Ebbie said:

OK, I already know that I'm a literal-minded person but- SURELY you jest, Claymore? Ice sheets and glaciers at the poles are ABOVE the water, and if they were to melt and fall into the ocean, there would be MORE water.

Two things here:

First: As noted by someone above, ice packs in the NORTH polar region are floating, mostly submerged. The reason there is some ice above the water line is because the water tied up in ice underwater is more bulky frozen that that tied-up water would be if it were liquid. The total weight of the north polar ice is equivalent to the weight of the liquid water displaced. If it all melted, both the submerged and above-water-line ice would shrink in volume, and the water released from the melting above-water-line ice makes up for the decrease in volume due to melting of the underwater ice. This is because water, unlike any other common material, does not expand with heat in a straight line; it actually enlarges as it cools below the freezing point. So water, as it cools, shrinks until it freezes; as it goes below the freezing temperature it expands again.

Second: Ice tied up in glaciers on land, as in the southern polar regions, on the other hand, do not affect sea level until the time they drop off into the water, when, of course, they tend to raise the water level by displacement. But once in the water, whether they melt or remain ice is irrelevant, for the reasons discussed in the paragraph above.

Dave Oesterreich