• Question: Why don't the oceans freeze?

    Asked by camel12 to Mike, Pip, Tim, Tom on 4 Jul 2012.
    • Photo: Tim Stephens

      Tim Stephens answered on 4 Jul 2012:

      They do! The arctic ocean freezes every winter.
      The whole ocean doesn’t freeze because (salty) sea water freezes at a lower temperature than fresh water and because the ocean currents move warm water from the tropics up to higher latitudes.

    • Photo: Tom Lister

      Tom Lister answered on 4 Jul 2012:

      Like Tim said, they do (unless they are too warm or too salty).

      Interestingly, the Thames used to freeze in London every year, enough for people to have huge parties on it. The main reason it doesn’t any more is because it is so full of pollutants (pure water doesn’t need to get so cold to freeze) – and not because of global warming (although this might contribute a tiny bit).

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