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Jim Hunt

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Drift, Deformation and Fracture of Sea Ice
« on: October 28, 2013, 12:04:35 PM »
The title is shamelessly plagiarised from the book of the same name by Jérôme Weiss.

The discussion started over on Wipneus' AMSR2 thread, but drifted off that topic and has now fractured off in this direction. If you don't have the book, here's a paper from Weiss that briefly covers the same sort of ground.

"Sea ice rheology from in-situ, satellite and laboratory observations: Fracture and friction".

To give you a flavour of things, here's an extract from the book:

Quote
In 2006-2007 the polar schooner Tara repeated the Fram's journey along the transpolar drift. She became locked in the ice in the Laptev Sea in early September 2006, but crossed Fram strait only 16 months later in December 2007, drifting on average more than twice as fast as the Fram 115 years before. Was this surprisingly fast journey just by chance, due to a specific Arctic atmospheric circulation pattern enhancing the transpolar drift and therefore export through Fram Strait? Or was it a sign of a more fundamental, long-term evolution of sea ice kinematics?

Perhaps we might also discuss in more detail what's been happening to export via the Nares and Fram Straits in 2013?!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Neven

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #1 on: October 28, 2013, 12:08:45 PM »
What export via the Nares and Fram Straits in 2013?  ;)
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ChrisReynolds

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #2 on: October 28, 2013, 08:04:42 PM »
I never follow Nares, it's tiny, but yes - Fram export this year will have been low - that's weather for ya!

Deformation and fracture driven by the wind. The less mass there is the easier the wind will find it to drag the ice, but the more FYI the more likely a smooth surface is which means less drag...

Anyway, as I've just been playing around with some data I did for my latest blog post, here's a graph of ice thickness between 90 and 190 degE north of 70degN.



A thinning from around 3m to around 2m implies up to 1/3 less mass for the wind to drag in May. By September the thinning implies about 2/3 less mass to drag.

Laurent

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #3 on: October 28, 2013, 08:18:33 PM »
It seems there is an acceleration compare to this summer, it is amazing, someone did open the door !
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif
« Last Edit: October 29, 2013, 11:23:55 AM by Laurent »

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #4 on: October 28, 2013, 09:17:10 PM »
Someone did open the door!

The buoys (what's left of them!) confirm things do now seem to be moving Framwards. Here's 2013E:
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Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #5 on: October 28, 2013, 09:21:30 PM »
The less mass there is the easier the wind will find it to drag the ice, but the more FYI the more likely a smooth surface is which means less drag...

I don't recall Weiss making that point, though he does refer to other differences between first year and multiyear ice. I don't suppose you have a similar chart for the Atlantic side of things do you?
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ChrisReynolds

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #6 on: October 28, 2013, 09:41:57 PM »
The less mass there is the easier the wind will find it to drag the ice, but the more FYI the more likely a smooth surface is which means less drag...

I don't recall Weiss making that point, though he does refer to other differences between first year and multiyear ice. I don't suppose you have a similar chart for the Atlantic side of things do you?

Not yet! I'm just watching Frankie Boyle vids on Youtube, so I'll run it off while I'm wasting time.

ChrisReynolds

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #7 on: October 28, 2013, 10:12:39 PM »
Here you go Jim,



What's going on in the Atlantic sector is that ice is in movement to a higher degree than in the Siberian sector. The transpolar drift is driving ice towards Greenland, and there is also flow towards the Atlantic, when pressure over the pole is high. The flow towards the Atlantic is ice going to melt, in the warm Atlantic waters, the ice edge kept in place by the drop off into the Eurasian Basin.
https://pangea.stanford.edu/research/groups/structure/gfx/amerasia.png

So the ice in the Atlantic sector has thinned less, and thins less over the melt season, because it's subject to continual replenishment.

At least that's what I think is going on.

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #8 on: October 28, 2013, 11:52:59 PM »
looking at the images http://ocean.dmi.dk/arctic/images/MODIS/Nord/201310270348.NOAA.jpg
together with the animated thickness maps
It seems their is an acceleration compare to this summer, it is amazing, someone did open the door !
http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif
shows how little cohesion the ice has, even ice which shows up with larger thickness accelerates quite freely towards open water, opening preexisting(?) cracks
Also note entrance to Nares Strait where ice thickness is even higher but support allows an ice arch to form relying on resistance to shear and compression rather than tensile strength. Although the bulk of the ice moving across in easterly direction seems to destabilize the arch.http://ocean.dmi.dk/arctic/images/MODIS/MorrisJessup/201310281326.NOAA.jpg

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #9 on: October 29, 2013, 07:43:28 AM »
I will say, while the Fram export was fairly slow over significant periods of the melt season, there were still times where it was quite fast, and differentially dumped out a significant fraction of what MYI we did have at the end of 2012.

The lack of cohesion will play a role I think, and I also think we are starting to see it.  As noted we have more probability of a somewhat persistent polar high, and in the absence of a solid pack, will encourage flow out into the significantly warmed (as compared to previous years) Greenland and Barents seas.  The ice margin *still* hasn't reached Svalbard.
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Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #10 on: October 30, 2013, 11:36:07 AM »
Here you go Jim

Thanks Chris. To summarise then, ice is getting thinner and hence more mobile. However in 2013 thus far the weather hasn't favoured export through the Fram Strait for much of the time?

Broadening the debate somewhat, here's an extract from the NOAA's Arctic Ocean "Report Card" for 2012:

Quote
September 2011-August 2012. The wind-driven anticyclonic Beaufort Gyre circulation between September 2011 and August 2012 was weaker than the average over the preceding 12 months. In 2011-2012, the somewhat weaker wind stress curl over the BG does not appear to have affected freshwater accumulation by Ekman transport, i.e., in 2012 there was no evidence of reduced freshwater in the BG.

Obviously it will be very interesting to see what the 2013 version says, but in the meantime do you think there's anything in Andrey Proshutinsky's fears expressed in the video at the bottom of this overview of Ice Tethered Profilers that:

Quote
It's possible too much freshwater will be released [from the Beaufort Gyre]. In this case we can have some dramatic changes in climate.
« Last Edit: January 13, 2014, 05:13:46 PM by Jim Hunt »
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ggelsrinc

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #11 on: October 31, 2013, 07:35:25 PM »
The title is shamelessly plagiarised from the book of the same name by Jérôme Weiss.

The discussion started over on Wipneus' AMSR2 thread, but drifted off that topic and has now fractured off in this direction. If you don't have the book, here's a paper from Weiss that briefly covers the same sort of ground.

"Sea ice rheology from in-situ, satellite and laboratory observations: Fracture and friction".

To give you a flavour of things, here's an extract from the book:

Quote
In 2006-2007 the polar schooner Tara repeated the Fram's journey along the transpolar drift. She became locked in the ice in the Laptev Sea in early September 2006, but crossed Fram strait only 16 months later in December 2007, drifting on average more than twice as fast as the Fram 115 years before. Was this surprisingly fast journey just by chance, due to a specific Arctic atmospheric circulation pattern enhancing the transpolar drift and therefore export through Fram Strait? Or was it a sign of a more fundamental, long-term evolution of sea ice kinematics?

Perhaps we might also discuss in more detail what's been happening to export via the Nares and Fram Straits in 2013?!

On Wipneus' AMSR2 thread you asked:

Quote
ggelsrinc - I'm no expert in these matters, but the emphasis in the past seems to have been on compression rather than tension. Does this paper from Weiss help at all?

"Sea ice rheology from in-situ, satellite and laboratory observations: Fracture and friction"

Yes, that paper is very helpful. It's proof that over 7 years ago, scientists came to the conclusion that a model of sea ice being a granular plastic was lacking. I've been seeing evidence of that and even saw it in the Wipneus' animation. I believe if we are going to understand things like drift, deformation and fracture, we need a better understanding of the physical properties of sea ice from various means of formation. We need to examine sea ice as a material made by various processes to understand it's behavior.

I've been thinking about a thread like "Studies of the physical properties of sea ice" and using the references in your link to guide me to those studies. Those references have a good list of past studies and the scientists working in that field. Such a subject is very technical and may not interest many people, but it should be appropriate for a forum on Arctic sea ice. 

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #12 on: October 31, 2013, 09:19:35 PM »
Such a subject is very technical and may not interest many people, but it should be appropriate for a forum on Arctic sea ice.

A slightly different tack perhaps, but you might also be interested in the work of Flocco and Feltham on incorporating the effects of adding melt ponds into sea ice models.
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ggelsrinc

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #13 on: November 01, 2013, 01:30:10 AM »
Such a subject is very technical and may not interest many people, but it should be appropriate for a forum on Arctic sea ice.

A slightly different tack perhaps, but you might also be interested in the work of Flocco and Feltham on incorporating the effects of adding melt ponds into sea ice models.

I think it's part of the same subject. I view sea ice through the eyes of chemistry and consider anything that can change the material's properties to be a part of the process that created it. Melt ponds aren't the type of variable in sea ice formation that quickly comes to my mind, but I doubt same thickness sea ice, with and without a melt pond source, are of identical quality in every aspect of measuring the physical properties of sea ice. Consider what happens when it snows in an area with melt ponds, or just the simple differences if there is wind! I can picture major changes in the sea ice structure for many reasons, including potential sea ice strength improvements, because of melt ponds. When it comes time for drift, deformation or fracture to occur, certain qualities of the sea ice are going to affect the outcome.

It's just one of the many things I haven't spent much time thinking about.

Phil.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #14 on: November 02, 2013, 02:09:48 PM »
I will say, while the Fram export was fairly slow over significant periods of the melt season, there were still times where it was quite fast, and differentially dumped out a significant fraction of what MYI we did have at the end of 2012.

The lack of cohesion will play a role I think, and I also think we are starting to see it.  As noted we have more probability of a somewhat persistent polar high, and in the absence of a solid pack, will encourage flow out into the significantly warmed (as compared to previous years) Greenland and Barents seas.  The ice margin *still* hasn't reached Svalbard.
To follow up my post on the 'Buoy' thread, the N Pole web cam after spending a long time around the 84ºN region has been steadily drifting into the Fram, the last week travelled about 0.8º to 81ºN.

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #15 on: November 02, 2013, 05:26:11 PM »
viewing drift track map from http://psc.apl.washington.edu/northpole/PAWS819920_atmos_recent.html
with ice drift speed from http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticicespddrfnowcast.gif
and image http://ocean.dmi.dk/arctic/images/MODIS/Nord/201311010253.NOAA.jpg
I would expect it to be not very far from the ice edge and to speed up more soon.
It will be good to have wind direction information from in situ measurements, but can somebody explain how to put direction from magnetic north onto the map?

I have been staring at images from north of greenland http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201310290501.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201311020737.NOAA.jpg
Being fairly new to this I am fascinated by the appearent ease with which those cracks open up. Surface air temp are now below -20degC but continuous movement seems to keep floes mobile. According to thickness map that stuff going down Nares Strait should be some of the thickest ice in the arctic.
Can somebody explain the dark "shadows" in the images? My guess is that they represent relatively warm surface temps caused by wind moving over snow surfaces of low heat capacity, higher altitude air temps are probably still a lot above these radiatively cooled surfaces. But would like to be able to back this up or be put right.

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #16 on: November 03, 2013, 08:33:46 PM »
....
I'm betting part of the reason behind the sharp delineation may be northward-moving warm water that's still a couple of degrees above freezing.  That would tear apart the ice we see (probably much not more than a meter thick) at the rate of 5-10 CM/day.  If the flow doesn't have much of an E-W component to its movement, that might tend support the boundary we see, along with other factors like surface wind and current.
I came across this map of drift tracks from the 2000s http://psc.apl.washington.edu/northpole/Buoys.html which noticeably funnel through a narrow section of the Nares Strait without ever straying further towards Svalbard. Small sample, I know but seabed contours may suggest a link with current? Wind direction would be expected to be more variable?
I may seem to be a bit obsessive about this part of the arctic but I would like to understand more about this major export route at this time of the year, see


On my earlier question regarding "dark cloud shadows" , thank you Wipneus this makes good sense:
.....
Now, for the shadows on the image. Brightness in a particular spectral range will depend on radiative properties of the surface and its temperature and those of the atmosphere.
Here I would agree that clouds cause darkish shadows. In the Arctic night under clear sky conditions a temperature inversion creates a colder surface compared with the lower atmosphere.  So the satellite will see low clouds that are warmer than some clear surface nearby. That is opposite from other seasons and lower latitudes.

So since these are IR images taken without external source (sunlight) white means cold and dark means warm (like negative film darkened by light) low clouds are warmer than ice surface and tops of high clouds, correct?

forkyfork

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #17 on: November 04, 2013, 10:12:24 PM »
this looks like a lot of transport.  do we know how this compares to average?


Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #18 on: November 04, 2013, 11:06:00 PM »
Noticeable is the movement of ice along the coast of north east greenland, where as Espen has pointed out, landfast ice used to be, if I get the geography right.
This can be seen in this image from today http://ocean.dmi.dk/arctic/images/MODIS/NEW/201311040613.NOAA.jpg
My guess is that to make comparisons with other years we will have to see how this plays out for the rest of the season, but I am just a beginner.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #19 on: November 04, 2013, 11:24:37 PM »
this looks like a lot of transport.  do we know how this compares to average?



I only know what I've seen and I concentrate on what MYI is left, so Fram isn't that important to me. If MYI starts leaking through CAA, the game is over very soon. Fram and Nares will transport all sea ice capable of becoming MYI and any hope of regenerating MYI stops. We are simply watching a game, like football on reruns happening and forgetting we already know who wins the game. Reality isn't as dramatic as watching the game, once the outcome is established. Summertime ASI is toast based on what mankind has already done. It's as predictable as when someone will die, who you know is terminally ill. The only way I know to save summertime ASI is direct human activity designed to prolong and save it's life.

Dr. Dubya/Gary/ggelsrinc finds himself rejoicing in a Denialista camp about the health of our ASI, but my joy is knowingly short lived. Without an operation, there is absolutely no chance of survival.

Without direct human effort to save summer Arctic sea ice, it's terminal. When, I'd say 2015, but perhaps 2020, if conditions favor it existing.

Let's take a logical approach to forecasting! Let's define the end of ASI by a particular metric and get gambling involved, so they can make odds on when.   

forkyfork

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #20 on: November 04, 2013, 11:45:00 PM »
it is multi year ice:



the pressure pattern has been anomalous.  compare to last year which was completely different for transport

ggelsrinc

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #21 on: November 05, 2013, 12:59:59 AM »
MYI in Fram is tomorrow's history. MYI in the gyre has some chance to survive, if it can get to CAA and the same applies to all ASI with a potential to become MYI. The comforts of a bed north of Greenland stopped last year as I remember seeing and I'm talking about the refreeze and not the summer minimum.

People who want ASI to exist aren't going to get what they want without massive human effort to make that possible, like clogging up the leak from CAA and then some more effort.

The game is over and ASI lost. People don't have the will to change that future. ASI's last hope rests on it fragmenting during winter and people coming to their senses to intervene. Fat chance on the people doing that!

I just call it as I see it.   

jdallen

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #22 on: November 05, 2013, 08:47:33 AM »
The game is over and ASI lost. People don't have the will to change that future.

We don't have the *capability* to change that future.  We will lose the ASI, I think that is absolutely certain, possibly as you say by 2015, but I think more likely a few years beyond that.

I think the combination of shattered pack, plus altered flow and increasing ocean temperature are the key lethal combination. 

I watched the loss of "fast" ice along the Northern and Eastern shores of Greenland with interest during the melt season, and the last of it breaking up in August/early September put the topper on it.  I'm not sure weather will be able to re-establish that hold, and not having it I think may increase the flow out the Fram by as much as 15%.  That may not seem much, considering the relatively modest flow... previously.  But, it is by preference going to be MYI rather than new, and that certainly does not bode well.

It will also not be well for the ice next spring, as without the fast ice to provide an anchor, our ice grinder now crosses the full span of the arctic.  2014 will for certain be an interesting year. 

Now, what is this I hear about El Nino starting to return (ENSO shift in 2014)?  Well, maybe not next year, but the trend is up.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html
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jdallen

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #23 on: November 05, 2013, 09:09:05 AM »
...I believe if we are going to understand things like drift, deformation and fracture, we need a better understanding of the physical properties of sea ice from various means of formation. We need to examine sea ice as a material made by various processes to understand it's behavior.

Concur, but I think one problem we have is simply comprehension of scale; both of physical dimension and time.  The ice is on the top of a highly energetic system, which in proportionate terms, is starting to reach a "boil".  As the forces driving circulation change, it will disappear just as thoroughly and suddenly as the skin on stock in a soup pot. The time is just stretched over years rather than minutes, and thousands of kilometers rather than a few centimeters.

It could *all* be MYI, and still vanish just as quickly once the correct level of energy is reached; compared to the scales of energy, there is little difference between old ice or new, mechanically in their ability to resist force.... the metaphor that comes to mind is, in a hurricane, how much longer would a cardboard structure last, than a paper one?

In scale, Arctic sea ice has about as much chance to resist as that skin on that stock pot.  We're just trying to understand the timing.
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #24 on: November 05, 2013, 01:01:28 PM »
...I believe if we are going to understand things like drift, deformation and fracture, we need a better understanding of the physical properties of sea ice from various means of formation. We need to examine sea ice as a material made by various processes to understand it's behavior.

Concur, but I think one problem we have is simply comprehension of scale; both of physical dimension and time.  The ice is on the top of a highly energetic system, which in proportionate terms, is starting to reach a "boil".  As the forces driving circulation change, it will disappear just as thoroughly and suddenly as the skin on stock in a soup pot. The time is just stretched over years rather than minutes, and thousands of kilometers rather than a few centimeters.

It could *all* be MYI, and still vanish just as quickly once the correct level of energy is reached; compared to the scales of energy, there is little difference between old ice or new, mechanically in their ability to resist force.... the metaphor that comes to mind is, in a hurricane, how much longer would a cardboard structure last, than a paper one?

In scale, Arctic sea ice has about as much chance to resist as that skin on that stock pot.  We're just trying to understand the timing.

I concur. The damage to destroy our ASI is already done and it will cease to exist during the summer without human geo-engineering efforts to save it. Important governments are too interested in playing with their new toy than focusing on the true costs of having that toy. The Arctic needs to be placed as a sanctuary for all of mankind and governments need to step forward, put their territorial claims in a moratorium for about 50 years and attempt to repair the damage done.

I can totally understand how life can consume a person and don't expect someone to share my concerns at a particular moment of time. I was too busy in life to notice the stars falling from heaven and see the damage we did to our world. I'm not a prophet who can say with certainty when summertime ASI will disappear, but I'm sensitive enough to know when someone is blowing smoke up my ass, even when I'm asleep. I'm just one person on this planet, but I believe, if I brake something, I should fix it. It's called behaving like an adult and I believe even governments will act like adults and grow up eventually.

The countdown for summertime ASI destruction has already begun. Instead of focusing on the benefits imagined, governments need to examine the full balance sheet. Losing ASI to convince fools who don't believe in global warming is too high of a price to pay. My logic on environmental issues is as simple as this. If my world was a certain way when I was born and it was damaged on my watch, it's my obligation to fix it, making it as good and hopefully better than the day I entered it. It's called growing up and taking responsibility, even if Joe Blow did it during your watch. I have enough sense to know I failed during my watch and I don't play blame games. I should have been a better steward of my Earth and wasn't. During my lifetime, I should have been more concerned and wasn't. Even a mouse that squeaks can be like a lion that roars, if placed in a proper ear.

Now, what does any of that have to do with drift, deformation and fracture of sea ice? Nothing at all, it's just the ramblings of an old fool.

My desire was to get too technical on solutions like Thorium MSRs and science like the physical properties of sea ice, but I gave my word in my first thread. I'm sure the lawyer in me put an escape clause, but subjects like nuclear physics and physics/chemistry aren't very popular. Jim Hunt was kind enough to start this thread related to what I was saying.

This is only my second year watching drift during the refreeze and I don't like what I see. The days of ASI getting caught in the gyre and Russia protecting it are gone faster than Reagan falling asleep in a meeting. Fram and Nares is giving up their somewhat normal stuff, but I don't like what I see in the CAA. If those islands can't allow refreeze to stop MYI going south, the game is over. 

Phil.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #25 on: November 06, 2013, 01:27:07 PM »
MYI in Fram is tomorrow's history.


The N Pole webcam has sped up over the last few days, covered the 1º to 80ºN in 4 days.
Seems to indicate that the Fram flow is picking up speed.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #26 on: November 07, 2013, 12:02:46 AM »
Wind speed has picked up too, 20m/s today. But direction says from magnetic north, which from Fram straight lies more west than north. That makes 220deg a southerly wind, or am I getting this wrong?
http://psc.apl.washington.edu/northpole/PAWS819920_atmos_recent.html
« Last Edit: November 07, 2013, 12:47:11 AM by Andreas T »

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #27 on: November 07, 2013, 01:30:37 AM »
On another thread there was a question on katabatic winds in Greenland. I have read up on katabatic wind in Antarctica and posted some images in the "Antarctic images" thread, but haven't heard them metioned in Greenland, but then there are these IR images from yesterday and today:
http://ocean.dmi.dk/arctic/images/MODIS/Kennedy/201311051339.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Kennedy/201311061328.NOAA.jpg
Yesterday's image shows low warmish clouds (darker gray) which obscure the underlying surface structures. But today's dark streaks don't obscure, just darken the surface structures and exit from valleys dropping down towards the coast, therefore I interpret this as wind warming as it drops to lower elevation, starting with high potential temperature and warming the snowcovered surface (from a temperature well below -20degC). A lead has opened along the coast, which would fit with seaward wind.
Alert http://www.weather-forecast.com/locations/Alert/forecasts/latest
reports for afternoon today: SSW wind, clear sky and air temp up to -16 degC from -19degC this morning maybe colder yesterday?. Whether that is enough of a temp difference to change intensity this much I have no idea.
« Last Edit: November 07, 2013, 01:39:05 AM by Andreas T »

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #28 on: November 07, 2013, 01:35:19 AM »
It's obvious Fram has picked up and it's only unusual when it isn't leaking sea ice from the Arctic. It's the express and will be so until the end days of ASI.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #29 on: November 07, 2013, 11:06:18 AM »
On another thread there was a question on katabatic winds in Greenland.

Here's what happened last year in the same vicinity, slightly later in the season:

http://econnexus.org/the-day-after-tomorrow-coming-soon/#Nord

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #30 on: November 07, 2013, 09:20:01 PM »
The N Pole webcam has sped up over the last few days, covered the 1º to 80ºN in 4 days.
Seems to indicate that the Fram flow is picking up speed.
NOAA has "Latitude/Longitude Distance Calculator" at
http://www.nhc.noaa.gov/gccalc.shtml?
should anyone wish to view (calculate) distance.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #31 on: November 09, 2013, 09:25:30 AM »
Thanks Jack, that's very useful.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #32 on: November 09, 2013, 11:20:25 AM »
Thanks Jack, that's very useful.

That's already been done in my assorted Google maps. Since it seems to be of interest I'll go away and bring them up to date!

http://batchgeo.com/map/imb-2013e

Click on the "pushpins"

P.S. Two days ago seems to have been the record with 53.4 km travelled, as the Arctic Tern flies:
« Last Edit: November 09, 2013, 11:35:33 AM by Jim Hunt »
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #33 on: November 10, 2013, 05:15:25 PM »
Regarding your question about dark shadows: Those dark shadows you see on the MODIS image on the ice are actual shadows from high cloud. Due to the low sun angle at that lattitude, you can't see the actual clouds causing the shadows as they are south of the image footprint.

viewing drift track map from http://psc.apl.washington.edu/northpole/PAWS819920_atmos_recent.html
with ice drift speed from http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticicespddrfnowcast.gif
and image http://ocean.dmi.dk/arctic/images/MODIS/Nord/201311010253.NOAA.jpg
I would expect it to be not very far from the ice edge and to speed up more soon.
It will be good to have wind direction information from in situ measurements, but can somebody explain how to put direction from magnetic north onto the map?

I have been staring at images from north of greenland http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201310290501.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201311020737.NOAA.jpg
Being fairly new to this I am fascinated by the appearent ease with which those cracks open up. Surface air temp are now below -20degC but continuous movement seems to keep floes mobile. According to thickness map that stuff going down Nares Strait should be some of the thickest ice in the arctic.
Can somebody explain the dark "shadows" in the images? My guess is that they represent relatively warm surface temps caused by wind moving over snow surfaces of low heat capacity, higher altitude air temps are probably still a lot above these radiatively cooled surfaces. But would like to be able to back this up or be put right.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #34 on: November 10, 2013, 07:23:17 PM »
Regarding your question about dark shadows: Those dark shadows you see on the MODIS image on the ice are actual shadows from high cloud. Due to the low sun angle at that lattitude, you can't see the actual clouds causing the shadows as they are south of the image footprint.

viewing drift track map from http://psc.apl.washington.edu/northpole/PAWS819920_atmos_recent.html
with ice drift speed from http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticicespddrfnowcast.gif
and image http://ocean.dmi.dk/arctic/images/MODIS/Nord/201311010253.NOAA.jpg
I would expect it to be not very far from the ice edge and to speed up more soon.
It will be good to have wind direction information from in situ measurements, but can somebody explain how to put direction from magnetic north onto the map?

I have been staring at images from north of greenland http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201310290501.NOAA.jpg
http://ocean.dmi.dk/arctic/images/MODIS/Lincoln/201311020737.NOAA.jpg
Being fairly new to this I am fascinated by the appearent ease with which those cracks open up. Surface air temp are now below -20degC but continuous movement seems to keep floes mobile. According to thickness map that stuff going down Nares Strait should be some of the thickest ice in the arctic.
Can somebody explain the dark "shadows" in the images? My guess is that they represent relatively warm surface temps caused by wind moving over snow surfaces of low heat capacity, higher altitude air temps are probably still a lot above these radiatively cooled surfaces. But would like to be able to back this up or be put right.

We discussed that on another thread, but a good scientist always questions their findings. My appeal to expertise, confirmed the same observation and added other avenues to explore. We all walk our world one step at a time and life is more interesting if something can't easily be explained when it's found. A simple explanation that it looks like clouds isn't good enough to confirm suspicions that many sensors aboard a satellite can detect various conditions and images can be produced by combining and subtracting various wavelengths of light. Thanks to people like Neven, Wipneus and Andreas T asking a question, I've learned something that I wouldn't have looked at all, if not brought to my attention. So the world goes around!
« Last Edit: November 10, 2013, 10:21:00 PM by ggelsrinc »

Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #35 on: November 10, 2013, 07:52:42 PM »
Regarding your question about dark shadows: Those dark shadows you see on the MODIS image on the ice are actual shadows from high cloud.....
[/quote]I did think that at first too but when you look at more images before and after the one shown you see that the "shadow" north of Nares strait is not moving when the sun should be shining at a different angle. Looking at the weather information for Alert  http://www.weather-forecast.com/locations/Alert/forecasts/latest which is close to that location you see sunrise and sunset times given as 12:00 / 12:00 or 5pm /5pm http://www.wunderground.com/q/zmw:00000.1.WCYLT
which I take as no sunrise, I should look at sun angle north of 80deg but haven't done that yet.
Most importantly I have come to realize that  since what we see in these images are negative IR images which means snow and ice is white because of low temperature and low emission, water is black because of higher temperature and higher emission (I don't know what the exact wavelenths are but at longwave IR emissivity is high for both) The level of contrast is surprising , surface temperatures in that area don't seem to get above -10degC but the contrast of the image may be tuned to maximum for the temperature range seen.
In other images the brightness of the ice changes from one day to the next, with some floes lighter than others, which makes sense when considering different thickness responding to temperature changes at different rates. As ggelsrinc says, I am learning more as I get deeper into the whole topic.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #36 on: November 11, 2013, 02:03:26 PM »
Very interesting and well-considered.  I maintain however, that the dark patches are meteorlogical, not ice-related. In my attachment (some analysis on the image you put up) I identify the clouds causing some of the dark patches. Also I identify a Multi-year floe, and a First-year floe; note how the dark patch passes equally over both - these two ice types have much different temperatures, thus only non-ice phenomenon would affect them equally.

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.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #37 on: November 11, 2013, 06:31:04 PM »
Very interesting and well-considered.  I maintain however, that the dark patches are meteorlogical, not ice-related. In my attachment (some analysis on the image you put up) I identify the clouds causing some of the dark patches. Also I identify a Multi-year floe, and a First-year floe; note how the dark patch passes equally over both - these two ice types have much different temperatures, thus only non-ice phenomenon would affect them equally.

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.

Your analysis is consistent with the consensus. Your attachment tells more of a story than someone can easily see, who is focused on something else.

I've seen evidence the ASI will weaken, until it regenerates during the winter by fragmenting, releasing trapped heat, making it last longer than expected. Then again, it could just be the wishful thinking of an old man.

If you run into Putin across the "pond", please request the release of those Greenpeace characters and if he has his shirt on, ask for American English translations of works from Anton Chekhov, Fyodor Dostoyevsky and Leo Tolstoy to name a few. I promise in return to let Obama know the same details, wearing a shirt or not, should I get that close to him. 


Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #38 on: November 12, 2013, 01:09:06 AM »
polynya, I am not sure how much different our views are so let me check: do we agree that there is no sunlight north of 80deg latitude in November http://www.esrl.noaa.gov/gmd/grad/solcalc/solardec.gif, so when we talk of "shadows" we just mean dark streaks in the infrared image?
Do we agree that light / dark in these images indicates temperature (emitted infrared radiation)?
The image which made me look deeper into this is http://ocean.dmi.dk/arctic/images/MODIS/Kennedy/201311061328.NOAA.jpg
maybe that is fog, I am not sure about that anymore.
My comment on lighter(cold) and darker(warmer) ice floes is based on other images like  http://ocean.dmi.dk/arctic/images/MODIS/MorrisJessup/201311091257.NOAA.jpg the cloud free area on the right. sorry for not posting an annotated image like yours, but it is getting late for me.

Polynya88

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #39 on: November 12, 2013, 04:37:09 AM »
Greetings,
I'm not from across the "pond", but actually in Canada - the true land of ice! However if I did have influence over the Greenpeace characters I would recommend they get an all expense paid one-way trip to the gulag.  Radical environmentalists have no place messing with industry...

Very interesting and well-considered.  I maintain however, that the dark patches are meteorlogical, not ice-related. In my attachment (some analysis on the image you put up) I identify the clouds causing some of the dark patches. Also I identify a Multi-year floe, and a First-year floe; note how the dark patch passes equally over both - these two ice types have much different temperatures, thus only non-ice phenomenon would affect them equally.

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.

Your analysis is consistent with the consensus. Your attachment tells more of a story than someone can easily see, who is focused on something else.

I've seen evidence the ASI will weaken, until it regenerates during the winter by fragmenting, releasing trapped heat, making it last longer than expected. Then again, it could just be the wishful thinking of an old man.

If you run into Putin across the "pond", please request the release of those Greenpeace characters and if he has his shirt on, ask for American English translations of works from Anton Chekhov, Fyodor Dostoyevsky and Leo Tolstoy to name a few. I promise in return to let Obama know the same details, wearing a shirt or not, should I get that close to him.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #40 on: November 12, 2013, 11:06:58 PM »
To bring this back to strength and mobility of ice, my musings on interpretation of the satellite images on the DMI site do have a relevance, if they allow to gain an impression of the state of the ice. I think the image below shows how there is thick ice but not much of it in a coherent stretch to offer much resistance to movement. What that does to keep ice from leaving the arctic and melting may well have much to do with the weather. Increased movement to the west would keep it safe if clouds play their part.

Jim Hunt

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #41 on: November 26, 2013, 12:32:44 PM »
IMB 2013E set a new daily distance record of 72.2 km a couple of days ago, and is now south of Svalbard:
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #42 on: November 26, 2013, 07:18:49 PM »
.... set a new daily distance record of 72.2 km a couple of days ago, and is now south of Svalbard:

Wow.  That implies a Fram export rate of upwards of 10,000 KM2/day... Possibly quite a bit more... And older ice at that.

That's dwarfed by daily reductions during melt season, and doesn't impeded the refreeze, but the "preference" towards older ice has implications for the physical integrity of the pack.
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Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #43 on: November 27, 2013, 12:27:45 AM »
older, thicker ice is being moved east along the north coast of greenland lining it up for the fram strait exit.
http://ocean.dmi.dk/arctic/images/MODIS/MorrisJessup/201311261313.NOAA.jpg
Of course for now than means expansion and leads which quickly freeze over. What I take from this is that ice extent now is a short term effect.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #44 on: November 27, 2013, 12:58:31 AM »
older, thicker ice is being moved east along the north coast of greenland lining it up for the fram strait exit.
http://ocean.dmi.dk/arctic/images/MODIS/MorrisJessup/201311261313.NOAA.jpg
Of course for now than means expansion and leads which quickly freeze over. What I take from this is that ice extent now is a short term effect.

It is a conveyor, for certain, with new ice filling in behind the old.  I think the key aspect is, that while the discharge rate isn't necessarily greater than in the past, the *proportionate* export of older ice as compared to MYI extent, especially ice more than two years old, is much higher than in the past. I think the eventual result will be an ice grinder writ large... The entire arctic as opposed to just the Beaufort.  2013 may have given us a modest preview of that.
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Andreas T

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #45 on: November 27, 2013, 10:18:36 PM »
Watching the 30 day animation of sea ice thickness via the Arctic Sea Ice graphs page
http://www7320.nrlssc.navy.mil/hycomARC/arctic.html,I am surprised how quickly thickness changes in the colour range representation. In the Lincoln Sea it goes from 4.5 to 5m in not a lot of days. Some possibilities come to mind, e.g. issues with representation and rounding or more physical isues of averaging when ridges could rise fairly quickly or compaction pushes thicker ice floes into thinner ice infill. Satellite imagery available doesn't seem to have the resolution to answer that question. Bottom freezing just wouldn't happen that quickly with heat transfer having to go through over 4m of ice, I would guess.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #46 on: December 07, 2013, 02:19:45 PM »
older, thicker ice is being moved east along the north coast of greenland lining it up for the fram strait exit.
http://ocean.dmi.dk/arctic/images/MODIS/MorrisJessup/201311261313.NOAA.jpg
Of course for now than means expansion and leads which quickly freeze over. What I take from this is that ice extent now is a short term effect.

Having reached about 74ºN on Dec 1 the N Pole webcam appears to have given up reporting its position, still some weather data though.  Still indicates a rapid flow through the Fram up until then.

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #47 on: December 08, 2013, 01:49:34 AM »
Watching the 30 day animation of sea ice thickness via the Arctic Sea Ice graphs page
http://www7320.nrlssc.navy.mil/hycomARC/arctic.html,I am surprised how quickly thickness changes in the colour range representation. In the Lincoln Sea it goes from 4.5 to 5m in not a lot of days. Some possibilities come to mind, e.g. issues with representation and rounding or more physical isues of averaging when ridges could rise fairly quickly or compaction pushes thicker ice floes into thinner ice infill. Satellite imagery available doesn't seem to have the resolution to answer that question. Bottom freezing just wouldn't happen that quickly with heat transfer having to go through over 4m of ice, I would guess.

I think it is fairly safe to assume a couple of things.... That ice didn't thicken via freezing, and most of it isn't actually that thick.  The insulative quality of ice makes it necessary for temps to fall consistently below -40 C for that.
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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #48 on: December 25, 2013, 06:31:57 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

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Re: Drift, Deformation and Fracture of Sea Ice
« Reply #49 on: December 25, 2013, 10:05:04 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.
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