Stupid science sea ice melting question

[Maljonic]

I keep reading reports about sea ice melting and water levels rising because of it, but I'm sure I learnt at school that ice displaces more water than, well water... so why isn't the melting ice making the water levels drop?

I'm not being sarcastic by the way, probably just a tard.

 

[Rubber Bullets]

You read right, but you have to factor in the volume of ice that lies above the water line.

RB

 

[Maljonic]

I wonder what the equation is for that for ice? Like the amount of water level lost from the larger piece of ice under the water melting plus the water level gained from the ice above the water melting.

 

[Mabs]

if memory serves, one of the poles is a bit of land with frozen bits on it, the other is a big ice cube floating around, so theres quite a lot of it out of the water atm

 

[Maljonic]

Yeah, that's why I said "sea-ice".. all the reports I read are about sea-ice melting, not ice, snow and permafrost on the landmass of Antarctica.

 

[Tom]

You read right, but you have to factor in the volume of ice that lies above the water line.

RB

No you don't. Have you ever seen a drink with ice cubes overflow once the ice cubes melt? Neither have I.

The sea level may rise slightly because of the difference in density between freshwater ice and saltwater ocean, nothing more.


The changes in sea level are suggested because of Greenland and Antarctica.

Ice caps aren't actually present throughout most of the Earth's history. They're cyclical in nature.

 

[WPKenny]

How about the simple fact that things expand when they get warmer? That much water, getting just 1 degree warmer could expand quite a bit.

 

[Litmus]

How about the simple fact that things expand when they get warmer? That much water, getting just 1 degree warmer could expand quite a bit.

Dont think this applys to water tho? And i dont think 1 degree higher temp would have that much of an effect on water either useing that theory.

 

[Rulke]

I always thought the problem was the mile thick ice that was sitting on land melting

 

[Kryten]

Good question indeed,

But personally, I always thought the problems existed mostly in the heads of those who think they matter most.

 

[old.Tohtori]

How about the simple fact that things expand when they get warmer? That much water, getting just 1 degree warmer could expand quite a bit.

But also, ice is expanded water right? Or water with air in it or some such.

As in, it takes more space then the same amount of water in normal temp.

 

[Scouse]

The sea level may rise slightly because of the difference in density between freshwater ice and saltwater ocean, nothing more.
.

Actually, the point about thermal expansion of the oceans is correct and accounts for much of the projected (and already measured) sea level rise.

Get yourself to the Maldives with your camera. They're not going to be around for much longer and they do look great

 

[Tom]

I really couldn't give a stuff. I'm waiting for the day I get my Chimaera again, this time I'm going to de-cat it and put a cherry bomb exhaust on.

Then I'm going Greenpeace hunting.

 

[rynnor]

Yeah, that's why I said "sea-ice".. all the reports I read are about sea-ice melting, not ice, snow and permafrost on the landmass of Antarctica.

Interestingly Antarctica has actually accumulated more sea ice in the last 25 years and now covers more area so maybe the north pole shrinks and Antarctica grows - net effect not much - dunno but dont believe the doom sayers

 

[bob269]

It's all an excuse to charge you more taxes and to make you feel good about paying said taxes.


I blame all the veggies, it's the cows that cause the most problems, eat more beef

 

[dysfunction]

Ice caps aren't actually present throughout most of the Earth's history. They're cyclical in nature.

Yes which is why this whole global warming thing being humans fault is a sham...

 

[dysfunction]

How about the simple fact that things expand when they get warmer? That much water, getting just 1 degree warmer could expand quite a bit.

Why don't you test your theory out...get some really cold water. Warm it up and see if the level rises.

Let us know how you got on...

 

[yaruar]

Yes which is why this whole global warming thing being humans fault is a sham...

Not necessarily, climate change is cyclical in nature, although a lot of people think we really should be going the other way at the moment as we are in the lull of an ice age and things should be getting colder, not warmer and man made stuff is actually making the clamate do the opposite of where it should be going. It's all marginal changes, but on a global scale marginal changes can have huge impacts.

 

[WPKenny]

Why don't you test your theory out...get some really cold water. Warm it up and see if the level rises.

Let us know how you got on...

lol. I'd be impressed if you noticed a visible change in a body of water as small as a pint glass. Although I can give you something to think about. Why do you think pressure cookers are called such? It's not cos you pump them full of gas it's because heating the moisture in the food causes it to expand, eventually forming a gas (steam).

It's been over ten years since I did any physics stuff but from what I remember it's all about activation energy. The more you heat something the more energy you're giving it. this excites the molecules making them vibrate. These vibrations need space. The more you heat something (ie the more energy you add) the more they need to vibrate until they eventually break away from each other to form a gas.

You know how long stretches of concrete motorway are broken up into small sections. Well the stuff that joins those sections is squashy to allow the road to expand so it doesn't break itself apart. Same thing on coastal walks where they lay lots of concrete, you'll see this black tar like substances squeezed between long sections.

But, meh, if you don't get that heat expands things and large items will expand a lot (comparatively), are you sure that the plane leaves the runway?

 

[DaGaffer]

How about the simple fact that things expand when they get warmer? That much water, getting just 1 degree warmer could expand quite a bit.

Blimey, did you ever do science at school? Liquid water doesn't expand. Its density changes, but not its volume. If anything liquid water takes up less volume than the equivalent mass of ice, although its a bit more complicated with sea ice because of the dissolved salts.

The reason why melted sea ice would cause sea levels to rise is purely because of its location. Its currently trapped at the poles, but thanks to good old Archimedes if it melts it would find a new equilibirium within the wider (liquid) system.

 

[Will]

Err, WPKenny is confused, but so are you. Density cannot change without volume also changing.

The term thermal expansion refers to the increase in size of an object as that object is heated. With relatively few exceptions, all objects expand when they are heated and contract when they are cooled. Perhaps the most important exception to this rule is water. Water contracts as it cools from its boiling point to about 39.2°F (4°C). At that point, it begins to expand as it cools further to its freezing point. This unusual effect explains the fact that ice is less dense than water.

 

[DaGaffer]

Err, WPKenny is confused, but so are you. Density cannot change without volume also changing.

Well, sort of, but water has extremely low thermal expansivity properties, and is also regarded as incompressible (its not, but for practical purposes its treated that way), so its density can increase without apreciable volume increase.

 

[Wazzerphuk]

No you don't. Have you ever seen a drink with ice cubes overflow once the ice cubes melt? Neither have I.

This is because people drink the liquid. They don't just get a full drink with ice cubes in and leave it, do they? Rubbish analogy

 

[rynnor]

One thing I dont quite understand is why the artic is melting now with a barely discernable change in temperature when only a few hundred years ago during the medieval warm period it was a lot warmer for a number of centuries - surely that should have done for the lot?

Is the arctic we have gotten used to just a few hundred years old maybe?

Another thing to consider is once long ago the arctic seas were as warm as the tropics (we know this from the fossil record).

 

[WPKenny]

So forgetting about the ice at the poles melting for a second, surely ALL the water on the planet raising by a single degree would have some sort of expansion to it? From what Will says, any water above 4 degrees C will expand as it gets warmer until boiling point when it becomes a gas.

But then DaGaffer raises another point that regardless of expansion or contraction, the ice/water is clumped together at the poles, so when it melts it becomes liquid and spreads out. Not having a clue about exactly HOW MUCH water expands when it's temperature is raised, I'd have to say DaGaffer's point is easier to get your head around and quite possibly more likely as a cause of the sea levels rising.

Come to think of it it's been nearly 13 years since I did any sort of physics. They never really covered the exact expansivity (is that a real word?) of water, I just remember warm things expand and cold things contract, as most men can testify to.

 

[Will]

Ice which is floating on water displaces exactly the same amount of water as it will replace. Hence it won't increase sea levels when it melts. But it will increase the albedo of the poles, causing them to absorb more solar energy, and reflect less.

Ice which in on land, on the other hand, will cause sea levels to rise. Such as Antarctica and Greenland. I'm not sure when this is predicted to happen. Whether it is a natural cycle or not, people are pretty much fucked when this happens.

 

[rynnor]

Ice which is floating on water displaces exactly the same amount of water as it will replace. Hence it won't increase sea levels when it melts. But it will increase the albedo of the poles, causing them to absorb more solar energy, and reflect less.

It shouldnt be as extreme a shift as is stated for normal snow in the arctic - arctic snow and ice are 'dirty' - the northern hemisphere has a lot of atmospheric pollutants some of which taint the arctic - thus their albedo is already higher than that of pure ice.

 

[Will]

I still think the Arctic snow has a higher albedo than the sea. Pure snow is 90% reflective, the Antarctic is 80%, I've failed to find a figure for the Arctic because I don't care enough, the oceans albedo is 3.5%.

Of course, its far more complicated than my paragraph makes out, because clouds are more reflective then most land. I'm not a climatologist, so I'm not going to give you any predictions.

 

[rynnor]

I still think the Arctic snow has a higher albedo than the sea. Pure snow is 90% reflective, the Antarctic is 80%, I've failed to find a figure for the Arctic because I don't care enough, the oceans albedo is 3.5%.

I read that Wiki too - seems odd that the figure for the better known arctic is missing? Antarctica is pretty clean - it has its own self isolating wind system surrounding it - would be funny if its just general air pollution lowering the albedo causing the arctic to melt?

 

[Embattle]

One of the real issues as I understand it is if landlocked ice melts, the issue with sea ice melting is to do with having a less reflective surface but I could be wrong.