is wrong. But I do appreciate the chart.

Shared Humanity

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Re: The 2019 melting season
« Reply #4426 on: July 23, 2019, 09:16:40 PM »
Insolation at 90 degrees is greater than at the Equator until the first week in August.

Ought to settle this question.
Except that the albedo of the underlying surface is in large part a function of the angle of incidence of the solar radiation. This is true not just for water but also for sea ice.


Source: Hudson, 2011 https://doi.org/10.1029/2011JD015804

At 90°N latitude at this time of year the solar zenith angle is about 70° so that all the time is spent in the high-albedo part of the curve. South of 30°N, once the sun rises, almost all daylight hours have a solar zenith angle less than 70° and for much of the day less it's than 40°; at tropical latitudes it can obviously reach 0° at high noon. The end result is a great deal of time is spent in the low-albedo part of the curve.

I have no idea how to quantify this difference. My point is that it's not as simple as calculating the theoretical 24-hour solar insolation based on latitude alone and calling it a day.

Thank you for this.

Alphabet Hotel

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Re: The 2019 melting season
« Reply #4427 on: July 23, 2019, 09:26:52 PM »
The ice north of the New Siberian Islands looks very strange today. It's gone dark except for those little strips that have stayed light. Zhokhova Island is just visible at the bottom edge of the frame.


Ossifrage

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Re: The 2019 melting season
« Reply #4428 on: July 23, 2019, 09:34:40 PM »
The ice north of the New Siberian Islands looks very strange today. It's gone dark except for those little strips that have stayed light. Zhokhova Island is just visible at the bottom edge of the frame.

My eyeball guess is that those white linear features are the remains of ridging structures in the ice field.

Shared Humanity

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Re: The 2019 melting season
« Reply #4429 on: July 23, 2019, 09:37:12 PM »
Wet ice ready to melt away IMHO.

Shared Humanity

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Re: The 2019 melting season
« Reply #4430 on: July 23, 2019, 09:38:13 PM »
The ice north of the New Siberian Islands looks very strange today. It's gone dark except for those little strips that have stayed light. Zhokhova Island is just visible at the bottom edge of the frame.

My eyeball guess is that those white linear features are the remains of ridging structures in the ice field.

Sounds right. Melting snow is not ponding on them which delays the melt on the ridges.

Tor Bejnar

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Re: The 2019 melting season
« Reply #4431 on: July 23, 2019, 09:47:00 PM »
Thanks for sharing the cultural perspective, Ossifrage!
Arctic ice is healthy for children and other living things.

aslan

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Re: The 2019 melting season
« Reply #4432 on: July 23, 2019, 09:47:27 PM »
For the forecast, we can underline the 2 - 3 meters sea with a period of 8 - 10 seconds. Nothing extraordinary (an Irish sailor would probably call it a pleasant day XD) but for the Arctic this is quite a lot of energy for the sea state. I don't have a lot of memory for this kind of stats, but I think the last time the sea was so powerful in Arctic was during late August 2016.
The wind is funneled along the Alaskan coast and has the potential to bring mighty waves even though there is only a shallow low with min pressure hovering around 1000 hPa.
https://www.tropicaltidbits.com/analysis/models/gfs/2019072312/gfs_mslp_wind_ak_13.png
This is not going to help the halocline, by the way. Perhaps ITP110 will whisper something to ours ears in the coming days.



Wait ... this would imply (via the correlation) that sea ice is responding to insolation levels ... what about CO2...?   I would be interesting to see a multivariate regression including both.  Asking for a friend lol.

Of course longwave radiations are increasing at surface, but the effect for sea ice in June is not as important as the increased solar radiation. I did not do a multiple regression, this was not pertinent. The correlation and the variance explained are too low for trying to play with stats. I built the correlation with the net downward longwave radiation, which is negative (the surface gets longwave flux from the atmosphere but in the same time cools to space emitting longwave. The net result is negative). The flux at surface is of course increasing (surface can not radiate heat as effectively now as CO2 increases), but this does not explain a lot of things in Arctic in June. I could have built the correlation with downward flux alone, to eliminate the effect of higher temperature radiating more energy in longwave, but it would have not changed much.

https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2014JD022013
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JD025819

This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph. But July is trying hard to push 2019 ahead.

[...]

Yeah I think I agree.

UCMiami

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Re: The 2019 melting season
« Reply #4433 on: July 23, 2019, 09:49:31 PM »
The ice north of the New Siberian Islands looks very strange today. It's gone dark except for those little strips that have stayed light. Zhokhova Island is just visible at the bottom edge of the frame.
A while back we had a section where various thoughts were presented on the dark ice bands in the ESS and elsewhere. A few competing ideas were presented with no conclusions, but the white in this image is probably more intact flows of ice with a bit greater thickness than the surrounding rubble.

The dark ice may have active algae growth, sea floor sediment, river sediment, particulate deposits from smoke, or simply be thin enough/fragmented enough to be absorbing more light/passing it through to the ocean below.

The sediment above would have been integrated into the ice either by wave action while it formed in shallow water, or picked up when the ice froze to the river delta/ocean floor.

bbr2314

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Re: The 2019 melting season
« Reply #4434 on: July 23, 2019, 10:14:58 PM »
The smoke-cyclone in Siberia is now approximately the size of the remaining sea ice. Wow. Paris is expected to breach its all-time high by 3-4F on Thursday as well, with 108F currently forecast.


werther

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Re: The 2019 melting season
« Reply #4435 on: July 23, 2019, 10:15:58 PM »
"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...

bbr2314

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Re: The 2019 melting season
« Reply #4436 on: July 23, 2019, 10:17:52 PM »
"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...
This May was the record warmest. Anything stated otherwise is a falsehood, and Aslan's statement is objectively wrong.

Ossifrage

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Re: The 2019 melting season
« Reply #4437 on: July 23, 2019, 10:19:44 PM »
A while back we had a section where various thoughts were presented on the dark ice bands in the ESS and elsewhere. A few competing ideas were presented with no conclusions, but the white in this image is probably more intact flows of ice with a bit greater thickness than the surrounding rubble.

The dark ice may have active algae growth, sea floor sediment, river sediment, particulate deposits from smoke, or simply be thin enough/fragmented enough to be absorbing more light/passing it through to the ocean below.

The sediment above would have been integrated into the ice either by wave action while it formed in shallow water, or picked up when the ice froze to the river delta/ocean floor.

Fundamentally, there are a lot of ways to make ice dark. There are considerably fewer ways to make ice white. More or less, it comes down to two options: relics of older ice embedded in a weaker matrix (such that they retain albedo while the surrounding material goes to slush) or the weathered remains of pressure ridges (for much the same reason). Or both.

The pattern of fairly small linear features in that ice near the New Siberian Islands suggests the latter.

Since we're on the topic... Pressure ridges are an extremely important aspect of Arctic sea ice, but don't get much discussion here because the large-scale models gloss over them. Basically, where floes are forced together by currents or winds, the ice shatters into blocks. Some of these blocks are pushed upward, in a small-scale equivalent of orogeny, to form visible ridges that can peak several meters above the floes' "ground level". But more importantly in many regards, this process also forces ice blocks below sea level, somewhat akin to the keel of an iceberg writ large. Leppäranta (2005) argued that these pressure ridges, in total, amounted for about half of ASI volume. We can quibble about that number, but the ridging process unquestionably provides for hidden stores of ice.

Also, these large pressure-ridge keels help to stabilize the pack against wind and current. The apparent cryosphere-scale rotation strongly suggests that there has been widespread erosion of this hidden volume store. In areas where sea ice abuts fast ice, the shallow water depth can allow pressure ridges to actually anchor to the sea floor. These structures are called stamukha; I suspect that the persistence of stamukha immediately north of the Sverdrup Islands is what has protected the Prince Gustav Adolf Sea and nearby channels from melt ... but that the shearing off of the sea ice from these anchors is what as allowed the CAA/CAB crack to torque open.

It's hard to back up any of my suspicions about pressure ridge keel behavior because these structures, despite historically being huge volume reserves, are individually too small-scale to be easily identified in the pack, and certainly too small-scale to be represented by most models. I suspect that, system-wide, most of that hidden volume is now gone, and the self-evident increases in motility and dispersion are the consequence.

bbr2314

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Re: The 2019 melting season
« Reply #4438 on: July 23, 2019, 10:22:29 PM »
If modeling is correct it looks like the smoke over Siberia is going to be sucked into the imminent LP developing over the ESS / Laptev, and thereafter will be entrained across most of the CAB after the insolation + heat event. That is a double-whammy.

This is the worst run yet of the ECMWF btw.



The ATL front is about to do a lot of caving.

edmountain

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Re: The 2019 melting season
« Reply #4439 on: July 23, 2019, 10:26:00 PM »
You suddenly changed the goalposts from 85N to 90N. I think your argument is wrong. But I do appreciate the chart.
It was binntho who first mentioned 90°N, not me.

But I'm curious as to how the argument is wrong. Like I said, I don't know how to quantify it, but the effect is real.

aslan

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Re: The 2019 melting season
« Reply #4440 on: July 23, 2019, 10:26:15 PM »
"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...
This May was the record warmest. Anything stated otherwise is a falsehood, and Aslan's statement is objectively wrong.


The graph is about the solar energy, not air temperature....

"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...
.

The graph is about the solar energy, not air temperature....

P.S. And yeah, of course, the phrase "good year" was a bit ironic, and yeah being above the 2010-2018 is of course already something. But again this is NOT about air temperature....

Davidsf

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Re: The 2019 melting season
« Reply #4441 on: July 23, 2019, 10:30:31 PM »
Glad to see you back Friv and glad you jumped in with both feet!

Thanks for the Baffin 4-week video Oren.

I know it's OT, but I also like the occasional cultural info.

be cause

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Re: The 2019 melting season
« Reply #4442 on: July 23, 2019, 10:38:38 PM »
Hi aslan .. the accumulated solar anomaly north of 70'  is interesting but 2019 needs an update .. is it keeping up with 2012 .. or fading with 2016 ?   We need to know ! :)  b.c.

  p.s. .. Friv returning with his CAPS ! suggests my forecast remains safe .
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Shared Humanity

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Re: The 2019 melting season
« Reply #4443 on: July 23, 2019, 10:42:23 PM »
Ossifrage... Thank you for that...learned a great deal from a single comment.

aslan

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Re: The 2019 melting season
« Reply #4444 on: July 23, 2019, 10:45:16 PM »
Hi aslan .. the accumulated solar anomaly north of 70'  is interesting but 2019 needs an update .. is it keeping up with 2012 .. or fading with 2016 ?   We need to know ! :)  b.c.

Probably keeping up, but this are MERRA2 data, which update monthly only, around the 20th. The definitive answer for July is going to be in one month so... But Reanalysis from the NCAR, a bit less good for radiation flux,  but still good enough, and in near real time, is in fact showing that 2019 is still pumping a lot of solar energy in July. Spatial pattern is also important. Maximum anomalies in 2012 were over Atlantic and Greenland front and over land due to record low snow, while in 2019 it is really the Arctic Ocean which is exploding.

slow wing

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Re: The 2019 melting season
« Reply #4445 on: July 23, 2019, 11:12:43 PM »
I think, for reference purposes regarding this season, it doesn't hurt to be aware of what the mercator model shows at 34m depth over the last 2 years (The current mercator model began ~ jun2017)
Thanks uniquorn, that is fascinating. I've played it several times already and will play it again.

Just a brief question so as not to get too far off-topic with this melting season:
Is there any prospect of extending the model back in time to before June 2017?

(I've always been very interested in the longer term trend in salinity.)

pietkuip

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Re: The 2019 melting season
« Reply #4446 on: July 23, 2019, 11:18:56 PM »
With low-concentration ice extending to the pole and the ice in general thin enough that an icebreaker could run through at full speed without taking damage. 
My climate-skeptical friends are pointing out that the Norwegian "Kronprins Haakon" had to return from a planned trip to the North Pole.
https://www.arctictoday.com/for-norways-newest-icebreaker-its-almost-to-the-pole-and-back/

Sterks

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Re: The 2019 melting season
« Reply #4447 on: July 23, 2019, 11:22:46 PM »
If modeling is correct it looks like the smoke over Siberia is going to be sucked into the imminent LP developing over the ESS / Laptev, and thereafter will be entrained across most of the CAB after the insolation + heat event. That is a double-whammy.

This is the worst run yet of the ECMWF btw.



The ATL front is about to do a lot of caving.
This is a powerful ridge. The better aligned with the ridge over Northern Europe, the more powerful. Short-lived though.

The smoke effect on the melting season is near zero. If anything, it blocks the sun but even that’s nothing compared with clouds cover for the past ten days for instance. Smoke is usually correlated with warm Southerlies. So if smoke is gonna be entrained, it is just a dye indicating warm air is gonna be entrained.
Every year the same song.

slow wing

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Re: The 2019 melting season
« Reply #4448 on: July 23, 2019, 11:25:15 PM »
... the albedo of the underlying surface is in large part a function of the angle of incidence of the solar radiation. This is true not just for water but also for sea ice.


Source: Hudson, 2011 https://doi.org/10.1029/2011JD015804

At 90°N latitude at this time of year the solar zenith angle is about 70° so that all the time is spent in the high-albedo part of the curve. South of 30°N, once the sun rises, almost all daylight hours have a solar zenith angle less than 70° and for much of the day less it's than 40°; at tropical latitudes it can obviously reach 0° at high noon. The end result is a great deal of time is spent in the low-albedo part of the curve.

I have no idea how to quantify this difference. My point is that it's not as simple as calculating the theoretical 24-hour solar insolation based on latitude alone and calling it a day.

Excellent plot, thanks edmountain.

Any melt ponds will presumably act like the 'clear sky over ocean' line and so, at the current solar zenith angle of ~70 degrees, the plot suggests they will still absorb about 85% of the incident solar radiation - which the plot shows to be about twice as much energy absorbtion as even dark ice.

This might be 85% x 460 W/m^2 ~ 390 W/m^2, if binntho's plot is applicable. Is it? Can anyone confirm that the insolation plot is for ground level and not for the top of the atmosphere?

uniquorn

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Re: The 2019 melting season
« Reply #4449 on: July 23, 2019, 11:26:07 PM »
Is there any prospect of extending the model back in time to before June 2017?
(I've always been very interested in the longer term trend in salinity.)
I have looked but mercator data pre june2017 is, I think, in different format, netcdf?, larger file sizes and only 0m, ie out of my download volume and probaby low results for effort. I would love to see it though if anyone has the skills and the internet connection.