Ice caps????

[crazy legs]

(This will sound stupid but here goes). I hear that if the ice caps melt then the sea level will rise , but I thought that water expanded when frozen so if they melt wont they take up less space?????

[CrazyWolfman]

Actually you're basically right. It's a common misconception that the melting ice caps are causing the sea level to rise as there'll be almost no difference due to this. If you bung a chunk of ice in a bucket of water, then measure the water level before and after the ice has melted it will be the same. This is because the ice floats so as to only displace the same volume which liquid water would occupy. The extra due to the ice's expansion is the chunk that floats above the surface.

What actually will cause the sea levels to rise is the expansion of water as it warms. Like any material it gets larger when the temperature increases, so although there will be the same amount of water, it will simply get bigger.

[CrazyWolfman]

However the above statement only applies to floating ice (which makes up the vast majority). Melting land ice will make a small difference to sea levels.

[brachiopod]

Nice thinking, crazy legs, but flawed.

As CrazyWolfman points out, the fact that floating ice displaces its own weight of water, ,means that when it melts it won't make a difference to the water level.
(Try this yourself my marking the level in a container of water, firstly with ice cubes floating in it, and then after the ice has melted.)

Unfortunately, the two largest ice sheets on the planet are the Greenland and Antarctic ice sheets.
These are quite happily sitting on dry (albeit frozen) land, and are not floating about in the oceans, therefore, they do not displace any water - so if they melt, there is only one place that water will end up.

Try this also with your container of water, and a separate tray (with some very large chunks of ice frozen to it) carefully sloped at an angle towards your container.
Mark the level of water in the container.
Now wait for the ice to melt a bit so that the drips of water end up in your container, or, alternatively, wait 'til the whole frozen chunk becomes detached from the tray and slips down into container with a large splash.

Hmmmmm..., do you think the water level will go up then?