Rights: The University of Waikato Published 21 June 2007 Download

Dr Mike Williams from NIWA explains the difference between ice formed in the sea and ice that has calved off the Antarctic ice sheet.


Icebergs and sea ice are quite different things. Sea ice is frozen sea water - so that’s where cold air has moved over and frozen the top of the ocean. Although salt is pushed out as the water is formed, there’s still a little bit there, so if you tasted sea ice it would taste salty.

Whereas icebergs come from compressed snow. Originally, snow’s fallen on Antarctica, and then more snow’s fallen on top of that, compressing the snow into ice. And that’s flowed off Antarctica as a sort of big glacier, and then the icebergs have calved off the front off that big glacier, or ice sheet.

Icebergs are important because they’re the final stages of the Antarctic ice sheet coming into the sea. And changes in the number of icebergs coming off Antarctica are key signs for changes in the Antarctic ice sheet.

Zee Evans, National Science Foundation (USA)