How much Salt is in Sea Ice?

Marilyn is Wrong Copyright © 1999-2005 Herb Weiner. All rights reserved.


In her Parade Magazine column of December 18, 2005, Marilyn states that 95% of the ice in oceans is sea ice (composed of salt water), although she did correctly note that ice formed from compressed snow is indeed fresh water. Marilyn's statement strongly implied, although it did not explicitly state, that the salinity of the ice is the same as the salinity of the sea water.

Sorry, Marilyn, but you left many readers with an incomplete understanding

Charles Booth <> wrote: As any introductory oceanography text will tell you, when seawater freezes, the salts are excluded from the developing ice crystals. The excluded salts remain in the unfrozen water, forming tiny pockets of brine which, having a lower freezing point and higher density than the surrounding freshwater ice, gradually migrate out of the ice into the seawater below. At very low temperatures, rapid freezing will trap the brine pockets giving saltier ice, but these brine pockets will eventually migrate out of the ice, as well. As a result, most sea ice is relatively pure frozen water (salinity of zero at the top; the lowest layer may have a salinity of around 4, which is still far below the seawater salinity of 35); this is why arctic explorers are able to melt sea ice and obtain fresh water suitable for drinking. last updated December 27, 2005 by