The last few people are making this more complicated than it needs to be. If you choose to divide floating ice into above water level and below water level portions, it seems complex. But if you realize that a floating object displaces its weight in water, you realize that the water level will not change when floating ice melts.
For a more information on the fate of the Pacific islands (specifically the Maldives) see http://www.detnews.com/1997/nation/9711/29/11290093.htm
True, TheDude, but we’re really not concerned here with the weight of the water. What we’re concerned with is the water’s volume – a very different beast, indeed.
~ Complacency is far more dangerous than outrage ~
According to this EPA study http://www.epa.gov/globalwarming/reports/pubs/sealevel/probofsea/index.html , by far the largest contributor to potential sea level rise due to global warming is not the melting of ice, but rather thermal expansion of ocean water. Their mean estimates are as follows:
Thermal Expansion: 21 cm
Small Glacier Melting: 9 cm
Greenland: 4 cm
Antarctica: -1 cm
Antarctica is negative because the effect of melting ice is offset by increased precipitation.
Yes, indeed, volume and mass are quite different beasts. But that is irrelevant to this discussion. Here’s a small numerical example:
For simplicity’s sake, allow us to assume that the density of ice is 0.9 and the density of water is 1. Say we have 9 g of ice and 100 g of water. The 9 g of ice has a volume of 10 mL and the 100 g of water has a volume of 100 mL. However, the volume of the ice is irrelevant; it still only displaces 9 g of water or 9 mL. So the total volume of the water is 109 mL. When the ice melts we now have 100+9=109 g of water which takes up 109 mL. No difference.
TheDude