Global Climate Disruption.

[Fragony]

I was watching Frozen Planet with the great David Attenborough. One stat he mentioned is that the Artic ice since 1981 has retreated to 2/3s the surface cover...a third of the ice has disappeared!

But it's not that bad, it's worse. Another stat in the same section... Military submarine data that measures Artic ice thickness ... And they have measured it a lot... After all if you need to surface for an emergency you need to know where. The ice thickness has halved.

So the Artic ice has halved in amount.

That's bad, but wait its worse.

You need to multiplie the two area x thickness = volume.

Artic ice volume 2011 = 1/2 * 2/3 = 1/3 the volume of 1981.

Now if the Antartic lost 2/3 of its ice the oceans would rise 40m. Nothing to worry about there.

Oh dear, somehow we sub-sealevel dutchies must have missed any effect of that.

[Papewaio]

Antarctic isn't diminishing like the Artic.

It's colder, larger and on land. Artic is floating in water so it's melting will not have the same sea level contribution as ice tha is melting on land.

As such if the Antartic melts it will have a much more visible effect then the Artic.

[Fragony]

And if a train falls on my head I'll be dead, guaranteed. But there has to be a train above me, can't fall on my head if there isn't any

[Papewaio]

Simple experiment:

Need:
Ice cubes
Water
Three glasses
Whiskey
Marker pen.

First glass put three ice cubes in, add water until all the ice cubes are floating. Mark a line on the cup where the water level is.

Second glass put three ice cubes in, add water, but make sure the ice is not floating and still touches the bottom of the glass. This is difficult so do this before glass three. Mark the water level.

Third glass put in as much or little ice as you like, add the whiskey and sit back , drink and watch the ice melt in the other two glasses.

Report back which of the first two glasses had the highest rise in water level.

The first one is the Artic, the second is the Antartic.

[Fragony]

No need I know what the outcome will be, ice has more volume than water. But tell me, if the artic did all that melting stuff since 1981, where did the water go. It sure didn't end up here. Odd n'est pas

[Papewaio]

Do the experiment and we can discuss the results

[Fragony]

Do the experiment and we can discuss the results

Why don't you think of somethingg yourself, take the actual mass off ice and think of how sea levels can rise 40 meters. All the ice that is below sea level melting will lower sea levels, and what's above sea level will have to be spread out. No need for fancy calculations, it's simply impossible

[Ironside]

No need I know what the outcome will be, ice has more volume than water. But tell me, if the artic did all that melting stuff since 1981, where did the water go. It sure didn't end up here. Odd n'est pas

It ended up taking the same spot as the void left by the melted ice. Basic chemistry.

current sea level rise, so with current trend (that seems to be slowly accelerating) it's about 3,1 mm/year, or 31 cm/century.

Models of much more rapid sea rise are mentioned further down.

[Fragony]

It ended up taking the same spot as the void left by the melted ice. Basic chemistry

No it doesn't, as ice has more volume than water the submerged ice melting will lower the water level.

[Papewaio]

Basic physics and I tested it with Bailey's and ice tonight.

Marked the glass, waited for the ice to melt. Same level.

The ice floats because it is less dense than water. When it melts it's density increase...the over all effect is that the level of the water (Bailey's in my case) does not rise.

Now. If the ice wasn't floating in the water as is the Antartic, any ice melting there will rise sea levels.

Antartic is much much larger and much colder then the Artic. So it currently is not melting like the Artic.

All the Artics melting is not adding anything to sea levels.

However if the Antartic lost 2/3 of its volume sea levels would rise by 40m.

[Fragony]

Less baily's would be my advice. Ice is a solid object, that is why you don't drown when being on it. It has weight so it displaces water, water being fluid. Netto effect of submerged water melting is still an overall lowering of water level, not a rise. VERY basic stuff what do they teach you kids these days

[Fragony]

current sea level rise, so with current trend (that seems to be slowly accelerating) it's about 3,1 mm/year, or 31 cm/century.

Missed this, 31cm in a centuryy for whatever reason, to even consider a rise of 40 meters, doubt there even exists enough water to raise the sea by just one sorry meter. How. From where

[Papewaio]

Simple experiment you can do at home as already outlined.

Glass of water, put in some ice. Make sure the ice isn't touching the bottom of the glass. Mark a line on the glass at the current water level. Sit back and watch. Basic experiment.

I'm not asking you to believe me. I'm asking you to be a true skeptic and verify for yourself.

What you will find is that the weight of water displaced by the ice is the same weight as the ice. Hence once the ice melts it will not cause the water level to rise up anymore.

That is why the melting of the Artic is not a danger in itself. It is a warning sign.


Now the Antartic is a much much larger and colder piece of land with a lot more ice on and around it. The ice on that land of it was ALL melted is sufficient to raise sea levels by 60m. Luck has it that it isn't melting yet as it is far colder then the Artic. Actually it isn't luck again it's colder therefore it will melt after the north pole is water on summer.

Anyhow test the floating ice, read up about the differences between the two poles and come to your own conclusions.

[a completely inoffensive name]

Basically arctic ice is already displacing volume of water (more or less) it would create when melted. Antarctic ice is not displacing any water due to it being on land. Frag asks where is this 40 meter rise coming from. Basically the ocean and antarctic ice are two separate systems, not a single one. So when antarctic ice melts, you are essentially pouring more water in the glass.

At least that's my understanding.

[Nowake]

Pape and ACIN did a very good job explaining it just now and personal experiment is the most riveting way of approaching any such subject, yet I am a bit incredulous as to whether we are actually debating this – buoyancy is a ~2200 years old principle, gravity itself has a much shorter history in science.
Archimedes established in On floating bodies:

Any floating object displaces its own weight of fluid.
Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

[Fragony]

Basically arctic ice is already displacing volume of water (more or less) it would create when melted. Antarctic ice is not displacing any water due to it being on land. Frag asks where is this 40 meter rise coming from. Basically the ocean and antarctic ice are two separate systems, not a single one. So when antarctic ice melts, you are essentially pouring more water in the glass.

At least that's my understanding.

let me know when you have found a way to have sea levels rise 40 meters, there just isn't nearly enough water for that.. it would have to rise 40m EVERYWHERE, how do you see thatto be possibl. Right, it isn't, ocean is only a few km deep

[Nowake]

Ehmmmm the current depth of the ocean is irrelevant in relation to a rise in sea levels.


It is very easy to calculate the volume of added water.
Antarctica holds about 90 percent of the world's ice (and 70 percent of its fresh water).
It is covered with ice an average of 2,133 meters (7,000 feet) thick.
If all of the Antarctic ice melted, sea levels around the world would rise about 61 meters (200 feet).

[Ironside]

No it doesn't, as ice has more volume than water the submerged ice melting will lower the water level.

Indeed, ice has more volume. And that extra volume is the thing sticking up above the water surface. Take 1 kg (1L) of water, freeze it (roughly 1.1L). The ice cube will float, but also displace 1 kg (1L) of water. This is one version to weight things less dense than water. If an object becomes completely submerged (by weight or force) the you get its volume, by the displacement of water.
Melting completely submerged ice would lower the water level, but it would require something to keep the ice from floating up.

Missed this, 31cm in a centuryy for whatever reason, to even consider a rise of 40 meters, doubt there even exists enough water to raise the sea by just one sorry meter. How. From where

The worser scenarios are about 0.5-2 meters in a century.

Antartica contains ice equivalent to about a 60 meter water rise.

Greenland about 7 meters.

And yes, melting all of it would take thousands of years.

Land bound or bottom frozen (with abundant ice above sea level) regions are those that increases the sea level. It's the same principle that made the water level more than 100 meters lower than today during, the ice ages.

And for the fun of it. Fragony, the only relevance the depth has, is that increased water temperature increases the volume of water. It's very minor, but on 4 km (estimated average water depth) of water it makes a difference. Going from 4 C water to 30 C would cause a sea level rise of 17 meters. I doubt this factor is going to matter much normally (an average sea temp of 30 C is proably a half desert Earth or something like that), but it exists.

[Fragony]

'Antartica contains ice equivalent to about a 60 meter water rise.Greenland about 7 meters.'

So they say but it's impossible when you think of it. Take it's volume and the volume it would require to even raise it with just one meter. Absolute bull that sea levels can rise 7, or even 60 meter, they may say so but that doesn't make it true, calculare it for me and i will listen

[Nowake]

What’s so difficult about it?
It's an elementary school problem.


You convert the ice volume of the ice sheets into the water volume it would create.
The volume of Antarctica’s ice is 29,315,965 km³.
Now, of course, we have different densities. Specifically, because of the various gasses trapped within it, ice is about 90% as dense as water – hence a 0.9 conversion rate.
Thus the volume of said water is 29,315,965 x 0.9 = 26,384,368 km3.


Now, you take your newfound water volume of the ice sheets and divide it by the total surface area of the oceans, which is 346,976,563 km².
You now have 26,384,368 km3 / 346,976,563 km² = 0.0760 km = 76m.
Basic arithmetic.


I suppose they come up with only 61 meters because there are a few independent atmospheric variables which intervene to lessen the impact.

[Tellos Athenaios]

Why not? In heavily simplified terms which serve only to illustrate orders of magnitude:

~71% of the earth's surface area is covered by ocean so assuming that we can just stack water vertically what would a 60m increase entail? Well, the 6.4km radius of the earth implies that the volume required would be something in the order of magnitude of: 7,1 * 6,0 * 4 * pi* (6.4*10^3)^2 m^3 = 2.2*10^10 m^3 in liquid water.

So what is Antarctica's surface area, then? According to the wiki, that is 14 million square kilometer, i.e. 14 *10^3 *10^3 m^2. Therefore if all that area was, on average covered with just 1m thick layer of ice what do we have: 1,4* 10^7 m^3. So how thick are these ice sheets apparently?

Well according to teh wiki 98% of that surface area is covered by layers of ice averaging at least a mile in height (1.6*10^3m). So using similar simplified calculation that yields a volume of: 1,4*10^7 * 0,98 *1.6*10^3 = 1.4*1.6*0.98 * 10^10 = 2.2*10^10 m^3 in ice... As a lower bound... Looks familiar?

[drone]

What’s so difficult about it?
It's an elementary school problem.

Actually, it becomes a very difficult calculus problem. Since water does not stack, knowing the total volume of water released from the melt only gets you half way. The percentage of the earth's surface covered with water will change as the volume of water increases, in a very not-easily-computable way. How much coastline and brackish riverbank gets eaten with a 20 meter rise in water levels? 30 meters? They have computer models for it, it is not as easy as you make it out to be.

[Tellos Athenaios]

It doesn't but the same holds true for ice as well at those volumes. Given the height of the ice sheets even in terms of order of magnitude this is a non-trivial volume as well.

[Nowake]

@drone
It is already accounted for


Vertically, as I show above, you obtain 76m.
70-75% of the earth is already covered in water.
It appears to me that this, combined with the atmospheric variables I was mentioning above, makes the 61m they are advancing as a figure just about right.


Perhaps it's not 61, perhaps it's 59, or 55, but easily above the 40m figure they were debating about? Definitely.

[Ironside]

Actually, it becomes a very difficult calculus problem. Since water does not stack, knowing the total volume of water released from the melt only gets you half way. The percentage of the earth's surface covered with water will change as the volume of water increases, in a very not-easily-computable way. How much coastline and brackish riverbank gets eaten with a 20 meter rise in water levels? 30 meters? They have computer models for it, it is not as easy as you make it out to be.

10%-20% margin error on quick calculations is usually close enough to be acceptable. If you're toying with really large numbers, a factor 100 is still a small error.
Yes, the good calculations takes that into consideration and as Nowake already displayed, is already considered in the given calculations.

[drone]

But it's not an elementary school problem.

[a completely inoffensive name]

But it's not an elementary school problem.

Pssshhhh, I was calculating this kind of stuff in 5th grade.

[Papewaio]

You could make it a primary school problem. Measuring melting ice in a cup is kitchen physics, cooking is kitchen chemistry.

Get a globe if the world.
Trace Antartica.
Photocopy tracing.
Cut out the photocopies.
Blue tack them to the globe.
Count the number of Antarticas that now cover the globe.

Take the thickness of the ice in Antartica (averages ~ mile)

Divide thickness by number of Antarticas to cover the globe.

You have an approximation on how much the worlds waters could rise.

[drone]

I prefer the martini glass exercise. Take a shot glass, fill it with vodka, and pour it into a martini glass. Mark the level with a marker. Fill shot glass, pour, mark again. Fill, pour, mark again. Notice the lines get closer as more shots are poured in. This is what will happen when the icepack melts. Now drink the vodka.

[Fragony]

But the water doesn't rise all that much since 1981, surely we dutchies must have noticed it if it did. Attenwhatshisnam is full off it, should stick to filming polar bears in Amsterdam's zoo. Nothing to be absolutely terrified about, it ain't happening