• Question: why don't oceans freeze when like ponds and rivers can?

    Asked by sophiesweeneyx to Kate, Kieren, Nicola, Rowena, Roy on 13 Mar 2014. This question was also asked by .
    • Photo: Kate Nicholson

      Kate Nicholson answered on 13 Mar 2014:

      Well the water in them can – this is why we have the polar ice that thaws and freezes each year. They are less likely to freeze because of all the salt in them, so the freezing temperature will be a lot lower than fresh water that you find in ponds and rivers.

    • Photo: Rowena Fletcher-Wood

      Rowena Fletcher-Wood answered on 13 Mar 2014:

      They do – hence ice caps and ice territory beyond the land masses of the poles! A few things mean that that the whole sea doesn’t freeze.

      – Volume. A big amount of water takes longer to freeze than a small one. Oceans are much bigger than lakes!
      – Impurities. Especially salt. This lowers the freezing point so it takes a lot colder temperatures to freeze (though they still can! Look at Neptune and Europa and Saturn’s moons!)
      – Climate. The seas are all.mixed together and its not cold enough all over the planet all the time.
      – Current. This mixes hot and cold water and disperses crystals as they form meaning harsher conditions are needed to freeze them. Lucily it’s jut not that harsh on Earth!

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