Originally posted by Phily Baby
Large chunks of ice falling into the sea doesn't affect water levels at all. The ammount of ice in the wate is the same when frozen as when liquid (water expands when frozen remember). It's the fact that when the water warms up it gets bigger. So all the pictures you see of massive chunks of ice falling into the sea aren't affecting the sea level much at all.
er... not quite. Ice has a lower density than water (about 5/7, if I remember correctly), and therefore floats. That means that a large proportion of the ice is above the level of the water. This means that when it melts, this additional volume is added to the volume of the water already there.
Also, you have to bear in mind that ice sheets cover land masses, and therefore have no effect on the sea level until they melt and icebergs break off and fall into the ocean. This can cause more icebergs to form by weakening the glaciers, causing more cracks and making ice more likely to break off. As soon as the ice falls into the ocean, the ocean rises a little.
The main ice covered landmass is Antarctica at the South Pole, with about 90 percent of the world's ice (and 70 percent of its fresh water). Antarctica is covered with ice an average of 2,133 meters (7,000 feet) thick. If all of the Antarctic ice melted, sea levels around the world would rise about 61 meters (200 feet).