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Anonymouse

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Brinicle - is this a thing?
« on: April 15, 2013, 06:08:35 AM »
I was recently introduced to the concept of a "brinicle".  Kind of fascinating in its own right, but in shallower water does it have any implications for the Arctic and its wildlife given weird thaw/freeze conditions this spring? (Sorry for the strange tangent if not relevant in the least.  :-[)


ggelsrinc

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Re: Brinicle - is this a thing?
« Reply #1 on: April 15, 2013, 06:55:47 AM »
Little of that fragmented arctic area was shallow.



Does the Arctic Ocean have starfish and sea urchins like Antarctica? Can phytoplankton survive the freezing? Where do the jellyfish hang out?



« Last Edit: April 15, 2013, 07:03:38 AM by ggelsrinc »

ChrisReynolds

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Re: Brinicle - is this a thing?
« Reply #2 on: April 15, 2013, 07:40:10 AM »
For context: Those brinicles are from the Antarctic.

Anonymouse

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Re: Brinicle - is this a thing?
« Reply #3 on: April 15, 2013, 09:33:54 AM »
Hi Chris,
Thanks for the reply. I do (and did) realize the attached vid was referencing the Antarctic, I wondered if it had any relevance to the Arctic.  Just a freaky thing that happens, attached to an antarctic ice shelf, and I wondered if anything like that might be happening up north under the ice.  It seems logical to me that if this is happening in the Antarctic, it might also be happening in the Arctic. A quick google is unsatisfying, as I have been unable to determine how related the phenomenon is to ice near land.  Has this been seen in the Arctic regions?
« Last Edit: April 15, 2013, 09:45:34 AM by Anonymouse »

ggelsrinc

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Re: Brinicle - is this a thing?
« Reply #4 on: April 15, 2013, 10:31:10 AM »
Hi Chris,
Thanks for the reply. I do (and did) realize the attached vid was referencing the Antarctic, I wondered if it had any relevance to the Arctic.  Just a freaky thing that happens, attached to an antarctic ice shelf, and I wondered if anything like that might be happening up north under the ice.  It seems logical to me that if this is happening in the Antarctic, it might also be happening in the Arctic. A quick google is unsatisfying, as I have been unable to determine how related the phenomenon is to ice near land.  Has this been seen in the Arctic regions?

About a minute into the video I posted, the upside down diver moves what appears to be a brinicle and they said they were at the North Pole. Mortality would appear to require a slow moving organism that dies if frozen. An area with starfish is going to have to have slow moving bivalves and that area of fragmentation has walrus which also eat them. I've seen slow bottom dwellers in the Arctic Ocean in the Greenland and Barent Seas, but not in the areas of that cracked and refroze. I would expect cracking around shallow areas allowing new sea ice to form to be common in the arctic.

The interesting thing about the brinicles is how fast they formed. That tells me sea ice can lose salinity faster than I imagined.   

anonymous

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Re: Brinicle - is this a thing?
« Reply #5 on: April 15, 2013, 12:20:39 PM »
For context: Those brinicles are from the Antarctic.
Brinicles are a feature of sea ice, not of the Antarctic. However, since they are very fragile they grow that big only in calm water below non moving floes - conditions very rare in the Arctic.

Vergent

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Re: Brinicle - is this a thing?
« Reply #6 on: April 15, 2013, 03:38:24 PM »
Thanks for the videos. Brinicles form under rapidly freezing sea water, there must have been millions  in the Feb. break-up. They are instructive of how salinity is redistribute under thickening sea ice. This is happening even when the rate constant is too slow to freeze pipes. But then, it is invisible and more chaotic.

This is one of the factors that is surely missing from the models! Brinicles conduct cold(heat that has been conducted out of the ice) away from the ice without thickening it. In the first video, it contributes to bottom freeze rather than thickening. In deep water it would contribute to deep cooling, not thickening. This is why PIOMAS overestimates thin ice thickness!?

V
« Last Edit: April 15, 2013, 04:03:58 PM by Vergent »

ChrisReynolds

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Re: Brinicle - is this a thing?
« Reply #7 on: April 15, 2013, 07:59:03 PM »
I'm confused now.

The first video, which I can't see (not available in UK), I recall as being from the Antarctic, showing brinicles trapping starfish. It's from Frozen Planet which I saw when it aired and have bought on DVD. The second video of divers was from the Arctic.

The initial reason I thought that brinicles might not form in the Arctic is that Antarctica gets far colder coastal katabatic winds. And given the depth of the water, this was obviously coastal. However it's not unreasonable that the -30degC typical of the Arctic could cause brinicles. Arcticio's point about currents and the need for still water is valid, however under much of the Antarctic sea ice there is still the circumpolar current. So I think it's probably reasonable to see them as a feature of ice in still water in inlets etc along the coast.

And to answer the initial question, a brinicle is definitely a thing.  ;D


ggelsrinc

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Re: Brinicle - is this a thing?
« Reply #8 on: April 16, 2013, 02:44:48 AM »
Quote
The formation of ice from salt water produces marked changes in the composition of the unfrozen water. When water freezes, most impurities are forced out of solution; even ice from seawater is relatively fresh compared with the seawater it is formed from. As a result of forcing the impurities out, sea ice is very porous and spongelike, quite different from the solid ice produced when fresh water freezes.
 
As the seawater freezes and salt is forced out of the pure ice crystal lattice, the surrounding water becomes more saline. This lowers its freezing temperature and increases its density. The lower freezing temperature means that the surrounding water does not freeze to the ice immediately, and the higher density means that it sinks. Thus tiny tunnels called brine channels are created all through the ice as this supersaline, supercooled water sinks away from the frozen pure water. The stage is now set for the creation of a brinicle.
 
As this supercooled saline water reaches unfrozen seawater below the ice, it will cause the creation of additional ice. If the brine channels are relatively evenly distributed, the ice pack grows downward evenly. However, if brine channels are concentrated in one small area, the downward flow of the cold water, now so saline that it cannot freeze at its normal freezing point, begins to interact with unfrozen seawater as a flow. Just as hot air from a fire rises as a plume, this cold water descends as a plume. Its outer edges begin to accumulate a layer of ice as the surrounding water, cooled by this jet to below its freezing point, ices up. This is a brinicle: a "chimney" of ice that contains a flow of this supercold, supersaline water.
 
When the brinicle becomes thick enough, it becomes self-sustaining. As ice accumulates around the down-flowing cold jet, it forms an insulating layer that prevents the cold, saline water from diffusing and warming. As a result, the ice jacket surrounding the jet grows downward with the flow. It is like an icicle turned inside-out; rather than cold air freezing liquid water into layers, down-rushing cold water is freezing the surrounding water, enabling it to descend even deeper. As it does, it creates more ice, and the brinicle grows longer.
 
A brinicle is limited in size by the depth of the water, the growth of the overlying sea ice fueling its flow, and the surrounding water itself. In 2011, brinicle formation was filmed for the first time.[3]

Source: http://en.wikipedia.org/wiki/Brinicle

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=385906&fulltextType=RA&fileId=S0022112074001017

My impression is the requirements for brinicle formation are much more dependent on still waters and brine channels being concentrated in a small area, because the chilling conditions are very common. The downward growing ice on a brinicle is very fragile and once they strengthen they grow enough weight to break off in areas that aren't shallow.

What I find significant is it changes my perspective on how fast sea ice can lose salinity and how brine channels with or without brinicles can remove salinity to lower depths. A spongy first year sea ice should be able to fill up with less saline water more quickly than I imagined.

Chuck Yokota

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Re: Brinicle - is this a thing?
« Reply #9 on: April 16, 2013, 04:09:34 PM »
So, in areas where brinicles do not form due to currents or depth, are there still descending plumes that carry the cold brine down from the surface levels?  Is this what is meant by "brine rejection"?

Yuha

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Re: Brinicle - is this a thing?
« Reply #10 on: April 16, 2013, 04:52:55 PM »
Here's a BBC story about the filming of that video clip:

http://www.bbc.co.uk/nature/15835017

ChrisReynolds

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Re: Brinicle - is this a thing?
« Reply #11 on: April 16, 2013, 05:30:06 PM »
So, in areas where brinicles do not form due to currents or depth, are there still descending plumes that carry the cold brine down from the surface levels?  Is this what is meant by "brine rejection"?

Yes.

Brine rejection is the rejection of brine from the ice as it forms, because ice cannot contain salt. The first year ice contains a remnant of brine as brine pockets. But most of the brine is rejected, in models this rejected very salty, cold, dense, brine falls through the ocean column and plays a role in ventilating the ocean column, i.e. it falls through the layers of the ocean mixing as it goes.

The only reference to this process I've seen in observational studies is from the late 1990s.
Rudels et al, 1996, Formation and evolution of the surface mixed layer and halocline of the Arctic Ocean. It referred to brine rejection causing mixing at the shelf edge, the shelf edge being the edge of the continental shelf. The summer ice edge at the time was much closer to the Siberia at the time, which means less autumn/winter ice growth was occurring at the time. So brine rejection was much more limited in volume and was occurring nearer to the coast. In recent years there's been excessive open water away from the coast, even away from the continental shelf. I'm not sure what effect this is having.

Anyone got more up to date literature?