If the iceberg is sitting on the bottom of the ocean and NOT floating, would the water level rise as the ice melts?
Your iceberg must be ANCHORED to the bottom to keep it from floating to the surface, since its density is less than that of the liquid water around it. Because water EXPANDS when it freezes, a melted iceberg takes up less space than a frozen one. That means the level of water it is immersed in will LOWER, theoretically, as it melts. In a body of water as large as the ocean, of course, the change would be impossible to measure.
Paul Walorski, B.A., Part Time Physics/Astronomy Instructor
Short answer - No. The explanation follows.
Alright. Holding an iceberg under the ocean would be just like holding an ice cube in a coffee cup in the lab. Let me explain. Measure the water level in the coffee cup. Put the ice cube in. Push it down until it's completely submerged. Measure the water volume. Pull it out, melt it, and pour that water back into the cup. Measure the volume a third time. You will find that after you melt the ice cube and pour it back into the cup, the water level is LOWER than when you held the cube in.
Ice is less dense than water (which is why it floats). That means that a 1 pound of ice is actually physically bigger (has more volume) than when it's 1 pound of melted ice. Water expands when it freezes. It actually gets bigger. So the iceberg takes up more space frozen than it did when it wasn't frozen. Therefore... assuming the whole iceberg is underwater, the water level will actually go down a little as it melts.
Frank DiBonaventuro, B.S., Air Force Officer, Physics grad, The Citadel
'The important thing is not to stop questioning. Curiosity has its own reason for existing. Never lose a holy curiosity.'