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Author Topic: The Nares Strait thread  (Read 435098 times)

numerobis

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Re: The Nares Strait thread
« Reply #1250 on: August 23, 2017, 04:59:11 PM »
CIS doesn't analyze very far up the straits, but the outflow of Nares has been moving fairly fast the past couple days, 10 - 15 miles a day (around 1 km/h).

Thomas Barlow

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Re: The Nares Strait thread
« Reply #1251 on: September 19, 2017, 03:20:31 PM »
Do you think the Nares will freeze this winter?

Shared Humanity

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Re: The Nares Strait thread
« Reply #1252 on: September 19, 2017, 04:06:42 PM »
Do you think the Nares will freeze this winter?

Yes.

Thomas Barlow

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Re: The Nares Strait thread
« Reply #1253 on: September 19, 2017, 10:10:43 PM »
« Last Edit: September 19, 2017, 11:44:31 PM by Thomas Barlow »

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Re: The Nares Strait thread
« Reply #1254 on: September 20, 2017, 08:05:18 PM »
I certainly do not have any solid scientific rationale for expecting a freeze. It is just that the Nares freezes over more often than not and this causes me to think that it is more likely to freeze this year.

Nares did not freeze last year because the more southern ice arch did not form, blocking transport of ice. Last freeze season was remarkably warm. I suppose if we have a repeat of this ridiculously warm winter, it may happen again.

Thomas Barlow

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Re: The Nares Strait thread
« Reply #1255 on: October 06, 2017, 04:32:35 AM »
I suppose if we have a repeat of this ridiculously warm winter, it may happen again.
It is off to a horrendously bad start - see below. Add to that, the latest assessments are that globally, September shattered records.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1256 on: November 07, 2017, 07:11:09 PM »
Still flowing.  Poorly colorized floes in DMI Sentinel images - Nov 5 and 6 - showing Kane Basin.  I tried to create a GIF, but it didn't work.
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Brigantine

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Re: The Nares Strait thread
« Reply #1257 on: November 08, 2017, 12:42:49 AM »
Interesting. The red one seems to be right on the margin of the fast ice? It rotated slightly, but many features around it are static.

Phil.

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Re: The Nares Strait thread
« Reply #1258 on: November 10, 2017, 02:43:14 PM »
As I recall from the summer the region where the red one is was an eddy.  We had a floe that everyone was interested in which travelled very rapidly until it reached there then got held up for quite a long time.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1259 on: November 20, 2017, 03:22:35 PM »
I'm occasionally watching ice get exported out through Nares Strait via DMI's Sentinel imagery.  Here is yesterday's Kane Basin image showing ice flowing in the channel on the northwest side of the basin.  A large piece of the fast ice appears to be peeling off on the south end of the basin
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Niall Dollard

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Re: The Nares Strait thread
« Reply #1260 on: November 26, 2017, 06:10:18 PM »
Here is the Kane Basin for the 24th to 26th Nov. There is a blockage now just below 79 N.

There is a large block of what looks like multiyear ice (circled magenta) that hasn't moved much and has drifted back slightly north between 25th and 26th.


Brigantine

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Re: The Nares Strait thread
« Reply #1261 on: November 26, 2017, 09:10:30 PM »
So the southerly winds in Baffin Bay are having an impact.

How long would it need to stall like that to have a chance to freeze fast? (and stay fast after the wind changes).
I imagine it would take a lot. Even under colder conditions.

oren

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Re: The Nares Strait thread
« Reply #1262 on: November 27, 2017, 12:44:00 AM »
Normally the strait gets "stuck" and arches form at the narrow points (Kane Basin exit and Lincoln Sea entrance) in January/February.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1263 on: November 30, 2017, 07:09:17 PM »
Crosspost (abbreviated)
Here is a sea ice thickness product for 27 Sep to 30 Nov plus 9 day forecast taken from the Mercator Ocean site.
...
Export out the Nares Strait is quite effective.

It is more convenient in some ways to view animations at the MercOcean site, for example salinity x depth from May-Nov are linked below though there's no practical way to capture these or rescale (other than full screen mode). They do work well as previews however. The forecast salinity for Dec 9th shows the freshening in the Beaufort Gyre to 318 m depth (but not beyond) as well as the Atlantic Water salt finger wrapping along the Svalbard/Siberian shelf.

MercOcean uses a javascript library called Leaflet which works ok overall but has various limitations and bugs. The server is quite fast. The site may be fairly new as most of the cross sections are not yet available.

http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170501/20171130/2/1
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170501/20171130/2/2
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170501/20171130/2/3
http://bulletin.mercator-ocean.fr/en/permalink/PSY4/animation/3/20170501/20171130/2/4
Go to A-Team's post to see the images...
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A-Team

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Re: The Nares Strait thread
« Reply #1264 on: December 01, 2017, 07:33:01 AM »
I'm  really surprised by what this is showing passing through the Nares, don't really see how it could be an artifact of Mercator Ocean ice thickness series. The CAA also has actively flowing floes. Both are in the lower left.

There's a way to cross-post images and animations already uploaded to another forum: paste the url, select it, and hit the second button in the second row next to the flash icon. This inserts the image within the text, rather than putting on the bottom. There seems to be no limit to how many images can be inserted whereas it's been set to four for new uploads.

May be able to do more of this area at a better scale  by re-orienting into 'Greenland down' position ... also adding a couple of sea ice concentration views from UH AMSR2 colored so as to facilitate motion visualization. All four animations have the same date range, 27 Sep to 30 Nov 2017.

« Last Edit: December 01, 2017, 09:08:46 AM by A-Team »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1265 on: January 02, 2018, 04:12:59 AM »
Cross post
Lincoln Sea and Nares Straight -Jan 1
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A-Team

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Re: The Nares Strait thread
« Reply #1266 on: January 02, 2018, 05:29:23 PM »
Check out this one: unbelievable break-up and Nares export of the very thickest Lincoln Sea ice, late May/early June of 2017. Sentinel-1AB has the advantage of seeing through clouds. The massive processing of these files was provided by R Saldo at DTU.

I'm hoping that Neven can tweak the blog software admin settings for attachments to get rid of long-gone 'mpg' and allow 'mpg4' so these could display like youtubes on the forums. The link and image are to the lowest resolution version of this file.

Making a gif generates a couple thousand frames and a file size of 78 MB, too large for the forum. Only cropped+down highlights of the animation are shown below.

« Last Edit: January 02, 2018, 06:46:18 PM by A-Team »

Neven

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Re: The Nares Strait thread
« Reply #1267 on: January 02, 2018, 06:30:46 PM »
I'm hoping that Neven can tweak the blog software admin settings for attachments to get rid of long-gone 'mpg' and allow 'mpg4' so these could display like youtubes on the forums. The link and image are to the lowest resolution version of this file.

Turns out I could check a box for 'Local MP4' in the Simple Audio Video Embedder settings. Seems to work.
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A-Team

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Re: The Nares Strait thread
« Reply #1268 on: January 02, 2018, 06:54:39 PM »
Thx, that works great! (Not real sure why, it does not change the 'allowed file types' of attachments but it may be similar to allowing youtubes.) This mp4 format is popular in climate-change journals whereas gif is rarely seen. It has more favorable compression, allowing smaller file sizes. Also having a controller is much more convenient than with gifs. Believe twitter also uses this under the hood too.

After installing the 'SaveAsMovie' plugin into Fiji/ImageJ, a 48 MB gif consisting of a full year of daily Ascat files reduced to an astonishing 1.4 MB. (However that's just on my computer so unless photobucket etc are used to provide a url, it can't be uploaded to the forum!)

Quote
Allowed file types: gif, jpg, mpg, pdf, png, txt, jpeg
« Last Edit: January 02, 2018, 11:13:59 PM by A-Team »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1269 on: January 02, 2018, 07:09:25 PM »
... Nares export of the very thickest Lincoln Sea ice, late May/early June of 2017 ...
I'm delighted to see this animation, A-Team.  I knew 'at the time' that it was all mobilized.  Your gif (or whatever file type it is) shows that about half was actually exported. 

Like so much multi-year ice (MYI) across the Arctic, the remaining thick ice is highly fractured with interstitial first year ice (FYI).  Few, if any, of the remaining Lincoln Sea MYI hunks (separate floes last summer, but now 'welded' together with FYI) are large enough to form an ice bridge by themselves, should they continue to approach Nares Strait.  (Most of what is transported into Nares Strait is ice that formed west or northwest of the Lincoln Sea, and is less coherent than, and surely thinner than, the northeast Lincoln Sea ice that appears whiter than other ice in the gif.)
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A-Team

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Re: The Nares Strait thread
« Reply #1270 on: January 02, 2018, 09:26:04 PM »
The higher resolution versions load but only in miniature so need to be opened in new tabs which are slow to play so visit the site itself to view at better resolution (95 MB, 273 MB). These run from 01 Jan 17 to 25 Sep 17.

It's not clear why different swaths and even the same swath on different dates vary in contrast but clouds, water vapor, fog, salinity, ice roughness, ice melt ponds, and residual daylight may have small effects on the consistency of what Sentinel-1AB sees.

http://www.seaice.dk/movies/S1AB-LincolnSea-JanSep17/
« Last Edit: January 02, 2018, 09:40:11 PM by A-Team »

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Re: The Nares Strait thread
« Reply #1271 on: January 02, 2018, 11:43:30 PM »
Quote
gif shows about half [or the NE Lincoln Sea MYI was actually exported.
Good eye! Blue to pink area ratio below is 46%.

So did Piomas catch the massive loss of half the very thickest ice in the entire Northern Hemisphere? No, it's oblivious to events like this because 20m Sentinel is not used to reset accruing model errors, only daily ice concentration data which gets the ice edge outline right but doesn't see internal ice motion very well nor this Lincoln Sea ice breakup and Nares export.

Quote
the remaining thick ice is highly fractured with interstitial first year ice
That point is made forcefully in the new sea ice age paper: it does not work to assign large footprint pixels to a single ice age, better to use color to represent the proportions of each ice age class.

A new tracking algorithm for sea ice age distribution estimation
AA Korosov et al
https://www.the-cryosphere-discuss.net/tc-2017-250/tc-2017-250.pdf
« Last Edit: January 03, 2018, 12:00:52 AM by A-Team »

Neven

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Re: The Nares Strait thread
« Reply #1272 on: January 03, 2018, 09:04:55 AM »
Thx, that works great! (Not real sure why, it does not change the 'allowed file types' of attachments but it may be similar to allowing youtubes.) This mp4 format is popular in climate-change journals whereas gif is rarely seen. It has more favorable compression, allowing smaller file sizes. Also having a controller is much more convenient than with gifs. Believe twitter also uses this under the hood too.

After installing the 'SaveAsMovie' plugin into Fiji/ImageJ, a 48 MB gif consisting of a full year of daily Ascat files reduced to an astonishing 1.4 MB. (However that's just on my computer so unless photobucket etc are used to provide a url, it can't be uploaded to the forum!)

Quote
Allowed file types: gif, jpg, mpg, pdf, png, txt, jpeg
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A-Team

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Re: The Nares Strait thread
« Reply #1273 on: January 03, 2018, 09:22:56 AM »
Quote
Allowed file types: gif, jpg, mpg, pdf, png, txt, jpeg, mp4
Awright!

But weirdly, it is accepting the attachment upload but not displaying it the way it would accept and display a gif, jpg, or png. Unclear why it will display an external link to a mp4 but not an internal link. (txt makes no sense to display because it could just be entered in the text box.) mpg ... not seen that file format in a while, not sure what happens there.

Upon clicking, the attached mp4 (of a full year of Ascat ice movement) does not display in a new browser tab but instead downloads to your hard drive. There upon clicking, it will display in QuickTime etc. So not ideal for group discussion sharing.

I am trying the converter: https://convertio.co/mp4-converter/

"Dec 20, 2017 - The only reason a file is ever given the "mpg" extension is because older file systems and operating systems are restricted to 8.3 file names- that is, 8 letters, a period, and a three letter extension... In this case, MPG mostly uses file converted from VHS tape or VCD players. On the other hand MP4 is latest and widely use video format around the world. MP4 uses MPEG-4 compression which is the advanced / updated form of MPEG-1 compression technique."

Now I am trying long forgotten dropbox, photobucket, mediafire and gdrive accounts; while the first works as a link, it doesn't display here as mp4:

https://www.dropbox.com/h
https://drive.google.com/open?id=1_aJBIA_Hv7bWRs2EF5KQevhN4nLPY4Na
http://www.mediafire.com/file/zpd5qi51hjtc9n7/2017-ascat-year.mpg

« Last Edit: January 03, 2018, 11:22:05 AM by A-Team »

oren

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Re: The Nares Strait thread
« Reply #1274 on: January 03, 2018, 09:51:29 AM »
A-Team, thank you for that wonderful Lincoln breakup animation. I remember that spectacular event vividly.

Neven

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Re: The Nares Strait thread
« Reply #1275 on: January 03, 2018, 11:45:16 AM »
Something went wrong with my last comment (should've been posted yesterday, and this morning I got some error), but anyway.

Yeah, I could check a 'local mp4' box in the settings of the 'Simple Video Audio Converter' package for SMF forums, so that links to mp4 files can be played like YouTube links. I've also added mp4 to allowed attachments, but these don't seem to play automatically. I'll see if I can fix that, but even if I can, I fear that mp4 attachments may take up too much space on the server. I don't know what the data limits/costs are.
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Neven

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Re: The Nares Strait thread
« Reply #1276 on: January 03, 2018, 01:11:11 PM »
I've installed a mod called 'Play Media Attachment'.

Test...


Edit: In Chrome only the bar with the play button appears, nothing happens when pressed. In Firefox there's a window, but pressing play results in "No video with supported format and MIME type found".

Edit2: I'll try and solve this later today. BTW, it is now also possible to send other members attachments through PM, because it says here that installation of 'Play Media Attachment' should be preceded by installation of this mod called 'PM Attachments'. And so that's what I did.
« Last Edit: January 03, 2018, 03:59:23 PM by Neven »
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Mozi

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Re: The Nares Strait thread
« Reply #1277 on: January 03, 2018, 04:31:35 PM »
Hi Neven, the reason that is not playing here is because the video link is for an http:// address and this forums runs on https://, and Chrome and other browsers don't like including insecure content in a secure webpage. I'm afraid there isn't a simple solution for this other than hosting the video on an https:// address (or users can adjust their browser configuration, though this is probably a bad idea in general.)

lurkalot

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Re: The Nares Strait thread
« Reply #1278 on: January 03, 2018, 05:25:36 PM »
The play button works perfectly for me in Chrome, Neven.

Neven

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Re: The Nares Strait thread
« Reply #1279 on: January 03, 2018, 06:44:09 PM »
The play button works perfectly for me in Chrome, Neven.

Thanks for the feedback. To be clear: Is that the play button in my previous comment (two comments above yours)?
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lurkalot

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Re: The Nares Strait thread
« Reply #1280 on: January 03, 2018, 07:53:19 PM »
Yes

Neven

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Re: The Nares Strait thread
« Reply #1281 on: January 04, 2018, 02:17:25 PM »
Tor Bejnar posted a mp4 as attachment in another thread, and it worked for me there, both in Chrome and FF. That's encouraging.

Knock yourself our, A-Team, but please, no huge files.  ;)
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A-Team

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Re: The Nares Strait thread
« Reply #1282 on: January 05, 2018, 03:01:49 PM »
Quote
no huge files
The mp4 works some major magic through different compression that exploits visual illusions, reducing a 48 MB gif to a 1.8 MB mp4. So in theory could run the Ascat for 5 consecutive years and still stay within bounds. However other things break as the number of individual frames gets too large.

It is all playing fine in the Opera browser (which I use because of its totally effective code level ad blocker).

A-Team

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Re: The Nares Strait thread
« Reply #1283 on: January 07, 2018, 03:55:30 PM »
Now the question is, what got changed to cause our usual gif animations not to play? Below is a tiny 3-frame animation intended show what ice ages are being exported out the Nares. This is animating normally so let's try a larger one but still well within the 700x700 pixel and file size constraints. It is not animating without a click which somewhat localizes the admin settings problem. A half-size also does not animate but a quarter size does. Weird!
« Last Edit: January 07, 2018, 04:03:56 PM by A-Team »

Neven

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Re: The Nares Strait thread
« Reply #1284 on: January 07, 2018, 04:55:29 PM »
I'll try and have a look what the thresholds for gif animations are, but I fear it may be in code somewhere, and I lack skills in that department.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #1285 on: January 25, 2018, 04:50:45 PM »
cross post (and copied GIF):
Lincoln Sea Nares Export from 2017-12-24 to 2018-1-24. One tracked section of ice traveled approximately 115 miles (185km) in 31 days.  Furthest travel in one day was approximately 12 miles (19.3km).
Thank you, Ice Shields!
Note that the last 5 or 8 frames show mobilization of the north-of-Greenland ice.  This includes the remaining 'half' of thickest ice in the Lincoln Sea environs written about above.
« Last Edit: January 25, 2018, 04:56:52 PM by Tor Bejnar »
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A-Team

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Re: The Nares Strait thread
« Reply #1286 on: February 02, 2018, 12:21:37 PM »
Quote
Note that the last frames show mobilization of the north-of-Greenland ice the remaining 'half' of thickest ice in the Lincoln Sea environs
I'm also thinking that Lincoln Sea ice has two really distinct areas (despite often being described as the stagnant oldest thickest ice in the Arctic). The western part (on the 'left') turns over very rapidly as the caving-in arc recedes; the ice there at any given moment may be old and thick but it hasn't been in residence for even half a year, it moved over from the CAA or down from central.

The second portion of the Lincoln Sea ice to the east (on the 'right') has found a very quiet spot  hugging the western corner of Morris Jesup. It is neither caught up in the oceanic current exiting the Nares nor in shear lines of a large scale rotating icepack (like we'll see from this super-storm on Tuesday).

However Ascat too is now showing the second half of this quiescent ice heading to collapse and exiting the Nares. The three versions show developments since the 15 Sep 2018 minimum. The spots that serve as movement trackers do not have any obvious counterpart in NOAA or Sentinel-1AB and may just be rough or smooth areas rather than floes or lead features.

The second mp4 compares the ice movement action along the whole CAA strip from Banks Island to the Fram for the last 8 years. It is slightly stretched (distorted) in the vertical direction to expand the key narrow area along the CAA.

Technical note: conversion of a gif to mp4 seems to work better if the size is kept at 680x680 or below (because movies aim for 720 pixel standard width, which rescales the 700 pixel forum width down to 680.) Another workaround would be adding a blank gray edge 20 pixels wide to the right of 700 pixel wide content. In ImageJ, saving at the default 7.0 frame rate in the .mov container using RAW codec at high video quality, followed by online conversion to mp4 at https://www.online-convert.com/, gives a forum-acceptable outcome.

The mp4 forum viewer has a popup menu that can loop the movie and hide the floating control bar .
« Last Edit: February 02, 2018, 02:04:36 PM by A-Team »

oren

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Re: The Nares Strait thread
« Reply #1287 on: February 02, 2018, 01:38:45 PM »
Thanks for these wonderful animations A-Team.
If I recall correctly there was another such movement of the protected ice off the North of Greenland towards Nares in spring or summer 2017, but then most of it stopped before it got there and moved back a bit. This time it seems the motion has continued in at least three big "waves", each one more damaging than the last as the cumulative motion is what counts. And I can't really see a Lincoln "arch" forming anytime soon with this kind of mobility.

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Re: The Nares Strait thread
« Reply #1288 on: February 02, 2018, 03:38:35 PM »
Quote
Lincoln sea protected ice motion has continued in three big "waves", each one more damaging than the last...can't really see a Lincoln "arch" forming with this kind of mobility.
The last two days have been stable with only floes already broken off the arc moving. A large crack in the floating glacier ice shelf appeared somewhere between the 11th and 18th of January but has not developed further (arrow).

Winds from this impending storm may blow Lincoln Sea ice to the northeast though the overall effect on the ice pack is hard to anticipate. Winds, even from extreme low pressure systems, depend on the distance to the nearest high pressure zones and a steep gradient between them.

The slides below show nullschool GFS winds forecast three days out over yesterday's Ascat ice. A couple of days of strong consistent winds from the Barents/Kara will push the ice towards the Alaskan coast and out the Bering Strait; the cyclonic rotation applies stronger torques with distance from the drifting low pressure center (of 551 hPa!) which will cause massive radial shears of the ice pack but not so much new leads.
« Last Edit: February 02, 2018, 04:36:16 PM by A-Team »

oren

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Re: The Nares Strait thread
« Reply #1289 on: February 02, 2018, 04:49:20 PM »
The last two days have been stable with only floes already broken off the arc moving. A large crack in the floating glacier ice shelf appeared somewhere between the 11th and 18th of January but has not developed further (arrow).
Thanks. I believe this arc is too wide to be able to hold, but that's just a hunch.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1290 on: February 02, 2018, 06:36:45 PM »
Monday's forecast winds (per Windy.tv) in the Lincoln Sea are for 60+ kt wind gusts most of Monday and 50+ kt gusts the first half of Tuesday.
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Re: The Nares Strait thread
« Reply #1291 on: February 02, 2018, 10:09:33 PM »
Monday's forecast winds (per Windy.tv) in the Lincoln Sea are for 60+ kt wind gusts most of Monday and 50+ kt gusts the first half of Tuesday.

Last three days (Jan 31 - Feb 02). Would be interesting to see "after wind gusts" image. Images: http://ocean.dmi.dk/arctic/lincoln.uk.php

romett1

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Re: The Nares Strait thread
« Reply #1292 on: February 03, 2018, 09:27:33 PM »
Last 4 days - I thought it will be calm before storm, but lot of action already today. Images: http://ocean.dmi.dk/arctic/lincoln.uk.php


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Re: The Nares Strait thread
« Reply #1293 on: February 03, 2018, 09:32:50 PM »
Helluva a big plug-hole.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #1294 on: February 04, 2018, 06:34:23 AM »
Further to my 2/2/18 post (above), today's windy.tv shows 50+ kt wind gusts on Monday and 40+ kt wind gusts on Tuesday. (basically, 10 mph less) [I know, knots are nautical miles per hour and mph are statute miles per hour.]
« Last Edit: February 04, 2018, 09:53:47 PM by Tor Bejnar »
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Re: The Nares Strait thread
« Reply #1295 on: March 02, 2018, 10:22:40 PM »
Sentinel shows a temporary arch at 79'N in Kane .. as everything N and S is still in motion I doubt the arch will last . I guess current is driving current momentum ? b.c.
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Niall Dollard

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Re: The Nares Strait thread
« Reply #1296 on: March 15, 2018, 12:38:25 AM »
Looking at recent Worldview images, it seems there is an ongoing attempt at making a new arch south of the original arch that formed March 1st.

I cannot see this as clearly though on the sentinel images (but I haven't seen the March 14 image yet).

Niall Dollard

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Re: The Nares Strait thread
« Reply #1297 on: March 15, 2018, 08:03:29 PM »
Yes the sentinel images confirm that a new arch has formed below the first arch.


Niall Dollard

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Re: The Nares Strait thread
« Reply #1298 on: March 21, 2018, 10:15:35 PM »
A close up of the lower (2nd arch) that formed circa March 13th. From Sentinel Playground. Image acquired March 20th.

Niall Dollard

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Re: The Nares Strait thread
« Reply #1299 on: March 23, 2018, 03:10:35 PM »
A big chunk has broken off the lower arch on the 22nd March.