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Alphabet Hotel

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Re: The Nares Strait thread
« Reply #1700 on: May 25, 2019, 12:05:27 AM »
Other maps are showing that there's a lot of five year old ice in this mix. I see some parallel white ridges in some of these frames. Could this be the older ice?

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Re: The Nares Strait thread
« Reply #1701 on: May 25, 2019, 12:16:26 AM »
Other maps are showing that there's a lot of five year old ice in this mix. I see some parallel white ridges in some of these frames. Could this be the older ice?


post a map or at least a link please.

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Re: The Nares Strait thread
« Reply #1702 on: May 25, 2019, 01:11:06 AM »
Other maps are showing that there's a lot of five year old ice in this mix. I see some parallel white ridges in some of these frames. Could this be the older ice?


post a map or at least a link please.

https://forum.arctic-sea-ice.net/index.php/topic,176.msg200883.html#msg200883

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1703 on: May 25, 2019, 02:42:19 AM »
... I see some parallel white ridges in some of these frames. Could this be the older ice?
I wish I knew more about interpreting Sentinel radar (if that's what it is).  Clearly the parallel white features identify some sort of structure.
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Re: The Nares Strait thread
« Reply #1704 on: May 25, 2019, 11:10:43 AM »
Other maps are showing that there's a lot of five year old ice in this mix. I see some parallel white ridges in some of these frames. Could this be the older ice?

If me mean the same, i think these are refrozen melt ponds from last year.

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Re: The Nares Strait thread
« Reply #1705 on: May 25, 2019, 01:50:06 PM »
Other maps are showing that there's a lot of five year old ice in this mix. I see some parallel white ridges in some of these frames. Could this be the older ice?


post a map or at least a link please.

Here is an animation copied from the current melt thread that suggests there is a lot of older ice moving into the Nares.

https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2591.0;attach=121022;image

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Re: The Nares Strait thread
« Reply #1706 on: May 25, 2019, 02:08:41 PM »
I read the black as being the freshest/smoothest ice, that implies the white is the most jagged surface, probably recently compressed ridges, so, and i'm guessing, the older ice being less compactable may be either side of the ridges.

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Re: The Nares Strait thread
« Reply #1707 on: May 25, 2019, 06:02:10 PM »
Close up of Franklin Island (lower right) on 23th.

Tidal wave galore. Also, notice how that one floe is beaten in pieces.

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Re: The Nares Strait thread
« Reply #1708 on: May 25, 2019, 06:09:22 PM »
Not just a floe. That looks like fast ice be torn to ribbons.

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Re: The Nares Strait thread
« Reply #1709 on: May 25, 2019, 06:16:42 PM »
Not just a floe. That looks like fast ice be torn to ribbons.

The most stuff that's bouncing there is not fast ice but floes from above 'stranded' there. In this Sentinel shot from the same day, you can see it quite well. I marked the fast ice in red.
« Last Edit: May 25, 2019, 06:54:20 PM by b_lumenkraft »

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Re: The Nares Strait thread
« Reply #1710 on: May 25, 2019, 06:30:24 PM »
Thank you for that image. It is a relief that tidal flows lack the power to cause fast ice to disintegrate.

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Re: The Nares Strait thread
« Reply #1711 on: May 25, 2019, 06:52:10 PM »
You are welcome SH. :)

I think tidal waves have some say in gnawing on the fast ice, only not that rapidly.

And if it's only for this effect: This GIF is showing a bit of fast ice in Hall Kane Basin chipping off. For how i see it, it's because a tidal wave bumping that bigger floe (which was fast ice itself) against it.

Edit!
« Last Edit: May 25, 2019, 06:58:06 PM by b_lumenkraft »

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Re: The Nares Strait thread
« Reply #1712 on: May 25, 2019, 09:26:08 PM »
You are welcome SH. :)

I think tidal waves have some say in gnawing on the fast ice, only not that rapidly.

And if it's only for this effect: This GIF is showing a bit of fast ice in Hall Kane Basin chipping off. For how i see it, it's because a tidal wave bumping that bigger floe (which was fast ice itself) against it.

Edit!

There is  no fast ice in Kane Basin or Nares Strait, there is 1 year ice max!
Have a ice day!

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Re: The Nares Strait thread
« Reply #1713 on: May 25, 2019, 09:36:18 PM »
Oh, looks like i still haven't understood how 'fast ice' is defined. Could you define it for me Espen?

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Re: The Nares Strait thread
« Reply #1714 on: May 25, 2019, 10:06:29 PM »
We've had the exact same discussion on definitions last year. But in any case, the ice in Kane Basin (at the mouth of Humboldt glacier and adjacent areas) is unmoving and attached to the shore, but it's first year ice. I call it fast ice, Espen doesn't.

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Re: The Nares Strait thread
« Reply #1715 on: May 25, 2019, 10:27:31 PM »
Why does ice going through Nares become 1st year ice when it arrives in Baffin whilst ice exiting via Fram retains it's age until it's demise ?  ref recent ice age discussions ..

 Fast used to mean land-fast and refer to ice that had spent years in situ along the coasts .. now it means coastal ice that is fast to disintegrate or melt as soon as the opportunity arises .. b.c.

 
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1716 on: May 25, 2019, 10:56:03 PM »
Fast ice:  NSIDC definition referenced in the ASI Glossary:
Quote
ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents.
Note: nothing about more than one year old, unless you're talking about year-old fast ice or multi-year fast ice.

Also, Wikipedia
Also, see Wikipedia's Outline of oceanography definition (same as above)
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Re: The Nares Strait thread
« Reply #1717 on: May 26, 2019, 03:04:55 AM »
Animation from DMI's Sentinel-1 Lincoln images. May 16-19,21-25

Everything on the right side shifts left in the last frame and pulls away from the coast.

http://ocean.dmi.dk/arctic/lincoln.uk.php


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Re: The Nares Strait thread
« Reply #1718 on: May 26, 2019, 07:48:44 AM »
This is not a new crack, it cracked there two weeks ago. But meanwhile, it closed and is now open again. This time i'm having the impression by looking at it, that it is caused by wind. The event two weeks ago made the impression of being a current driven movement.

GIF 1 showing Greenland north coast, on 23.05. 21:45h to 26.05. 01:21h UTC.
GIF 2 showing a closeup of the crack to give you an impression of the ice movement. (25.05. 01:40h to 26.05. 01:21h UTC)

(Both GIFs require a click to start)

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Re: The Nares Strait thread
« Reply #1719 on: May 26, 2019, 07:56:20 AM »
Tor, B.C., Oren, thanks, guys for the answers. I take it, the definition does not include multi-year ice (anymore) and if it ever did it's no more useful because MYI has become a rare thing anyway these days. TIL :)

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Re: The Nares Strait thread
« Reply #1720 on: May 26, 2019, 09:34:56 AM »
Can any of the good folks here make an estimate of the sea ice area being exported through the Lincoln - Nares gateway per day or per week this year/season?
It would be something like the width of the northern part of the strait (Robeson Channel), times the average speed of progress along the channel, times the average sea ice concentration.
I'd say width is 20 km, concentration is 75%, but both these numbers can be improved and speed needs to be measured.

With another assumption of average thickness of let's say 3m, a volume export estimate will be available as well.

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Re: The Nares Strait thread
« Reply #1721 on: May 26, 2019, 09:54:57 AM »
Very crude measure of estimating....I would say something like 300 km2 per per day.

If the entrance is 20km wide and observing a gif shows that a piece of ice moves about the same distance forward as the width of the channel then you get 20*20*.75 = 300. That's ~0.5% of average loss for the entire Arctic this time of year.


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Re: The Nares Strait thread
« Reply #1722 on: May 26, 2019, 02:19:39 PM »
Next weeks temperatures in Nares Strait will be ~0˚C meaning the impatient ice can already melt while travelling down the strait. No need to wait for an arrival in the Baffin Bay anymore.

The week starts with weak winds that will become stronger towards the second half with southern winds.

Tidal amplitudes will be minor first, then increasing towards the weekend.

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Re: The Nares Strait thread
« Reply #1723 on: May 26, 2019, 06:16:39 PM »
Very crude measure of estimating....I would say something like 300 km2 per per day.

If the entrance is 20km wide and observing a gif shows that a piece of ice moves about the same distance forward as the width of the channel then you get 20*20*.75 = 300. That's ~0.5% of average loss for the entire Arctic this time of year.
Thank you. Nice and quick estimate.
Assuming a 3m thickness, we get to almost 1km3 exported per day, which is about 1% of the daily arctic-wide volume loss.
Of course the exported area/volume is not immediately lost, but the eventual outcome is clear.

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Re: The Nares Strait thread
« Reply #1724 on: May 27, 2019, 12:54:13 AM »
Animation from DMI's Sentinel-1 Lincoln images. May 16-19,21-26
(This time as an .mp4 file)

Things are really moving along the Greenland coast.

http://ocean.dmi.dk/arctic/lincoln.uk.php

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Re: The Nares Strait thread
« Reply #1725 on: May 27, 2019, 02:19:27 AM »
Wonder what chance a blockage in Naire Strait. There is a large piece that fast approaching Hans Island. It has remained largely intact since entering the strait. Possibly some of the last true floes of MYI. Another large piece has just entered the strait, also somewhat intact. If these 2 come together at Hans Island, it could be interesting.

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Re: The Nares Strait thread
« Reply #1726 on: May 27, 2019, 02:29:25 AM »
My guess is it disintegrates.

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Re: The Nares Strait thread
« Reply #1727 on: May 27, 2019, 02:49:37 AM »
To continue the discussion on the quantitative effects of Nares export, if volume lost is indeed around 1km3 per day, having the strait open for an extra of 3-4 months this year means the extra export of roughly 100 km3 over the season. OTOH, if the ice had not been exported it still would have lost some of its thickness to bottom and top melt, so the net volume lost to export should be around 60 km3. As the minimum volume of the CAB in September can often reach 4000 km3, and in 2012 reached 3400 km3, the loss amounts to 1.5%-2% of the volume at minimum. Not negligible, though not decisive either.
Of course, there are the qualitative effects of export - making the ice in the Lincoln Sea mobile, perhaps making it more vulnerable to waves and winds, potentially increasing Fram export through unlocking of the whole ice pack in the region, and more.

Note: if anyone can come up with better measurements to the numbers used in the quantitative estimate that would be appreciated.

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Re: The Nares Strait thread
« Reply #1728 on: May 27, 2019, 03:28:41 AM »
Hi Oren .. it would appear you have seen the back of my envelope . :)  although I would suggest the potential of loss through melt will be transferred to melting other ice in the basin so should not be subtracted ..
  rather , an open Nares is facilitating movement of and within the pack and contributes to the fractal fracturing which is currently allowing sunlight to penetrate the ice and water throughout the basin 24/7 . This may account for more volume loss than direct export this year . b.c.
 
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

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Re: The Nares Strait thread
« Reply #1729 on: May 28, 2019, 05:40:13 AM »
Initial melting and breakup of the fast ice (=static shore-attached ice) in my favorite corner of the Arctic - Kane Basin, May 1st-27th. This is still mostly bottom melt enhanced by currents, when the heat/sun turns up the remaining fast ice will be heavily melt ponded.
Click to animate.

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Re: The Nares Strait thread
« Reply #1730 on: May 28, 2019, 06:16:03 AM »
Animation from DMI's Sentinel-1 ASAR Lincoln Sea images. May 21-27

I forgot to mention last time that I'm applying a contrast enhancement filter in GIMP. I arrived at these settings by trial and error.
Filters | Enhance | Sharpen (Unsharp Mask) : Radius 4.913, Amount 0.3

Images from http://ocean.dmi.dk/arctic/lincoln.uk.php

There were 3 images on May 26 and one that I used has disappeared from their site.

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Re: The Nares Strait thread
« Reply #1731 on: May 28, 2019, 06:30:53 AM »
Thanks a lot for those Alphabet Hotel.

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Re: The Nares Strait thread
« Reply #1732 on: May 28, 2019, 03:56:05 PM »
Wonder what chance a blockage in Naire Strait. There is a large piece that fast approaching Hans Island. It has remained largely intact since entering the strait. Possibly some of the last true floes of MYI. Another large piece has just entered the strait, also somewhat intact. If these 2 come together at Hans Island, it could be interesting.

The first one of those is stranded at Hans since yesterday. I can't figure out though why that is. It's small enough to pass by, but makes no move to do so. Just sitting there.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1733 on: May 28, 2019, 05:06:21 PM »
This GIF uses DMI Sentinel images from May 24, 26 and 27 (no 25th image available) and shows the "First" floe (crudely outlined) getting stuck on fast ice above Hans Island.  It doesn't block the channel, however.  As it is 'surely' made of MYI, I expect it to just sit there awhile.  For me the question is what happens with regard the "Second" floe.  When it hits First, will either shatter?  Will First get nudged along?  Will they block the Kennedy Channel?  If so, for how long?  (It could be until July.)

So much for my "they always shatter" experience (maybe).  :o ::) :P
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Re: The Nares Strait thread
« Reply #1734 on: May 29, 2019, 12:10:59 AM »
In the last optical image, the first ice floe has already reached a small island. Now it will either be cut in half, or it will squeeze into the passage entirely.

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Re: The Nares Strait thread
« Reply #1735 on: May 29, 2019, 11:03:10 AM »
Oh look at that, the triangle is back!

The picture was taken today, 06:18h UTC.

'Second' is rotating.

'First' floating upstream. (wat?) Correction: Still sitting in front of Hans.
« Last Edit: May 29, 2019, 11:12:24 AM by b_lumenkraft »

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Re: The Nares Strait thread
« Reply #1736 on: May 29, 2019, 11:54:34 AM »
Has anyone else noticed the dance of the large chunks that broke off a couple of weeks ago further down the channel ? They have been rotating merrily but have gone nowhere since their liberation . It looks like flow has dramatically slowed after months of continuous southerly momentum . They have been easily seen everyday on Worldview .. and would make a fun gif on their own .. :) .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

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Re: The Nares Strait thread
« Reply #1737 on: May 29, 2019, 12:47:34 PM »
Of course, Be Cause!  8)

This is a GIF showing the Kane Basin. Franklin Island upper left.

Timeframe shown: 17.05. ~14:00h UTC to 29.05. ~15:30h UTC

Notice how the surface current after Franklin is dominant only on the right side (if you go downstream) of the Strait. A standing wave in Kane Basin exports floes very quickly but only in a narrow band. The movement of floes in the rest of the basin is mainly caused by tidal waves, not the downstream current. The big floes dancing around there is fast ice originating here in the Kane Basin. Only if they somehow manage to make it fully into the narrow standing wave they will be sucked down into the Baffin Bay.

Nothing has slowed down export wise as i see it.



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Re: The Nares Strait thread
« Reply #1738 on: May 29, 2019, 01:34:38 PM »
Oh look at that, the triangle is back!

The picture was taken today, 06:18h UTC.

'Second' is rotating.

'First' floating upstream. (wat?) Correction: Still sitting in front of Hans.

Wow.

Is that a huge chunk of multi year ice?

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Re: The Nares Strait thread
« Reply #1739 on: May 29, 2019, 01:46:31 PM »
The triangle Rich? No, that's a cloud.

The big floe in the Strait? Most likely, but very hard to say for sure.

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Re: The Nares Strait thread
« Reply #1740 on: May 29, 2019, 02:48:20 PM »
BTW BC,

i posted a closeup of that standing wave a while ago here:

This GIF is showing an interesting S-curvy pattern the floes take in hight of Hall Basin in Nares Strait.

I meant to say Kane there 👆🏾

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Re: The Nares Strait thread
« Reply #1741 on: May 29, 2019, 03:55:07 PM »
Only if they somehow manage to make it fully into the narrow standing wave they will be sucked down into the Baffin Bay.

Looks like one of them is doing just that right now. Showing here the last 28 frames from the RAMMB. Latest frame 11:24h UTC.

Tor Bejnar

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Re: The Nares Strait thread
« Reply #1742 on: May 29, 2019, 05:50:41 PM »
The Kane Basin Gyre is 'famous'.

Looking to the Kennedy Straight, I see the stout "First" floe has settled into Hans Island (i.e., yesterday, it moved southward some since the day before where it had been 'frozen in place' for over a day, per DMI Sentinel images).  "Second" floe is now in Hall Basin (opposite Petermann Fjord). 

For those new to the ASIF (actually, for everybody), there are Greenland place name maps.
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Re: The Nares Strait thread
« Reply #1743 on: May 29, 2019, 07:37:22 PM »
Animation from DMI's Sentinel-1 ASAR Lincoln Sea images. May 21-28
Images from http://ocean.dmi.dk/arctic/lincoln.uk.php

I don't know why the last frame is so dark. Can anyone explain it?
All the ice along the Greenland coast is on the move now.

Putting these here so I don't lose them (again):
Cropped from position 108, 130  size 1024, 704
mp4 created with: ffmpeg -i 20190521-20190528.lincoln.gif -pix_fmt yuv420p -vf "scale=iw*.75:ih*.75" 20190521-20190528.lincoln.mp4



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Re: The Nares Strait thread
« Reply #1744 on: May 29, 2019, 07:56:31 PM »
I don't know why the last frame is so dark

Not an expert, but i see this with other satellite bands/products too. Depending on the position of the sun they turn out darker or brighter.

Now, this is radar imagery, so i think it's the variating position/altitude of the satellite in the orbit.

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Re: The Nares Strait thread
« Reply #1745 on: May 29, 2019, 09:42:13 PM »
+++ BREAKING +++

Floe stuck in Nares Strait!

The last 3 frames showing Second to not move.

+++ BREAKING +++

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Re: The Nares Strait thread
« Reply #1746 on: May 29, 2019, 09:51:58 PM »
I wouldn't declare it stuck .. just yet .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

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Re: The Nares Strait thread
« Reply #1747 on: May 29, 2019, 09:58:13 PM »
But it felt so good to report a stuck floe. Even if it's only stuck for a couple of hours, it's stuck. :P

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Re: The Nares Strait thread
« Reply #1748 on: May 30, 2019, 06:37:25 AM »
Nice and clear Sentinel shot of the situation yesterday.

Likely no updates today because it's very cloudy and you can't see anything.

First sitting put for at least 2 days not making any attempt to pivot is a mystery to me.

Also, what Second is doing there is unusual. In my mind, it should move.

Perhaps you are right B.C., the current might have slowed down.

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Re: The Nares Strait thread
« Reply #1749 on: May 30, 2019, 08:10:50 AM »
Animation from DMI's Sentinel-1 ASAR Lincoln Sea images. May 22-29
Images from http://ocean.dmi.dk/arctic/lincoln.uk.php