A large slab of ice is breaking off an Antarctic glacier(businessinsider.com)
businessinsider.com
A large slab of ice is breaking off an Antarctic glacier
http://www.businessinsider.com/antarctica-giant-iceberg-breaking-off-2017-1
122 comments
A few questions:
* How long will it take for "Deleware" to melt?
* Is ocean ice this large called an iceberg?
* Does is get an official name, like IIS Wilmington (international ice station, capital of Deleware)?
* Have large ice sheets in the past forced/caused changes in human behavior, such as altering shipping lanes, in the same way planes fly around a storm?
* How long will it take for "Deleware" to melt?
* Is ocean ice this large called an iceberg?
* Does is get an official name, like IIS Wilmington (international ice station, capital of Deleware)?
* Have large ice sheets in the past forced/caused changes in human behavior, such as altering shipping lanes, in the same way planes fly around a storm?
> * How long will it take for "Deleware" to melt?
Potentially a very long time, although it will likely break into smaller pieces first. A lot of icebergs get caught in the Antarctic Coastal Current, and just drift around the edge of Antarctica, not melting very much at all. Over time, most of them break free and drift north into warmer waters and melt, but others stick around. Iceberg B-9, which calved in 1987, still has a few chunks sitting around.
> * Is ocean ice this large called an iceberg?
Yes. You'll sometimes see the bigger bergs described as "ice islands", but that's just a subcategory of iceberg.
> * Does is get an official name, like IIS Wilmington (international ice station, capital of Deleware)?
It'll get a numeric designation, A-nn, where A indicates which quadrant of Antarctica it originated from (in this case 0-90W) and nn is a sequential number, probably in the high sixties depending on whether any other large bergs calve first. Then, as it breaks up, the resulting bergs will get letters added to the name, A-nnA, A-nnB, etc.
> * Have large ice sheets in the past forced/caused changes in human behavior, such as altering shipping lanes, in the same way planes fly around a storm?
In 2005, B-15A blocked the entrance to McMurdo Sound, where the main US and New Zealand Antarctic bases are located, and they were unable to get cargo ships in for a few weeks. And of course, ships are redirected around icebergs in the open ocean all the time.
Potentially a very long time, although it will likely break into smaller pieces first. A lot of icebergs get caught in the Antarctic Coastal Current, and just drift around the edge of Antarctica, not melting very much at all. Over time, most of them break free and drift north into warmer waters and melt, but others stick around. Iceberg B-9, which calved in 1987, still has a few chunks sitting around.
> * Is ocean ice this large called an iceberg?
Yes. You'll sometimes see the bigger bergs described as "ice islands", but that's just a subcategory of iceberg.
> * Does is get an official name, like IIS Wilmington (international ice station, capital of Deleware)?
It'll get a numeric designation, A-nn, where A indicates which quadrant of Antarctica it originated from (in this case 0-90W) and nn is a sequential number, probably in the high sixties depending on whether any other large bergs calve first. Then, as it breaks up, the resulting bergs will get letters added to the name, A-nnA, A-nnB, etc.
> * Have large ice sheets in the past forced/caused changes in human behavior, such as altering shipping lanes, in the same way planes fly around a storm?
In 2005, B-15A blocked the entrance to McMurdo Sound, where the main US and New Zealand Antarctic bases are located, and they were unable to get cargo ships in for a few weeks. And of course, ships are redirected around icebergs in the open ocean all the time.
> Iceberg B-9, which calved in 1987, still has a few chunks sitting around.
Thanks for posting, and curious about this. When icebergs subdivide, how is tracking accomplished?
I assume late 80s was recent enough for decent resolution space imagery?
Thanks for posting, and curious about this. When icebergs subdivide, how is tracking accomplished?
I assume late 80s was recent enough for decent resolution space imagery?
Yeah, once these things are moving, you don't need much resolution to see them - we're talking about objects several kilometers wide, at the very least. Easily visible on even the most primitive satellite imagery. The difficulties would be cloud cover and orbital inclination.
> I assume late 80s was recent enough for decent resolution space imagery?
Landsat (https://en.wikipedia.org/wiki/Landsat_program) was likely the best available imagery back then. In the 80's it looks like they had 60m resolution - I assume that would be big enough to see an iceberg?
Landsat (https://en.wikipedia.org/wiki/Landsat_program) was likely the best available imagery back then. In the 80's it looks like they had 60m resolution - I assume that would be big enough to see an iceberg?
I'm not an expert on icebergs but I have used enough satellite imagery to answer... Yes the 60m Landsat imagery would show large icebergs under its ground track.
Thanks!
That bit about McMurdo is interesting. I doesn't surprise me, but I didn't know, that they send and receive thinhs via ships. I always hear about McMurdo as being inaccessible by plane during some chunk of time during the cold season, usually tied to some real world emergency or movie plotline with a sense of urgency.
That bit about McMurdo is interesting. I doesn't surprise me, but I didn't know, that they send and receive thinhs via ships. I always hear about McMurdo as being inaccessible by plane during some chunk of time during the cold season, usually tied to some real world emergency or movie plotline with a sense of urgency.
Potentially a very long time, ...
It's almost like the conventional terminology for bergs (http://www.ccg-gcc.gc.ca/e0010735) might need to be expanded for these monsters. Some of them may as well be floating glaciers.
FYI, Dover's the capital of Delaware.
(pedantic Blue Hen here.)
(pedantic Blue Hen here.)
Will there be a man made ravine breaking it into northern & souther halves, though?
My bad :). My head said Dover, and my hands wrote biggest city I could remember. Don't tell my 8th grade U.S. History teacher. He'd have an anuerism.
Or your spelling teacher (aneurysm)
Don't tell his spelling coach either!!
Wouldn't your geography teacher be more annoyed than your history teacher, or have I missed the point?
My U.S. History teacher grilled us every week on knowing US states & their capitols. You have to show weekly improvement, and finish the term w/ 100%.
Regarding spelling, I plead not guilty by reason of autocorrect+gorilla-fingers-on-little-screen.
Regarding spelling, I plead not guilty by reason of autocorrect+gorilla-fingers-on-little-screen.
In some schools (like mine) we did a geography segment as part of the history class. So same teacher, primarily teaching history.
> Have large ice sheets in the past forced/caused changes in human behavior
Not human in this example, but they can be devastating to penguin populations:
https://www.theguardian.com/world/2016/feb/13/150000-penguin...
Not human in this example, but they can be devastating to penguin populations:
https://www.theguardian.com/world/2016/feb/13/150000-penguin...
I have a really stupid question. Here it goes, anyway. Isn't there a way to "glue" these big block of ice back to the main part?
I was going to add a few ideas on how to glue it back, but then I deleted them as it would sound more stupid than it already does.
I was going to add a few ideas on how to glue it back, but then I deleted them as it would sound more stupid than it already does.
I think you might need to recalibrate your idea of the scale of this object. The iceberg weighs about a trillion (10^12) tons. For comparison, a Nimitz-class aircraft carrier is about a hundred thousand (10^5) tons. So you're talking about moving an object which weighs about a million times as much as the whole US Navy carrier fleet.
Then, once you had it back into position, you'd need to apply your "glue" to the whole crack surface, which is around 40 square kilometers, a little smaller than Manhattan Island. Also, the majority of that crack surface is hundreds of meters deep in sub-zero waters in one of the most inaccessible places on the planet.
Then, once you've done that, the same forces which caused this bit to calve off would cause a new bit to calve a year or two later.
Then, once you had it back into position, you'd need to apply your "glue" to the whole crack surface, which is around 40 square kilometers, a little smaller than Manhattan Island. Also, the majority of that crack surface is hundreds of meters deep in sub-zero waters in one of the most inaccessible places on the planet.
Then, once you've done that, the same forces which caused this bit to calve off would cause a new bit to calve a year or two later.
What would be the point? Even if you could somehow freeze it back on, the natural forces that caused it to calve off are going to continue, so all you've done is bought a little time, perhaps not even a full season.
Get 10,000 snow machines to dredge the water and spray snow and water everywhere ;) If people can build islands, why not glaciers?
Nuclear winter.
I saw some footage on the BBC over the weekend showing the are around the Larsen Ice Shelf and I was stuck by how perfectly sheered many of the ice bergs in the area were. They looked like precision cuts, perfectly flat, they looked like blocks. I have not seen this before. Is there an explanation to this phenomenon of near perfect cleaving?
Also are there implications for the glacier(s) that feed this ice shelf after this part of the shelf breaks off?
Also are there implications for the glacier(s) that feed this ice shelf after this part of the shelf breaks off?
Yes, the edges are impressive, aren't they? The ice is floating, almost flat, and has had hundreds of years to reach equilibrium, so there's practically zero vertical shear stress in the ice shelf. As well as that, the ice itself is very laterally homogeneous - there are layers within it, but all the horizontal variability is on scales of kilometers or more. There are no particular faults or planes of weakness within the material. This means that when it breaks under tension, like this, it breaks in a very clean and even way.
Also, remember, you're only seeing the top 10% or so of the berg. There can be interesting shapes below the waterline, caused by preferential melting.
As for the glaciers feeding the shelf, that's an interesting question. Floating ice on its own provides very little resistance to their flow, but the mouth of the ice shelf is narrower than the back, so the converging flow has a resistive effect, like squeezing toothpaste out of a tube. If a gap is made in the ice blocking the mouth, then there should be some speedup of the glaciers. It all depends on exactly where the rift goes next, and on the exact balance of stresses in the shelf, which there's some uncertainty about.
Also, remember, you're only seeing the top 10% or so of the berg. There can be interesting shapes below the waterline, caused by preferential melting.
As for the glaciers feeding the shelf, that's an interesting question. Floating ice on its own provides very little resistance to their flow, but the mouth of the ice shelf is narrower than the back, so the converging flow has a resistive effect, like squeezing toothpaste out of a tube. If a gap is made in the ice blocking the mouth, then there should be some speedup of the glaciers. It all depends on exactly where the rift goes next, and on the exact balance of stresses in the shelf, which there's some uncertainty about.
Fascinating. Thank you for the detailed response. This is a really iteresting project, its wonderful that you get to work on such things. I will now have to stay updated with the progress. That photo in the article of the plane wing and the fissure extending to the horizon really puts the beauty of the Antarctic in perspective. I would like to make it down there one day. Cheers.
Hi, there seems to be some mixed messages on the implications of this for the rest of the Larsen C shelf. Are we likely to see a collapse of the whole thing in the next few years, Larsen B style?
Probably not. The Larsen B collapse was preceded by widespread surface melting across the shelf, which caused lots of crevasses to fill with water, driving them open, and the whole shelf pretty much shattered under the stress. We don't see that sort of melt on Larsen C - even though it's quite nearby, the climate is a couple of degrees colder.
A more probable (but still fairly unlikely) scenario is that this could destabilise the ice shelf over a longer timescale (maybe decades). Removing ice from the front would let the ice behind accelerate, stretch and thin, which makes it more vulnerable to calving again, and so forth.
The most likely outcome though is that there's no significant change to the ice shelf, except maybe the flow of the ice speeds up a bit, which is interesting glaciologically, but probably not something the rest of the world will get excited about.
Obviously, any and all of this could change as the climate continues to warm. If we start to see significant levels of surface melt ponding across the shelf, then we can worry.
A more probable (but still fairly unlikely) scenario is that this could destabilise the ice shelf over a longer timescale (maybe decades). Removing ice from the front would let the ice behind accelerate, stretch and thin, which makes it more vulnerable to calving again, and so forth.
The most likely outcome though is that there's no significant change to the ice shelf, except maybe the flow of the ice speeds up a bit, which is interesting glaciologically, but probably not something the rest of the world will get excited about.
Obviously, any and all of this could change as the climate continues to warm. If we start to see significant levels of surface melt ponding across the shelf, then we can worry.
And what if you are wrong about that prediction?
Thanks for these facts! The article has somewhat of a different spin on it.
Well, there's not a whole lot of factual difference between "Big Thing Could Happen" and "Big Thing Probably Won't Happen", and I know which one I'd lead with if I was an editor. I don't think there's anything in the article which I'd disagree with on a scientific level.
Is there anything living on/around that ice? Will this have any immediate ecological effects if it does start to drift away?
I think there are some microorganisms in the snowpack, but other than that it's a pretty barren place, at least above the water. Below, a lot of sea life congregates around the ice front - there are nutrients that melt out of the ice - and this supports an ecosystem, but that should all just move to the new ice front. The iceberg itself will probably support a small marine ecosystem as it floats away and melts.
I'm not an ecologist though, so I'm hazy on the details.
I'm not an ecologist though, so I'm hazy on the details.
>I think there are some microorganisms in the snowpack, but other than that it's a pretty barren place, at least above the water.
Just guessing:
There might be tardigrades. They can withstand extremes of hot and cold. First saw them mentioned here on HN some time ago. Amazing creatures. From the Wikipedia article:
Tardigrades are notable for being the most resilient animal: they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C),[8] pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.[9] They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.[3][10][11][12]
https://en.wikipedia.org/wiki/Tardigrade
Just guessing:
There might be tardigrades. They can withstand extremes of hot and cold. First saw them mentioned here on HN some time ago. Amazing creatures. From the Wikipedia article:
Tardigrades are notable for being the most resilient animal: they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C),[8] pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.[9] They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.[3][10][11][12]
https://en.wikipedia.org/wiki/Tardigrade
Is this event likely to cause large waves in the area? I ask because I will be taking a cruise next month which stops in the Antarctic sound, and I would like to live.
No, not particularly. It's already floating, so it will just drift away for the most part. Some smaller bits will probably fall off and produce some spectacular waves. By smaller bits, I mean stuff up to a cubic kilometer, so I wouldn't want to be standing next to it when it happens.
This is all much further south than cruise ships normally go though.
This is all much further south than cruise ships normally go though.
Just curious if large ice shelves like this ever start to separate and end up refreezing before they actually break. Looking at the diagram in the article leads me to think that this part of the ice shelf is a goner, but I don't actually know that much about the environment in or near Antarctica.
It's unlikely in this case, but it has happened in some other areas. The Brunt Ice Shelf (where the British Halley VI station is located) is largely made of reconstituted icebergs like you describe.
Of course, that shelf is also having some crack problems: https://www.theguardian.com/world/2016/dec/07/british-antarc...
Of course, that shelf is also having some crack problems: https://www.theguardian.com/world/2016/dec/07/british-antarc...
So what should we (the people) do about it ?
What is your theory ? What should society as a whole do now in order to stop these processes ?
What is your theory ? What should society as a whole do now in order to stop these processes ?
Nothing! This is a completely natural process - ice builds up over time in the shelf and it has to be lost somehow. The calving of the iceberg is, in itself, not a result of human activity.
If you mean more broadly how can we help prevent the loss of ice from Antarctica, then I'm not a climate policy expert, but https://350.org/ is a good place to start.
If you mean more broadly how can we help prevent the loss of ice from Antarctica, then I'm not a climate policy expert, but https://350.org/ is a good place to start.
I have read that Antarctic ice is overall increasing. Is there a reason to be concerned with loss of ice from Antarctica? https://insideclimatenews.org/news/31052016/why-antarctica-s...
We need to distinguish between sea ice (a ~1m thick layer of frozen seawater), and land ice (up to 3000m thick layer of compacted snow). Sea ice is quick to respond to climate change (because it's so thin), and has a large seasonal component to its extent. Land ice is much slower to respond, and harder to replace once it's gone.
Antarctic sea ice extent has been increasing, largely because of a change in wind patterns. Winds blow ice away from the coast, leading to more open water, which leads to more sea ice formation. Even though Antarctica is getting warmer, it's still much too cold to melt sea ice in most places, so climate warming isn't having a huge direct effect on sea ice.
However, the land ice in the Antarctic is almost certainly decreasing (exact measurements are quite hard), and the trend is definitely towards more ice loss. Ice shelves, although floating, are the outer extremes of this land ice.
This is a good review paper on the subject of the mass balance of land ice: http://www.vliz.be/imisdocs/publications/248038.pdf
Antarctic sea ice extent has been increasing, largely because of a change in wind patterns. Winds blow ice away from the coast, leading to more open water, which leads to more sea ice formation. Even though Antarctica is getting warmer, it's still much too cold to melt sea ice in most places, so climate warming isn't having a huge direct effect on sea ice.
However, the land ice in the Antarctic is almost certainly decreasing (exact measurements are quite hard), and the trend is definitely towards more ice loss. Ice shelves, although floating, are the outer extremes of this land ice.
This is a good review paper on the subject of the mass balance of land ice: http://www.vliz.be/imisdocs/publications/248038.pdf
Worse, melting land-ice increases sea level, while melting sea ice does not.
If the entire Antarctic ice shelf melted, global sea levels would rise about 60 meters (200 feet).
http://science.howstuffworks.com/environmental/earth/geophys...
Though it would take a huge temperature rise for that to happen -- enough that the other climatic effects would probably be as bad or worse than the sea level rise.
Greenland is not nearly so cold, so it's more likely that its ice shelf would melt, which would add about 7 meters (20 feet) to sea level.
If the entire Antarctic ice shelf melted, global sea levels would rise about 60 meters (200 feet).
http://science.howstuffworks.com/environmental/earth/geophys...
Though it would take a huge temperature rise for that to happen -- enough that the other climatic effects would probably be as bad or worse than the sea level rise.
Greenland is not nearly so cold, so it's more likely that its ice shelf would melt, which would add about 7 meters (20 feet) to sea level.
The larger problem with melting sea ice, as I understand it, is that the reflectivity of water is much lower than that of ice, so less of the incoming energy from the sun is reflected, accelerating warming.
The antarctic is fundamentally different from the Arctic (it is the Arctic that is the canary in the coalmine for global warming). It is surrounded by >30 degrees of latitude of water, and the Coriolis effect ensures that winds blow without the interference of land around the globe between the roaring forties and screaming sixties. This insulates the antarctic and is the main reason it is colder than the Arctic - there is little heat transfer from warmer latitudes. In contrast, the Arctic is all about heat transfer and global warming simulations show it will warm much faster than the antarctic.
Reference: http://www.livescience.com/40125-climate-change-affecting-ar...
Reference: http://www.livescience.com/40125-climate-change-affecting-ar...
Here's a good reference explaining the data:
https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-o...
The article says that this is "likely accelerated by rapid human-caused global warming." Is that actually true? Does a degree or two make such a difference to something so huge?
What that bit is referring to is that the ice shelf has been thinning as a result of climate change. The temperatures on the Antarctic Peninsula have increased by about 3˚C (5˚F) over the past half century or so, which is a huge change to the climate of a region.
I get that the temperature increase is happening, but I don't get how this in turn increases the melting and thinning of ice. According to Wikipedia, summer temperatures in the warmest part of Antarctica still average below 0°C. Can someone explain?
There's a big difference between average temperatures and peak temperatures. On Larsen C, we regularly measure localised temperatures in excess of 10˚C for days at a time. That's enough for some serious melt.
Also, surface melt is only half the story. The base of the ice is in contact with the ocean, which is also warming. Water in contact with ice is (more or less by definition) at the freezing/melting point - if it warms, the ice melts a bit, if it cools, the water freezes. So a change in ocean temperatures can have a big effect on melt rates.
Finally, it's not enough that the shelf be in equilibrium, melt-wise. The ice is constantly thinning, as it stretches and flows under its own weight. There needs to be enough extra mass added (mostly as snow) to compensate for that, if the shelf is to remain a constant thickness.
Also, surface melt is only half the story. The base of the ice is in contact with the ocean, which is also warming. Water in contact with ice is (more or less by definition) at the freezing/melting point - if it warms, the ice melts a bit, if it cools, the water freezes. So a change in ocean temperatures can have a big effect on melt rates.
Finally, it's not enough that the shelf be in equilibrium, melt-wise. The ice is constantly thinning, as it stretches and flows under its own weight. There needs to be enough extra mass added (mostly as snow) to compensate for that, if the shelf is to remain a constant thickness.
Thank you! :)
Here's a question: Are you at all comfortable with the realization that a website as bad as Business Insider is carrying your story? Understanding, of course, that the grand majority of the stories on that site are out and out clickbait garbage.
Well, it's a major news story - according to our press office, over a thousand outlets worldwide were carrying the story. So it would be weird if Business Insider didn't cover it. That said, I'm slightly surprised that this is the version of the story linked on HN. Personally, I like the BBC version better: http://www.bbc.co.uk/news/science-environment-38522954
[deleted]
How far could it float away? Any chance of crashing into South America?
Unlikely, it's hard for these things to get close to the coast - remember that the base is several hundred meters below sea level, so it will ground if it gets into even remotely shallow water. More likely it'll break up, and bits will wander off into the South Atlantic and Indian oceans.
There are quite a few inhabited islands spread between south America and southern Africa.
They're mostly old volcanoes some are still active but so pointy there wouldn't be much for a berg to catch on until it was right on top of them.
https://upload.wikimedia.org/wikipedia/commons/8/8e/British_...
They're mostly old volcanoes some are still active but so pointy there wouldn't be much for a berg to catch on until it was right on top of them.
https://upload.wikimedia.org/wikipedia/commons/8/8e/British_...
Thank you for using proper units in your spreadsheet :)
you may also be interested in:
largest glacier calving ever filmed:
https://www.youtube.com/watch?v=hC3VTgIPoGU
largest glacier calving ever filmed:
https://www.youtube.com/watch?v=hC3VTgIPoGU
For some context on size, the calving event in this video is about 7 cubic kilometers. The Larsen C berg will be about 1000 cubic kilometers. On the other hand, this berg is overturning, so the calving is, to put it mildly, quite energetic (equivalent to a couple of hundred kilotons of TNT). The Larsen C berg will just drift away in a much less dramatic fashion.
yeah, thx for the numbers. i wasn't implying the scale was comparable :)
This article is about Larsen C-- so this is borderline off-topic, but I always enjoyed this ode to Larsen B. "British Sea Power - Oh Larsen B" https://www.youtube.com/watch?v=_HN0rqVJT4U
Thank you @mewo2 for your insider responses - a fantastic ammendum to the original article!
"The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive." — Donald J. Trump (@realDonaldTrump) November 6, 2012
Doesn't seem like that big of a deal considering it's already floating on water, so it's displacing the water it'll make when it melts. No sea rise at all.
I believe part of the concern is that this ice shelf is holding back land ice that would cause sea level rise. Quoting Wikipedia on the Larsen C shelf:
"After breaking away from Antarctica, it will leave the remainder of the shelf vulnerable to future collapse. If all the ice that the Larsen C shelf currently holds back were to enter the sea, it is estimated that global waters would rise by 10 cm (3.9 in)."
https://en.wikipedia.org/wiki/Larsen_Ice_Shelf#Larsen_C
"After breaking away from Antarctica, it will leave the remainder of the shelf vulnerable to future collapse. If all the ice that the Larsen C shelf currently holds back were to enter the sea, it is estimated that global waters would rise by 10 cm (3.9 in)."
https://en.wikipedia.org/wiki/Larsen_Ice_Shelf#Larsen_C
Ice shelves act as a "plug" to slow glaciers running into the sea. So the melting of ice shelves causes glaciers to run into the sea and melt faster. Check out the BBC documentary "Frozen Planet", episode 7 goes into detail.
It's a big symptom, not a big cause of additional problems (though, IIRC, breaking a big piece of the glacier off will increase the speed that the remaining glacier -- including the parts upstream still on land -- flows out into the ocean, which will result in sea level rise.)
Also, melting sea ice itself increases absorption of solar energy and accelerates global warming slightly. Its not a huge factor, IIRC, but you never want a positive feedback loop that reinforces and undesirable trend.
Also, melting sea ice itself increases absorption of solar energy and accelerates global warming slightly. Its not a huge factor, IIRC, but you never want a positive feedback loop that reinforces and undesirable trend.
The concern is that ice in general is melting, not that this particular instance is going to cause global sea rise.
The Artic (north pole) is the one floating on water. Antartica (south pole) is a continent just like North America, and its melting contributes to sea level rise just as much as a melting glacier does.
Sort of. The dramatism of melting ice is played up quite a bit in popular media.
Sea ice doesn't contribute to sea level rise when it rises; continental ice sheets and grounded ice shelves do. There are three great ice sheets: West Antarctica (~2.2 million km³), Greenland (~2.8 million km³) and East Antarctica (~20 million km³). By contrast, the largest ice shelf, Ross Ice Shelf, is only ~0.1-0.2 million km³. I don't know how much of that is grounded and thus capable of inducing sea level rise on loss. By comparison, the piece that's breaking off is only 1700 km³ or so.
Our knowledge of the exact state of these ice sheets and shelves has a lot of holes in them, but it's clear that the East Antarctic Ice Sheet is gaining in mass, West Antarctic Ice Sheet about stable to slightly negative, and Greenland is shedding at a fast clip of a few hundred km³/year. The ice shelves, particularly in West Antarctica, do seem to generally be in retreat.
At current rates of loss, the melting of the ice sheets provide only a very modest rate of sea level rise--maybe 0.5mm/yr. By comparison, in, say, Norfolk, the isostatic rebound from the loss of the Laurentide Ice Sheet contributes about 1.5mm/yr in sea level rise. The fear is that there could be some kind of tipping point that causes the ice sheets to very suddenly and dramatically collapse (à la Larsen B), but we don't have much evidence to suggest that this is likely to happen.
Sea ice doesn't contribute to sea level rise when it rises; continental ice sheets and grounded ice shelves do. There are three great ice sheets: West Antarctica (~2.2 million km³), Greenland (~2.8 million km³) and East Antarctica (~20 million km³). By contrast, the largest ice shelf, Ross Ice Shelf, is only ~0.1-0.2 million km³. I don't know how much of that is grounded and thus capable of inducing sea level rise on loss. By comparison, the piece that's breaking off is only 1700 km³ or so.
Our knowledge of the exact state of these ice sheets and shelves has a lot of holes in them, but it's clear that the East Antarctic Ice Sheet is gaining in mass, West Antarctic Ice Sheet about stable to slightly negative, and Greenland is shedding at a fast clip of a few hundred km³/year. The ice shelves, particularly in West Antarctica, do seem to generally be in retreat.
At current rates of loss, the melting of the ice sheets provide only a very modest rate of sea level rise--maybe 0.5mm/yr. By comparison, in, say, Norfolk, the isostatic rebound from the loss of the Laurentide Ice Sheet contributes about 1.5mm/yr in sea level rise. The fear is that there could be some kind of tipping point that causes the ice sheets to very suddenly and dramatically collapse (à la Larsen B), but we don't have much evidence to suggest that this is likely to happen.
I think this is somewhat misleading. Antarctica likely is still gaining ice mass overall, for complex reasons, even as the overall stability and health of the ice shelves and sheets weaken.
To boil it down to one key point, west antarctica has grounding lines which slope inward, such that the ice melting is already causing a positive feedback loop as melt accelerates the process of warm water working its way under the ice sheet.
So while no one is predicting an immediate collapse, there absolutely is reason to think we will and already have been crossing tipping points which will cause irreversible, continuing acceleration in melt.
[1] http://news.nationalgeographic.com/2016/04/160412-ice-sheet-...
[2] https://www.youtube.com/watch?v=YQMtb1Pd07E
[3] https://en.wikipedia.org/wiki/File:West_Antarctic_Collapse.o...
To boil it down to one key point, west antarctica has grounding lines which slope inward, such that the ice melting is already causing a positive feedback loop as melt accelerates the process of warm water working its way under the ice sheet.
So while no one is predicting an immediate collapse, there absolutely is reason to think we will and already have been crossing tipping points which will cause irreversible, continuing acceleration in melt.
[1] http://news.nationalgeographic.com/2016/04/160412-ice-sheet-...
[2] https://www.youtube.com/watch?v=YQMtb1Pd07E
[3] https://en.wikipedia.org/wiki/File:West_Antarctic_Collapse.o...
>Sea ice doesn't contribute to sea level rise when it rises
Isn't there a small but not insignificant sea level rise due to warming of the water due to less sea ice (less light reflected, greater warming of the sea than with an ice layer)?
Isn't there a small but not insignificant sea level rise due to warming of the water due to less sea ice (less light reflected, greater warming of the sea than with an ice layer)?
I think you need to caveat this only slightly.
1) At the moment when the sea ice breaks off there is no rising in overall level due to fact that the ice displaces the same volume of water as is in it.
2) during the melting phase if the sea water around the ice is greater than 4 degrees, the melting will cause a temporary drop in the local temperature of water causing the water level to in fact drop slightly.
3) in the LONG term, the additional volume of liquid water added by the ice will be warmed and expand causing a slight increase in water level due to thermal expansion (assisted by the change in albedo of the whole system as you mentioned)
1) At the moment when the sea ice breaks off there is no rising in overall level due to fact that the ice displaces the same volume of water as is in it.
2) during the melting phase if the sea water around the ice is greater than 4 degrees, the melting will cause a temporary drop in the local temperature of water causing the water level to in fact drop slightly.
3) in the LONG term, the additional volume of liquid water added by the ice will be warmed and expand causing a slight increase in water level due to thermal expansion (assisted by the change in albedo of the whole system as you mentioned)
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The numbers you give are generally supported by the 2013 consensus summary linked above by @mewo2 (http://www.vliz.be/imisdocs/publications/248038.pdf), although that summary pegs the sea level rise due to ice sheets (worldwide) to be more like 1 mm/year (see also their Table 1), within a total sea level rise of 2-3 mm/yr (all sources):
"The consensus picture emerging: whereas Antarctica as a whole is losing mass slowly (assessed to be contributing 0.2 mm/yr sea-level equivalent by IMBIE2), Greenland, the Antarctic Peninsula and parts of West Antarctica are together losing mass at a moderate (~1 mm/yr sea-level equivalent) rate today (~70% of this mass loss is from Greenland) and rates for each are becoming increasingly negative."
*
That summary is not willing to commit to a + or - sign for mass change in East Antarctica specifically, although some individual studies have shown mass growth there.
"The consensus picture emerging: whereas Antarctica as a whole is losing mass slowly (assessed to be contributing 0.2 mm/yr sea-level equivalent by IMBIE2), Greenland, the Antarctic Peninsula and parts of West Antarctica are together losing mass at a moderate (~1 mm/yr sea-level equivalent) rate today (~70% of this mass loss is from Greenland) and rates for each are becoming increasingly negative."
*
That summary is not willing to commit to a + or - sign for mass change in East Antarctica specifically, although some individual studies have shown mass growth there.
Yes, it's called a shelf for a reason.
Most of the sea level rise comes from melting land ice.
Most of the sea level rise comes from melting land ice.
Water in the form of a solid takes up less spaces than as a liquid so not sure I agree... Plus there is a large part of this that is above sea level currently so that part is not current being displaced.
I agree with Firebrand (^above) that if the ice is already floating (sea ice) and it melts it will cause no other immediate displacement of volume (even if a large part of that floating ice is above sea level and even if solid water takes up less space than liquid water). That's an application of Archimedes principle and can be explained here: http://physics.stackexchange.com/questions/110645/why-does-i.... Indeed it's land ice melting that causes sea level rise. However, sea ice melting still changes the albedo and does directly contribute to climate change.
True, I was thinking that its not truly free floating sea ice and that much of it may be supported by the remaining ice its attached to (hence the crack).
Water in the form of a solid is less dense than as a liquid
Source: Put some ice cubes in water. Observe that they float.
Source: Put some ice cubes in water. Observe that they float.
Of course it floats. But that's not what I was trying to say. Go to your cup, put some ice in it and then mark the water level. Now let the ice melt and remark the water level. They will be at the same level.
What happens when you add an ice-cube? That's what happens when ice slides off of continents.
A break-up this huge may not directly alter sea-levels but it's certainly symptomatic of a larger disruption that's playing out on a massive scale.
A break-up this huge may not directly alter sea-levels but it's certainly symptomatic of a larger disruption that's playing out on a massive scale.
Water takes up more space as a solid.
For the metric people who don't know random US states: 335 meters thick and about the size of Palestine.
Without getting too political, I don't think Palestine is a great comparison. Are we talking the original borders? The current borders? West Bank plus Gaza? The State of Palestine or the Palestinian Territories?
Palestine in particular is a country that is very difficult to judge the size of, for very political reasons. It's actually far easier for someone to look at a map of Delaware and judge its size than to look at a map of Palestine and judge its size.
Palestine in particular is a country that is very difficult to judge the size of, for very political reasons. It's actually far easier for someone to look at a map of Delaware and judge its size than to look at a map of Palestine and judge its size.
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Product idea: automatically generate dimensional metaphors with regional cultural context based on geoIP.
That's actually a great idea! Kind of what Wolfram|Alpha does when it gives you various comparisons to the number you've entered. E.g. for "10 kilotons":
EDIT:
For the ice slab in question, W|A gives following comparisons:
≈ (0.2 to 0.3) × mass of a Handy size cargo ship ( 28000 to 40000 lg tn )
≈ (0.3 to 0.5) × mass of a Small Handy size cargo ship ( 20000 to 28000 lg tn )
≈ 0.83 × daily mass of trash produced in New York City (≈ 1.2×10^7 kg )
EDIT:
For the ice slab in question, W|A gives following comparisons:
≈ ( 0.25 ≈ 1/4 ) × total area of Wales (≈ 8023 mi^2 )
≈ 1.7 × total area of Rhode Island ( 1212 mi^2 )
≈ 3 × area of forest flattened by the asteroid explosion over Tunguska in 1908 (≈ 2000 km^2 )Ha, sometimes I wonder if I've ever had an original idea.
I don't know if your idea is original - but it hasn't (?) been implemented yet - so implement it, if know how!
Maybe make it a greasemonkey script - then hook into Wolfram Alpha and display from that. GeoIP might not be too big on an issue, either...
Ultimately, it's not about whether the idea is original, but how the idea is executed. Think about it - how many social networks were there before Facebook? It isn't like Facebook is original, or the first, or even the last! Similar with Google (do you really think there won't be something that takes over Google's position with search, or does it better, or different?).
Don't worry about originality! Just take your idea(s) - and try to execute them - worry about what you can control, instead of what others control.
Maybe make it a greasemonkey script - then hook into Wolfram Alpha and display from that. GeoIP might not be too big on an issue, either...
Ultimately, it's not about whether the idea is original, but how the idea is executed. Think about it - how many social networks were there before Facebook? It isn't like Facebook is original, or the first, or even the last! Similar with Google (do you really think there won't be something that takes over Google's position with search, or does it better, or different?).
Don't worry about originality! Just take your idea(s) - and try to execute them - worry about what you can control, instead of what others control.
Sometimes I'd like that for new gadgets' comparison, say, a new iPhone or Android phone compared to previous iterations, a visual comparison, side by side or on top.
I always check that before buying a new phone: http://www.phonearena.com/phones/size
Brilliant, thanks!
Rhode Island isn't a random state, it was chosen for a reason.
I will say that I'm live in the US and don't have any real sense of the size of Rhode Island, or Palestine for that matter.
I will say that I'm live in the US and don't have any real sense of the size of Rhode Island, or Palestine for that matter.
"Smaller than Alaska"
The graphic from the MIDAS project also has a picture of Wales to compare with :)
They have their own brief blog post at: http://www.projectmidas.org/blog/larsen-c-ice-shelf-poised-t...
They have their own brief blog post at: http://www.projectmidas.org/blog/larsen-c-ice-shelf-poised-t...
Wikipedia has some pages with relatable examples of items of various sizes/area etc. from the very small to the very large.
In this case, it tells us this shelf is slightly taller than the Eiffel Tower [0] with an area a bit smaller than Bali. [1]
0: https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(length)
1: https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(area)
In this case, it tells us this shelf is slightly taller than the Eiffel Tower [0] with an area a bit smaller than Bali. [1]
0: https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(length)
1: https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(area)
Global warming (even if it were to happen again) is not the problem that it's made out to be. History has proven this several times, such as during HCO [1].
Not that most people on Hacker News would agree, but I encourage people to do more research on the topic. MIDAS is funded by NERC, so they obviously aren't going to share this view.
https://en.wikipedia.org/wiki/Holocene_climatic_optimum
Not that most people on Hacker News would agree, but I encourage people to do more research on the topic. MIDAS is funded by NERC, so they obviously aren't going to share this view.
https://en.wikipedia.org/wiki/Holocene_climatic_optimum
In an effort to keep this topical, how does the HCO show it to be less of a problem?
As I understand the origin of this phenomenon is understood to have to do with the axial rotation of the earth, and mostly had effects on the nothern hemisphere.
The reasons and effect of the warming we experience now are harldy comparable.
As I understand the origin of this phenomenon is understood to have to do with the axial rotation of the earth, and mostly had effects on the nothern hemisphere.
The reasons and effect of the warming we experience now are harldy comparable.
Sorry you got downvoted to hell, but certain subjects are echo chamber religion with a lot of folks. It's just how it is. I don't know how some people can be so open-minded to scientific inquiry one the one hand, but when it comes to the matter of climatology, they treat skeptics as sub-human heretics.
I tend to think it is a deep-seated personality flaw that a lot of people have but don't realize they have. They think they are more open-minded that they actually are.
I'm heartened knowing that not long ago, the majority of people believed the sun revolved around the earth and anyone who dared to speak against that "settled science" was excommunicated by the Catholic Church.
I tend to think it is a deep-seated personality flaw that a lot of people have but don't realize they have. They think they are more open-minded that they actually are.
I'm heartened knowing that not long ago, the majority of people believed the sun revolved around the earth and anyone who dared to speak against that "settled science" was excommunicated by the Catholic Church.
There is little need to be open minded when laymen challenge educated scientists. Climate denial has all the same mechanisms as Evolution denial. It all tends to boil down to the idea "But the scientist have an against religion / american lifestyle / whatever ".
I don't deny that many progressives are less open minded than they think. But better challenge them things like anti-GMO / pro-organics ideas that don't really have much base in real science.
Unlike in the climate field, you'll find that actually lots of people who research GM / food safety will not agree with the alarmist headlines of GMO or "processed foods".
I don't deny that many progressives are less open minded than they think. But better challenge them things like anti-GMO / pro-organics ideas that don't really have much base in real science.
Unlike in the climate field, you'll find that actually lots of people who research GM / food safety will not agree with the alarmist headlines of GMO or "processed foods".
You think someone with a doctorate is a layman? We're educated people, we can form our own opinions, thanks.
If your doctorate is in a completely unrelated field, yes, you are a layman.
Oh, so I am without the ability to reason? Hardly.
Your ability to reason is not being assessed, it's your level of exposure to and understanding of the facts. Which, if you are not a climate scientist, is unlikely to be exhaustive.
And the equivalent here are the ones denying the scientific discoveries and the consensus.
The climate deniers are the ones like the Catholic Church
The climate deniers are the ones like the Catholic Church
If that were so, then why is the majority the ones all in agreement? The people who are skeptics are few. Doesn't sound like any Catholic Church I am aware of.
The analogy is not by quantity, is by evidence.
The ones that doesn't have any evidence and deny all the experimental facts are the deniers.
The same with evolution/creationism
The ones that doesn't have any evidence and deny all the experimental facts are the deniers.
The same with evolution/creationism
You can't prove a negative "we don't have any evidence" is a fallacy.
Ask yourself: Why are there no conservative voices in the climate science field? Why is only one certain type of political class so obsessed with it?
Where are the skeptical scientists of any political stripe hiding out? If these people are all in 100% agreement on this matter it tells me that much more is going on than just science because not even in math and physics do we see that level of agreement going on! It's only in this one area where there is no room to speak one's mind.
The "evidence" you speak of is all based on models. I have seen some of these, been in presentations where they were discussed, and have shaken my head in wonderment that these models are taken so seriously.
Climate science is a religion, there's no mistaking the behaviors of the people involved in it. They even want to pass laws now to limit anyone asking questions!
Ask yourself: Why are there no conservative voices in the climate science field? Why is only one certain type of political class so obsessed with it?
Where are the skeptical scientists of any political stripe hiding out? If these people are all in 100% agreement on this matter it tells me that much more is going on than just science because not even in math and physics do we see that level of agreement going on! It's only in this one area where there is no room to speak one's mind.
The "evidence" you speak of is all based on models. I have seen some of these, been in presentations where they were discussed, and have shaken my head in wonderment that these models are taken so seriously.
Climate science is a religion, there's no mistaking the behaviors of the people involved in it. They even want to pass laws now to limit anyone asking questions!
> Climate science is a religion, there's no mistaking the behaviors of the people involved in it.
The only religion is your view.
You're wrong in the claim that there are no conservative voices, you are wrong in your claim that consensus only exists in climate science, you are wrong in your claim about models .
> They even want to pass laws now to limit anyone asking questions!
And now you're just plainly lying.
Ps, a secret, there is a world outside of USA.
The only religion is your view.
You're wrong in the claim that there are no conservative voices, you are wrong in your claim that consensus only exists in climate science, you are wrong in your claim about models .
> They even want to pass laws now to limit anyone asking questions!
And now you're just plainly lying.
Ps, a secret, there is a world outside of USA.
I'm one of the scientists on Project MIDAS (the team that made the announcement). Happy to answer questions about this. I've also been keeping a spreadsheet of things roughly the size of the iceberg, for journalistic comparisons: https://twitter.com/mewo2/status/818826891545210881