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Dharma Rupa

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Re: The 2018 melting season
« Reply #3400 on: September 17, 2018, 08:49:32 PM »
Some definitions here:  +/- 6 deg defines "civil" twilight  +/- 6-12 deg for "nautical" & +/- 12-18 deg for "astronomical" so take your pick !


https://www.timeanddate.com/astronomy/different-types-twilight.html

I meant the first, which I named, and the last; which you reminded me the name of.

Just wait until they have to figure out that that is 6 degrees from the normal -- and no, I am not going to compute it.

Anyway, the Sun is approximately hidden north of the Arctic Circle half the year -- and I don't remember how long a year is.


Aluminium

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Re: The 2018 melting season
« Reply #3401 on: September 17, 2018, 08:58:40 PM »
You being so...um...how far north of the Arctic Circle do you have to be before 1) you have no sunlight at least one day of the year, 2) you have no civil twilight at least one day of the year, and 3) it is dark all year?
1) Given refraction (35') and Sun radius (16') you have to be 51' north of the Arctic Circle or 67°25'N.
2) 6° north of Arctic Circle or 72°34'N.
3) There is no sign of sunlight all day at Winter Solstice 18° north of Arctic Circle or 84°34'N.

harpy

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Re: The 2018 melting season
« Reply #3402 on: September 17, 2018, 09:00:46 PM »
Does the sun just rotate around the edge of the horizon in the arctic for the 24 hours of sunlight?




magnamentis

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Re: The 2018 melting season
« Reply #3403 on: September 17, 2018, 09:04:59 PM »
What location does that graph refer to? 
66.5°N. Salekhard, for example.

if we mean the same graph, simply draw the line at that latitude ;)

magnamentis

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Re: The 2018 melting season
« Reply #3404 on: September 17, 2018, 10:38:59 PM »
since it has been a frequent topic and i haven't seen much about it today it's perhaps worth to mention that the remaining ice in the beaufort sea is "quasi" gone and will most probably and in fact be gone for good during the next 2-3 days since the wind is blowing the rest westward and mechanical impact with those waves is quite high.

Neven

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Re: The 2018 melting season
« Reply #3405 on: September 17, 2018, 10:42:01 PM »
I have sort of called when the minimum can be called in the latest ASIB blog post. My guess is 3-4 days from now. Based on this mostly:

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Sterks

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Re: The 2018 melting season
« Reply #3406 on: September 17, 2018, 10:42:32 PM »
Does the sun just rotate around the edge of the horizon in the arctic for the 24 hours of sunlight?
That's true (in the ideal world of two perfect spheres, no atmosphere effects, no refraction etc)
But that still makes 12h of sun...
24 h of half sun over horizon = 24 * 1/2 hours of sun = 12 hours of full sun

oren

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Re: The 2018 melting season
« Reply #3407 on: September 17, 2018, 10:48:12 PM »
A. All the sun angle / arctic sunlight discussion belongs elsewhere, maybe in the questions thread.
B. I have a suspicion that some kind of refreeze happened in the CAB-Beaufort sector in the last couple of days. The low concentration ice there turned into high concentration purple in slow-wing's animation, at first I thought this was cloud-induced or export-related but looking at uniquorn's temps animation from Windy it appears to be around -10C in that area.

Sterks

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Re: The 2018 melting season
« Reply #3408 on: September 17, 2018, 10:51:30 PM »
Please Oren, this thread has a date of expiry of... two days at most... dont be so zealous

Sterks

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Re: The 2018 melting season
« Reply #3409 on: September 17, 2018, 10:52:40 PM »
Oren, open up the freezing season thread to talk about freeze  ;)

gerontocrat

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Re: The 2018 melting season
« Reply #3410 on: September 17, 2018, 11:23:55 PM »
Oren, open up the freezing season thread to talk about freeze  ;)
At this point in time, it is a question of where it is still melting and where it has started to freeze. The balance of the two will determine whether the freezing season has started or not.

And that decision, to close the melting season thread and open the freezing thread, is in the gift of He Who Must Be Obeyed.
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oren

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Re: The 2018 melting season
« Reply #3411 on: September 17, 2018, 11:40:40 PM »
Oren, open up the freezing season thread to talk about freeze  ;)
You got me there  :)  :-X

Archimid

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Re: The 2018 melting season
« Reply #3412 on: September 17, 2018, 11:57:49 PM »
I like to use Daylight Hours Explorer. It lets you choose latitude and day of the year and gives you a visualization.

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html
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litesong

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Re: The 2018 melting season
« Reply #3413 on: September 18, 2018, 01:01:59 AM »
I like to use Daylight Hours Explorer. It lets you choose latitude and day of the year and gives you a visualization.

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html
Oh, so cool, it is!!!!  Far north people got to move to Cancun during the winter to get extra vitamin D...... if'n they don't mind the extra bullets being recently sprayed across the beaches. 
« Last Edit: September 18, 2018, 01:07:02 AM by litesong »

jacksmith4tx

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Re: The 2018 melting season
« Reply #3414 on: September 18, 2018, 02:31:19 AM »
Everything you need to track the Sun.
https://www.timeanddate.com/astronomy/

Also:
SunEarthTools.com
https://www.sunearthtools.com/index.php

Although aimed at solar energy production (and some other environmental issues) I found it useful for a number of other things solar related. Not sure about how good it is for polar ice watching or if the data is useful for other global observations but it is pretty cool.

I will cross post this in the renewable energy thread since it's main purpose seems to be for solar energy.
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Hefaistos

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Re: The 2018 melting season
« Reply #3415 on: September 18, 2018, 06:33:25 AM »
Does the sun just rotate around the edge of the horizon in the arctic for the 24 hours of sunlight?

No, it doesn't.
If you use the tool linked by jacksmith4tx you can that e.g. at Barrow, sun has an elevation of around 45 degrees at the end of June.

SunEarthTools.com
https://www.sunearthtools.com/index.php

slow wing

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Re: The 2018 melting season
« Reply #3416 on: September 18, 2018, 07:02:53 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-17...

Aluminium

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Re: The 2018 melting season
« Reply #3417 on: September 18, 2018, 07:57:10 AM »
September 13-17.

oren

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Re: The 2018 melting season
« Reply #3418 on: September 18, 2018, 08:14:41 AM »
The whole central pack appears to be solidifying, while the Little Blob and the ESS arm continue shrinking.

uniquorn

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Re: The 2018 melting season
« Reply #3419 on: September 18, 2018, 11:04:25 AM »
On a longer time scale it still looks like melt on the periphery, but Oren may be correct about the cab/beaufort.
amsr2-uhh, aug1-sep17.
Today's ecmwf waves and temps from windy
Worldview beaufort ice edge,  sep13-17, cloudy day removed.(click to run)
https://tinyurl.com/yb7ado64

slow wing

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Re: The 2018 melting season
« Reply #3420 on: September 19, 2018, 07:50:04 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-18...

Human Habitat Index

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Re: The 2018 melting season
« Reply #3421 on: September 19, 2018, 09:09:38 AM »
The whole central pack appears to be solidifying, while the Little Blob and the ESS arm continue shrinking.

ESS arm disappearing completely may be significant ?
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Phil42

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Re: The 2018 melting season
« Reply #3422 on: September 19, 2018, 02:23:51 PM »
As the freezing season thread has opened and the 2018 melting season comes (has come?) to an end, I'd like to throw a big THANK YOU at everyone who has contributed to this thread and the interesting discussions.

I am mostly a lurker on this forum but come here almost daily reading through the posts. This was the first melting season I followed like this and I have really learned a lot because of everyone here.

Looking forward to the freezing season now

uniquorn

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Re: The 2018 melting season
« Reply #3423 on: September 19, 2018, 02:38:03 PM »
Yes, thanks everyone.
Today's ecmwf waves and temps from windy.
« Last Edit: September 19, 2018, 02:43:15 PM by uniquorn »

Klondike Kat

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Re: The 2018 melting season
« Reply #3424 on: September 19, 2018, 02:40:13 PM »
I suspect that the 2018 melting season has come to an end.  The NSIDC extent has increased for the past two days, although the 5-day trailing average reached a new low.  The 5-day average has most likely bottomed, as even no increase on a daily basis would push the average higher.

uniquorn

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Re: The 2018 melting season
« Reply #3425 on: September 19, 2018, 03:06:53 PM »
Nullschool has some pretty odd currents in the ESS. https://tinyurl.com/ybrqp459

Dharma Rupa

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Re: The 2018 melting season
« Reply #3426 on: September 19, 2018, 07:51:29 PM »
"In the freezer it goes, and I'll pull it out again once JAXA goes 25K above the preliminary minimum reached yesterday. Traditions are there to be respected.  ;)"

Neven, I think you should start a new Thread with your name as the one who started it.  Some "traditions" need to be rejected.

uniquorn

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Re: The 2018 melting season
« Reply #3427 on: September 19, 2018, 10:12:33 PM »
Gentle compaction on the beaufort/cab ice front with similar winds forecast for the next couple of days (there's plenty of space). Probably a little more melt to come in the ESS/Chukchi. SST's still quite warm on the Atlantic side and a storm coming up the Greenland Sea so maybe not quite over yet....
Worldview, beaufort/cab sep18-19

slow wing

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Re: The 2018 melting season
« Reply #3428 on: September 20, 2018, 05:19:38 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-19...

Aluminium

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Re: The 2018 melting season
« Reply #3429 on: September 20, 2018, 06:40:56 AM »
September 15-19.

Niall Dollard

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Re: The 2018 melting season
« Reply #3430 on: September 20, 2018, 10:49:38 AM »
Big contrast again between Pacific and Greenland sides of the Arctic today. Temperatures as low as -16 C streaming out from top of Greenland almost to the Pole whereas southerlies are wafting warm air through the Chukchi and into that part of the CAB nearest the Pacific. Air temperatures above zero as far as 83 N at 170 W.

No sign then of any freeze any time soon for the ESS arm - sandwiched between warm Chukchi and Laptev.  It is looking very isolated.

uniquorn

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Re: The 2018 melting season
« Reply #3431 on: September 20, 2018, 02:17:05 PM »
Today's ecmwf waves and temps from windy.
edit:Regarding the coming stormy weather, it's the waves breaking through the SZ gap into the Laptev that cause me concern. (but it is just a forecast)
Windy, ecmwf wam, sep20-29.(3.7MB)
« Last Edit: September 20, 2018, 02:47:09 PM by uniquorn »

gerontocrat

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Re: The 2018 melting season
« Reply #3432 on: September 20, 2018, 07:50:45 PM »
GFS five day averages attached.

If you like the cold, go to Central Canada North of 60,
If you want to stay warm, go to Central Siberia as far north as you like.

So, which will have the greater effect, warmth on the Russian side, or cold on the Canadian side.

ps: DMI North of 80 Temperature is regarded as of little value as
-the calculation is weighted by latitude and not by area,
- the area measured is such a small faction of the total ocean area.

Is it not worse than that, at least in the sea ice minimum months as open water extends North of 80?
The summer value is held down close to zero because, we are told, North of 80 is ice covered.
This is no longer true. The image below shows a lot of open water North of 80. 25% of the total area of North of 80? In this area presumably surface air temperatures are not held down in the same way as the ice-covered region. To that extent DMI's published data is wrong?

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Michael Hauber

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Re: The 2018 melting season
« Reply #3433 on: September 21, 2018, 01:59:17 AM »

If you like the cold, go to Central Canada North of 60,
If you want to stay warm, go to Central Siberia as far north as you like.


Or If you like it warm go to Hawaii.  If you like the cold go to Central Siberia.  But stay away from North Central Canada as no one could possibly like it that cold lol. 
Climate change:  Prepare for the worst, hope for the best, expect the middle.

sark

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Re: The 2018 melting season
« Reply #3434 on: September 21, 2018, 01:59:27 AM »
Necrobump this old thread.
« Last Edit: September 21, 2018, 02:46:00 AM by sark »

uniquorn

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Re: The 2018 melting season
« Reply #3435 on: September 21, 2018, 03:17:19 AM »

slow wing

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Re: The 2018 melting season
« Reply #3436 on: September 21, 2018, 05:22:38 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-20...

Neven

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Re: The 2018 melting season
« Reply #3437 on: September 21, 2018, 11:33:12 AM »
JAXA has dipped below the previous preliminary minimum again, so this baby stays open.  ;D
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uniquorn

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Re: The 2018 melting season
« Reply #3438 on: September 21, 2018, 02:42:45 PM »
Today's ecmwf waves and temps from windy
ESS over the last 10 days as seen by ascat. (enhanced using clahe and unsharp mask)
« Last Edit: September 21, 2018, 04:01:22 PM by uniquorn »

uniquorn

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Re: The 2018 melting season
« Reply #3439 on: September 21, 2018, 10:15:15 PM »
Since the forecast looks even more stormy and the ice is, arguably, at it's most fragile, here is the ecmwf temperature forecast, sep21-30 from windy. (edit 3MB) Maybe the Svalbard hotspot will get to see some ice..
« Last Edit: September 21, 2018, 10:45:39 PM by uniquorn »

Aluminium

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Re: The 2018 melting season
« Reply #3440 on: September 22, 2018, 12:03:28 AM »
As a result of the huge heat intrusion on the Pacific side, extremely warm September is observed near Cape Dezhnev:

Anadyr:

Pevek:


Red line is the daily maximum. Blue line is the daily minimum. Green line is the daily mean. Red and blue dots are the highest and lowest for this day. Thin lines are the normal minimum, average and maximum.
« Last Edit: September 22, 2018, 07:56:36 AM by Aluminium »

Eco-Author

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Re: The 2018 melting season
« Reply #3441 on: September 22, 2018, 04:19:45 AM »
Since the forecast looks even more stormy and the ice is, arguably, at it's most fragile, here is the ecmwf temperature forecast, sep21-30 from windy. (edit 3MB) Maybe the Svalbard hotspot will get to see some ice..

Looks like a lot of upcoming potential for export incl. the garlic press?..  Do we have export figures this year?
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slow wing

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Re: The 2018 melting season
« Reply #3442 on: September 22, 2018, 05:18:05 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-09-21...

slow wing

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Re: The 2018 melting season
« Reply #3443 on: September 22, 2018, 05:40:18 AM »
Interesting to see, even after the equinox, this storm predicted to bring +1.3 degrees C all the way to the North Pole.

Presumably won't be melting much. With storms at this time of year I wonder mostly about the potential effects of waves and mixing of the fresh water layer from the recently melted ice with the more saline water underneath.

It's hard to speculate on the significance without seeing the physical data or even a plausible model. Could there be significant retardation of the refreeze? And even if so, could that have significant consequences for the ice pack at the end of the freeze season? Does retardation necessarily mean thinner ice? And saltier ice so less resistant in the melt season? Or, instead, is more heat radiated out into space before the ice cover arrives and might that lead to thicker ice eventually?

The system is just too complicated and unconstrained by data. As far as I can tell, it evades simple understanding on these questions.

charles_oil

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Re: The 2018 melting season
« Reply #3444 on: September 22, 2018, 07:44:19 AM »
Aluminium - what do the different lines lines etc represent ?  I cant see a key to the graphs.  Thanks

Pmt111500

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Re: The 2018 melting season
« Reply #3445 on: September 22, 2018, 07:52:52 AM »
The most equal day of autumn starts at 22nd of September, 14:54 (and continues until 23rd of September 14:54. That, for ye americanos out there, means 2:54PM (GMT) Have a happy Autumn Equinox, everyone!
(Fixed the time zone)
« Last Edit: September 22, 2018, 09:22:03 AM by Pmt111500 »

Aluminium

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Re: The 2018 melting season
« Reply #3446 on: September 22, 2018, 08:08:49 AM »
Aluminium - what do the different lines lines etc represent ?  I cant see a key to the graphs.  Thanks
My mistake. I am too used to these graphs. Message was modified.

September 17-21.

uniquorn

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Re: The 2018 melting season
« Reply #3447 on: September 22, 2018, 01:15:26 PM »
Interesting to see, even after the equinox, this storm predicted to bring +1.3 degrees C all the way to the North Pole.
Presumably won't be melting much. <snippage>
Presumably won't be freezing much either - while slow melt probably continues at the periphery.
Today's ecmwf waves and temps from windy
edit note: temps are posted because they also show some wind info. Keeps the size down and saves time.

@eco-author I don't have figures for CAA export
« Last Edit: September 22, 2018, 01:24:14 PM by uniquorn »

Sterks

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Re: The 2018 melting season
« Reply #3448 on: September 22, 2018, 01:33:54 PM »
Interesting to see, even after the equinox, this storm predicted to bring +1.3 degrees C all the way to the North Pole.
Presumably won't be melting much. <snippage>
Presumably won't be freezing much either - while slow melt probably continues at the periphery.
Today's ecmwf waves and temps from windy note: temps are posted because they also show some wind info. Keeps the size down and saves time. Wind is probably more important as we move towards the freezing season

@eco-author I don't have figures for CAA export

The CAA refreeze is well underway. It has to balance out the ever-slower melt at the periphery. Around CAB, little sun radiation compared to longer nights unbalanced outgoing radiation. I am very surprised melting season has survived the whole week. But time is over now. Can those waves counteract the effect of the coldness that is extending from the pole outwards?

uniquorn

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Re: The 2018 melting season
« Reply #3449 on: September 22, 2018, 02:16:10 PM »
The CAA refreeze is well underway. It has to balance out the ever-slower melt at the periphery. Around CAB, little sun radiation compared to longer nights unbalanced outgoing radiation. I am very surprised melting season has survived the whole week. But time is over now. Can those waves counteract the effect of the coldness that is extending from the pole outwards?
I don't know, but I suspect it will be enough to extend the melting season a few more days.
Wipneus amsr2 concentration CAA and CAB sep21
edited response as it starts new page (for me) and added cab chart
« Last Edit: September 22, 2018, 02:32:35 PM by uniquorn »