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Tor Bejnar

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Re: The Nares Strait thread
« Reply #750 on: September 03, 2015, 05:47:33 PM »
I just compared MODIS images of Sept. 1 and Sept. 2.  The biggest floe in Robeson Channel (just south of Lincoln Sea) went southward about 17 km between those dates.  The largest floe behind in went about 33 km and a floe ahead of it went about 28 km.  Some floes opposite Petermann Fjord moved over 60 km (as best I can tell). [Incidentally, the narrowest part of Petermann Fjord is about 15 km wide for scale.  When I write “southward”, I usually mean “southwestward” as Nares Strait is really aligned Northeast-Southwest.]  Floes in Lincoln Sea moved generally 5 to 15 km westward or toward Nares Strait (i.e., westward, southwestward or southward) except for floes west of the strait’s mouth that mostly moved a little westward.
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TerryM

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Re: The Nares Strait thread
« Reply #751 on: September 03, 2015, 09:12:08 PM »
Tor
Did it seem to you that Nares was first of all late to break, then when it was open to flow, most of the ice just remained in place?
Hopefully Dr. Muenchow's ride home will be uneventful.
Terry

Tor Bejnar

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Re: The Nares Strait thread
« Reply #752 on: September 03, 2015, 09:50:47 PM »
Tor
Did it seem to you that Nares was first of all late to break, then when it was open to flow, most of the ice just remained in place?
Hopefully Dr. Muenchow's ride home will be uneventful.
Terry
Yes, the ice, even after the ice bridge broke, mostly sat around waiting for the moment nobody was looking before heading south.  The winds, of course, were mostly from the south at the time.

I recall last early NH (that's Northern Hemisphere, not New Hampshire, where I once lived) winter when ice 'flew' south.  It appears it is migration season again.  (Sorry for, not exactly anthropomorphizing, but avianomorphizing, the poor innocent ice.)
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cats

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Re: The Nares Strait thread
« Reply #753 on: September 04, 2015, 12:42:24 AM »
Some interesting observations from the Oden as it headed back down the Nares Strait -
"The irony of all of this is that the big icebergs and floes streaming southward out of the Arctic Ocean and blocking the strait may be an indicator of Arctic warming. Although icebergs are not unknown here, those who have been on past expeditions did not report so many. Normally they tend to stay put up in the Arctic, but we think maybe the ice there has loosened up enough that the bergs are free to drift southward. We are not sure of this; will have to check satellite images and commentaries from ice tracking programs when we get home."
Full blog post at https://petermannsglacialhistory.wordpress.com/updates-from-co-chief-scientist-alan-mix/august-29-80-degrees-north/


Jim Hunt

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Re: The Nares Strait thread
« Reply #754 on: September 04, 2015, 08:10:59 AM »
Maybe the ice there has loosened up enough that the bergs are free to drift southward.

A bit like this do you suppose?

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/summer-2015-images/#Nares
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Wipneus

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Re: The Nares Strait thread
« Reply #755 on: November 22, 2015, 07:34:57 AM »
A big float in the Lincoln Bay is attempting to block the Nares Strait (or break in the attempt).
Seen in the last frame, strong winds from the south (77 km/h according to nullschool) blow the float away for now.

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Re: The Nares Strait thread
« Reply #756 on: December 11, 2015, 12:28:06 PM »
Arches are forming at both ends of the Nares.

(The image of Kane needs a click)

Neven

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Re: The Nares Strait thread
« Reply #757 on: December 11, 2015, 07:29:49 PM »
And so the game begins yet again.  8)
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oren

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Re: The Nares Strait thread
« Reply #758 on: December 13, 2015, 12:27:05 AM »
Actually it feels rather early. Let's see if it holds.

Wipneus

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Re: The Nares Strait thread
« Reply #759 on: December 29, 2015, 02:15:47 PM »
The two arches are still there.

Shared Humanity

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Re: The Nares Strait thread
« Reply #760 on: February 29, 2016, 02:56:50 PM »
I thought I would pull this thread up to the top by commenting that, in my very inexpert opinion, the Nares will be open for business early this year. The heat anomalies for western Greenland have been simply ridiculous all winter and I think the arches will collapse very early.

Jim Hunt

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Re: The Nares Strait thread
« Reply #761 on: March 04, 2016, 01:26:27 PM »
The first "visual" images of the southern arch are now available via Worldview:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/winter-2015-16-images/#Nares
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solartim27

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Re: The Nares Strait thread
« Reply #762 on: April 12, 2016, 08:24:38 AM »
A bit broke off yesterday.
FNORD

A-Team

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Re: The Nares Strait thread
« Reply #763 on: April 12, 2016, 05:36:04 PM »
Faster, easier, better to use EarthExplorer preview image? Neat cloud pattern. The 15 m band 8 Landsat is also quite remarkable in its detail. Is that some sort of melt fringe or wetted ice?
« Last Edit: April 12, 2016, 06:44:10 PM by A-Team »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #764 on: April 18, 2016, 06:51:20 PM »
A-Team:  The Landsat images are awesome!
I'm pretty sure the rim on the south edge of the bridge is 'fast ice' (frozen sea water), whereas the bridge 'proper' is composed almost entirely of pieces of older and thicker Arctic Ocean floes frozen together. 

Anybody know what happened to DMI's  TERRA images?  The last image is dated April 5, 2016.  (There are daily images from March 1, 2016 to April 5, 2016 available through the link.)
« Last Edit: April 18, 2016, 06:56:21 PM by Tor Bejnar »
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A-Team

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Re: The Nares Strait thread
« Reply #765 on: April 18, 2016, 11:16:35 PM »
Quote
Anybody know what happened to DMI's TERRA images?  The last image is dated April 5, 2016

I'm seeing Terra images are provided up to 12 Apr 16 for Pituffik, Lincoln and Morris Jesup but as you say not past the 5th for Kennedy, Kane and Quunaaq. Even the 12th is bordering on dated here on the 18th.

Quote
I'm pretty sure the rim on the south edge of the bridge is 'fast ice' (frozen sea water), whereas the bridge 'proper' is composed almost entirely of pieces of older and thicker Arctic Ocean floes frozen together.

Have you looked at a GRD IW class Sentinel 1A scene of the rim and bridge? It seems like salt water and salty ice should appear black in radar because of ion dipoles where as frozen freshwater ice would be reflective. The download hub is here:

https://scihub.copernicus.eu/dhus/#/home [broken down again despite 'root cause' fixed yet again yesterday!]

Sonia

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Re: The Nares Strait thread
« Reply #766 on: April 19, 2016, 05:33:25 AM »
Have you looked at a GRD IW class Sentinel 1A scene of the rim and bridge? It seems like salt water and salty ice should appear black in radar because of ion dipoles where as frozen freshwater ice would be reflective
Thank you for that explanation.  It's a tip that helps a lot with image interpreation!

Tor Bejnar

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Re: The Nares Strait thread
« Reply #767 on: April 20, 2016, 07:23:02 PM »
...
Anybody know what happened to DMI's  TERRA images?  The last image is dated April 5, 2016.  (There are daily images from March 1, 2016 to April 5, 2016 available through the link.)

DMI's TERRA images are back! At, least, there are images dated the 18th and 19th. (Everything is basically still covered with snow, except for the open polynya below the ice bridge.)
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #768 on: May 03, 2016, 07:50:00 PM »
The little polynya at the northern end of Kane Basin just off Cape Jackson is back.  It forms every year long before the ice bridge collapses.  Attached is a piece of the latest DMI Terra image showing just the northern end of Kane Basin with Cape Jackson and the polynya circled.
« Last Edit: May 03, 2016, 07:57:58 PM by Tor Bejnar »
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Tealight

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Re: The Nares Strait thread
« Reply #769 on: May 03, 2016, 11:20:28 PM »
Interesting. Are these formed by rocks, grounded icebergs or something else? I'm not sure because the Nares Strait is littered with icebergs and its hard to tell the difference.

Attached is a S2A image of the polyna from 30th April. Click to see full resolution.
« Last Edit: May 04, 2016, 12:03:34 AM by Tealight »

johnm33

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Re: The Nares Strait thread
« Reply #770 on: May 04, 2016, 09:40:02 AM »
The polynya, I think there are two strong contenders for the cause, my preferred option is that the west greenland slope current has been drawn north by tidal forces and it's kinetic energy and heat are being dissipated beneath this fast ice, the other is that Barents water  has been forced to the top of Nares by the huge gyration and movement taking place in Beaufort, and this forms coherent overturning currents which flow down the east side of Nares where again the kinetic and heat content erode the fast ice from below. The normal flow through Nares appears to be Arctic waters which due to their inertia are forced to flow on the west side of the strait.
You can see on this Nullschool anim. gyres forming off the west coast of Greenland, and to the south of Nares [though they have been more pronounced than this recently] and if you click back a couple of days you'll see the anomoly in the south changes considerably.
http://earth.nullschool.net/#2016/05/03/0000Z/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-58.78,67.53,1336/loc=-56.730,55.527
« Last Edit: May 04, 2016, 09:48:19 AM by johnm33 »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #771 on: May 04, 2016, 04:33:38 PM »
The polynya, I think there are two strong contenders for the cause,  ...
Thanks!  I sorta figured it was something like what you describe. 

Edit:  P.S. - thanks for the detailed image, Tealight!
« Last Edit: May 07, 2016, 03:31:20 PM by Tor Bejnar »
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bbr2314

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Re: The Nares Strait thread
« Reply #772 on: May 07, 2016, 09:08:09 AM »
If DMI's model is correct it looks like Nares may break within next few days.

oren

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Re: The Nares Strait thread
« Reply #773 on: May 07, 2016, 10:23:54 AM »
Looking at recent images of Kane Basin, I would put it at zero probability. This is not the proper time of year, and everything looks whole and healthy there.

johnm33

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Re: The Nares Strait thread
« Reply #774 on: May 07, 2016, 10:46:19 AM »

bbr2314

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Re: The Nares Strait thread
« Reply #775 on: May 07, 2016, 08:54:35 PM »
I am no expert on Nares but DMI still shows same outcome. I wonder if it is because the entire CAB is fracturing?

Not complete image, but today's satellite shows the cracks from the Beaufort catastrophe nearly reaching Nares vicinity...

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Re: The Nares Strait thread
« Reply #776 on: May 13, 2016, 03:30:28 PM »
Werther thinks we may see some action here soon, so heres a reference point

the currents are running south at -1.5C and up to .13mps [nullschool] and salinity has dropped according to hycom so bottom melt is underway. I think they're internal waves to the south which is why they're so big,[and they've shown up before in that spot] google internal waves images for comparison. for a bigger pic. http://ocean.dmi.dk/arctic/images/MODIS/Kane/20160512s01a.ASAR.jpg

Tor Bejnar

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Re: The Nares Strait thread
« Reply #777 on: May 13, 2016, 03:57:34 PM »
DMI's Terra images of the north end of Kane Basin (and up Nares Strait) show how thin the snow cover is there.  Individual floes can be seen, now, as well as brown earth.  (The Sentinel images always show the floe outlines.) (Edit: you can compare this snapshot with the one I took 10 days ago of the same area.)
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johnm33

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Re: The Nares Strait thread
« Reply #778 on: May 27, 2016, 12:34:29 AM »

ghoti

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Re: The Nares Strait thread
« Reply #779 on: May 27, 2016, 03:13:09 AM »
Seeing little nibbles of ice have been coming off the arch in the last week or so via worldview. Seems early for the arch to fail but if bits keep falling it might lose stability.

oren

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Re: The Nares Strait thread
« Reply #780 on: May 27, 2016, 06:16:34 AM »
Seeing little nibbles of ice have been coming off the arch in the last week or so via worldview. Seems early for the arch to fail but if bits keep falling it might lose stability.

Indeed. Here's a big piece detached from the Ellesmere side. Little bits falling off is typical for the date but the action seems stronger this year.
Usually movement starts north of the arch and the ice becomes mobile in June, and then the arch collapses (last year it was early July). As the whole Arctic is on the loose this year, there is a chance of this process happening much earlier.

« Last Edit: May 27, 2016, 06:32:29 AM by oren »

Neven

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Re: The Nares Strait thread
« Reply #781 on: May 27, 2016, 10:03:13 AM »
There was a clear LANCE-MODIS image yesterday, and those beautiful wisps of cloud caught my eye. And how about that small polynya on the western (upper) side of the arch? Could that impact stability?
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bbr2314

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Re: The Nares Strait thread
« Reply #782 on: May 27, 2016, 11:48:15 PM »
There was a clear LANCE-MODIS image yesterday, and those beautiful wisps of cloud caught my eye. And how about that small polynya on the western (upper) side of the arch? Could that impact stability?
Believe it already has, note today's image, a huge chunk has broken off and drifted significantly.


Tor Bejnar

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Re: The Nares Strait thread
« Reply #783 on: May 28, 2016, 01:13:15 AM »
...
And how about that small polynya on the western (upper) side of the arch? Could that impact stability?
Believe it already has, note today's image, a huge chunk has broken off and drifted significantly.
A polynya forms there "early" every year (e.g., see this 2011 ASIB post), so I doubt it has much affect on the Kane Basin arch, at least not differently from any other year.
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Neven

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Re: The Nares Strait thread
« Reply #784 on: May 28, 2016, 11:11:22 AM »
Thanks, Tor, but I'm referring to the polynya near the arch, not the one above it.
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Neven

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Re: The Nares Strait thread
« Reply #785 on: May 28, 2016, 11:57:58 AM »
Here's an animation showing the last 5 days on LANCE-MODIS. I think that arch looks stable enough, and the ice will have to turn blue before it breaks. There was a polynya in a similar position back in 2012, and that's where the arch failed first, but this year's arch is a bit further back, so I'm not sure if the polynya will impact that corner. Either way, I think it's going to take a couple of weeks for the arch to break, probably before June is out.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #786 on: May 29, 2016, 01:36:20 PM »
Woops  ::)
(- At the Florida Folk Festival all day yesterday and today - oldest continuously held annual folk music event in the US  :) )
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Re: The Nares Strait thread
« Reply #787 on: May 31, 2016, 12:48:19 AM »
Below is an animation showing changes in the past week (some ice broke off and that small polynya got bigger). And in the second image - regional ASAR from the DMI website - the white circle represents my curiosity at what will happen if that piece of ice between the small polynya and the open water in Kane Basin gives way. Will that compromise arch stability, or will the arch just retreat to a more stable position?
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oren

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Re: The Nares Strait thread
« Reply #788 on: May 31, 2016, 12:53:09 AM »
The animation shows small differences that are hard to see when browsing each image separately. How very interesting - it really does look as if it might lose stability if that small remaining part breaks apart, even though the date is early and the ice is not slushy yet behind the arch.

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Re: The Nares Strait thread
« Reply #789 on: June 02, 2016, 11:44:57 AM »
I thought i'd take a look at last year, just a hint on this image
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150606TERR.jpg not much more on the next
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150609TERR.jpg some progress
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150613TERR.jpg at last it's open but take a look to the north
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150616TERR.jpg more action to the north[east] and some straight lines appearing along Ellesmere coast
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150617TERR.jpg nothing to see here move along
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150619s01a.ASAR.jpg it begins
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150620TERR.jpg shame about the clouds
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150622AQUA.jpg what?
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150626TERR.jpg a little cloudy but the west side gives
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150703TERR.jpg now the greenland side
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150704s01a.ASAR.jpg clouds
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150706TERR.jpg sentinel
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150706s01a.ASAR.jpg here we go
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150709AQUA.jpg ditto
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150710TERR.jpg ditto
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150712TERR.jpg boom
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150714TERR.jpg boom
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150720TERR.jpg boom boom
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150722TERR.jpg
A more or less local tide timetable for last year http://www.dmi.dk/fileadmin/user_upload/vandstand_txt_pdf/2015/Pituffik2015.pdf and this years http://www.dmi.dk/fileadmin/user_upload/vandstand_txt_pdf/2016/Pituffik2016.pdf and the Ellesmere side http://www.tide-forecast.com/locations/Payer-Harbour-Cape-Sabine-Ellesmere-Island-Nunavut/tides/latest
So it sort of kicks off when the tidal peak happens around the 17/6 but then eases, the next tidal peak is around the 5/7/15 [or07/05/2015 US style] which proves enough and it doesn't recover, and is smashed in the build up to the next peak tides. Will the high/low tides coming around the 5/6th be enough?

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Re: The Nares Strait thread
« Reply #790 on: June 06, 2016, 09:24:39 AM »
Big changes at the Western end of the Nares Strait this weekend. The polynya closest to the Strait is joining the main stream. Collapse of the current arch imminent?

https://lance.modaps.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r03c02.2016157.terra
« Last Edit: June 06, 2016, 09:34:58 AM by silkman »

A-Team

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Re: The Nares Strait thread
« Reply #791 on: June 06, 2016, 03:56:13 PM »
At the maximum resolution available, 250 m. Terra and Aqua aren't too far apart in image timing so the Nares Strait is changing rapidly (or we got lucky in capturing the event). Bands 367 processed out to the scan line limit show frozen-in floes and possibly future break lines.

Quote
Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon [in the A-train].

It's not clear from the metadata how much time elapsed between the two swaths relevant to the Nares arch (which is on the extreme right of the image), so possibly 10:50 for Aqua and 13:40 for the Terra for 2 hours and 50 minutes. The orbit map is unreadable: https://lance.modaps.eosdis.nasa.gov/imagery/realtime/orbitmaps/2016157/orbitmap1.global.2016157.gif

5 minute swath data used for Terra image:
13:40 UTC
13:45 UTC
15:20 UTC
15:25 UTC
17:00 UTC
18:35 UTC
18:40 UTC
20:15 UTC
21:55 UTC

5 minute swath data used for Aqua image:
10:50 UTC
12:25 UTC
14:05 UTC
15:40 UTC
15:45 UTC
17:20 UTC
18:55 UTC
19:00 UTC
« Last Edit: June 06, 2016, 04:32:03 PM by A-Team »

oren

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Re: The Nares Strait thread
« Reply #792 on: June 06, 2016, 05:15:59 PM »
Amazing. The whole Ellesmere side of the lower arch is gone in one big poof. I looked yesterday for changes and there was no hint of this coming.
Is the ice mobile enough above the arch to follow on this structural loss of support? We shall soon see.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #793 on: June 06, 2016, 07:56:56 PM »
A close comparison between the latest (2016-06-06) and an earlier (2016-06-03) DMI Sentinel image suggests to me that there has been a small movement of the ice away from the rocky (southern) Greenland side of Kane Basin.  If this is real, most of the ice in at least Kane Basin will break up soon.
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Shared Humanity

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Re: The Nares Strait thread
« Reply #794 on: June 07, 2016, 03:39:02 PM »
If you look at the animated image just above (orange) you will see a feature in the arch that is absolutely critical to stability of the arch. From an architectural point of view, the most important stone is the keystone, the stone that sits at the very top of the arch in the center. This stone carries the highest stress load and when this stone is compromised or removed, the arch will collapse quickly. Often, you will find the keystone is larger than the other stones that form the arch. On this animation, the keystone, a large ice flow of multi-year ice is clearly visible. If we see this floe fracture or if we see the ice around it which is mainly small bits of MYI and FYI which has frozen them in place begin to disintegrate, it is a suggestion of imminent collapse. I would pay particularly close attention to the prominent bulge of ice that protrudes into the open water at the top of the arch on the west side of the keystone. If this gives way, the keystone will lose its support and the arch will collapse IMHO. In that most recent calving, it appears as if this bulge was compromised or chipped away at.

By the way, having ice peel away from the sides, near the base of the arch, increases the load and stress on the keystone.
« Last Edit: June 07, 2016, 03:56:45 PM by Shared Humanity »

Neven

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Re: The Nares Strait thread
« Reply #795 on: June 07, 2016, 04:14:22 PM »
what will happen if that piece of ice between the small polynya and the open water in Kane Basin gives way. Will that compromise arch stability, or will the arch just retreat to a more stable position?

It looks like it's going to be the latter. I still think this is going to take a while longer, until the ice gets blue.
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johnm33

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Re: The Nares Strait thread
« Reply #796 on: June 07, 2016, 04:26:23 PM »
An alternative veiw could be that the thrust from Humbolt is what forces the collapse, so as more warm water passes through and thins out the 'structural' ice eventually the build up of pressure in Humbolt proves too much.

http://ocean.dmi.dk/arctic/images/MODIS/Kane/20140607rs02.ASAR.jpg

Sonia

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Re: The Nares Strait thread
« Reply #797 on: June 09, 2016, 01:31:51 PM »
I thought i'd take a look at last year, just a hint on this image
http://ocean.dmi.dk/arctic/images/MODIS/Kane/20150606TERR.jpg not much more on the next
...
Will the high/low tides coming around the 5/6th be enough?
I like this summary a lot because it shows how the breakup was spread out over a month.  Tides in early June last year anyway might have helped start things but weren't enough for a complete breakup.  This year is looking similar.

Neven is watching for blue ice; he may not have long to wait.  Wipneus observes some melting starting from the AMSR2 data.  http://forum.arctic-sea-ice.net/index.php/topic,382.msg79648.html#msg79648  That's consistent with the recent temperatures at Hans Island.
« Last Edit: June 09, 2016, 01:38:15 PM by Sonia »

Neven

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Re: The Nares Strait thread
« Reply #798 on: June 10, 2016, 08:11:05 PM »
I didn't expect this, looks weird. What happened here (day before yesterday, day 160)?



Ice broke off, and then got pushed back against the arch? Animation shows days 151, 157, 158, 160 and 162 (today).

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johnm33

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Re: The Nares Strait thread
« Reply #799 on: June 10, 2016, 08:20:52 PM »
Very odd maybe the wind?  https://earth.nullschool.net/#2016/06/08/1800Z/wind/surface/level/orthographic=-74.44,76.18,3000/loc=-72.967,78.818

Sonia"I like this summary a lot" thanks. It's worth looking at 2014 too, best on worldveiw http://go.nasa.gov/1UqX6xh this is the 20th apart from Humbolt ice getting bluer nothing much has changed since the 10th but it breaks on the 23rd and just slowly continues to break from then on. The full moon was on 13:06 and new moon 27:06
 The next big tides are on the 20/21 but will everything be in place for the break?
« Last Edit: June 10, 2016, 09:02:29 PM by johnm33 »