The Nares Strait thread

[b_lumenkraft]

I don't think though, there is a (strong) current ATM because when there is, the floe movement is normally confined to the right side of the strait.

Now that the current is back, you can see open sea all along the left side with the exception of Franklin of course.  Interesting phenomenon i think.

I can't help thinking Franklin and hydraulic jump have something to do with it.

[b_lumenkraft]

Huge melt event in Kane Basin.

27.06. 20:48h to 30.06. 08:00h UTC

M8 Band

[b_lumenkraft]

Huge melt event in Kane Basin.

Looks like this in Sentinel with return [B8A*1,B03*1,B02*1]

Blue = Liquid

[anaphylaxia]

Nares Strait export now chugging along its theoretical maximum, with the whole Kennedy Channel filled with rounded rubble from Lincoln. And the big chunk is right about to enter the strait. Any chance of a guesstimate on area or volume export?

[b_lumenkraft]

What's the theoretical maximum, Anaphylaxia?

[anaphylaxia]

Well, i just meant that practically the whole Kennedy Channel is full of flowing debris. The event started at June 22, when a small blockade burst in Hall Basin and its been interrupted by Hans Island just on the 28 th, until then it was flowing at the maximum speed, not hindered by obstacles, so it should be near the theoretical maximum ice carrying capacity of the current. I was interested in if anyone has crunched the numbers on this.

[b_lumenkraft]

... not hindered by obstacles, so it should be near the theoretical maximum ice carrying capacity of the current ...

Oh, ok. That makes sense. I understand your question now.

Sorry, i can't answer it correctly though. The speed of the current variates widely.

The counter-clockwise velocity shear of southward ocean currents in Nares Strait is present both at the surface and below the surface even when the winds are in the opposite, northward direction. This velocity difference across the channel forms a gyre in both Hall and Kane Basins. Velocity differences of 0.2 m/s over 20-40 km are not uncommon. They emerge most clearly after the much larger tidal currents are removed.

Link >> https://icyseas.org/2012/07/27/currents_winds_nares_strait_ice_arches/

[Tor Bejnar]

The fastest I've watched a floe go from top to bottom is, IIRC, seven days.  (Nares Strait is 500 km long, so 70 km/day average, but always slower near the northern end [maybe 30 or 40 km/day]).  It is about 70 km from Nares' northern entrance to the top of Hall Basin.

So how many days did floes take to go that first leg this week?

I recall the fastest movement, therefore greatest area (~volume), is transported in December.  If it was up to me, I'd prefer attempting to run a marathon (or 12 in a row!) in December, rather than in July!  (But I suspect a floe has a different set of 'cares', just the same results!.  )

[be cause]

for old times sake .. have a look back to 2012 on Worldview .. this is the week Nares opened and the view is good !   Perfect time to see w2016 as well .. breakup slower but just starting now .
  ! am using the meltpond blue with Nares tilted to lie across the screen in the 50km zoom . It is a thing of beauty . b.c.

[magnamentis]

end of the story

more contrast shows more cracks and ruptures but this one is severy meters wide and visible with naked eyes and without any filters applied.

as i said up-thread, collision imminent, now 1st impact happened with this result so we know what to expect upon further touch-downs

[Alphabet Hotel]

Animation of radar images from http://ocean.dmi.dk/arctic/lincoln.uk.php
Jun 24-27, 29, two frames from July 01. I guess both satellites got an image today.

[oren]

Thanks AH. It seems the Nares export machine is at the top of its game. The whole Lincoln Sea is being sucked down into the abyss.

[Sam]

Well, with She now broken into bite sized chunks, any thought that the export of ice through the Nares might slow or be blocked this year are surely gone.

The former thick ice has been demolished and the majority exported through the Fram, the Nares, or the grinder in the abeaufort.

We now enter the seeming pinch in extent from July 2 until August 2. Does that still hold this year? Or will we now see a strong downward deviation earlier than any other year?

With so much thick ice demolished and such enormous heat inputs into the Arctic, I for one certainly wouldn't bet that the pinch in extent holds. And if it doesn't, we could well set new records this year. The next month may well tell the tale.

Sam

[b_lumenkraft]

Well, with She now broken into bite sized chunks, any thought that the export of ice through the Nares might slow or be blocked this year are surely gone.

We can always hope for another current interruption. Sad we don't know what caused it but it's not irrational to think it can happen again.

We now enter the seeming pinch in extent from July 2 until August 2. Does that still hold this year? Or will we now see a strong downward deviation earlier than any other year?

All ice is bits and pieces in Lincoln. As long as there is a current, we'll lose a lot of ice this way. But IMHO summer export is not the unusual figure here. The real harm was done last winter.

[wallen]

All ice is bits and pieces in Lincoln. As long as there is a current, we'll lose a lot of ice this way. But IMHO summer export is not the unusual figure here. The real harm was done last winter.

I would not underestimate the impact of Nares Strait, going forward. With so little MYI left, the longer it continues to pull ice out of Lincoln Sea, the poorer any winter recovery will be.  Actually a poll on when Nares strait stops flowing this year could  be very interesting. That is , IF it does stop flowing.

[b_lumenkraft]

I think this is a good poll idea, Wallen.

Make sure "It will not close at all" is an option to choose from.

Re: underestimating

It wasn't my intent to downplay the role of the summer extent loss via Nares. Only in comparison to other summers with an open strait, i can't see why there would be more export this year. The floes might be smaller this year, but i don't know if this influences the flowing speed. I think the current speed is the main driver here, not floe size.

[Rich]

Nares Strait export now chugging along its theoretical maximum, with the whole Kennedy Channel filled with rounded rubble from Lincoln. And the big chunk is right about to enter the strait. Any chance of a guesstimate on area or volume export?

If you go back in the thread a few months, there's an estimate of ~ 1km3 per day volume flowing through the Strait.

Iirc - the known element was the width of the opening. The assumptions were something like 75% capacity through the opening and 3m ice thickness. 
 
It's a SWAG, not anything official.

The takeaway is that Nares being open for an extra ` 4 months is quite meaningful.

[gerontocrat]

I was trying to find some background data on when the CAA might open up (& therefore the NW Passage) and came across a paper

 https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/jgrc.20330
The Canadian Arctic Archipelago throughflow in a multiresolution global model : Model ssessment and the driving mechanism of interannual variability July 2013

and I read

5. Driving Mechanisms of Volume Flow Through
the CAA
5.1. The Role of Sea Surface Height
[39] The SSH difference between the Arctic Ocean and Baffin Bay (Figure 7b) not only leads to a net outflow from the Arctic Ocean, its variability also drives the variation of the CAA throughflow. Annual mean volume transports though Lancaster Sound and Nares Strait are significantly
correlated with the along strait SSH gradients

and that is just the first few words that a long time later end up with....

The variability of the CAA transports is related to the large-scale atmospheric forcing pattern characterized by the NAO. Responses to the positive and negative phases of the NAO can be observed both in the Beaufort Sea and in the Labrador Sea. In the positive NAO phase, the atmospheric circulation over the western Arctic Ocean is mainly in the cyclonic phase [see, e.g., Proshutinsky et al., 2002], leading to a loss in the freshwater storage in the Beaufort Gyre and an increase in SSH along the American coast, and thus increased volume transport through Lancaster Sound. In the Labrador Sea the strong cooling during the NAO positive phase results in low sea level, which propagates northward along the west Greenland coast and leads to higher
transports through Nares Strait and Lancaster Sound.

You clever people can tell me what's with the NAO this year.

[b_lumenkraft]

What's your conclusion to what to look at Gerontocrat?

I was looking at SSH at Mercator in order to see if i can spot something. But i looked at short periods of time. According to that, the pattern only becomes clear when you watch longer periods, do i interpret that right?

[gerontocrat]

What's your conclusion to what to look at Gerontocrat?

I was looking at SSH at Mercator in order to see if i can spot something. But i looked at short periods of time. According to that, the pattern only becomes clear when you watch longer periods, do i interpret that right?

Longer-term, I thought, but then...
https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml

See attached.

If the NAO is +ve, the sea level differential increases and flow increases.
But the NAO has been and is looking somewhat -ve.

That would tend to low flows through the Nares and other CAA channels? (all other things being equal (which they never are)).

[be cause]

    Some reports talk of Nares 'opening' in March . It never closed . There was a brief break from export of multi-year ice but even then first year ice continually formed and was exported . b.c.
 

[gerontocrat]

    Some reports talk of Nares 'opening' in March . It never closed . There was a brief break from export of multi-year ice but even then first year ice continually formed and was exported . b.c.

Just to clarify my post was about the current, the flow, going down the Nares.

Two things are required for ice export from the Nares, mobile ice, and flow of water.

We saw what happened when we had the ice but not the flow over the last couple of weeks. "She", like many an abandoned redundant wooden warship, just rotted at the entrance to the Strait.

When the Nares is blocked by the Arch or big stuff stuck in the strait itself, the flow does not stop. It just does not move the ice, no matter how strong the flow.

[b_lumenkraft]

What's your conclusion to what to look at Gerontocrat?

I was looking at SSH at Mercator in order to see if i can spot something. But i looked at short periods of time. According to that, the pattern only becomes clear when you watch longer periods, do i interpret that right?

Longer-term, I thought, but then...
https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml

See attached.

If the NAO is +ve, the sea level differential increases and flow increases.
But the NAO has been and is looking somewhat -ve.

That would tend to low flows through the Nares and other CAA channels? (all other things being equal (which they never are)).

The only thing standing out here is the spike mid to end April. How would this cause a disturbance in surface current almost 2 months later?

Another thing to consider: Throughflow must not necessarily correspond with the surface current. We don't know if the current deeper down also stopped. Observations (i.e. Kane gyre still active) indicates the opposite imho.

[gerontocrat]

Most science papers about the Arctic start and end talking about the sparsity of data, need for more research etc etc.... I suppose they can't say - "We've not a bleeding clue of what's going on".

EDIT: Note, and inwardly digest, the phrase "all other things being equal"

[b_lumenkraft]

[johnm33]

"We can always hope for another current interruption. Sad we don't know what caused it but it's not irrational to think it can happen again."
Iirc there was a prolonged period of high mslp to the north and a shorter period of low mslp towards Labrador, so an exageration of the norm, when things returned to near average conditions the gradient took a while to recover.
Just now the atmospherics are enhancing flows in from both A.+P. so don't hold yer breath.
https://earth.nullschool.net/#current/wind/surface/level/overlay=mean_sea_level_pressure/orthographic=-0.08,87.17,512

[b_lumenkraft]

Wasn't sure if i understood you correctly, so i made a GIF for mslp in June. You might be onto something here.

For the record, the surface current interruption lasted roughly from 12.06. to 20.06.

[johnm33]

Nice gif, but go back a couple of weeks to see prolonged.

[b_lumenkraft]

14.05. to 20.06.

John, you are talking about that purple blob over Lincoln in the last frame?

[b_lumenkraft]

She completely in pieces now.

[johnm33]

"John, you are talking about that purple blob over Lincoln in the last frame?"
More the light area/high in the arctic lasting so long, from before the full moon on the 18th may until past the new on the 2nd, bear in mind I think the currents act a little like slime at this scale, so once established it takes on a life of it's own until something disrupts the flow, or it runs out of 'steam'. The low over Beaufort around the 12th coupled with the high in Baffin/Labrador may have been just such a disruption, and the low around the 20th reset the gradient, so to speak. Right now the lows are making it easy for tidal surges to pass north of Iceland-Faroes so building up pressure to drive Atlantic waters up onto the shelf beneath Barents, and through the Fram, whilst something similar is happening on the Pacific side, so the currents, I guess, are accelerating through CAA/Nares and back through Fram nearer the surface and will do for at least a couple of days.

[b_lumenkraft]

Thanks, John. I think i understand now. Will keep an eye on it.

[Alphabet Hotel]

Animation of radar images from http://ocean.dmi.dk/arctic/lincoln.uk.php
June 25-27, 29, July 01-02.

[BenB]

Having watched some of these large floes attempt, and occasionally fail, to make it through Nares, I've realised that the export is generally not steady at all, but rather unsteady, like a drunken person lurching and stumbling from side to side, sometimes dashing wildly ahead, sometimes stopping to prop themselves up on a wall (or Hans Island), sometimes spinning in circles, and sometimes collapsing into a heap before they even get properly going.

[b_lumenkraft]

Ben, that's gyres and tidal waves you are seeing.

The counter-clockwise velocity shear of southward ocean currents in Nares Strait is present both at the surface and below the surface even when the winds are in the opposite, northward direction. This velocity difference across the channel forms a gyre in both Hall and Kane Basins. Velocity differences of 0.2 m/s over 20-40 km are not uncommon. They emerge most clearly after the much larger tidal currents are removed.

Link >> https://icyseas.org/2012/07/27/currents_winds_nares_strait_ice_arches/

[BenB]

Thanks, B_lum, I imagined it was that kind of thing, but your link and quote are very helpful. I was mainly just playing with an image that came into my head in relation to steady/unsteady flow through Nares.

Anyway, I have a question for all you Nares experts:

How does this season compare with other recent seasons? Yes, Nares opened early or never closed, but is the overall export significantly higher than in other seasons? Is there any good way to quantify it?

[b_lumenkraft]

Not that someone measured it, but given the fact we had export almost all of the time, i'm sure the statement "way above average" can't be so wrong.

[BenB]

Thanks, B_lum, that's what I suspected, but I don't follow it as closely as you (and others) do.

[b_lumenkraft]

Welcome, Ben.

[b_lumenkraft]

Kane Basin, 28.06. to 02.07.

Note how the melt ponds on the landfast ice (bottom left) are draining. If i understand the processes there correctly, it should be gone soon due to thinning (2-3 days perhaps? idk!).

[BenB]

I think I can help you with that one. The scientific answer is "it varies". I imagine it depends on the internal structure of the ice when exactly the melt ponds drain during the thinning process, but sometimes the ice manages to hang on for quite a long time afterwards. Other times it disappears very soon. I would say that 2-3 days is the earliest, but some of that ice could hang around for up to 2 weeks. Obviously local conditions play a part in how it progresses.

[oren]

Surely the overall export is much higher than in other years, as 3 whole months of export went by. But how to quantify it? Maybe some powerful automated image processing, tracking floes in the Robeson Channel (northern end of the strait).

[b_lumenkraft]

Kane Basin in recent days was relatively cloudless so i did what i do, i made a GIF.

You can see the Kane gyre getting bigger with the current getting stronger. In the last frames, you can see a bulk of former stuck-in-the-north floes arrive in Kane.

[BenB]

Great GIF.

[b_lumenkraft]

Thanks, Ben.

[Tor Bejnar]

How does this season compare with other recent seasons? Yes, Nares opened early or never closed, but is the overall export significantly higher than in other seasons? Is there any good way to quantify it?

Further to Ben's question, I've read that in 2007 when Nares never closed, export through Nares Strait was about 10% of the export through Fram Strait.  Some years it is closed for most of half a year ( approximately January through June). 

Someone commented 'recently' that, probably, a significant affect an open-during-the-winter-and-spring Nares Strait has is on the Arctic Ocean above the Lincoln Sea.  Typically, the north end of the entire Western Hemisphere coastline acts as a wall for ice to build up on.  With Nares open, there is a zone that repeatedly collapsed.  For one, many floes that would have piled up on each other, making thick ice, didn't do that in this section, and, in fact, got exported instead.

For several reasons the ice north of the Canadian Arctic Archipelago (CAA) is the thickest in the Arctic, and Nares Strait drains from this part of the Arctic.  With the transpolar transport very active this year (since last October) (unlike most years, and unrelated to Nares openness), sending ice to various Atlantic graveyards, a great deal of the thickest ice in the Arctic isn't there right now.

[BenB]

Thanks for those thoughts, Tor. I was aware that you lose some of the thickest, oldest ice in the CAB through Nares, so the impact could be greater than the mere numbers suggest, but I hadn't considered the fact that an all-year open Nares potentially also prevents the build-up of thick ice.

[b_lumenkraft]

but I hadn't considered the fact that an all-year open Nares potentially also prevents the build-up of thick ice.

Me neither! Thanks, Tor.

[b_lumenkraft]

Since tidal waves are kinda smoothed out in the last GIF, here a GIF showing the latest one.

[Stephan]

This is just an idea or a proposal.
Wouldn't it be useful to quantify the Nares export (preferably volume- and not area-wise), maybe at its NE entrance and its SW mouth just like it is performed with the Fram Strait export? I know this is a lot of work, at least if you go into the past. But maybe it is an interesting topic for a scientific work. Maybe fundamental data like average temperature, average SSH or preferable wind patterns in that year/season should be added to get a better picture what the drivers of Nares export are.