if all of antarcticas ice were to melt this would result in a sealevel rise of some m to which the melting of greenlands ice would add a further rise in the order of m give or take an uncertainty of a few metres september is the month in which sea ice is at its yearly minimum and marks the first year that data of this kind became available in meaningful form the lowest concentration of sea ice on record was in september while thick ice with a snow covering has an albedo of percent that of a thin layer of ice is per cent and that of an icefree ocean is in the order of per cent