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Author Topic: The Nares Strait thread  (Read 295438 times)

Tor Bejnar

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Re: The Nares Strait thread
« Reply #950 on: March 05, 2017, 11:51:50 PM »
Screenshot from PolarView: we see the broken off floe clearly.  The rest of the bridge looks okay, I think.

« Last Edit: March 05, 2017, 11:59:03 PM by Tor Bejnar »
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oren

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Re: The Nares Strait thread
« Reply #951 on: March 06, 2017, 12:02:24 AM »
After intense cold and holding in place for a month, this breakage is unusual as far as I know. Now that it did happen, I would expect more pieces to follow suit.

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Re: The Nares Strait thread
« Reply #952 on: March 06, 2017, 10:01:59 AM »
The condition of that broken off floe is obviously a worry! It is just a conglomeration of old bits and bobs glued together with FY ice. How you can even begin to figure its structural integrity escapes me!!
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Shared Humanity

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Re: The Nares Strait thread
« Reply #953 on: March 06, 2017, 03:20:33 PM »
The condition of that broken off floe is obviously a worry! It is just a conglomeration of old bits and bobs glued together with FY ice. How you can even begin to figure its structural integrity escapes me!!

And the portion of ice that it separated from looks even worse. Would not be surprised if the whole thing gave way. What kinds of winds are we expecting to see? Anything strong down the strait?

bairgon

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Re: The Nares Strait thread
« Reply #954 on: March 06, 2017, 03:55:00 PM »
And the portion of ice that it separated from looks even worse. Would not be surprised if the whole thing gave way.

That's what was said 1 month ago....

That's no arch. A melangerie of ice chunks....

... and it is only just now showing signs of weakness. Winds aren't particularly strong. Temperature is low, so perhaps it's cemented together fairly well.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #955 on: March 10, 2017, 06:29:32 PM »
This "visible spectrum" DMI image of the Kennedy Channel (from yesterday) sure shows the streaming of clouds (fog?) over the strait!
« Last Edit: March 10, 2017, 06:38:32 PM by Tor Bejnar »
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johnm33

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Re: The Nares Strait thread
« Reply #956 on: March 12, 2017, 03:28:56 PM »
From http://go.nasa.gov/2lQwFfp [11th] the arcs looking fragile

Cate

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Re: The Nares Strait thread
« Reply #957 on: March 12, 2017, 10:15:14 PM »
It doesn't look very much like an arc(h) anymore.

http://www.arctic.io/explorer/4Xa5A/2017-03-11/9-N82.28114-W62.21348

mati

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Re: The Nares Strait thread
« Reply #958 on: March 12, 2017, 11:21:33 PM »
It's the MUMMY's foot stomping on the arctic ice
nooooooooooooooooooooooooo,,,...
and so it goes

Tor Bejnar

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Re: The Nares Strait thread
« Reply #959 on: March 13, 2017, 01:22:40 AM »
Screen print from today's PolarView shows the floes (one quite small) that broke off a few days ago, and the foot bridge [sorry about that] looking good.
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Re: The Nares Strait thread
« Reply #960 on: March 13, 2017, 02:22:57 PM »
If that's a foot, the poor bastard has flat feet, otherwise known as a fallen arch.

Doubly sorry about that.  ::)

DrTskoul

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Re: The Nares Strait thread
« Reply #961 on: March 13, 2017, 02:52:53 PM »
The attack of the puns.....
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― Richard P. Feynman


bairgon

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Re: The Nares Strait thread
« Reply #963 on: March 13, 2017, 08:38:19 PM »
For reference - a photo of Nares taken on March 10th (click title):

NASA Ice: Photo from yesterday's #IceBridge flight: View across the Nares Strait from Greenland to Ellesmere Island, Canada.
https://twitter.com/nasa_ice/status/840614419767918594

Shared Humanity

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Re: The Nares Strait thread
« Reply #964 on: March 13, 2017, 10:20:35 PM »
An arch commonly forms there and you are right, definitely an arch.

Neven

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Re: The Nares Strait thread
« Reply #965 on: March 14, 2017, 12:03:35 AM »
Yes, that looks more like it. I wonder how long it will hold, given how late it has formed. But these arches can sometimes hold on longer than expected.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #966 on: March 15, 2017, 04:06:21 PM »
Comparing DMI Sentinel images from the 14th and the 12th, I see the arch holding steady, but there was ice movement in the central and upper parts of Kane Basin. 

Years ago I recall watching a slow gyre in Kane Basin while a bridge kept all the ice within the basin.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #967 on: March 17, 2017, 06:00:09 PM »
The March 16 PolarView of Kane Basin looks more ominous.  There are new cracks radiating from the Canadian side (not in March 15 image) and a single crack going southward from the ice bridge's northern edge (in the central part of Kane Basin).

Arches and bridges can be self-healing, of course, so I don't know if this one will survive or not.
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bairgon

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Re: The Nares Strait thread
« Reply #968 on: March 18, 2017, 06:24:18 PM »
Looks like it's given way:


DrTskoul

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Re: The Nares Strait thread
« Reply #969 on: March 18, 2017, 06:46:09 PM »
Oh well....
“You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts.”
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #970 on: March 20, 2017, 05:55:14 PM »
Ice has flowed southward about 20 km in two days, per these DMI Kane Basin Sentinel images.  There is not a bridge across Kane Basin anymore.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #971 on: March 20, 2017, 06:48:31 PM »
Yesterday's MODIS of lower Kane Basin shows the snow-covered ice moving en masse.  (Ignore the artifact!)
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #972 on: March 20, 2017, 06:56:54 PM »
At Nares' north end (through the clouds): the Lincoln Sea 'foot' appears to be forming an arch (that is, it's looking less flat footed).
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Cate

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Re: The Nares Strait thread
« Reply #973 on: March 20, 2017, 07:30:33 PM »
The whole strait looks loosened up to me, like it's getting ready to move. Heading south through the strait from our giant foot----to the area just above the "knee", roughly at the mouth of Petermann, there is open water.

As usual, toggle the years to compare.

http://www.arctic.io/explorer/4Xa5A/2017-03-18/8-N81.71718-W64.88272
« Last Edit: March 20, 2017, 07:37:51 PM by Cate »

Cate

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Re: The Nares Strait thread
« Reply #974 on: March 21, 2017, 12:53:12 PM »
Some cloud cover on this 20 Mar 2017 image but it looks like there is even more open water in the Petermann outlet area than a couple of days ago.

This is only my second melt year and I don't use anything but Explorer, so maybe the other image sources and more experienced eyes have better info, please? but it looks to me like Nares ice is on the move. If so---well, it's a bit early, isn't it?

The link shows the entire strait. Zoom in for detail.

http://www.arctic.io/explorer/4Xa5A/2017-03-20/8-N80.53307-W68.45532

oren

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Re: The Nares Strait thread
« Reply #975 on: March 21, 2017, 01:26:58 PM »
...it looks to me like Nares ice is on the move. If so---well, it's a bit early, isn't it?

In the last couple of years the Strait opened up in early July.
However, the importance of Nares lies in its export of the thickest arctic sea ice that piles up in the Lincoln Sea. As long as one of the arches holds, the ice moving through the strait is mostly thin ice that will melt anyway later. And at this time of year there might even be refreezing of the resulting open water, depending on the weather. As of now, the northern arch still holds firmly. However, having just one arch increases the risk of an early totally-open strait, especially as the northern arch is less stable than the Kane basin arch due to its large width.

btw the easiest Nares resource is http://ocean.dmi.dk/arctic/kane.uk.php and/or http://ocean.dmi.dk/arctic/lincoln.uk.php. Filtering by Sentinel images gives daily hi-res images (which are very easy to animate as they are co-located).

Cate

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Re: The Nares Strait thread
« Reply #976 on: March 21, 2017, 01:35:20 PM »
oren, yes, that giant jackboot is still holding in the Lincoln Sea. As for the strait freezing and thawing, agreed, to be expected this time of year, and I think evident in the image today as well, a thin ice skim between thicker floes. We are now at 12 hours daylight and increasing daily, so if Nares loses ice cover/albedo, I suppose that might make a tiny difference in the surface temp, which could knock on in ice-melt farther north in the passage?

Thanks for the image sources, will have a look.

Cate

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Re: The Nares Strait thread
« Reply #977 on: March 24, 2017, 01:48:24 PM »
http://www.arctic.io/explorer/4Xa5A/2017-03-23/7-N79.9726-W66.63132

oren, refreeze has happened, as you indicated---the heel, toe, and sole of the bigfoot boot in the Lincoln Sea appear to have frozen over again, for now. That arch seems to be key to keeping the older sea ice in place since there's not much fast ice farther down the strait for arch-formation. It's all on the move---the ice all down the strait appears to be cracking and moving. I assume this is current-driven?
« Last Edit: March 24, 2017, 10:40:13 PM by Cate »

oren

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Re: The Nares Strait thread
« Reply #978 on: March 24, 2017, 10:19:56 PM »
Yes, there is an almost-constant current flowing from the Lincoln sea to Baffin bay, I seem to remember it's being driven by surface height differences, but people on this forum could shed more light on this. I also found this image on the net which might help a bit.

Cate

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Re: The Nares Strait thread
« Reply #979 on: March 24, 2017, 10:39:39 PM »
Cool image, oren. Thanks so much.

Here is an interesting piece on wind and currents in Nares, by a student of Andreas Muenchow.

https://icyseas.org/2012/07/27/currents_winds_nares_strait_ice_arches/
« Last Edit: March 24, 2017, 10:44:45 PM by Cate »

Tor Bejnar

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Re: The Nares Strait thread
« Reply #980 on: March 26, 2017, 05:16:15 AM »
The (virtually) only pieces of Arctic Ocean ice in Nares Strait, the ones that broke off the "foot" bridge in Lincoln Sea on March 5 (or very shortly before) are now off Petermann Fjord. (roughly 120 km in 20 days - the previous identifiable floe went Nares' entire 500 km in 10 days!)  (From 3/23 Polar View.)
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #981 on: March 29, 2017, 03:58:48 PM »
On March 27, DMI Sentinel shows the larger floe about 20 km 'south' of Petermann Fjord and on March 28 shows it to be opposite Petermann Fjord!  Windytv shows winds are currently from the south.  (I confirmed this ice movement with PolarView - no image included.)

We could try to guess which end of Nares Strait it will exit (first) and when!
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oren

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Re: The Nares Strait thread
« Reply #982 on: March 29, 2017, 05:41:17 PM »
I am wondering if a strong wind from the south can somehow break the Lincoln "arch". For now it looks to be frozen solid, but as the whole area of thick ice north of Greenland is currently cracking badly and flowing towards the Fram, except for the Lincoln Sea area directly adjacent to Nares, it means that there is a risk that cannot be discounted. And I assume the main strength of the arch is against stresses towards Nares, less so for stresses in the opposite direction.

Cate

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Re: The Nares Strait thread
« Reply #983 on: March 30, 2017, 06:39:31 PM »
Today (March 29) on Explorer, you can click back to 2014 in clear weather. Compared to previous years, the ice is almost all rubble, and any smooth ice is riven with cracks. There is no sign yet of the development of a strong arch in the strait, like 2014-2016, apart from the jackboot in the Lincoln.

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Re: The Nares Strait thread
« Reply #984 on: April 01, 2017, 09:20:21 AM »
Posting this in this thread, ice (arch) in the Lincoln Sea is often discussed and Nares Strait gets a mention.

From ESA's Space in Images:



Three Sentinel-1 images separted by a few months are combined as a RGB image showing the build-up of the ice pack.

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Re: The Nares Strait thread
« Reply #985 on: April 01, 2017, 02:05:57 PM »
Where some of the thickest MYI should reside, I am bothered by the broken up flows. Is that normal?

Tor Bejnar

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Re: The Nares Strait thread
« Reply #986 on: April 03, 2017, 03:55:45 AM »
On 3/28 the floe from the 'foot' bridge was opposite Petermann Fjord.  Now it it 40 km "upstream" (northwards), as of today's DMI Sentinel image.

The forecast winds this coming week show mostly winds out of the south, so the floe will likely stay where it is for a while.  I suspect the 'Nares Strait born' ice around it will prevent much movement northwards.  Further south, it does not appear a new arch is forming anywhere, so 'as soon as' the winds shift, (virtually) the entire Nares Strait should flush out again, as it did in early February.

So, how thick has the "Nares Strait born" ice grown during these two months?  If it has remained -30oC for these two months, it could be a meter thick!
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Re: The Nares Strait thread
« Reply #987 on: April 03, 2017, 09:04:52 AM »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Tor Bejnar

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Re: The Nares Strait thread
« Reply #988 on: April 03, 2017, 06:48:15 PM »
That "1 m" Nares Strait ice thickness was based on -30º C "constant for 2 months" (starting with basically no ice as most of the "old" ice was flushed out and no insulating snow [whose presence is obvious from MODIS images]).  Using DMI's FFD for 80N (an area that includes Kennedy Channel in Nares Strait, but is strongly influenced by the area north of 85N) between Feb. 1 and Apr. 1 [FDD=1250] , the formula from NSIDC
            Thickness (cm) = 1.33 * FDD (°C)0.58
returns 83 cm.   I do not know if it has been colder or warmer in Nares Strait/Kennedy Channel than at the North Pole, but this is certainly seems to me to be a reasonable estimate.
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crandles

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Re: The Nares Strait thread
« Reply #989 on: April 03, 2017, 07:17:54 PM »
SMOS does indicate some ice over 50cm (and even if it didn't, that wouldn't invalidate 'if cold, for 2 months then ...' logic presented).

Tor Bejnar

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Re: The Nares Strait thread
« Reply #990 on: April 03, 2017, 08:28:26 PM »
What surprises me is the 1.2-2 m thick ice (according to the March 3 to 30 CPOM CryoSat-2 map Jim Hunt referenced [GreatWhiteCon]) in the western (still flowing, albeit slowly) part of Kane Basin and in Smith Sound.
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #991 on: April 07, 2017, 05:55:12 PM »
cross post (there was some discussion about southern Baffin Bay ice in another thread, so I put this observation/question there):
I'm curious about the effect Nares Strait is having on Baffin Bay.  Specifically, Kane Basin (and the entire Strait) has not had an effective ice arch all winter, so Nares it has exported a lot of up-to-about-one-meter-thick (grown in Nares Strait) ice.  The volume (not thickness) of ice created in Nares Strait will be much greater than usual, as new ice with no snow cover is (virtually) continually being created in the northern parts of the Strait, and the first 10 or 50 cm grows much faster (in a given temperature) than the third.  And it is almost constantly being exported to Baffin Bay.
An edited and extended note can be found at
in the "2017 sea ice area and extent data" thread.
« Last Edit: April 10, 2017, 07:34:52 PM by Tor Bejnar »
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #992 on: April 09, 2017, 01:31:48 AM »
About 3/24 the floe from the 'foot' bridge was opposite Petermann Fjord gong southward.  It was also there on 3/28 going northward.  It was there again yesterday (going south).
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Tor Bejnar

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Re: The Nares Strait thread
« Reply #993 on: April 10, 2017, 07:14:44 PM »
Winds in Nares Strait will be out of the north, according to Windytv, all this week.  (Saturday's forecast, shown below, has the strongest winds.)  Although it has taken some 35 days to get 1/3rd of the way through, the "March 5" floe might be in Kane Basin (a 2nd third of the way) when the winds shift (predicted to be on Sunday).  I suspect all the ice in the Strait will not allow any floe to speed through as one did in early February, as it plays 'bumper cars' on its way south.
« Last Edit: April 10, 2017, 07:26:39 PM by Tor Bejnar »
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Cate

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Re: The Nares Strait thread
« Reply #994 on: April 13, 2017, 12:39:18 PM »
Big chunk out of the Lincoln Sea "boot" arch on April 12.

http://www.arctic.io/explorer/4Xa5A/2017-04-12/9-N82.26727-W60.25128

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Re: The Nares Strait thread
« Reply #995 on: April 13, 2017, 12:44:10 PM »
I think that's out of the new ice in the "polynya" which is breaking up. If you look carefully you can see the outline of the original boot arch which is bigger.

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Re: The Nares Strait thread
« Reply #996 on: April 13, 2017, 03:31:15 PM »
I think that's out of the new ice in the "polynya" which is breaking up. If you look carefully you can see the outline of the original boot arch which is bigger.

Agreed. Sure is a lot of fresh snow in that image.

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Re: The Nares Strait thread
« Reply #997 on: April 13, 2017, 07:50:05 PM »
I think that's out of the new ice in the "polynya" which is breaking up. If you look carefully you can see the outline of the original boot arch which is bigger.
Using the IR images on worldview (band31) shows the thinner therefore warmer ice surface which had frozen up after the 6th March https://go.nasa.gov/2oa0lkC
temperature scale squashed to 220 / 273K

Nares strait has not exported much ice. The direction of movement has been across the top of the Lincoln sea. The effect this has had on placing thick ice into the Fram funnel and reduced multiyear ice in the Beaufort is the bigger picture here and I am curious how this will play out later in the season.
« Last Edit: April 13, 2017, 08:17:41 PM by Andreas T »

Andreas T

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Re: The Nares Strait thread
« Reply #998 on: April 13, 2017, 08:28:10 PM »
some of the breakage from the middle of january is still in place (not so easy to see because of clouds but AMSR2 helps despite low resolution) also see radar images posted by wipneus:
Breaking further, as needed.



Cate

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Re: The Nares Strait thread
« Reply #999 on: April 15, 2017, 12:34:11 AM »
That big chunk that broke off between April 11 and 12 has now made its way into the strait. Would someone reckon the distance and speed, please?  :)