I’ve heard this argument more than once: Why would the sea level rise when the ice melts? When a cube of ice melts in a glass of water the level doesn’t rise. Correct! Sea ice melting in and of itself should not cause the sea levels to rise. I don’t blame people for not understanding the real reasons for the sea level rises – the media does a spectacularly poor job of communicating the link between global warming and sea level rises, and in fact almost seems to advocate this view that sea ice melting is the primary cause. So I did a bit of digging and in the interests of keeping this brief here are some quick facts about melting ice sheets and sea level rises.

1) Ice melts off the land and into the sea = extra water, but not that much
2) Fresh water ice melt does actually displace more salt water than frozen salt water, something about the density of it – look it up in the 2nd link below.
3) Ice melting is a sign that the atmosphere is getting hotter = the sea water is getting hotter = sea water is expanding. Water expands as it freezes and as it heats.This is the major cause of the increasing sea levels. Not extra water in the oceans, but the current water expanding as it heats up.
4) Ice sheets reflect up to 70% of the sunlight that reaches it, while water only reflects about 6% and absorbs the rest of the heat. Which in turn leads to hotter and ‘bigger’ water! When the ice sheets melt it means more heat is being absorbed into the water.
5) When ice sheets melt they release a lot of stored methane, which is a far more powerful greenhouse gas than carbon dioxide. So more greenhouse gas= hotter=ice sheets melt=more methane = hotter…blah blah….

So it’s a lot more complicated that ice turning to water. Those ice sheets are very important for reflecting sunlight away from the oceans. So next time you see one crashing into the ocean, or Al Gore shows you a picture of a polar bear clinging onto a square meter of ice you’ve got a whole other reason to feel concerned about that.

Further reading:

Current Sea Level Rise – Wikipedia

Melting of Floating Ice Will Raise Sea Level

Ice Melting Faster Everywhere