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Author Topic: Drift, Deformation and Fracture of Sea Ice  (Read 63955 times)

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #50 on: December 29, 2013, 02:50:33 PM »
Having reached about 74ºN on Dec 1 the N Pole webcam appears to have given up reporting its position

IMB 2013E (supposedly 1500 m from the webcams) looks to be on its last legs, but is still reporting its position occasionally. It travelled 77.3 km on Christmas Day, a new daily distance record. It's now at 68.87ºN.
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Polynya88

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #51 on: December 30, 2013, 02:45:20 PM »
comparing IR images from the Lincoln Sea, the size of floes and pattern of breaking looks different from last year. Could this be an indication that ice is indeed thicker? I am keeping an eye on this to get some experience of relating the various sources of information, i.e. modelled  / satellite based thickness to the way the ice behaves.
seehttp://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201312241310.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201212191241.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201301100352.NOAA.jpg


Seasons greetings, all;

Andreas, I don't think we can draw that conclusion, only that there appear to be fewer wide leads in one or the other.  That may be more an effect of persistent wind direction than the ice itself.

Happy New Year to all;
The larger features around the Lincoln Sea could be partly related to the Arctic Ocean being "more consolidated" than normal due to colder water and ice temperatures this year. Note in the attached Ice Chart the large area of Second-year ice, which also extends well into the Russian sector; incomplete melt supports rapid freeze-up and extensive consolidation (larger floes).

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #52 on: January 31, 2014, 08:51:55 AM »

.....
Also, as related to the dark patch over Nares Strait, that looks like low-cloud/fog. It is common there where super cold dry air from the polar pack drifts over the mostly Open Water area. This also explains why it is always there regardless of sun angle.
Coming back to this discussion on this thread some time ago, there is an interesting feature in recent images from the north east of Greenland
http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/201401180718.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/201401271350.NOAA.jpg
the dark (i.e. relatively warm ) fog in can be seen to cover valleys and lower mountain sides in the image from the 27th.

jdallen

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #53 on: January 31, 2014, 09:21:34 AM »

.....
Also, as related to the dark patch over Nares Strait, that looks like low-cloud/fog. It is common there where super cold dry air from the polar pack drifts over the mostly Open Water area. This also explains why it is always there regardless of sun angle.
Coming back to this discussion on this thread some time ago, there is an interesting feature in recent images from the north east of Greenland
http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/201401180718.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Joekelbugt/201401271350.NOAA.jpg
the dark (i.e. relatively warm ) fog in can be seen to cover valleys and lower mountain sides in the image from the 27th.

Not surprised considering the 10-20C positive anomalies we have been seeing recently.
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Laurent

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #54 on: May 29, 2014, 05:23:53 PM »
Ocean waves influence polar ice extent
http://www.bbc.com/news/science-environment-27591369

Anne

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #55 on: May 29, 2014, 10:22:56 PM »
This should go in Stupid Questions. Surely the greater amount of open water, the greater potential for wave amplification? And subsequent damage to the ice pack? But where does that energy go when the water is covered by ice? Sure, it produces these parallel fractures, but how much does the ice pack actually damp the forces?

Laurent

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #56 on: May 29, 2014, 10:53:16 PM »
I am not a specialist Anne but I think part of your question was in the text :
Quote
For smaller waves, less than 3m in height, the bobbing induced in the floes quickly decayed. But for waves over 3m, the disturbance sent propagating through the pack ice was sustained for up to 350km.

I would think the energy goes into moving the water below the surface, dissipating by increasing the temperature (slightly).

Anne

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #57 on: May 29, 2014, 11:23:38 PM »
Yup, Laurent - but what is the effect of greater open water?

Anne

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #58 on: May 30, 2014, 12:06:26 AM »
As I said, this really should be in Stupid Questions but I'm also thinking of wind, which with an icepack wouldn't interact directly with water.

Laurent

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #59 on: May 30, 2014, 09:12:53 AM »
I am waiting someone else to answer your question but my guess is that the more open water the higher the amplitude of the waves. For the winds on the ice sheet, I would think that for a thickness above one meter there is no wavy effect, it just moves the ice.

icefest

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #60 on: May 30, 2014, 09:18:59 AM »
A couple other discussions on the topic: http://www.antarctica.gov.au/about-antarctica/people-in-antarctica/diaries-and-stories/spotlight-on-the-sea-ice/measuring-waves-in-the-sea-ice
Open other end.

DoomInTheUK

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #61 on: May 30, 2014, 10:49:54 AM »
Anne,

The area of open water that the wind blows across is known as the fetch. The larger the fetch, then more energy gets stored in the movement of the water. This energy comes from slowing the wind down, so an ice covered Arctic would have higher average wind speeds than an open ocean Arctic.

Initially the wind across the surface of water will produce small ripples, this roughens the surface and so small waves appear. These waves provide a rougher surface that better grip the wind, and so impart more energy into the water. The longer the wind blows, and across greater distances, the more energy is imparted to the water - and it can be huge amounts of enery. Storm waves can have many Megawatts per meter of wave front.

Short wavelength waves can have a massive pounding effect around the edges of the ice pack, the energy being dissapated by damping effect of breaking and grinding the ice against itself.

The trouble is that waves can only reach a certain hight before they become unstable, a function of water depth, wind speed and other factors. Adding more wind energy into the waves will not produce bigger waves but instead will start to induce long term waves known as swells. Once the fetch gets into a distance of hundreds of miles or more then these swells will travel pretty much as far as there is water. Thousands of miles in some cases - swells from storms off Argentina can be measured off the coast of the UK and Ireland and even Iceland.

Once the open ocean of the Arctic has a large enough fetch to produce a good swell, then that wave will travel for hundreds of miles into the ice-pack, fracturing as it goes. Moving the ice up and down has almost no dampig effect, it's only the fracturing and small amount of grinding that that induces that will use up the waves energy. The huge amount of eneregy and the long wavelength of these swells means that the energy will be disappated across a very large area of ice.

The waves also have an effect deeper down. The effect of a wave can be mesured to a depth of twice it's wavelength. The water within any wave doesn't move along with the wave, but simple goes around in a vertical circular motion. This has a mixing effect on deeper waters and so helps break up the thermocline - layers of different temperature water.

An ice free Arctic is a totally different place to an ice covered one. The ice provides such a calming influence to the whole basin, and not just it's surface.

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #62 on: May 30, 2014, 01:32:48 PM »
We're drifting slightly off the original topic here, but as a surfer I've been following storms around the planet for decades now (on screen, not physically!):

http://econnexus.org/tag/surfing/

Until recently the distance across any open water in the Arctic has been insufficient for much of a swell to develop, which is of course very different to the situation in the Antarctic. Here's an FAQ on how the physics works:

http://www.stormsurf.com/page2/tutorials/wavebasics.shtml
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ritter

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #63 on: May 30, 2014, 05:51:38 PM »
Anne,

This was posted elsewhere and may be related to your question:

Big Waves Bust Up Sea Ice, May Be Playing Role in Melt
http://www.climatecentral.org/news/big-waves-sea-ice-climate-17490

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #64 on: May 30, 2014, 06:24:29 PM »

The waves also have an effect deeper down. The effect of a wave can be mesured to a depth of twice it's wavelength. The water within any wave doesn't move along with the wave, but simple goes around in a vertical circular motion. This has a mixing effect on deeper waters and so helps break up the thermocline - layers of different temperature water.

An ice free Arctic is a totally different place to an ice covered one. The ice provides such a calming influence to the whole basin, and not just it's surface.

This is a topic that I am very interested in. As the Arctic becomes increasingly ice free, what are the impacts on the thermocline and salinity layers.

I have been always fascinated by the Black Sea due to its unique ecology driven by a stable thermocline and salinity layers.

http://blacksea-education.ru/e2.shtml

I've posted this link on the Black Sea as something to be quickly scanned to understand how this unique ecology maintains its stability.

While the processes are different, there is also a unique Arctic thermocline and salinity environment and this environment depends, at least in part, on a stable sea ice sheet. Can  someone tell me what will happen as this stable ice sheet disappears? I have always felt that SIE and SIA are not very good indicators of Sea Ice sheet stability. The mechanical behaviors of the ice (fracturing throughout the year and enhanced mobility for example) suggest this stable ice sheet has degraded much more than SIE and SIA would suggest. Could the salinity layers and the thermocline be altered dramatically and what impacts might this have on the sea ice?

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #65 on: May 30, 2014, 06:36:52 PM »
Quoting from my link above:

Quote
A wave with a 14 second period reaches down into the ocean about 516 feet. A 17 second period wave at 761 ft, 20 second at 1053 ft and 25 secs to a whopping 1646 ft!
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Anne

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #66 on: June 01, 2014, 03:19:11 AM »
Thank you doom, Jim, ritter, for your input. My concern here is not only(!) for the icepack but for coastal erosion, though it's all starting to seem rather academic. So long as the ice can keep a lid on things it's absorbing enormous forces. Swell is the word I was groping for. I don't understand it as the energy must be going somewhere even now, but dumb ignorance suggests that maybe the icecap is a kind of shock absorber. This really should be in the Stupid Questions thread as I have a lot of stupid questions about the damping effect of the icepack on swell and so on. Anyway, thanks again.

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #67 on: June 01, 2014, 02:01:18 PM »
So long as the ice can keep a lid on things it's absorbing enormous forces. Swell is the word I was groping for.

For a decent swell to develop you need a stretch of open water hundreds if not thousands of miles across, with strong winds blowing across it. That is not currently the case in the Arctic, so the sea ice isn't currently "absorbing enormous forces" of that sort. However who knows what September holds in store for us?!

Meanwhile on the Pacific coast of Alaska:

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JMP

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #68 on: June 01, 2014, 10:09:31 PM »

For a decent swell to develop you need a stretch of open water hundreds if not thousands of miles across, with strong winds blowing across it. That is not currently the case in the Arctic, so the sea ice isn't currently "absorbing enormous forces" of that sort.



Any swell would probably not be generated in the arctic when covered in ice... but would not sea ice dampen the effect of a swell being typically generated from a storm say 10000 km away?

ghoti

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #69 on: June 02, 2014, 03:58:51 PM »
The Kimmirut webcam now has one week and one month time lapse videos. If you want to see ice deformation due to tides you have to check those out. Kimmirut has up to 30 foot tide swings.

http://www.lookr.com/lookout/1198520951-Kimmirut#action-play-day


Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #70 on: June 03, 2014, 03:49:00 PM »
would not sea ice dampen the effect of a swell being typically generated from a storm say 10000 km away?

The Bering Strait isn't very wide. The Atlantic side is more open to long distance swells of the sort that Antarctic sea ice exposed to, but Greenland rather gets in the way. I have to admit I've had my eyes focussed on long distance swells pointing at SW England up to now, rather than the Fram Strait. All of which suggests an interesting personal research project now that the 2014 Atlantic hurricane season has officially started!

http://www.nhc.noaa.gov/?atlc
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RunningChristo

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #71 on: June 03, 2014, 04:41:26 PM »
Here is a New time lapse "film" "Ice In Motion" showing the breakup of ice around Hopen, Svalbard, this very spring :D

My fancy for ice & glaciers started in 1995:-).

LRC1962

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #72 on: June 04, 2014, 10:16:25 AM »
This should go in Stupid Questions. Surely the greater amount of open water, the greater potential for wave amplification? And subsequent damage to the ice pack? But where does that energy go when the water is covered by ice? Sure, it produces these parallel fractures, but how much does the ice pack actually damp the forces?
Long period swells break up the Canadian Beaufort Sea pack ice. Remember seeing/hearing him talk about that time of research and his utter shock at what had happened. Traditionally when waves hit MYI floes it is much like hitting a cliff and the waves power dissipates very quickly within the floe (a floe is normally defined as one solid sheet of ice many many sq. km. in area). The problem now in the Arctic is that you no longer have any floes left and what you have is ice packs. The farther problem is as the article states is most of what appears as MYI is in fact thick rotten ice composed of many layers each of which is making the whole much weaker.
In this study they found the waves came from an Arctic storm. What the new study shows, is that the waves if the start big enough can come from a very long ways away with the same kind of impact.
This does lead us to  Drift, Deformation and Fracture of Sea Ice because now there is proof we not only have to think about local Arctic storms 'melting' sea ice, because of its stat of rot, but we also need to understand a major cyclone hitting Australia that is kicking up 3m waves can go through the Bering and 'melt' the ice there. You could also see that happening with a major hurricane in the Atlantic. Makes one wonder? Was there a melting that happened around Greenland at the time of Hurricane Sandy? I don't know where they archive that kind of info, but I suspect that there would have been something noticeable if their theory is correct because that Hurricane had very large swells.
This all changes what we think of as needing to 'melt' SI. If you have broken ice within a pact and 3m+ waves hitting the pact, that broken ice then could have a major 'melt' off from the waves alone.
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Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #73 on: June 04, 2014, 11:20:18 AM »
Thanks for the link LRC. As you've probably gathered I wasn't previously familiar with it. I am however familiar with the NOAA's WaveWatch III.

http://polar.ncep.noaa.gov/waves/viewer.shtml?-multi_1-latest-hs-atlantic-

Their historical data only seems to run until December 2010 though:

http://polar.ncep.noaa.gov/waves_old/nww3_hist.html

When I have a spare moment I'll do some digging, but if anyone else fancies doing so please feel free!  The gap through the Bering Strait is very small. Personally I can't see that a long range swell from Australia would be able to bust up the Beaufort, but I'll see if I can find any evidence to the contrary. It won't be this week however!
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #74 on: June 04, 2014, 04:07:42 PM »
This research may be paywalled...I can't seem to pull  it up but it would appear to address the issue of diffraction and impact on wave height when a wave passes through a gap.

http://adsabs.harvard.edu/abs/1949TrAGU..30..705B

LRC1962

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #75 on: June 04, 2014, 05:08:09 PM »
In all probability you are right, Geography really would cause a problem. Although if the wave front hit right it still might make a small impact. The bigger impact would be a Jan-Mar wave on the southern most area. Closest help for you could be Tidal Characteristics Along Coasts of Alaska
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #76 on: June 04, 2014, 05:21:02 PM »
Lets not forget the ability of tides to 'Lift' waters over narrow straights ( like through Bering?) when we have the highest lunar tides? Are we not approaching a full moon? I wonder how much sloshing of that Pacific warm water will go on over that period?
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Peter Ellis

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #77 on: June 04, 2014, 06:26:33 PM »
Considering that neither the Boxing Day tsunami nor the Fukushima tsunami had any detectable effect on Arctic ice, I think the chances of any much-less-energetic wind-driven swells making it through the Bering strait and fracturing ice are utterly minimal.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #78 on: June 04, 2014, 09:02:42 PM »
In all probability you are right, Geography really would cause a problem. Although if the wave front hit right it still might make a small impact. The bigger impact would be a Jan-Mar wave on the southern most area. Closest help for you could be Tidal Characteristics Along Coasts of Alaska

"Geography" might concentrate wave energy in some cases.  The land is going to absorb only a portion, the rest reflected away.

LRC1962

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #79 on: June 05, 2014, 02:44:27 AM »
That was why I am thinking direction of force so important. Fukushima was directed more SE. If you follow the wave patterns it got deflected sideways by the Aleutians.
Reading the tidal report of the Bering, it looks like there is some focusing, but the time it gets to the narrowest point the force is lost so much tides beyond it are almost nonexistent. This is probably because the shape is more like a sink with a hole in the middle rather then a nice funnel. On top of the the Aleutians would make a very effective breakwater for majority of waves. The only chance I see would be if it got caught up by either the Alaskan Current or Bering Sea Water.
Back to JH point is that the Atlantic would have the greatest chance although by the same token has far fewer south equatorial storms that would create those 3m waves.
So question becomes was it theoretical exercise that waves would get into the Arctic or did they follow a wave that actually made it?
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #80 on: June 05, 2014, 11:09:03 AM »
LRC,

I believe the study was on waves affecting Antarctic sea ice. The mechanics would be the same but geography helps shield the Arctic from the long range effects of these southern storm induced swells. It would really take a large storm off Norway to influence the Arctic via swell action and we don't get many of those.

Arctic storms over large stretches of open water will not produce such large swells, but the ones that are created will be directed straight at the ice, so proportionately will have a big effect.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #81 on: June 05, 2014, 11:54:34 AM »
Also keep in mind that swell in the Southern Hemisphere is, generally speaking, on another scale than in the NH. Down here we don't think much of it if it is below 5 meters (16 ft). Have a look at http://www.surf-forecast.com/weather_maps/Global-Pacific?over=none&type=htsgw

And Antarctica is fully exposed to all this wave energy (vs the Arctic being shielded by continent)

So you should be careful to apply Antarctic wave energy stuff to the Arctic  ;)

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #82 on: June 05, 2014, 01:25:28 PM »
My favourite UK based swell maps:

http://magicseaweed.com/World-Surf-Chart/64/?selectedStartTimestamp=1400630400&selectedEndTimestamp=1403308800

The dates will need changing as time goes by. Currently at least it reveals a swell that was generated off Japan that just about makes it into the Chukchi Sea, but that's nothing compared to the battering Antarctica is taking. Based on that small sample Baffin Bay looks to be favourite for taking a wave borne beating in the northern hemisphere.
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #83 on: June 05, 2014, 04:02:43 PM »
I would agree that wave heights (swell) in the Arctic is not a result of waves from the Pacific or Atlantic reaching the Arctic. The Arctic is protected by the continents. Wave height is a result of conditions in the Arctic itself (winds, duration, direction, fetch etc.) Because of the Arctic Oceans depth, we should treat these as deep water waves. This is important as deep water waves will be higher than  shallow water waves, given the same conditions.

Wind waves and swell waves are different beasts. Swell waves pack the most energy and they develop to maximum height over long distances, 1600 kilometers of fetch is needed for swell waves to reach maximum height. Any longer fetch has no impact on wave height. Given the Arctic Ocean size, wave heights in the Arctic could not possibly reach the height of waves found in the Pacific or Atlantic. I believe that wave height is an exponential function of fetch as well so this would also limit swell height in the Arctic.

Here is a Power Point that allows us to calculate wave height, both wind waves and swell waves. Wind waves are a result of nearby wind  conditions. Swell waves are a result of distant storms. The interaction of these two result in sea state.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCgQFjAB&url=ftp%3A%2F%2Fftp.wmo.int%2FDocuments%2FPublicWeb%2Famp%2Fmmop%2Fdocuments%2FJCOMM-TR%2FJ-TR-21-WWSS-CAR%2FDOCUMENTS_JCOMM%2F005_Presentations%2F01_Warren.ppt&ei=WXSQU5mRMNieyASb_oGACg&usg=AFQjCNHUYFQ0RzVTtU386rCN4hIEkhaYng&bvm=bv.68235269,d.aWw
« Last Edit: June 05, 2014, 04:24:28 PM by Shared Humanity »

Laurent

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #84 on: July 17, 2014, 03:42:47 PM »
May be already posted...
A wave 3 meters high can have an effect 200 km away on the ice...

Storm-induced sea-ice breakup and the implications for ice extent
http://www.nature.com/nature/journal/v509/n7502/full/nature13262.html

Rick Aster

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #85 on: July 30, 2014, 08:29:45 PM »
Arctic Ocean waves make it into mainstream media:

The Washington Post : Capital Weather Gang : “Giant waves found in Arctic Ocean could be accelerating sea ice loss” http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2014/07/30/giant-waves-found-in-arctic-ocean-could-be-accelerating-sea-ice-loss/

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… swells of 16 feet were recorded in the Arctic in 2012 during peak wave times, and the largest waves approached 29 feet. Waves like this are now not only possible because of Arctic sea ice melting, but they also have the power to cause sea ice melt, themselves.

(Story by Angela Fritz)

jdallen

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #86 on: July 30, 2014, 09:49:14 PM »
Arctic Ocean waves make it into mainstream media:

The Washington Post : Capital Weather Gang : “Giant waves found in Arctic Ocean could be accelerating sea ice loss” http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2014/07/30/giant-waves-found-in-arctic-ocean-could-be-accelerating-sea-ice-loss/

Quote
… swells of 16 feet were recorded in the Arctic in 2012 during peak wave times, and the largest waves approached 29 feet. Waves like this are now not only possible because of Arctic sea ice melting, but they also have the power to cause sea ice melt, themselves.

(Story by Angela Fritz)

Deep water to surface mixing, now in progress. The waves will push mixing down well below the cooler surface layers to where heat being imported from the Atlantic is hiding.

This may produce some interesting feedbacks - exchange from depth could lead to more heat loss and ice forming later in the season.  The question is, will the additional heat loss balance the budget back in favor of the ice, or weaken it further to permit more summer insolation to be captured.
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Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #87 on: August 03, 2014, 09:13:36 AM »
A surfing polar bear has been captured by The Telegraph's wildlife photographer!

http://blogs.telegraph.co.uk/news/geoffreylean/100282159/could-global-warming-bring-surfing-to-the-arctic/

North Devon surfers take umbrage at such a piss poor piss take:

http://GreatWhiteCon.info/2014/08/the-worlds-leading-arctic-surfing-expert/
« Last Edit: August 08, 2014, 05:56:48 AM by Jim Hunt »
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Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #88 on: August 03, 2014, 04:02:24 PM »
Another Arctic surf video, with rather less Red Bull and loud music :

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #89 on: August 08, 2014, 05:46:55 AM »
The University of Washington press release that includes a link to the Jim Thomson open access paper that has generated all the recent publicity:

Huge waves measured for first time in Arctic Ocean

Quote
His data show that winds in mid-September 2012 created waves of 5 meters (16 feet) high during the peak of the storm. The research also traces the sources of those big waves: high winds, which have always howled through the Arctic, combined with the new reality of open water in summer.

From the abstract to the paper itself:

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Ocean surface waves (sea and swell) are generated by winds blowing over a distance (fetch) for
a duration of time. In the Arctic Ocean, fetch varies seasonally from essentially zero in winter to hundreds
of kilometers in recent summers. Using in situ observations of waves in the central Beaufort Sea, combined
with a numerical wave model and satellite sea ice observations, we show that wave energy scales with fetch
throughout the seasonal ice cycle. Furthermore, we show that the increased open water of 2012 allowed
waves to develop beyond pure wind seas and evolve into swells. The swells remain tied to the available
fetch, however, because fetch is a proxy for the basin size in which the wave evolution occurs. Thus, both sea
and swell depend on the open water fetch in the Arctic, because the swell is regionally driven. This suggests
that further reductions in seasonal ice cover in the future will result in larger waves, which in turn provide a
mechanism to break up sea ice and accelerate ice retreat.

From the conclusions:

Quote
It is possible that the increased wave activity will be the feedback mechanism which drives the Arctic system toward an ice-free summer. This would be a remarkable departure from historical conditions in the Arctic, with potentially wide-ranging implications for the air-water-ice system and the humans attempting to operate there.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Bob Wallace

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #90 on: August 10, 2014, 01:12:55 AM »
Had I been the journal editor for this paper I suspect this sentence -

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It is possible that the increased wave activity will be the feedback mechanism which drives the Arctic system toward an ice-free summer.

Would have been something like -

Quote
It is likely that the increased wave activity will be one of the feedbacks which help drive the Arctic system toward an ice-free summer.

Steven

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #91 on: June 19, 2015, 08:58:27 PM »
Yesterday (18 June), Dr. Ron Kwok gave a talk about sea ice in the von Kármán Lecture series.  The video of Dr. Kwok's talk is here:

http://www.ustream.tv/recorded/64155974

Part of the talk is about sea ice drift (starting at minute 31:10 of the video), and sea ice deformation (starting at minute 38:00).

Here is a brief summary of the above video:

00:00   Introduction.
04:00   Some generalities about Arctic and Antarctic sea ice.
24:10   Arctic sea ice thickness: observations from submarine and satellites.
31:10   Sea ice drift and fracture.
38:00   Sea ice deformation/ridging.
43:30   Multi-year ice: distribution and trend.
45:00   Concluding remarks.
48:00   Dr. Kwok shows an old 1958 video by Norbert Untersteiner.
56:30   Questions from people in the audience.

Neven

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #92 on: June 19, 2015, 11:12:08 PM »
Thanks for that video, Steven. Ron Kwok is top of the scale.
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Steven

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #93 on: July 02, 2016, 07:52:08 PM »
This recent article about sea ice leads/fractures looks interesting:

https://www.dkrz.de/about-en/media/galerie/Vis/icesheet/sea-ice-leads

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Despite of the importance of sea ice leads, relatively little is known on how well they can be represented by commonly used sea ice models. The goal of this work is to show that small scale sea ice linear features can be simulated by the traditional sea ice models with a certain skill. The prerequisite is a sufficiently high horizontal resolution along with numerical convergence of sea ice solvers which is frequently neglected. We simulate Arctic sea ice using the elastic-visco-plastic (EVP) approach in a global sea ice ocean model at a local resolution of 4.5 km and show that many characteristics of the simulated 'cracks' agree with the available observations already at this resolution. This allows us to discuss the variability and trend of the lead features from long model-generated time series.

(Their paper is here, Wang et al. 2016).  On the above webpage they also have a video of their simulation for 2005-2014: