I’ve just read this Times article.
This statement caught me:
Surely if it’s already floating, then it won’t cause any sea level rise? Q.v ice cubes in a glass.
You are correct. But if ice which is on the landmass – ie, not floating – melts, that will cause the sea level to rise. Someone either misunderstood something, or they didn’t write it clearly enough.
I disagree with **Keeve **-- while the ice is floating, about 85-90% if it’s volume is displacing water. However, the remaining 10-15% are showing above sea level, and if all this ice melts, this part of the ice will contribute to rising sea levels.
I have no idea whether the facts stated in the OP are correct as specified, but the notion is not inherently ridiculous.
If the ice breaks up, it will melt faster than if it remained in one block. (This is due to the increase in surface area plus the opportunity for some chunks to drift into lower latitudes.)
Western Antartica has some peculiar geography, in that the ice sheet has caused the land mass under it to sink to below sea level. So, its bed lies below sea level, but that doesn’t mean it is floating (like an iceberg).
This is incorrect. 10% of the ice floats above sea level because ice is 10% less dense than water. When it melts it becomes more dense, and that extra 10% volume goes away.
Of course… :smack:
Carry on… :o
No. Ice is less dense than liquid water, which is why it floats. By definition, the whole lump of ice has a mass equivalent to that of the water it displaces. When it turns to liquid water, it will still have the same mass, but its volume will shrink to… exactly the same volume as it formerly displaced. Net result: no increase in level (ignoring expansion effects within the liquid due to temperature increase, of course).
Try it yourself, with ice cubes in a glass - top up the water right to the brim, with ice cubes floating in the water and protruding above the rim. As the ice melts, the water still won’t overflow.
Edit: too slow!
This sounds fallacious to me. Volume will not remain constant as the floating ice melts. It is already displacing as much space as the water that has the same mass, and its mass will remain constant through the melting process. Thus, simply melting will not affect the sea level.
Of course, that analysis doesn’t address the issue of if the sea level will rise because the water will expand as temperatures rise in the tropics, for instance, but that’s a seperate issue.
I once pointed this out to my sister, to explain why she shouldn’t poke the ice under cold water to ‘make sure it doesn’t float above’ when measuring one cup worth of ice cubes and water to put into Jello mix. 
I suspect he’s oversimplifying or misquoting a much more complicated process.
This is one possibility:
“The disintegration of floating ice shelves does not itself raise the sea level. But ice shelves serve as bulwarks for many glaciers on the Antarctic land mass, particularly those in western Antarctica, and the studies found evidence that the break-up of shelves is dramatically affecting the glaciers.”
Im sure theres a ton of other factors as well.
Otara
I wonder if John Mace sort of has it: the land is depressed by the mass of water and ice, but because the ice is anchored, it can’t flow away and thus keeps depressing the land. If the ice were not anchored, it would flow away, being replaced by water, and the land would rebound, just as parts of Europe are, shedding the water? But that rebound, as in Europe, would take thousands of years.
I don’t think that’s quite it. If the land were to rebound, it would take a very long time to do so. Thing is, the ice sheet may be more than 10% above sea level since it is sitting on the floor (the depressed land mass). The Antarctic ice sheet is 1.6kM thick in places.
Water continues to expand as it warms away from 0 celsius, so floating ice might not make up any more volume when it melts, but if it melts, and the whole ocean, including that melted ice, gets warmer, then it also gets bigger (deeper, in practical terms, although I’m not sure how much)
Does ice sink in hot water? (if it didn’t just melt)
Water (liquid) is most dense at 4C. It gets less dense as it heads toward 0C and freezing into ice as well as heading toward 100C and boiling.
That being said, ice (solid) is a latice and is less dense than any liquid water. So the answer is no, ice will not sink in any temperature water.
You’re right - one of the factors in sea level rise is the thermal expansion-related (or “steric”) changes in sea level.
[quote=http://www.environment-agency.gov.uk/yourenv/eff/1190084/natural_forces/sealevels/?lang=_e#cause
]
‘Steric’ change in sea level is due to water density changing. Density varies as water temperature and salinity goes up and down.
[/quote]
Another factor is that the ice shelf, being frozen ice, provide resistance to glaciers that would flow into the sea, and when the ice shelves melt, the idea is that the glaciers will now flow more quickly into the sea, thereby raising sea level.
He’s not a scientist and got mixed up. You are right, ice that is already floating will make no difference to sea level when it melts (although it will make a difference to salinity).
What is happening is that as the ice on the warming seas melts away it allows glaciers on the land to flow faster into the sea - not to mention that the melting of those glaciers before they reach the sea lubricates their base and so speeds their flow downhill. Global warming is increasing the amount of precipitation (snow) in Antarctica, which also adds to the weight pushing the land-ice into the sea faster and faster.
The same is happening in Greenland BTW.
Antarctica without ice, and from the same Wikipedia page:
