What it means when a huge Antarctic glacier is unstable | Hacker News Reader

What it means when a huge Antarctic glacier is unstable

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121 pointsJaruzel37 comments

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Was hoping there would be visual of an unstable glacier, not just text about sea level rise.

If you have never seen a glacier calve before, check out these videos:

https://www.youtube.com/watch?v=hC3VTgIPoGU

https://www.youtube.com/watch?v=RL3EjH9-WSs

https://www.youtube.com/watch?v=1s5-IvHVDqg

No penguins for scale :(

Near the end of the first video they overlay an image of Manhattan for scale. Penguins would be invisible - some of those chunks are as wide as the borough! Boggling.

The videos I paid attention to were all in the northern hemisphere - and penguins are only native to the southern hemisphere.

I'm actually somewhat sad about that as I'd be delighted to see penguins.

https://youtu.be/hC3VTgIPoGU?t=111 -- is that... a frozen whale?

So much bigger than a whale. Refer to the Manhattan size comparison later in the video.

A frozen Ancient then, maybe.

My favourite part: https://youtu.be/hC3VTgIPoGU?t=224

Shows scale compared to Manhattan, and replays the whole thing at speed.

This touches on one of most concerning questions about climate change. The entire west Antarctic ice sheet is predicted to raise sea levels by 16 feet in the northern hemisphere when it collapses [0]. 16 feet is enough to shut every working port in the world. What is the minimum time such a collapse would take? I have a feeling that most labs that model this stuff simply do not publish the minimum (worst case) numbers because no one would believe how quickly globalization could come to a screeching halt.

0. https://en.wikipedia.org/wiki/West_Antarctic_Ice_Sheet

Lets play with some hypotheticals...

If this happened in a day it would be complete pandemonium. Probably the collapse of globalization as we know it. But Humanity would survive and eventually rebuild.

If this happened in a century it would be gradual enough that republicans could keep denying as they sign the Tulsa/Denver/Omaha International port creation act of 2116.

A decade would be undeniable and would have costs both in life and money. What would those costs really look like? Would we evacuate and build new ports fast enough to keep something that looks like the modern system?

What does this look like in a single gradual year? Port takes time to open and people take time to evacuate. Would the population of New Orleans become residents in a suburb of Omaha on the Bay of Texas? Or could we muster something halfway organized?

The rise we're afraid of is around 4 meters. What you're hypothesizing is several hundred meters.

https://upload.wikimedia.org/wikipedia/commons/2/2d/USA_topo...

Four meters of mean sea level rise is plenty to completely disrupt global shipping and make many densely populated coastal cities uninhabitable.

In some places, nothing will change. In some places, sea level may decrease. In others, it will be very substantial.

Never mind the effect that the decrease in albedo and the increased heat capacity of liquid water would have.

In terms of timescales - it won't be instant. If the shelf collapses then it'll allow the rapid outflow of the glaciers behind it, but when we say rapid we mean 30km/yr (total guess, depends on so much, could be less, could be much more) rather than 4km/yr.

So far, however, everything has gone worse than our worst published models. I think we're going to see some nightmarish stuff in our lifetimes.

The Bay of Texas reaching Omaha was Hyberbole. The concept of a bay of Texas after a 4 meter rise in see level is reasonable. I just didn't think the specific location of the refugee camp mattered for high level discussion so rather than get lost in the details of Texas geography I picked something exaggerated but readily known to be inland: Omaha Nebraska.

No, the concept of a bay of Texas is not reasonable after a 4m rise. Believe it or not the coast rises pretty fast from the coastline. Here, play around with this: http://geology.com/sea-level-rise/

If you adjust the following to 5 metres, you can get an idea of how much of the coastline would be affected by this rise.

http://www.floodmap.net/

Let's say both of these glaciers let loose tomorrow. If I was at the beach on the Oregon or Washington coast, how long would it take before I noticed the three foot rise they are predicting? Days, weeks, years?

Isn't the rise just based on how much water these glaciers hold? Intuitively I would expect that to be noticeable within hours, a day at most.

If it was let loose tomorrow, you'll notice at some time around tomorrow, with some hours of delay.

And if it was let loose on a single day, you'll notice rises way bigger than 3'. I'd recommend you not to be on coast on such event.

Yeah, it would stabilize at three feet, but in the time before that it could wobble wildly between plus ten and minus seven feet.

For something of that size just falling on the sea? It's more likely that it would wobble between 10 and -10 meters.

I guess I was being optimistic.

So long civilization.

The numbers are for the ice sheet dropping into the ocean and melting completely. So, it would be quite a while before you got the last 10% of the sea level rise.

The first 90%, on the other hand, could get there fast. I guess this would cause waves that travel at speeds similar to those of seismic waves (hundreds of km/hour). So, within a day. Also, the initial ocean rise would be higher than what it would be once the water has calmed down.

The melting doesn't matter, just whether the ice is on land or in the ocean.

(H2O actually contracts slightly when it melts.)

Oops. Thanks.

But that can't happen, these glaciers are mostly located on land, so for them to let loose requires that the entire mass of the glacier slide across the land and into the ocean. Even at four kilometers per year, you and I won't be alive to see the end of that process.

Surprisingly, the rise is uneven and may lead to lower sea level depending on where you are. The mass of icecaps is so important that it attracts water around them by gravity, and it gets composed with the extreme centrifugal force. If the average rise is 5m, places like Vancouver could see a -0.5m movement while other places around the equator could see +6.5m.

http://harvardmagazine.com/2010/05/gravity-of-glacial-melt

But if the West Antartica melts, the cold stream may stop the Gulf Stream too... which leads to an ice age in Europe.

There is a captivating, not very long, scifi novel The Sands of Sarasvati (by Finnish scifi author Risto Isomäki) related to this topic.

Unfortunately Amazon seems to only have it in German (Die Schmelze, kindle and paper) and in Spanish (El deshielo, paper only). So for English, one would need to order a papercopy from a Finnish bookstore.

More on the NSF/UK Antarctic field campaign this press release is tied to: http://www.sciencemag.org/news/2016/10/us-and-uk-plan-thwait...

I've never understood, is an Antarctica glacier (or polar ice caps) melting akin to adding ice cubes to a glass of water, or is it akin to ice cubes already in the glass melting? Ice caps on mountain tops melting are clearly akin to the former, but what about ice that's in the water anyway?

In Antarctica, most ice chunks are at rest on solid ground.

So, yeah, it's like adding ice cubes to a glass of water.

And the big problem is, this could be a much faster process, than the melting itself. So we might face a considerable raise of the sea levels in very short times.

Right, if very large chunks start sliding downhill.

Sea ice melting doesn't change the sea levels, but Antarctica is a land mass with ice on it (and of course ice around it in the water), not just a massive chunk of floating ice.

Sea ice melting does expose bare ocean to more solar heating. Ice is a pretty good insulator, and it's also white which reflects a ton of light. Dark oceans absorb solar energy very well, there's nowhere else for it to go.

As a reference for those that aren't familiar with the Antarctic ice sheet - the average thickness is ~ 2,100m and it contains ~ 60% of all the freshwater on earth.

It's orders of magnitude thicker than most glaciers.

https://www.youtube.com/watch?v=0nOZwCitHgg

I hope someone could make some kind of an interactive game about the glacier mechanics, since it's very non-linear and thus hard to fathom.

Very uncool.

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