in lieau of someone telling me about the preview for the movie, the day after tomorrow, i want to ask a quesiton. suppose that the polar ice caps were to melt fully. does ice not displace it’s volume in water? so if they were to melt, would we not have the same amount of water we do now? also, since water slightly expands when frozen, would there not be less water?
This is true for the Arctic. But the mile-thick Antarctic ice is on land, so any melting would add to the ocean level.
I have no idea whether the movie gets this right or not.
Simple answer: the ice is piled above sea level, on the land and on itself. If it melts, the water goes into the sea, thus raising the level.
I do not believe that the difference between the solid water and liquid would be significant enough to save a city or anything.
Just a thought - the ice caps are pure water, not salt water; does this make a difference?
Besides Antarctica, there is a huge amount of ice sitting on Greenland’s land mass.
However, in even the most extreme global warming scenarios I’ve seen, only a tiny fraction of that ice would be expected to melt, raising global sea levels by inches or maybe a couple of feet. And this is the extreme pessimistic view. Of course, that much would be devastating to Bangladesh and some low-lying islands, but the popular idea of the Statue of Liberty mostly underwater is not going to happen.
I thought the mechanism for rising sea levels was increasing sea temperatures causing water expansion rather than melting ice caps.
Living at sea level, behind a flood defence only built to the level of the 1953 floods, a sea level rise of a couple of feet seems pretty damn significant. As it does to much of England, Holland, Denmark, etc etc etc.
And don’t forget, the very big concern is that changes in the ice cap formation could cause shifts in ocean currents - such as cutting off the Gulf Stream. Which not only would plunge most of Europe into mid-Canadian temperatures, but would also cause a catastrophic stifling of monsoon rains across the world.
Ray has it, although you are not entire wrong. Water contracts while cooling up to a point near freezing where it quickly expands, splitting open that bottle in the freezer. If the ice bergs were to melt, and other cooling mechanisms were to fail, the average temp of the oceans would rise, and the volume would increase.
Post Glacial Rebound will result in an increase of sealevel beyond that produced by the melting ice alone.
If the polar ice caps melted, how much would the oceans rise?
From this site, the maximum increase in sea level that might be expected from the complete melting of the Antarctic and Greenland ice caps is a total of 68 m, or 220 ft. (This does not include thermal expansion of the oceans.) However, as CurtC says, even the most extreme global warming scenarios for the near future do not predict anything like that. They would still be very significant for low-lying coastal areas and islands, though:
First of all, glacier rebounding only affects the areas covered by ice and only to a very small extent. I.e., New York City won’t rise up because Greenland is ice free. NYC is still going to be (soggy) toast.
Since we’ve never performed this particular “experiment” before, predictions are difficult. One important thing to note: Scientists tend to be overly conservative in making predictions on such a large scale. So it turns out, just like in the 1970s with the ozone layer predictions, things are happening much faster than recently predicted. A 1995 prediction is way too long ago and far too conservative.
There are recent studies that do indicate that all of Greenland’s glaciers will melt. Go search Yahoo! or Google News for recent stories.
A lot of it centers on Greenland of course. Esp. in regard to the North Atlantic circulations. If the Gulfstream keeps flowing, Greenland loses its glaciers within 300 years. If the Gulfstream stops, maybe not that much ice melts. So NYC becomes like Venice in the flood season, but OTOH most of Western Europe gets fairly arctic. (That’s right folks, “global warming” doesn’t mean all of the globe gets warmer.)
Pretty much every feasible outcome of the current process does not look good in the least for many areas of the planet. A few desert areas might get more rain, a few rainy areas might get less, etc. But you can assume that virtually every region is going to be quite disrupted. Very hard to predict.
I don’t really see the point of performing this particular experiment given the huge number of unknowns involved.
No one said that New York would rise up. Look at the map I linked to. All of Scandinavia, including areas currently under the sea, is rising. When the sea bed rises, the water goes elsewhere, raising global sealevels.
Check out the March 2004 issue of Scientific American for a good article. This talks about the idea that the main issue is the expansion of the sea water and not the melting of the ice caps.
Another problem is that the existing ice caps are good at reflecting the sun’s energy back into space. As the ice caps shrink, less energy is reflected away, and global temperatures go up even more.
Just out of morbid curiousity, in the case of a worst-case scenario–the 220 foot rise–how far would the waters extend onto the continents, especially North America? Would the new coastlines lie in Virginia? Or Kansas?
In Europe would they get to walk to the beach from Russia? I’m assuming Japan would be toast, but how far into the mainland would it go? Would the poles be completely aquatic? Is there any way of knowing this?
More likely Virginia than Kansas. Don’t forget that there is a mountain chain fairly near the eastern seaboard - from the Appalachians through the Catskills in New York down to the Blue Ridge to the Ozarks and all those other picturesque names for what is one old chain.
No state would be completely covered by a 220 foot rise. The highest point in Florida is 345 ft., followed by D.C. at 410 ft. and Delaware at 448 ft.
I assume the same is true for most of Europe outside of Holland. And Japan, which is heavily mountainous.
However, since the ice caps are near the poles, and the poles don’t get very much sunlight anyway, I don’t think it would be that big a deal. The corollary to this would be that as global temps warm, cloud cover increases, which means that more energy is reflected back into space. All these positive and negative feedbacks are exactly why it is extremely difficult to determine what exactly will happen.
Nonsense. Icecaps diffuse light, so it is travelling in all directions.
Here’s a fairly extreme case - this page shows what the world’s coastlines would look like with a 100-metre rise in sea level.
As you can see, much of Japan would be safe. I’m not sure what you mean by “walking to the beach from Russia” as Russia already has plenty of beaches.
Much of northern Europe would be underwater, as would a lot of the Gulf Coast of the US.
Downwards, too?
Ice caps increase the earth’s total albedo (light reflectance). Reducing their extent will have the effect of increasing global warming, absent other factors.