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A-Team

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Re: The Nares Strait thread
« Reply #350 on: January 02, 2015, 08:44:55 PM »
I wish some of these gigabyte satellite sites would set up a dual file system -- orthogonal to their current ones -- so that it would be possible to just smart-download say all the quick looks like this without first having to dumb-download gigantic folders of stuff almost all of which the user does not want. Do they not have scripts or access to cheap cloud storage? It would bring a huge savings all around on server loads.

I re-processed Wip's beautiful tiling of Nares Strait (can this be extended around the whole perimeter of Greenland?) using 'value invert' in Gimp not to be confused with 'invert'. The first command treats the RGB as HSV and inverts the V (taking x to 255-x) without the user having to actually go through the steps of decomposition to HSV color space.

This is surprisingly effective -- click to view full size. This may amount to something physical in terms of mixing original polarizations like HH VH VV.  The lower image is 2x enlarged by cubic convolution, followed by modest wavelet sharpening. (I was looked to see if the Next Big Thing coming in cracking could be anticipated.)

If these quick looks are at lower resolution than the high resolution Sentinel grayscales, we might try the latter for panchromatic sharpening (replacing V) as Wip described for Landsat-8s. (As tiled, they are a bit rotated from  the grayscale Sentinels at http://ocean.dmi.dk/arctic/morrisjessup.uk.php -- that would knock down some of the benefit.)
« Last Edit: January 03, 2015, 12:57:36 PM by A-Team »

Wipneus

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Re: The Nares Strait thread
« Reply #351 on: January 03, 2015, 02:12:59 PM »
That is a great looking image Wipneus, where on the ESA site do find them, I can only locate images that are about 1 month old?

Let me describe the typical way I get them.

First a Sentenial data set, product in ESA speak,  has an identifier and a name. Both uniquely identify the data, have you got one you can look up the other. In many cases you need them both.
The product name is something like S1A_EW_GRDM_1SDH_20150102T120132_20150102T120202_003992_004CEA_57D0
the corresponding product id
c71daeec-66d5-452e-a198-395a89c936fb

The product name is usually the base for file names used to store the product, it is an (insuficient) description as well.  The product id is just a UUID.

Lo-res, jpeg versions of the quicklook images can be seen in the sentinel data hub, graphical tool where you can do some selections, see some meta-data, see the quick-look image and request for the full (gigabyte) download.  Registration (free) is required.
Download of subsection of the data is planned 2015Q2, I think that may include the quicklook images.

Apart from the graphical tool there are programming interfaces (API's) to the data, the Open Data and Open Search. These are described here

Open Data works with URL, understandable by your browser and by automatic tools (wget).
For instance with the name and id above, this will download the full (gigabyte) package data set:

https://scihub.esa.int/dhus/odata/v1/Products('c71daeec-66d5-452e-a198-395a89c936fb')/$value

Get the preview quicklook image:

https://scihub.esa.int/dhus/odata/v1/Products('c71daeec-66d5-452e-a198-395a89c936fb')/Nodes('S1A_EW_GRDM_1SDH_20150102T120132_20150102T120202_003992_004CEA_57D0.SAFE')/Nodes('preview')/Nodes('quick-look.png')/$value

Copy the string in the browser and download the image.

The scripts take care of creating these URI's, downloading the result and sometimes interpret the results.

So what I did in this case:

- used the data hub graphical tool to select the correct product. Get the product name (copied from the screen).
- start the odata-demo.sh script
  - use option 7: get id from product name
  - use option 11: get quick look image from id

This barely scratches what is possible. Downloading ALL quicklook images, given some selection parameters, is already routinely done here.

Espen

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Re: The Nares Strait thread
« Reply #352 on: January 03, 2015, 07:06:59 PM »
Thanks Wipneus for the instruction!

Further expansion of the arch area in Lincoln Sea:
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Shared Humanity

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Re: The Nares Strait thread
« Reply #353 on: January 03, 2015, 07:47:43 PM »
Thanks Wipneus for the instruction!

Further expansion of the arch area in Lincoln Sea:

At what point do we stop calling it an arch and instead recognize it as a race to the exit?  ;)

Shared Humanity

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Re: The Nares Strait thread
« Reply #354 on: January 03, 2015, 07:55:31 PM »
I am amazed by the rubble of ice that appears in these images. Is this qualitatively different than in previous years or are we simply getting better at seeing the ice? Has there ever been a freeze season where the Nares transport simply did not shut own?

A-Team

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Re: The Nares Strait thread
« Reply #355 on: January 03, 2015, 11:11:10 PM »
Meanwhile down at Jakobshavn, which was supposed to be a featured location, we are not so thrilled with Sentinel. It malfunctions on about half the days and on the other half it needs to go another 100 km farther east. (Was there a miscommunication about why JI is being monitored, leading to centering on the fjord and Disko Bay?)

Like Nares, it seems JI is also anomalous for this date ... not fully frozen in by sea ice mélange. If so, this would reduce buttressing at the calving front and bump annual flux through the gate. Baffin Bay may be too warm these days.

Neven

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Re: The Nares Strait thread
« Reply #356 on: January 03, 2015, 11:32:30 PM »
At what point do we stop calling it an arch and instead recognize it as a race to the exit?  ;)

You mean, arch or march?  ;D
Compare, compare, compare

Rubikscube

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Re: The Nares Strait thread
« Reply #357 on: January 04, 2015, 02:23:39 AM »
Has there ever been a freeze season where the Nares transport simply did not shut own?

I recall that this is a topic which has previously been up for discussion in this thread, or at least somewhere on the forum, with the conclusion being that there has been a couple of winters in which proper arches have failed to establish. Can't remember the exact years, but I'm sure that others do.

Rubikscube

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Re: The Nares Strait thread
« Reply #358 on: January 04, 2015, 03:07:45 AM »
There you go SH. Hidden away in the "Home brew extent" thread was this most interesting link to Dr. Munchow's blog, which should answer your question.

http://icyseas.org/2012/06/19/nares-strait-ice-bridge-and-arctic-ice-thickness-change/

To sum it up with the same quote that TerryM chose back then.
Quote
"I processed and archived maps of Nares Strait satellite images to guide 2003-2012 analyses of how air, water, and ice change from day to day. Ice arches formed as expected during the 2003/04, 2004/05, and 2005/06 winters lasting for about 180-230 days each year. In 2006/07 no ice arch formed, ice streamed freely southward all year, and this certainly contributed to the 2007 record low ice cover. In 2007/08 the arch was in place for only 65 days. In 2009/10, 2010/11, and now 2011/12 ice cover appear normal as the arches formed in December and lasted until July."

Shared Humanity

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Re: The Nares Strait thread
« Reply #359 on: January 04, 2015, 05:10:55 AM »
Thanks Rubikscube.

Espen

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Re: The Nares Strait thread
« Reply #360 on: January 04, 2015, 09:05:48 PM »
Further deterioration seen above Nares Strait / Lincoln Sea:
Have a ice day!

Espen

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Re: The Nares Strait thread
« Reply #361 on: January 04, 2015, 10:31:25 PM »
Another version between January 2nd and 4th:
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A-Team

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Re: The Nares Strait thread
« Reply #362 on: January 05, 2015, 06:09:45 PM »
Less of an arch than a channel of weak ice that may be frozen onto rock on its periphery -- but enough to hold the center. Below is a Landsat8 quicklook of Nares from this fall at 120 m per pixel scale.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #363 on: January 06, 2015, 03:34:24 PM »
A recognizable floe on January 4 (DMI’s Sentinel) is in the Lincoln Sea due east of Ellesmere Island’s Cape Union (slightly north of the eastern-most point (assuming the Sentinel view shows north straight up*)).  It has two collinear black streaks with a couple of white spots.

On January 5, this floe is in the Robeson Channel south of Ellesmere’s Cape Frederik VII.  It moved about 40 km in one day (if the Sentinel views are 24 hours apart).  This corresponds with “up to 40 km/day at the northern (actually NE) end of Nares Strait” I wrote on Dec 5 on this thread (from Kwok, 2005).

[* Notes:  I think the Sentinel views do not have north straight up; straight up is actually about NW.  Place names are according to map at https://mapsengine.google.com/map/viewer?mid=zbdKKg4fRHYo.kugA5VIgp5ec.]
« Last Edit: January 06, 2015, 08:44:10 PM by Tor Bejnar »
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Wipneus

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Re: The Nares Strait thread
« Reply #364 on: January 06, 2015, 06:38:26 PM »
For a full Nares "quick-look" panorama the path of the satellite must be at the right distance of the Strait. Happens every 2 or 3 days around noon (UTC), but then ESA decides not to provide all the possible data: the last two opportunities where lost. Today a full set, but not the best orbit position.

(click for a bigger image)


Tor Bejnar

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Re: The Nares Strait thread
« Reply #365 on: January 06, 2015, 09:26:02 PM »
Earlier I wrote: 
Quote
A recognizable floe on January 4 (DMI’s Sentinel) is in the Lincoln Sea due east of Ellesmere Island’s Cape Union. ...  It has two collinear black streaks with a couple of white spots.
On January 6 it has moved another ~40 km and can be found "due north" of the east edge of Petermann Glacier.  (By due north I mean straight up the image...)
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Espen

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Re: The Nares Strait thread
« Reply #366 on: January 07, 2015, 06:47:26 AM »
The demolition team is having a break:
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Wipneus

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Re: The Nares Strait thread
« Reply #367 on: January 07, 2015, 07:34:09 AM »
Meanwhile in the Kane Basin the ice is rushing south. The strong, up to 40 km/h winds, are causing a break-up of the fast ice in the Basin as well.

(click needed)

oren

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Re: The Nares Strait thread
« Reply #368 on: January 07, 2015, 11:08:07 AM »
I feel like wathcing a thriller... thanks for all the great images

Espen

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Re: The Nares Strait thread
« Reply #369 on: January 08, 2015, 06:41:44 AM »
Potentially more expansion:
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viddaloo

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Re: The Nares Strait thread
« Reply #370 on: January 08, 2015, 06:53:29 AM »
Any info on real–estate prices by the Nares Strait, folks?

This is such a great thread, and I thank you all for posting your thrilling content here!  ;D
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Wipneus

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Re: The Nares Strait thread
« Reply #371 on: January 08, 2015, 07:25:21 AM »
I choose for the Kennedy channel. Good luck with following the ice flows. The images are about 15 hours apart, the first (6th) from ascending orbital position the other descending. The different positions of the satellite cause all kinds of interesting distortions and change in lightning.

A-Team

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Re: The Nares Strait thread
« Reply #372 on: January 08, 2015, 01:27:17 PM »
Here is  07 Jan 17. There is a host of new cracks working their way out while expanding the present shape (actually it's getting a little lopsided to the northeast). That shape may reflect fracturing due to residual compressive stresses, along the lines of sandstone and granite exfoliation. Loose ice has seemingly plugged the Nares exit but without forming an arch -- hard to say what will happen next and what lesson it carries.

http://www.nature.com/news/sandstone-arches-form-under-their-own-stress-1.15590

Tor Bejnar

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Re: The Nares Strait thread
« Reply #373 on: January 08, 2015, 07:15:01 PM »
'My' floe that "has two collinear black streaks with a couple of white spots" moved about 45 km in one day, and is straight up (pseudo-north) from Greenland's Cape Ulrich on the January 7 Sentinel image.  The collinear black streaks now parallel Kennedy Strait.  At this rate, the floe will get past Hans Island and to Franklin Island tomorrow. [Alert: I do not have successful prediction skills!  Watch the floe get stuck on Hans.]  (The floe is about 15 by 7 km is size, and the black streaks [becoming a single long streak?] are about 10 km long [combined] and 1/3 to 1 km wide.) [For scale reference, the narrow part of Petermann Fjord is about 14 km wide.]

An identifiable floe in Smith Sound on Jan. 7 image was about 60 km 'upstream' on Jan. 6.  A floe in Baffin Bay was 40 km upstream the previous day.  A large floe at the north end of Robeson Chanel was 20 km 'upstream' (within the Lincoln Sea) the previous day.  I don't see any evidence of floes plugging up anything within the flowing channel of Nares Strait and its up- and down-stream neighbors.  As there is a lot of chunky ice up there, of course something could get stuck any day.

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Tor Bejnar

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Re: The Nares Strait thread
« Reply #374 on: January 09, 2015, 06:49:41 PM »
"My" flow went about 90 km between January 7 and 8 images!  On the Jan. 8 Sentinel image, it is between Greenland's Capes Jefferson & Madison and Ellesmere Island's Rawlings Bay (just above Kane Basin) [thus validating my disclaimer yesterday about my ability to predict things].

Elsewhere, floes appear to still be on the move as well.
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Wipneus

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Re: The Nares Strait thread
« Reply #375 on: January 10, 2015, 08:49:04 AM »
Kane in the last few days. The previously fast ice that had been cracked into large chunks can be seen to have finally moved in the last frame. Winds up to 50 km/h keep blowing from the north of the Nares Strait.

A-Team

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Re: The Nares Strait thread
« Reply #376 on: January 11, 2015, 12:41:58 PM »
Here is some berg-tracking for 08-10 Jan 15. The top of the cracking is receding out of view of the Danmark Meterologiske Institut offerings at Lincoln into a region not picked up by Morris Jessup http://ocean.dmi.dk/arctic/morrisjessup.uk.php

The acceleration of ice is quite noticable as it nears the Strait. I'm thinking the blue shark will reach the narrows in six days or so.

Shared Humanity

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Re: The Nares Strait thread
« Reply #377 on: January 11, 2015, 04:14:13 PM »
Here is some berg-tracking for 08-10 Jan 15. The top of the cracking is receding out of view of the Danmark Meterologiske Institut offerings at Lincoln into a region not picked up by Morris Jessup http://ocean.dmi.dk/arctic/morrisjessup.uk.php

The acceleration of ice is quite noticable as it nears the Strait. I'm thinking the blue shark will reach the narrows in six days or so.

When the really heavy fracturing began to occur at the beginning of the month, my hope for a large floe of MYI plugging the strait went up. I think this is our last/best chance for having the Nares export shut down which would allow for ice formation to occur north of Greenland for the remainder of the freeze season.
« Last Edit: January 11, 2015, 05:16:55 PM by Shared Humanity »

Espen

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Re: The Nares Strait thread
« Reply #378 on: January 11, 2015, 05:07:13 PM »
Even MYI cant survive the Nares Mincer!
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Shared Humanity

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Re: The Nares Strait thread
« Reply #379 on: January 11, 2015, 05:19:17 PM »
Even MYI cant survive the Nares Mincer!

If this is the case (I thought I recalled floes plugging things up in prior years?) than I think export will not stop this winter if the winds keep up.

Espen

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Re: The Nares Strait thread
« Reply #380 on: January 11, 2015, 05:23:04 PM »
MYI is not like it used to be?
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Espen

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Re: The Nares Strait thread
« Reply #381 on: January 11, 2015, 07:30:51 PM »
Nice marble pattern, just waiting to enter the mincer?:
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A-Team

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Re: The Nares Strait thread
« Reply #382 on: January 11, 2015, 08:15:14 PM »
So, like what happens when the growing Nares collapse structure meets the Arctic Ocean crack system? Guessing the orangish below -- that might drawn in some of the very oldest ice. (Have not checked which way Arctoc ice pack is moving, guessing east.)
« Last Edit: January 11, 2015, 08:38:49 PM by A-Team »

viddaloo

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Re: The Nares Strait thread
« Reply #383 on: January 11, 2015, 08:21:44 PM »
It all goes down the drain? Very interesting question. Do we have any precedent from previous years?
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Espen

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Re: The Nares Strait thread
« Reply #384 on: January 11, 2015, 09:10:26 PM »
So, like what happens when the growing Nares collapse structure meets the Arctic Ocean crack system? Guessing the orangish below -- that might drawn in some of the very oldest ice. (Have not checked which way Arctoc ice pack is moving, guessing east.)

A-Team, the thickest ice is above Ellesmere Island, though a bit more to the west than the "arch" is reaching now.
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Espen

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Re: The Nares Strait thread
« Reply #385 on: January 11, 2015, 09:12:42 PM »
It all goes down the drain? Very interesting question. Do we have any precedent from previous years?

Hello Viddaloo, here is some news from Hardanger:

https://forum.arctic-sea-ice.net/index.php/topic,1041.msg43204.html#msg43204
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #386 on: January 12, 2015, 01:58:53 AM »
'My' floe disappeared after the January 8 Sentinel image; it would have been nice to watch it go all the way to Baffin Bay.  I agree, Espen, many floes get chopped up near the start, or after hitting an island or cape.  I too thought A-team's blue shark was a shark.  Wouldn't 6 days take it into Baffin Bay, given that floes start going 5 to 20 km/day and end up going 50-90 km/day?
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Wipneus

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Re: The Nares Strait thread
« Reply #387 on: January 12, 2015, 08:29:12 AM »
Winds have slowed to a slight breeze and come now from north-northwest direction. Currents will have to take care of the transport now and the large ice floats in Kane basing are pushed back.

viddaloo

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Re: The Nares Strait thread
« Reply #388 on: January 12, 2015, 10:38:05 AM »
Cracking up: Creating a channel from Fram to Nares?

PS: Espen, I have my own pet glacier in the Hardanger, though I have been to Folgefonna (sadly not Hardangerjökullen yet).
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A-Team

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Re: The Nares Strait thread
« Reply #389 on: January 12, 2015, 10:53:22 AM »
Closer in, the area above the strait rotated slightly CW but also continued its export, whether due to residual wind or current.

Speaking of which, Andrew Muenchow has the observational data on tides, winds and currents summarized in excellent posts of 14 Sep 20 14, http://icyseas.org/tag/nares-strait/ which includes a tidal harmonic analysis and 27 Jul 2012 (Allison Einolf) http://icyseas.org/2012/07/27/currents_winds_nares_strait_ice_arches/.

Tidal darwin symbols, other than gam2, are explained at https://en.wikipedia.org/wiki/Theory_of_tides  'Evectional' terms arise from periodic gravitational effects of the sun on the moon. I'm not sure what is intended by 'red noise', probably Brownian noise (spectral density inversely proportional to 1/freq²) which is the baseline upon which tidal signal is imposed. (That is, tides are a complex superpositioning of many incompatible frequencies, best represented by Doodson's.)

Things are pretty quiet today at the Hans Island weather station, http://dalriada.sams.ac.uk/aws_hans/

Quote
... ocean currents move water always to the south no matter if ice covers Nares Strait or not, no matter if the ice is moving or not, no matter which way the wind is blowing. The physical cause for this southward flow is that the sea level is always a few inches higher in the Arctic Ocean than it is in Baffin Bay... we measured this with tide gauges that we placed in protected coastal bays. We recovered 3 sensors; most rewarding was the recovery of one sensor in 2012 and 9 years of very good data.

The freeze-up of Nares Strait comes in one of three forms: 1. Ice stops moving in winter, because an ice barrier (ice arch or ice bridge) forms in the south that blocks all southward motion of ice; 2. only new and young ice moves southward, because an ice barrier forms in the north that blocks all entry of Arctic ice into Nares Strait; and 3. Arctic ice moves freely through Nares Strait, because no ice barriers are present. Our 2003-12 study period covers years for each of these different ice regimes.
« Last Edit: January 12, 2015, 04:11:26 PM by A-Team »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #390 on: January 12, 2015, 03:07:12 PM »
At the north end of Nares Strait, the shark’s mouth moved about 25 km between Sentinel 2015-01-10 and 2015-01-11.  (The shark (now red!), as shown in A-team’s animation, also rotated about 90 degrees counterclockwise – appropriately, it’s 'swimming' face forward!)  (A floe just south of the shark moved about 40 km – no rotation.)

At the north end of Baffin Bay, a round flow (~7 km diameter with a black comma shape in it) moved southward about 70 km between Sentinel 2015-01-10 and 2015-01-11.

Within Kane Basin, a floe (~5 km diameter with a black shallow S or integral sign across it) moved southward about 50 km between Sentinel 2015-01-10 and 2015-01-11.  On the 2015-01-11 image, it is just below the ‘no image’ part of the image.  This floe was opposite the south end of Petermann Fjord on 2015-01-08 where I can locate it; I think I see it in the 2015-01-06 image at the entrance to Nares Strait.  So this bit of ice will go from the Lincoln Sea to Baffin Bay in about 6 days.

I do not have a clue what is happening around Hans Island. 
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #391 on: January 13, 2015, 02:57:13 AM »
With no 2015-01-12 Sentinel, I'm looking at DMI's NOAA AVHRR images for 2015-01-11  13:19 UTC ('yesterday') and 2015-01-12  13:09 UTC ('today'), you can see the shark moving southward, all but filling the strait.  The lozenge shaped floe south of the shark did rotate during this day and may well hit Hans Island broadside about tomorrow.  (This morning I thought it would just torpedo its way past [if the odd scatter on yesterday's Sentinel image around Hans Island was 'meaningless', as it appears to have been].)  Even if this lozenge rotates and slips by or breaks up on impact, the shark will do something (break up) or nothing (that is, block Nares Strait) on or about 2015-01-13.
[My prediction disclaimer stands: is there another possibility?]
DMI images available here:  http://ocean.dmi.dk/arctic/kennedy.uk.php

I'm awed by how big the cracking pattern is around the busted Lincoln Sea short-lived bridge (via the NOAA AVHRR images).  I realize that although the 2006-07 winter never had a Nares Strait blockage, I do not know how much Arctic sea ice was exported.  was there a Lincoln Sea arch/bridge or did it look something like what we can see today with 'constant' export of 'thick' ice?  (Anyone know?) [Per A-Team's post quoting Andrew Muenchow, is a 'northern arch' an arch within Nares Straight or does an arch in the Lincoln Sea count?]
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #392 on: January 13, 2015, 03:15:48 AM »
Finally reading A-Team's link to Andrew Muenchow's bloghttp://icyseas.org/tag/nares-strait/, I have an answer to one of my questions:  a bridge in the Lincoln Sea counts as a Nares Strait bridge.  Therefore, I surmise, the 2006-07 winter had near constant 'thick' ice export through Nares Strait, and the effect on ice integrity in the Lincoln Sea and beyond was significant.

Another interesting excerpt from the above referenced blog:
Quote
Nares Strait ... is narrower than Fram Strait, but it transports as much fresh ocean water as does its wider sister facing Europe. Few people know this, including climate scientists who often model it with a bathymetry that is 10,000 years out of date from a time when Nares Strait did not yet exist.
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Wipneus

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Re: The Nares Strait thread
« Reply #393 on: January 13, 2015, 08:09:21 AM »
I cannot find DMI-processed Sentinel images of Jan 12. Here is a "panorama" composed from the quick-look images.

(click to enlarge)

nukefix

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Re: The Nares Strait thread
« Reply #394 on: January 13, 2015, 10:35:39 AM »
I cannot find DMI-processed Sentinel images of Jan 12.
They are on scihub, ~400MB each so relatively small.

A-Team

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Re: The Nares Strait thread
« Reply #395 on: January 13, 2015, 11:19:30 AM »
Nice cloud-free AVHRR overview from 12 Jan 15 but try to do a time series. We are getting spoiled by cloud-penetrating radar?

 http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201501121309.NOAA.jpg

A-Team

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Re: The Nares Strait thread
« Reply #396 on: January 13, 2015, 12:52:08 PM »
Quote
Nares Strait ... is narrower than Fram Strait, but it transports as much fresh ocean water as does its wider sister facing Europe. Few people know this, including climate scientists who often model it with a bathymetry that is 10,000 years out of date from a time when Nares Strait did not yet exist.
I'm not sure what Muenchow is getting at here. 'Fresh' ocean water sounds like icebergs + ice meltwater, leaving overall total salt+fresh volume comparison to Fram up in the air. Probably clarified in his 2006 paper http://dx.doi. org/10.1175/JPO2962.1

Over longer times scales (Paleogene) of Nares formational history, geologist have been arguing bitterly about the tectonic history of Nares Strait for 80 years, right up to 2014, the two camps being Ellesmere-Greenland same plate vs 300 km of plate boundary transform fault (Wegener fault).

Paleo-bathymetry under these circumstances is really problematic. I don't doubt though that Nares flow has been an inconvenience to modellers that quickly got replaced by something from Daisy World. The issue is probably Nares is too shallow for Atlantic Water so the flow is mostly Pacific-derived today, but due to rebound from crustal unloading the sea level was ~120 m higher (Nares that much deeper) in the early Holocene.

Prior to Holocene onset, it sounds like Nares Strait was completely plugged up by convergence of the Innuitian, Greenlandic and Arctic ice sheets. Seafloor glacial gouges down by Disco Bay go much deeper than Nares (~220 m deep today at its shallowest sill).

Quote
The Holocene History of Nares Strait: 
Transition from Glacial Bay to Arctic-Atlantic Throughflow
Oceanography 24(3):26–41 2011
free full: http://www.tos.org/oceanography/archive/24-3_jennings.pdf

Retreat of glacier ice from Nares Strait and other straits in the Canadian Arctic Archipelago after the end of the last Ice Age initiated an important connection between the Arctic and the North Atlantic Oceans, allowing development of modern ocean circulation in Baffin Bay and the Labrador Sea.

As low-salinity, nutrient-rich Arctic Water began to enter Baffin Bay, it contributed to the Baffin and Labrador currents flowing southward. This enhanced freshwater inflow must have influenced the sea ice regime and likely is responsible for poor calcium carbonate preservation that characterizes the Baffin Island margin today.

 Sedimentologic and paleoceanographic data from radiocarbon-dated core HLY03-05GC, Hall Basin, northern Nares Strait, document the timing and paleoenvironments surrounding the retreat of waning ice sheets from Nares Strait and opening of this connection between the Arctic Ocean and Baffin Bay.

Hall Basin was deglaciated soon before 10,300 cal BP (calibrated years before present) and records ice-distal sedimentation in a glacial bay facing the Arctic Ocean until about 9,000 cal BP. Atlantic Water was present in Hall Basin during deglaciation, suggesting that it may have promoted ice retreat.

A transitional unit with high ice-rafted debris content records the opening of Nares Strait at approximately 9,000 cal BP. High productivity in Hall Basin between 9,000 and 6,000 cal BP reflects reduced sea ice cover and duration as well as throughflow of nutrient-rich Pacific Water.
« Last Edit: January 13, 2015, 01:23:29 PM by A-Team »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #397 on: January 13, 2015, 05:12:31 PM »
Per the DMI (http://ocean.dmi.dk/arctic/kennedy.uk.php) NOAA AVHRR 2015-01-13  06:23 UTC image, the lozenge that was tumbling counterclockwise, now, the end of it surely having bounced off of Joe Island (off the end of Petermann Fjord), will tumble faster.  And the shark is catching up.  Will they meet up (again, having been together in the Lincoln Sea) at Hans Island?
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Laurent

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Re: The Nares Strait thread
« Reply #398 on: January 13, 2015, 06:33:25 PM »
I think there is some move also in one of the channels between bank island and Ellesmere. What data set do you use when using http://earthexplorer.usgs.gov/ ?


Tor Bejnar

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Re: The Nares Strait thread
« Reply #399 on: January 13, 2015, 07:58:36 PM »
The shark is kissing the fast ice off of Petermann Fjord (or is that a bit of ice it's thinking of eating? - see today's partial Sentinel image) - I didn't expect the shark to start spinning.  It, too, may bounce off of Joe Island or upstream fast ice.  The shark (its mouth, specifically) has moved 70 km in two days.

The lozenge sure slowed down.  Yesterday I thought it would reach Hans Island today.  Maybe tomorrow.
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