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How cold would it have to get before major rivers and the sea become frozen?
Markjuk
Posts: 30,436 Forum Member
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With all this cold weather I was wondering how cold it would have to get before major rivers such as the Thames and seas become frozen over?
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http://sasesearch.brighton.ac.uk/view/?film=1032
The URL says brighton but the film is Herne Bay.
Temp was as low as -16
Bridges had very short spans back then and many more supports. The result was that the flow was much reduced and made freezing more likely. The Thames hasn't frozen to that extent since the old bridges were demolished.
It'll only freeze properly if it's still though, otherwise you end up with a sort of salty "Mr Frosty" type effect.
Don't forget, as well, that the sea is heated by constant undersea volcanic activity so you almost always have hot currents under the surface.
The sea settles into layers of different temperatures so well-defined that sonar can bounce off the intersection of each layer.
As a result of this it's only ever the top layers ow water that freeze (or get warm in summer).
Thank you for that, those photos were fascinating.
Fab post - you really should have prefixed it with "here comes the Science Bit" though
After the old London Bridge was replaced in the 1830s, freeze-overs no longer occurred, despite conditions that were sometimes colder.
yup, plus the construction of the Embankment which narrowed the river made it less likely to freeze - I think because it became faster flowing.
Was walking along the canal which was frozen and little girl (6/7) was walking straight up the middle of the canal, with her father seemingly happy about it as he was walking the path along side and not calling her back, the pair carried on walking as they were. I was shocked really that someone would let there daughter do that, ok she was only lightweight but the ice thickness will certainly vary as it's only been freezing for a week and parts of the canal were not froze at all.
Geothermal flux is not a significant source of ocean heat, except locally in a few places. Most of it comes from solar heating of the surface water, and the circulation of that water into the deep oceans.
And that's wrong too. Whereas fresh water expands anomalously (it is most dense at 4C), sea water behaves like most other liquids, so that it is most dense at its freezing point. This means that the nearly-freezing water sinks and gets replaced by warmer water from below. This is why sea water (unless very shallow) is much less likely to freeze than freshwater, even though the freezing point isn't that much lower.
Lakes and canals will go first. Areas with faster moving water, like rivers, will be the last to go. Takes weeks of persistent frost though
I once walked over a deep frozen lake there were about 7 of us on it and we heard a almighty crack I could not get of that ice fast enough.