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Author Topic: The Nares Strait thread  (Read 429441 times)

Andreas T

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Re: The Nares Strait thread
« Reply #250 on: July 08, 2014, 03:52:17 PM »
looking for something else I was very surprised to see a noticeable temperature difference (If I understand band31 correctly) between water and ice at the ice arch and in front of Humboldt glacier.
http://1.usa.gov/1qf4kHl
cranking up the contrast makes it clearer ( I include the visible image but toggling between the two is easier on worldview)
Usually I find ice and water indistinguishable in band31 but here water flowing under the arch seems cooler (darker) than the ice whereas slightly further south there is warmer (lighter) water right between the ice floes. Elsewhere I would interpret this as river water but here the most likely source would be meltwater exiting below the glacier?

Jim Hunt

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Re: The Nares Strait thread
« Reply #251 on: July 12, 2014, 02:00:40 AM »
It's difficult to be certain through the clouds, but it looks like the "sturdy stopper" is now sporting some cracks:

http://1.usa.gov/1rfbvk1

Flip to Aqua to see some cracks in the Lincoln Sea also.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Sonia

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Re: The Nares Strait thread
« Reply #252 on: July 12, 2014, 07:54:32 AM »
It's difficult to be certain through the clouds, but it looks like the "sturdy stopper" is now sporting some cracks:

http://1.usa.gov/1rfbvk1

Flip to Aqua to see some cracks in the Lincoln Sea also.

Oh, very good catch.  You know, I had spotted the cracks in the Aqua image but didn't bother to try to look past the clouds in the Terra image.  Taking a closer look now, and blinking against images of a few days ago, the ice not only has new cracks but has noticeably bulged to the south.  (Sorry I don't have an animation to show.)  Hopefully we'll get a better look in several hours.

Espen

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Re: The Nares Strait thread
« Reply #253 on: July 12, 2014, 09:40:35 AM »
Here is a far more detailed image from Landsat:
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Jim Hunt

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Re: The Nares Strait thread
« Reply #254 on: July 12, 2014, 12:32:03 PM »
Oh, very good catch.

Thanks Sonia, and Espen. Where do you get hold of such recent Landsat images?

Actually I was prompted to look closely by Bob Wallace's intriguing thickness map

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Espen

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Re: The Nares Strait thread
« Reply #255 on: July 12, 2014, 12:48:34 PM »
Jim,

You can download from here: http://earthexplorer.usgs.gov/
Have a ice day!

Espen

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Re: The Nares Strait thread
« Reply #256 on: July 12, 2014, 01:11:10 PM »
Very soon Nares Strait will be open, big cracks are seen in front of Petermann Fjord:
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Jim Hunt

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Re: The Nares Strait thread
« Reply #257 on: July 12, 2014, 01:50:43 PM »
You can download from here: http://earthexplorer.usgs.gov/

Thanks Espen. I've been using LandsatLook. Sounds like the obvious place, but there seems to be much more available via EarthExplorer
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Espen

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Re: The Nares Strait thread
« Reply #258 on: July 12, 2014, 04:25:54 PM »
Now the cracks entered Petermann Fjord:

Please click on image to enlarge!

« Last Edit: July 12, 2014, 04:51:27 PM by Espen »
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johnm33

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Re: The Nares Strait thread
« Reply #259 on: July 12, 2014, 05:30:39 PM »
I suspect all the recent cracks are full moon /extreme tides but the ice looks like broken glass all the way into Lincoln. Soon be gone. Good catch.

Jim Hunt

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Re: The Nares Strait thread
« Reply #260 on: July 13, 2014, 01:10:05 AM »
Things are certainly starting to move: http://1.usa.gov/1sMRiCk
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ghoti

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Re: The Nares Strait thread
« Reply #261 on: July 13, 2014, 03:29:28 AM »
The Arctic Cap HYCOM thickness graphics seem to suggest the ice around the top of the Nares is 5m thick. Is that possible? The current images don't give the impression of such massive ice structure. Of course viewed from space you can't see thickness but it looks so fragile.

Jim Hunt

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Re: The Nares Strait thread
« Reply #262 on: July 13, 2014, 10:57:10 AM »
Here's a view from space that suggests that the ice around the top of the Nares isn't all 5m thick.

This is RADARSAT from June 11th:



By way of comparison this is from yesterday:

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

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Re: The Nares Strait thread
« Reply #263 on: July 13, 2014, 11:24:46 AM »
The radar images can be ambiguous for interpretation, they do not show thickness directly. I think the two images you show demonstrate that. Note how the small icecaps on the mountains change from light in the June image to dark in the july image. Maybe polarization or something is different in these images
What definitely shows age of the ice and indicates thickness through surface temperature are these IR images from when the stopper moved into place this winter:
top 2013/12/30 http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201312301205.NOAA.jpg
bottom 2014/01/09
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201401091336.NOAA.jpg


The images also show how the ice is always full of older cracks which allow it to move and are renewed by that movement. So ice average icethickness (better to look at icebridge data than HYCOM for that) is giving a measure of the thickness of shifting floes not a solid slab of ice.
The movement also produces ridges by tilting floes sideways which add  to the average thickness.
« Last Edit: July 13, 2014, 11:39:13 AM by Andreas T »

Andreas T

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Re: The Nares Strait thread
« Reply #264 on: July 13, 2014, 11:45:06 AM »
another thing: the older floes from the IR image are recognizable in the ASAR from june and in the visible from yesterday either through different ice structure (radar) or greater snow depth (whiter appearance in visible because meltponds take longer to form?)

Espen

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Re: The Nares Strait thread
« Reply #265 on: July 13, 2014, 02:29:48 PM »
The Nares Express is ready:

Please click on image to enlarge!
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #266 on: July 13, 2014, 02:55:50 PM »
The southern (southwestern actually) end is also breaking up.   Hans Island is just covered by the cloud bank where the recent ice bridge held for a few days.  Ice has broken up 10 or 15 kilometers northwards of there.
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TerryM

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Re: The Nares Strait thread
« Reply #267 on: July 13, 2014, 08:34:16 PM »
It's interesting that although the "Stopper" is fractured, it's still more or less in place.
Is the Lincoln Sea ice melting away in a polynia as opposed to being advected through Nares?
Terry

Andreas T

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Re: The Nares Strait thread
« Reply #268 on: July 13, 2014, 11:06:56 PM »
if you toggle between terra and aqua images on worldview http://1.usa.gov/1sbE44w
you see there is quite a bit of movement of the stopper within some hours. On the Lincoln side of it is first year ice which formed only at the end of december but doesn't look like melting away yet.

Jim Hunt

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Re: The Nares Strait thread
« Reply #269 on: July 13, 2014, 11:11:00 PM »
I was just typing much the same as Andreas. The "stopper" is clearly moving. Compare the last 3 days on Terra:
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Andreas T

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Re: The Nares Strait thread
« Reply #270 on: July 14, 2014, 09:40:01 AM »
looking back at the thread last year:
Here's the latest, lot's of disintegration!
http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/single.cgi?image=crefl1_143.A2013194171000-2013194171500.250m.jpg

Thanks to Phil, I thought it would be quite up there today, but obviously not:

Cracks developed close to Petermann Fjord, this afternoon.

Jmo

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Re: The Nares Strait thread
« Reply #271 on: July 15, 2014, 02:02:36 AM »
Nares express now well and truly open for business.  Modis images on DMI for 13/7 and 14/7 show incredible breakup and speed of flow.  I know it happens every year, but it's pretty speccy to see.  Seems like lots of loose fragments to export as you look north...
http://ocean.dmi.dk/arctic/kennedy.uk.php

Espen

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Re: The Nares Strait thread
« Reply #272 on: July 20, 2014, 10:23:08 PM »
Nares Strait is almost like when IKEA is opening one of their shops in a new market, the run is from above!
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Andreas T

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Re: The Nares Strait thread
« Reply #273 on: July 20, 2014, 11:12:28 PM »
comparing the 18th and 20th July images, looking for recognizable floes
http://1.usa.gov/1sBRwPq
http://1.usa.gov/1sBRBCK
Hall Basin looks like the IKEA carpark , its so congested nothing is getting in or out

ghoti

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Re: The Nares Strait thread
« Reply #274 on: July 21, 2014, 06:00:16 AM »
Nothing may be getting out but much of it is moving south. Seems like there are four floes roughly 10km in size in the southern 60km. They look like some of them moved around 5km in the 2 days. The southern most one did seem to move north though.

Sonia

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Re: The Nares Strait thread
« Reply #275 on: July 22, 2014, 10:38:47 PM »
Ice really is moving north through the Robeson Channel currently.  Clouds over the Nares have made ice watching frustrating lately so I was eagerly awaiting today's radar images on the DMI site.  They're here now, and though maddingly missing data across the Hall basin, reveal interesting ice movement.

If you blink against images from the 19th you see that while ice (including remnants of the sturdy stopper) is lazily floating south through the Kennedy Channel, it is quite clearly moving north through the Robeson!  That should ease the Ikea traffic jam, if we could only see it.

Looking farther up into the Lincoln Sea shows a rip where is ice is moving north on the west side of the sea and south on the east side.  Check your favorite source of surface wind data (I really like earth.nullschool.net) for insight into this.  Brisk winds are blowing straight up the Robeson and west Lincoln Sea driving this ice return.  A little farther south in the Kennedy, winds are not as strong and apparently do not overcome the drag of the current flowing south.

Jmo

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Re: The Nares Strait thread
« Reply #276 on: July 23, 2014, 01:45:58 AM »
Certainly still flowing from the "blockage" south, from what I can see in DMI Terra/Aqua images 20-22 July. Ice movement and/or in situ melting, as well as a colour change to stronger blues in remaining ice.  Petermann fiord appears to be clearing out rapidly also. Not strange, but interesting.

TerryM

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Re: The Nares Strait thread
« Reply #277 on: July 23, 2014, 07:39:00 PM »
Sonia
There are two currents in Nares Strait and like most Arctic passages the traffic stays to the right. The southerly current is usually much larger and stronger. At least two gyres occur, one in Kane Basin and the more prominent in Hall Basin where large chunks of ice will often go around 2 or 3 times before breaking free.
Winds in the steep walled canyon can be extreme as Dr. Munchow discovered when his anemometer was destroyed, but thick ice is usually directed more by current than by wind.


Terry


Espen

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Re: The Nares Strait thread
« Reply #278 on: July 23, 2014, 07:57:13 PM »
Terry, do we have any info regarding the P2s?
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DaddyBFree

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Re: The Nares Strait thread
« Reply #279 on: July 25, 2014, 01:43:45 AM »
Terry, do we have any info regarding the P2s?

Hi Espen,
I lost track of half of it (Maybe broke up), but the other half was near Lancaster Sound and Pond Inlet (NW Baffin Bay) yesterday.

Espen

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Re: The Nares Strait thread
« Reply #280 on: July 25, 2014, 02:20:26 AM »
Thanx Daddy! ;)
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DaddyBFree

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Re: The Nares Strait thread
« Reply #281 on: July 25, 2014, 04:41:29 PM »
My pleasure; and if anyone tracked any fragments from the other half, I would be curious to see where they ended up :)

Andreas Muenchow

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Re: The Nares Strait thread
« Reply #282 on: July 28, 2014, 06:01:00 PM »
My pleasure; and if anyone tracked any fragments from the other half, I would be curious to see where they ended up :)

The Canadian Ice Service is tracking as many of the ice islands as possible. The attached is what I received last week, more detail in RadarSat, but those data/imagery are not easily shared as it may violate copyrights.

Edit: "Kane Basin" should read "Lincoln Sea" in the circled bit at the northern edge. It probably indicates glacier ice from either Ryder or Steensby Glaciers that discharge into the Arctic Ocean to the north of Nares Strait.

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Jim Hunt

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Re: The Nares Strait thread
« Reply #283 on: July 28, 2014, 06:21:13 PM »
Thanks Andreas. That makes life much easier!

http://1.usa.gov/X4qlzX

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

DaddyBFree

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Re: The Nares Strait thread
« Reply #284 on: August 01, 2014, 03:21:47 PM »
Thanks Andreas! I have tracked some using Worldview, but it gets difficult at times. 8)

Phil.

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oren

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Re: The Nares Strait thread
« Reply #286 on: August 01, 2014, 05:41:28 PM »
Great image

solartim27

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Re: The Nares Strait thread
« Reply #287 on: August 05, 2014, 08:31:50 PM »
First clear day in a while, looks like there's another stopper
http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r03c03.2014217.terra
FNORD

solartim27

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Re: The Nares Strait thread
« Reply #288 on: August 05, 2014, 10:24:13 PM »
Nah, just a cloud.
FNORD

Espen

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Re: The Nares Strait thread
« Reply #289 on: November 30, 2014, 08:27:46 PM »
The "Nares Express" is still moving:
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A-Team

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Re: The Nares Strait thread
« Reply #290 on: December 01, 2014, 12:56:09 PM »
Whoa ... not so easy to track individual floes just a few days apart. A lot of break-up in the narrows. I've added a few more floes with fairly high confidence but still cannot account for the origin of everything in the Strait.

The idea with the translucent gradients was to define a directional polarity axis in the 'before' flow so any rotation would be evident when the gradient was applied in the same orientation to the 'after' floe. However I didn't manage to do this very consistently.
« Last Edit: December 02, 2014, 12:12:24 AM by A-Team »

Polynya88

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Re: The Nares Strait thread
« Reply #291 on: December 01, 2014, 02:49:19 PM »
The break-up of floes isn't too surprising. These floes are all conglomerate, and the "glue" between multi-year pieces is only thin First-year yet, so it doesn't take much to fracture them.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #292 on: December 01, 2014, 09:44:36 PM »
I note the Dec 1 DMI Sentinel-1 image (http://ocean.dmi.dk/arctic/kennedy.uk.php) shows the big 'red/orange colored' floe has moved quite a bit (5 or 8 km? since Nov 30) .  I hope to keep watching in order to see where it breaks up, slips through or gets stuck (or combinations of the three).
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Espen

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Re: The Nares Strait thread
« Reply #293 on: December 03, 2014, 05:12:25 PM »
Still on the move: ( Nov 30 - Dec 1 - Dec 2 )
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #294 on: December 04, 2014, 05:25:11 PM »
It sure is 'steaming' along: about 25 km in one day, on 2014-12-03 it was in Hall Basin off Ellesmere Island's Lady Franklin Bay (functionally opposite Petermann Glacier).  Today it will likely glide past Joe Island.  On Friday (at this rate) it will run into Hans Island and stop/split/splinter.  Hmmm, if a block of ice hits a rock hard enough, will any steam be produced? ;D

See place name map at https://mapsengine.google.com/map/viewer?mid=zbdKKg4fRHYo.kugA5VIgp5ec in the Forum's "Google Maps with place names Greenland" thread - http://forum.arctic-sea-ice.net/index.php/topic,277.0.html.  DMI radar (Sentinel-1) images available at http://ocean.dmi.dk/arctic/kennedy.uk.php

Thanks for the animations, A-Team and Espen!
« Last Edit: December 04, 2014, 09:03:28 PM by Tor Bejnar »
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Espen

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Re: The Nares Strait thread
« Reply #295 on: December 04, 2014, 05:37:39 PM »
I wonder if there are any quake sensors at Hans Ø?
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Espen

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Re: The Nares Strait thread
« Reply #296 on: December 04, 2014, 05:46:07 PM »
The large sea-ice island was reduced in size between Dec. 2 and Dec. 3:
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Espen

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Re: The Nares Strait thread
« Reply #297 on: December 05, 2014, 06:44:35 AM »
Even more minimized, notice the "new" large piece entering the Strait (red arrow):

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A-Team

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Re: The Nares Strait thread
« Reply #298 on: December 05, 2014, 12:31:58 PM »
indeed, it looks to me like word salad. Could spell trouble?

Laurent

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Re: The Nares Strait thread
« Reply #299 on: December 05, 2014, 02:49:39 PM »
Do we have an idea of the usual speed of the ice at that time ? It sounds to me very fast !?