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Author Topic: When will we see open ocean at the north pole?  (Read 80733 times)

Peter Ellis

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Re: When will we see open ocean at the north pole?
« Reply #100 on: August 17, 2013, 08:59:34 PM »
Not really a polynya either, but it is open pack ice rather than close pack ice. Uncommon near the Pole, but not unprecedented: see for example 2010
http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/?subset=Arctic_r04c03.2010250.terra
(Pole at bottom right)
http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/?subset=Arctic_r04c04.2010230.terra.1km
(Pole at bottom left)

Wipneus's homebrew calculations have us at almost exactly the same compactness as 2012 - this is using the ARTIST algorithm that's much less confused by melt ponds, and so is a true measure of divergence (unlike the apples-to-pears CAPIE metric).

I don't think this year is nearly as unusual as some people here are claiming.  Overall divergence is much the same, it's just that the pattern is different, with some of the diffuse areas at higher latitudes.

danp

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Re: When will we see open ocean at the north pole?
« Reply #101 on: August 17, 2013, 09:56:07 PM »
Thanks Peter!

Since my processing of this summer has obviously been cherry-picked towards exciting events, I've been hoping to find time to go back and find analogous events in the past for comparison.  I will start digging through swaths around that date to find the most open water right then and see what the n pole looks like, at least to have something to compare this year to.

Ideally I could use those 8-day composites (once I fill in past years) for fair comparisons of things like this but to be honest I find the small-scale detail over ice to be pretty bad.  I believe it comes from a combination of reprojection distortion and that the algorithms are optimized for land where features are not changing on a daily basis.

-Dan

Vergent

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Re: When will we see open ocean at the north pole?
« Reply #102 on: August 17, 2013, 11:02:53 PM »
Dan,

An easy way to scan the recent past is on Neven's concentration maps page.

https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0813

The big difference between now and 2010 is ice thickness in the low concentration areas.

Vergent

jdallen

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Re: When will we see open ocean at the north pole?
« Reply #103 on: August 18, 2013, 05:33:55 AM »
Not really a polynya either, but it is open pack ice rather than close pack ice. Uncommon near the Pole, but not unprecedented: see for example 2010

I don't think this year is nearly as unusual as some people here are claiming.  Overall divergence is much the same, it's just that the pattern is different, with some of the diffuse areas at higher latitudes.

I'll respectfully disagree with you Peter.  What we're seeing in 2013 is a lot more dispersed, over a much larger area, than 2010.  But even then, 2010 is exceptional in its own way, and represents a significant departure from pre-2000 ice.  I still think what we are seeing is unprecedented.
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no1der

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Re: When will we see open ocean at the north pole?
« Reply #104 on: August 18, 2013, 06:32:45 AM »
I'm struck by the bimodal grain-size distribution of much of the low-concentration ice. There is a population of large very round and abraded floes, and another of much smaller debris.

That grain-size spectrum should contain information regarding the responsible processes. Sedimentologists and materials scientists who deal with abrasive grain-size reduction processes might have some insights and applicable models.

If visibility will ever allow, it might be interesting to look at the individual trajectories of the larger rounded bits in some region. I suspect they will not all be traveling in exactly the same direction. I wonder if the momentum and (possibly)  various trajectories, imparted by a passing cyclone might eventually decay into a sort of Brownian motion as the ice churns and mills itself to smaller and smaller bits.

At least, the rounding of the remaining larger floes implies that there is a mechanical grain-size reduction process at work, in addition to the melting.
« Last Edit: August 18, 2013, 06:42:24 AM by no1der »

jdallen

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Re: When will we see open ocean at the north pole?
« Reply #105 on: August 18, 2013, 07:16:48 AM »
I'm struck by the bimodal grain-size distribution of much of the low-concentration ice. There is a population of large very round and abraded floes, and another of much smaller debris.

That grain-size spectrum should contain information regarding the responsible processes. Sedimentologists and materials scientists who deal with abrasive grain-size reduction processes might have some insights and applicable models.

If visibility will ever allow, it might be interesting to look at the individual trajectories of the larger rounded bits in some region. I suspect they will not all be traveling in exactly the same direction. I wonder if the momentum and (possibly)  various trajectories, imparted by a passing cyclone might eventually decay into a sort of Brownian motion as the ice churns and mills itself to smaller and smaller bits.

At least, the rounding of the remaining larger floes implies that there is a mechanical grain-size reduction process at work, in addition to the melting.

Thank you for the observation no1der.  It actually crystallizes a thought on my part when considering the ice.

I've noticed earlier on Lance Modis, in areas about to melt out en masse.  For example, consider this shot of the Beaufort:

http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r05c02.2013229.terra.250m

If you note the ice off of Banks Island, you'll see large expanses of it appear to be 100% concentration. However, it has a texture and color very much different from ice towards the center of the pack.  You'll also notice that at the periphery, where it is breaking up, it is for the most part separating into far smaller individual units than other portions of the pack where we have large expanses opening up around a relatively limited number of larger, rounded floes. When I look at it, I find myself thinking of froth at the edge disturbed water.

I really wish we could get a closer look at it, as I suspect it is mostly very small, fairly thin floes which have been concentrated by wind into a small area, and which are rotten and very close to a complete melt out, which will leave a few larger, thicker flows isolated in open water.  I think we'll see a lot of this played out over the next two weeks, even with the melt season winding down.
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Pmt111500

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Re: When will we see open ocean at the north pole?
« Reply #106 on: August 21, 2013, 05:53:11 AM »
stiched & a bit adjusted Modis 20.08.2013 (25km rings). no clearance this year, I dare to say. A ship captain should see ~half way to the second ring unless he's a flat-earther in which case he might shout that the 'whole ocean is half full of ice!'

PeterCranie

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Re: When will we see open ocean at the north pole?
« Reply #107 on: August 21, 2013, 09:08:42 AM »
Thanks all for replies. I'll resume lurking but thank you to everyone contributing knowledge here.

danp

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Re: When will we see open ocean at the north pole?
« Reply #108 on: August 21, 2013, 11:26:20 AM »
Nice Pmt!  Here's a grayscale ch. 1 grab again from swath day 232 (Aug 20), 0500 UT:

5 km (20 pixel) diameter circle this time.

Santa has got to be pretty uncomfortable on that rubble.

Chuck Yokota

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Re: When will we see open ocean at the north pole?
« Reply #109 on: August 21, 2013, 01:23:33 PM »
I posted an image of the North Pole yesterday on the "Arctic image of the day" thread. that I had grabbed about 15:40 GMT.


Pmt111500

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Re: When will we see open ocean at the north pole?
« Reply #110 on: August 21, 2013, 05:58:07 PM »
 
Quote
that I had grabbed about 15:40 GMT.
yes I know there are plenty swaths covering the pole but mixing modis mosaic and world view images gives a bit additional headache for the rotation of the projection. additionally, i usually start with the 250m px images and the final step is reducing the image size 2*/4*/5* according to the use and original size... here's what I got from your grab (size reduced by 2)

werther

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Re: When will we see open ocean at the north pole?
« Reply #111 on: August 28, 2013, 11:37:21 PM »
The quest to document ice quality took another evening over my CAD screen.

This is the SE quadrant with a radius of 50 km on the North Pole today on MODIS.



For 27 August CT showed this at about 65-70% concentration. What UB supposes for 27 August is hard to tell, because their Pole-hole is large (radius about 100 km). But both to the W and E adjacent swaths are yellow and green, also suggesting 65-70% concentration.

As you can see, I’ve digitized polylines around obviously unified floes. As their reflection fades over about three pixelwidths, the lines are arbitrary. That’s what should be kept in mind when interpreting the CAD-numbers.

What did the program find?

The area covered by the quadrant is app. 1964 km2. There were 177 surfaces, the smallest just about pixel-width covering  about four soccer-fields. The biggest were undivisible stretches but obvious thick packed rubble. When these two swaths are set apart, the largest floe is app. 70 km2, the average of the lot is under 4 km2.

CAD found 982 km2 ice, about 50%.

As the total edge-length is app. 1440 km1, the possible uncertainty through the fading can be fathomed. Given the half of the fading zone, it could be as much as 500 km2.
I presume the fading zone might feature small rubble, nilas e.o.

The area that is open for sure is at least around 500 km2.

When would have been the last time to have shown so much open water over a relevant distance?

BTW, when counting in the fading-zone, both UB and CT are quite accurate over the place today...

TerryM

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Re: When will we see open ocean at the north pole?
« Reply #112 on: August 29, 2013, 07:41:31 AM »
Every time we get a peek between the clouds it scares the holy hell out of me. I can't help but think that PIOMAS is having real difficulties when the ice is hollowed out this way. The season is too late for this to play itself out, but if something similar should occur next year a little earlier in the season I think we'll be in big trouble.
Terry

jdallen

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Re: When will we see open ocean at the north pole?
« Reply #113 on: August 29, 2013, 08:09:43 AM »
Every time we get a peek between the clouds it scares the holy hell out of me. I can't help but think that PIOMAS is having real difficulties when the ice is hollowed out this way. The season is too late for this to play itself out, but if something similar should occur next year a little earlier in the season I think we'll be in big trouble.
Terry

You very much echo my own sentiments, TerryM....
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