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ajouis

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The caa-greenland mega crack
« on: July 29, 2019, 10:23:23 AM »
It is unprecedented, i think to have such a huge crack at that place, this early. This thread is for data, speculation, and potential causes and consequences of this event.
To my knowledge only the nares restarting to export is blocking a further continuation of the crack at the moment

bluice

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Re: The caa-greenland mega crack
« Reply #1 on: July 29, 2019, 11:13:50 AM »
It's probably reasonable to expect The Crack to become a standard in future melt seasons. I wonder how this will affect future minimums and especially the somewhat arbitrary 1 million km2 BOE threshold.

If Northern CAA & Greenland can no longer be counted as the last bastion of thick MYI, do we such a place anywhere in the Arctic?  Will the last remaining ice be an ice island circulating at the pole, and if so, is such development a start to a BOE or the Arctic Ocean to become a seasonally open sea.

Interesting.
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be cause

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Re: The caa-greenland mega crack
« Reply #2 on: July 29, 2019, 11:24:21 AM »
the craic was good in 2009 .. :) .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Coffee Drinker

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Re: The caa-greenland mega crack
« Reply #3 on: July 29, 2019, 11:37:50 AM »
I go with ice island circling around the pole. Northern Greenland can get surprisingly hot.

ajouis

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Re: The caa-greenland mega crack
« Reply #4 on: July 29, 2019, 11:54:52 AM »
the craic was good in 2009 .. :) .. b.c.
Do you have pics?

be cause

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Re: The caa-greenland mega crack
« Reply #5 on: July 29, 2019, 11:56:56 AM »
the craic was good in 2009 .. :) .. b.c.
Do you have pics?
sorry,no  .. Worldview does
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Lou

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Re: The caa-greenland mega crack
« Reply #6 on: July 29, 2019, 01:51:17 PM »
I won't pollute this topic with my wildly uneducated guesses about the future of this crack, but I do want to say that watching such things arise and develop as we slide ever closer to the first BOE and beyond is one of the more grimly fascinating parts of watching the doings on top of the world.

Sterks

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Re: The caa-greenland mega crack
« Reply #7 on: July 29, 2019, 03:21:27 PM »
This is not unprecedented. Seen several times. One year there was one as big or bigger so that a loon decided to take precedence on its discovery and put his name on it.
Of course it resealed.

Rich

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Re: The caa-greenland mega crack
« Reply #8 on: July 29, 2019, 04:16:34 PM »
I think le' crack is a big deal as a leverage point for wind.

My BOE vision involves a couple of weeks of steady late season 30+ knot winds pushing the pack toward Fram.

We're set in a few days to at least get a glimpse of what that would look like. Theoretically, it could still happen this year. Who knows what the weather lottery will produce?

Tor Bejnar

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Re: The caa-greenland mega crack
« Reply #9 on: July 29, 2019, 04:48:31 PM »
I've seen open water just north of the CAA several times, and north of Greenland last year, but having a nearly continuous stretch of open water along the entire North American continent, and for as long a period of time this year, is unprecedented, I believe.   Polynyas that recur in certain locations are often named, such as the North Water Polynya.  A 'full' list of Canadian polynyas [plus some inAlaska, Greenland and eastern Russia] .

Should this become a feature, I've proposed calling it the NAC: North American Crack.  Of course we could call it McCAG: Mega-crack - Canadian Arctic/Greenland: this doesn't 'look' like any other abbreviation...  Movement of ice along this boundary, of course, happens 'all' the time.  What is less usual is for the ice to pull away (and melt) along most of this boundary at one time, so maybe the NACP:  North American Coastal Polynya.

The Canadian list of polynyas identifies the location of un-named "major shore lead polynyas", including one along the entire North American continent.  So maybe the NASLP: North American Shore Lead Polynya.

See more discussion of polynya in Wikipedia, Encyclopedia Britannica and elsewhere.

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Sterks

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Re: The caa-greenland mega crack
« Reply #10 on: July 29, 2019, 05:08:27 PM »
OK that may be true. Maybe it's a new feature enhanced by the very weak ice over there compared to pre-2010s
Yet I am unable to see the potential effects a frequent reappearance can have. Not saying it CAB have...

Pmt111500

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Re: The caa-greenland mega crack
« Reply #11 on: July 29, 2019, 05:23:08 PM »
Ice is taking a shore leave. Likely comes back to serve next spring as the albedo enhancer. But the job is dull and increasingly difficult, so might leave alltogether some spring.
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Rich

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Re: The caa-greenland mega crack
« Reply #12 on: July 29, 2019, 05:46:32 PM »
I've seen open water just north of the CAA several times, and north of Greenland last year, but having a nearly continuous stretch of open water along the entire North American continent, and for as long a period of time this year, is unprecedented, I believe.   Polynyas that recur in certain locations are often named, such as the North Water Polynya.  A 'full' list of Canadian polynyas [plus some inAlaska, Greenland and eastern Russia] .

Should this become a feature, I've proposed calling it the NAC: North American Crack.  Of course we could call it McCAG: Mega-crack - Canadian Arctic/Greenland: this doesn't 'look' like any other abbreviation...  Movement of ice along this boundary, of course, happens 'all' the time.  What is less usual is for the ice to pull away (and melt) along most of this boundary at one time, so maybe the NACP:  North American Coastal Polynya.

The Canadian list of polynyas identifies the location of un-named "major shore lead polynyas", including one along the entire North American continent.  So maybe the NASLP: North American Shore Lead Polynya.

See more discussion of polynya in Wikipedia, Encyclopedia Britannica and elsewhere.

[I share my opinions and you choose!]


I like the initiative to find a name for this feature. My understanding is that polynya refers to open water completely surrounded by ice and the crack doesn't meet that definition to the west.

I'm cool with crack or NAC until it gets bigger. When it hits 50k km2 or 100k km2, it become something else.

How about CABCOW? (Central Arctic Basin Coastal Open Water)

This is pretty much covers the entire region where the CAB comes into contact with land ( excluding small features like Svalbard and FJL. )

sailor

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Re: The caa-greenland mega crack
« Reply #13 on: July 29, 2019, 06:03:04 PM »
I think le' crack is a big deal as a leverage point for wind.

My BOE vision involves a couple of weeks of steady late season 30+ knot winds pushing the pack toward Fram.

We're set in a few days to at least get a glimpse of what that would look like. Theoretically, it could still happen this year. Who knows what the weather lottery will produce?
I don't understand what you mean... if the wind pushes steadily the pack toward Fram, the natural tendency of the ice will be to be steered by Coriolis force to the right of the winds, and close whatever gap there is between the ice and CAA/Greenland.
Unless you are thinking on a very particular circulation that I can't really see.


(ahh that was it, The GAP... Barry's Gap was it?)
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sailor

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Re: The caa-greenland mega crack
« Reply #14 on: July 29, 2019, 06:04:35 PM »
OK that may be true. Maybe it's a new feature enhanced by the very weak ice over there compared to pre-2010s
Yet I am unable to see the potential effects a frequent reappearance can have. Not saying it CAB have...
Think on it as more the effect than the cause ...
I don't see it however as a feature that survives during winter. That is obvious for every one?
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ajouis

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Re: The caa-greenland mega crack
« Reply #15 on: July 29, 2019, 06:08:58 PM »
OK that may be true. Maybe it's a new feature enhanced by the very weak ice over there compared to pre-2010s
Yet I am unable to see the potential effects a frequent reappearance can have. Not saying it CAB have...
could enhance ssts in the region, where thick ice is supposed to be, keeping volume down, and changing the safe ice reduit.
It might mean another change of paradigm in the arctic, which is one of the reasons why I opened this thread, to compile data to know whether this is the case, I have only been following the arctic for a couple of years, so I am only really aware of the north Greenland crack late summer last year.

Tor Bejnar

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Re: The caa-greenland mega crack
« Reply #16 on: July 29, 2019, 07:11:35 PM »
Some do define polynyas as being [completely] surrounded by sea ice.  However, "coastal polynyas" must be close to a coast, meaning next to land, and many of the named polynyas around Canada are bounded by land on at least one side.

CABCOW's pretty good! :)

OK that may be true. Maybe it's a new feature enhanced by the very weak ice over there compared to pre-2010s
Yet I am unable to see the potential effects a frequent reappearance can have. Not saying it CAB have...
Think on it as more the effect than the cause ...
I don't see it however as a feature that survives during winter. That is obvious for every one?
I sure hope so!
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UCMiami

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Re: The caa-greenland mega crack
« Reply #17 on: July 29, 2019, 07:36:25 PM »
If this becomes a more frequent yearly situation, the largest effect I could see would be changing the nature of the ice in the CAA. The CAA has been an exit route for MYI leaving the CAB late in the melt season. If the gap remains open, it suggests the winds are steadily blowing from the south and the gap could be an exit point for the ice in the CAA. The CAA would then be home of mostly FYI rather than a mixture of large thick chunks of MYI tied together with FYI.

If that happens the CAA would start melting earlier and more completely each year. Not sure if that would increase temperatures into the CAB but suspect it would.

Sterks

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Re: The caa-greenland mega crack
« Reply #18 on: July 29, 2019, 08:47:01 PM »
OK that may be true. Maybe it's a new feature enhanced by the very weak ice over there compared to pre-2010s
Yet I am unable to see the potential effects a frequent reappearance can have. Not saying it CAB have...
could enhance ssts in the region, where thick ice is supposed to be, keeping volume down, and changing the safe ice reduit.
It might mean another change of paradigm in the arctic, which is one of the reasons why I opened this thread, to compile data to know whether this is the case, I have only been following the arctic for a couple of years, so I am only really aware of the north Greenland crack late summer last year.

Yes I understand better now. However, if in summer there’s a “Garlic press” like event (strong compaction against the CAA and Greenland) expect a lot of ridged ice to occupy that breach over the shelf, delaying the reappearance  of that gap that we witness now.

 I see typical events of the Arctic (drift towards America, Fram currents) as tending to keep the thing closed and with thickened and ridge ice. I agree with sailor above there should not survive in Winter, but I think beyond, it would  typically recover thick ice.

binntho

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Re: The caa-greenland mega crack
« Reply #19 on: July 30, 2019, 08:16:52 AM »
New depths are being plumbed here (and yes, horrible pun intended). June 28 omitted for dramatic effect. (click to run)
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Peter Ellis

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Re: The caa-greenland mega crack
« Reply #20 on: July 30, 2019, 10:12:21 AM »
The phrase you're looking for is "flaw lead".

Tor Bejnar

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Re: The caa-greenland mega crack
« Reply #21 on: July 30, 2019, 05:48:32 PM »
Wow, I get to learn something every other day! (in this case the terms, not the concept):flaw leadshore lead, coastal lead
Quote
A shore lead (or coastal lead) is an oceanographic term for a waterway opening between pack ice and shore. While the gap of water may be as narrow as a tide crack if closed by wind or currents, it can be as wide as 1,000 feet (300 m). Its formation can be influenced by tidal action, or subsurface conditions, such as current and ocean floor.[2] Commonly, a shore lead is navigable by surface vessels.[3]

An opening ("lead") between pack ice and fast ice is referred to as a flaw lead.

NACL: North Am. Coastal Lead (there's a distinct taste to that)
but only when it is less that 300.01 (or is it 304.81?) meters wide. :o
NaFl: Sodium Flerovium? I mean NAFL: North Am. Flaw Lead
this is getting dangerous
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Glen Koehler

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Re: The caa-greenland mega crack
« Reply #22 on: July 30, 2019, 08:39:26 PM »
"Sodium Flerovium"
   Could be a spell from Hogwarts to desalinate seawater.

pearscot

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Re: The caa-greenland mega crack
« Reply #23 on: July 30, 2019, 09:24:44 PM »
According to the 7/30 imagery, it appears as though (within reason and for hypothetical purposes) save for one section, it is almost possible to sail around Greenland. I'm not sure if I've ever known this to be possible. Depending on how July unfolds, I wonder if this will completely open up. I'm inclined to say it is, given the fact that the crack continues to expand north and the open water will be absorbing more heat. Either way, this is the single most notable formation of this season.

pls!

aslan

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Re: The caa-greenland mega crack
« Reply #24 on: July 31, 2019, 01:20:12 PM »
It was already note in the melt season topic, but the paleoclimatology yield some interesting results regarding Greenland beaches :

https://s3.amazonaws.com/academia.edu.documents/39706551/A_10000-Year_Record_of_Arctic_Ocean_Sea-20151105-20427-ypl12t.pdf?response-content-disposition=inline%3B%20filename%3DA_10_000-Year_Record_of_Arctic_Ocean_Sea.pdf&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWOWYYGZ2Y53UL3A%2F20190731%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20190731T103208Z&X-Amz-Expires=3600&X-Amz-SignedHeaders=host&X-Amz-Signature=432ae45252627a5e521862c4450140b2ac01590c2e9659657457cc992e700760

I know it is sometimes difficult to be a weather man, but some definitive sentences are not going to pass the test of time : "and the ocean bordering North Greenland is expected to be the very last area to become ice-free in summer (2–4). "
Well, it is not looking quite likely now...

Beches are also found on the northwestern coast of Greenland, along the Smith Sound -wich is clear of ice now also- : http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.474.336&rep=rep1&type=pdf

Differents results are found elsewhere also : https://courses.seas.harvard.edu/climate/pdf/DeVernaletal2005PA001157.pdf

Ossifrage had some good insights about this subject, saying that the last bit of sea ice would probably be found more to the west, near the northern border of Canadian Archipelago. This can also have consequences for glaciers which are still buttstressed by sea ice : https://www.cambridge.org/core/services/aop-cambridge-core/content/view/5E27A9E9493AC5A9FEE361A4248AF8FF/S0260305500264549a.pdf/div-class-title-sea-ice-and-the-stability-of-north-and-northeast-greenland-floating-glaciers-div.pdf
The pack being fully detached from land is also bringing new questions. If the ice is more mobile, this can have effect on wind stress, currents, sea ice movements, etc. Can it also means that the pack can break in multiple parts ?

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Re: The caa-greenland mega crack
« Reply #25 on: August 01, 2019, 01:06:44 AM »
Aslan - on the topic of benches, the crack actually offers an explanation that doesn't require a full melt out of the basin.  Factor in post melt elastic rebound and you have a working theory for how they got there.
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binntho

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Re: The caa-greenland mega crack
« Reply #26 on: August 01, 2019, 04:40:06 AM »
Aslan - on the topic of benches, the crack actually offers an explanation that doesn't require a full melt out of the basin.  Factor in post melt elastic rebound and you have a working theory for how they got there.
I'm a bit suspicious here - I don't think a crack of 10 to 20 km, even occurring every year, can explain beach formation. Waves inshore would be very small and insignificant, espcecally since the crack seems to form mainly when offshore winds are strong and persistent.

The beach ridges described in the literature above seem quite substantial, indicating a large wave fetch in onshore winds.
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jdallen

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Re: The caa-greenland mega crack
« Reply #27 on: August 01, 2019, 07:11:59 AM »
Aslan - on the topic of benches, the crack actually offers an explanation that doesn't require a full melt out of the basin.  Factor in post melt elastic rebound and you have a working theory for how they got there.
I'm a bit suspicious here - I don't think a crack of 10 to 20 km, even occurring every year, can explain beach formation. Waves inshore would be very small and insignificant, espcecally since the crack seems to form mainly when offshore winds are strong and persistent.

The beach ridges described in the literature above seem quite substantial, indicating a large wave fetch in onshore winds.
Agree 10-20 is not sufficient.  100-200 would be. 

Also consider, what are those benches cut in? Bedrock or sediment?  If sediment, it could have been frozen; we've seen how even modest surf has been chewing up permafrost along the Alaskan coast.

Like I said though, its the core of a hypothesis, which could be tested.
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binntho

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Re: The caa-greenland mega crack
« Reply #28 on: August 01, 2019, 07:16:52 AM »
The paper seems to be talking about beach ridging, not benching. Ridging requires a fair degree of sand and gravel being moved by wave action and is a later stage than erosion of bedrock cliffs. Although sand and gravel from alluvial fans might be the source, rather than wave erosion of bedrock.
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binntho

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Re: The caa-greenland mega crack
« Reply #29 on: August 01, 2019, 08:12:49 AM »
Agree 10-20 is not sufficient.  100-200 would be. 
The shortest distance between Svalbard and Greenland is 300 km, the Lincoln sea is about 200 km wide in the middle, and the distance from Greenland to the geographic North Pole is just over 400 km.

The present crack is 10 to 20 km wide, a 100-200 km wide crack wouldn't be a crack, would it? Difficult to see what the Arctic would look like with that much open water north of Greenland, I'd guess it would be extremely shortlived, either closing up or rapidly on the way to a BOE.
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aslan

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Re: The caa-greenland mega crack
« Reply #30 on: August 01, 2019, 09:29:15 AM »
Yeah, I am not sure if I was clear in my last message but a crack of 10 - 20 km would not be enough for a beach. Of course we are probably not yet to the same situation than during Holocene. But it is starting to become really significant. Locally ocean is open over 50 km, excepted for small floes here and there. And, despite the title, it is probably not a "pure" crack. I mean, it is wind driven, but there is definitively some melt ongoing.  For example fjord Frederik Hyde is fully open since the 29th, with some melting, and now around the coast and Kap Ole Chiewitz, Kap Bridgemann, Kap etc... ocean is fully open over 30 - 40 km at least, save for small floes here and there. And around Kap Prins Knud etc... ( https://books.google.fr/books?id=uXwXL966F1cC&pg=PA261&lpg=PA261&dq=prinsesse+ingeborg+halve&source=bl&ots=JqhIF-Fsf5&sig=ACfU3U30-2i_yFBKmiH-tZT2ME0rwwm5VA&hl=fr&sa=X&ved=2ahUKEwjQseTql-HjAhV95eAKHXK1CQYQ6AEwDHoECAgQAQ#v=onepage&q=prinsesse%20ingeborg%20halve&f=false ) and somewhere in this corner of Greenland, ocean is even more open and exposed to Atlantic. And if there is still a ribbon of floes to the east, south of 80°N the Greenland sea is not really closed. And we have still at least one month to go before the end of melt season. This is not looking yet like Holocene, but there is definitively some tentative ongoing. And it is not looking like we will need a BOE for beach ridging over this caps.
« Last Edit: August 01, 2019, 10:04:33 AM by aslan »

binntho

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Re: The caa-greenland mega crack
« Reply #31 on: August 01, 2019, 10:23:45 AM »
And it is not looking like we will need a BOE for beach ridging over this caps.

But I think we do - I don't think there are any realistic scenarios where you can have so much open ocean north of Greenland / CAA with continuous incoming wave action for long enough periods without what is effectively a BOE.

The "crack" or whatever we should call it is too narrow, too shortlived, and most importantly, it is dependent on offshore winds so there will be no long-fetch waves capable of creating beach ridges.
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gerontocrat

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Re: The caa-greenland mega crack
« Reply #32 on: August 01, 2019, 12:30:04 PM »
And it is not looking like we will need a BOE for beach ridging over this caps.

But I think we do - I don't think there are any realistic scenarios where you can have so much open ocean north of Greenland / CAA with continuous incoming wave action for long enough periods without what is effectively a BOE.

The "crack" or whatever we should call it is too narrow, too shortlived, and most importantly, it is dependent on offshore winds so there will be no long-fetch waves capable of creating beach ridges.
The crack is wider going east to the open water NE of Greenland.
How wide can this crack get and for how long can it persist?

GFS says moderate southerly winds for the next 5 days at least, while that Greenland high - extending north and east as far as Svalbard and even FJL- is looking rather permanent.

Mere speculation - but there is always a chance that the rules are changing. Mind you, that still means not much chance of  beach ridges as it is the offshore winds making the crack wider, and wider, and wider?
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misfratz

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Re: The caa-greenland mega crack
« Reply #33 on: August 01, 2019, 02:30:57 PM »
According to the 7/30 imagery, it appears as though (within reason and for hypothetical purposes) save for one section, it is almost possible to sail around Greenland. I'm not sure if I've ever known this to be possible. Depending on how July unfolds, I wonder if this will completely open up. I'm inclined to say it is, given the fact that the crack continues to expand north and the open water will be absorbing more heat. Either way, this is the single most notable formation of this season.
The next step, which also seems to be closer than I can remember seeing it, would be for the main body of remaining Arctic Sea Ice to completely detach from any coastal land, so that it would be possible to circumnavigate the sea ice, without also circumnavigating land.

aslan

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Re: The caa-greenland mega crack
« Reply #34 on: August 01, 2019, 03:49:19 PM »
Sea state is the sum of wind waves and sweel. And swell from Atlantic can be quite long even in summer. If swell from Atlantic can reach Greenland coast -and this is almost the case now-, you don't need a great fetch.

pearscot

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Re: The caa-greenland mega crack
« Reply #35 on: August 02, 2019, 01:22:37 AM »
I had a spare moment at work and made this hella ghetto analysis of the crack above Greenland, it's over 7,202 square miles.

edit: I feel like that value is just wayyyy too large, but then again Greenland is huge so I don't know. If anyone thinks it is wrong, please let me know.

« Last Edit: August 02, 2019, 01:28:58 AM by pearscot »
pls!

be cause

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Re: The caa-greenland mega crack
« Reply #36 on: August 02, 2019, 01:43:21 AM »
Pearscot .. is that area or extent ? b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

philopek

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Re: The caa-greenland mega crack
« Reply #37 on: August 02, 2019, 01:55:54 AM »
Pearscot .. is that area or extent ? b.c.

I think pearscot meant the open water that is neither area nor extent but open water.

Hope that I'm not wrong but cant's see another meaning at the moment ;)

petm

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Re: The caa-greenland mega crack
« Reply #38 on: August 02, 2019, 02:01:09 AM »
7k sq. mi. looks about right to me for the Greenland segment (>300 x 20 mi).

pearscot

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Re: The caa-greenland mega crack
« Reply #39 on: August 02, 2019, 02:05:12 AM »
Pearscot .. is that area or extent ? b.c.

I think pearscot meant the open water that is neither area nor extent but open water.

Hope that I'm not wrong but cant's see another meaning at the moment ;)

yes, my bad for any confusion - I just calculated the area in square miles for open water in that section above Greeland based on a polygon I created from a screenshot which I georeferenced.
pls!

be cause

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Re: The caa-greenland mega crack
« Reply #40 on: August 02, 2019, 02:06:36 AM »
sorry philopek .. it was an attempt at humour .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

philopek

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Re: The caa-greenland mega crack
« Reply #41 on: August 02, 2019, 02:22:09 AM »
sorry philopek .. it was an attempt at humour .. b.c.

That's the risk always ;)

Recommending to hint at least a tiny bit, else it's kind of roulette and since I'm luckily in love for decades I generally have bad luck with gambling ;) ;) ;)

[JK]
 


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Re: The caa-greenland mega crack
« Reply #42 on: August 02, 2019, 11:38:45 PM »
Pearscot .. is that area or extent ? b.c.
add emoticon :)

aslan

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Re: The caa-greenland mega crack
« Reply #43 on: September 03, 2019, 06:42:42 AM »
This topic has drowned into the abyss of this forum, but the mega crack is still here and alive. And there is still sign of melt going on. To justify, Kap Moris Jesup hit 10.3°C the last day of August, a record for this time of year. And to the the North of Ellesmere, the Nares strait export has lead to a big, big hole. Fortunately the season is ending.

blumenkraft

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Re: The caa-greenland mega crack
« Reply #44 on: September 03, 2019, 06:48:40 AM »
Aslan, the polynya in Lincoln is not caused due to export through Nares. It's caused by winds blowing north. No ice was exported through Nares for months.

Check this post for a GIF showing it. >> https://forum.arctic-sea-ice.net/index.php/topic,176.msg224602.html#msg224602
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binntho

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Re: The caa-greenland mega crack
« Reply #45 on: September 03, 2019, 07:04:07 AM »
Aslan, the polynya in Lincoln is not caused due to export through Nares. It's caused by winds blowing north. No ice was exported through Nares for months.

Check this post for a GIF showing it. >> https://forum.arctic-sea-ice.net/index.php/topic,176.msg224602.html#msg224602

That actually looks very interesting, that "plume" of open water stretching into the Lincoln sea. Looking back on Worlwiew and Nullschool, one can see how a large area opens up when the intense cyclone over the Beaufort pulled warm air up over the CAA and particularly, one guesses, throught the Nares. The following animation shows the opening and impeding closure of the Lincoln open ocean area.

Requires a click
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aslan

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Re: The caa-greenland mega crack
« Reply #46 on: September 03, 2019, 07:17:06 AM »
Yes, it was bad wording on my part, not reflecting what I was actually thinking. It was more like, there was a strong preconditioning earlier with the lack of blocking in Nares strait, and now winds have an easier job.

blumenkraft

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Re: The caa-greenland mega crack
« Reply #47 on: September 03, 2019, 07:21:36 AM »
No worries, Aslan. :)

I wonder why there is no export. In winter with closed sea ice, there is a strong current southward. In summer, when the ice is cracked and mushy, the current stops. Why is that? Is a homogeneous ice cap causing some kind of pressure or what?
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P-maker

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Re: The caa-greenland mega crack
« Reply #48 on: September 03, 2019, 07:53:50 AM »
Blumenkraft,

Every year in the freezing season, the volume of the Arctic sea surface expands by roughly 10 percent (due to the fact that density of sea ice is lover than that of sea water). If everything (including air pressure and sea level) remains constant, something will have to give in. Thus, when it's freezing in the Arctic, we will most of the time have southbound flows in the various straits. When it's melting, the opposite (deeper) flows will dominate.

It may be possible for some clever guy to come up with a simple indicator based on these principles.

Please enjoy the southward flowing ice as long as you can...

aslan

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Re: The caa-greenland mega crack
« Reply #49 on: September 03, 2019, 03:05:44 PM »
Yes, the conditions are more suitable for ice export in Winter, mostly due to variation in sea surface elevation :

Our model results based on 26-years of simulation with monthly output demonstrate that SSH gradients (calculated between two points north and south of each passage, which are denoted with asterisks shown in Figure 12) do explain the annual peak volume fluxes (around March) through both Nares Strait (Figure 14a) and Lancaster Sound (Figure 14b). The volume flux anomalies and SSH gradient anomalies are also highly correlated. Volume flux anomalies through Nares Strait (Figure 15a) and anomalies of the SSH gradient (measured from the Lincoln Sea to Smith Sound) (Figure 15b) were highly correlated (R = 0.89). Volume flux anomalies through the mouth of Lancaster Sound (Figure 15c) and anomalies of the SSH gradient (measured between the Queen Elizabeth Islands and western Baffin Bay) (Figure 15d) were also highly correlated (correlation R = 0.85).

https://pdfs.semanticscholar.org/870a/ad3242a2f319c69031342c9cedfa291df51e.pdf