although it is believed that the melting of floating ice shelves will not raise sea levels, technically, there is a small effect because sea water is ~2.6% more dense than fresh water combined with the fact that ice shelves are overwhelmingly "fresh" (having virtually no salinity); this causes the volume of the sea water needed to displace a floating ice shelf to be slightly less than the volume of the fresh water contained in the floating ice. therefore, when a mass of floating ice melts, sea levels will increase; however, this effect is small enough that if all extant sea ice and floating ice shelves were to melt, the corresponding sea level rise is estimated to be ~4 cm.