Ice that is floating displaces an amount of water whose weight equals its weight. That's why a little bit floats above the water and most is under the water. W

Ice that is floating displaces an amount of water whose weight equals its weight. That's why a little bit floats above the water and most is under the water. When that ice melts, it still weighs the same amount and fills exactly the amount of space that it was displacing. In other words, it fits perfectly in the space in the water that it was already occupying. So floating ice that melts (above or below the water) doesn't change sea levels at all. Only melting ice that is currently supported by land will increase sea level.