Change in Volume Converting Ice to Water. To determine how much sea level would rise as a result of a given volume of ice melting, you first need to calculate the volume of water that would result from melting. Ice is less dense than water. It has a density that is 0.9 times (90%) that of water. Therefore, when one km3 of ice melts, it will decrease its volume by 10%. Thus, the conversion factor you need is: 1 km3 of ice = 0.9 km3 of water