How cold would it have to be...

To completely freeze the ocean? If it were to freeze fairly quickly, then thaw out would all the animals be dead or just frozen waiting to be thawed and alive as well? Interesting indeeeeed…

Out of a hat, probably cold enough to kill all/most life on Earth, and I do mean killed dead, non-reviviable.

Huh? Not all that interesting. With the exception of some micro organisms, lichens, and a few other specialized flora and fauna 99.99 % of all life would die if “just frozen”. Mammals aren’t popsicles and if water crystals propagate throughout living tissue irreversible cell damage will occur.

Well, slightly lower than 32 f, everywhere in the world. But for quite some time, in order for the heat already gathered to dissipate, or flash frozen at a much quicker rate, e.g. Earth transported comic book style to near absolute-zero conditions somewhere. Either everything on Earth most likely dies before it freezes solid, or dies instantly as it is near instantly frozen solid.

WAG, mind you, pretty science fictiony stuff here.

hey, my 3rd post I think, love to lurk so much to learn
anyway has anyone ever heard of a story called The Catalyst
from a science mag in the 70’s . Its about an experiment that
when added to water causes ice as the water freezes
to sink to the bottom of a glass . Well some of it escapes in the
drainage system and the rest is history. I cannot find the article
or the science mag in question, sorry. but I thought the fit the op
in a way.

I thought that the temperature would have to be much lower to freeze the deeper parts of the ocean. But check this out: A calculator for the freezing point of seawater!

A typical value for salinity using PSS-78 is about 35. Pressure increases at approximately 1 dbar per meter. So even 5000 meters depp, the freezing point is just -5.6 C. Huh.

Here’s a better calculator


I think that you might be refering to the book Cat’s Cradle by Kurt Vonnegut. Quite the nice read actually.

Well, I cant be bothered looking up this kind of info but what you would need is:

Average Temp of water
Volume of Water
Latent Heat of water
Heat of Fusion of water
Theraml coefficient of Water to Air, Water to Ice, Ice to air

Then you could work out, given a air temp, just how long it would take to freeze all the water on the earth. I am guessing even at 0.001 K, water would not “flash freeze” After all, that is less than a 300K difference and water doesnt show signs of flash boiling if I put it in a 400 degree oven.

It doesn’t have to get all that cold to freeze the oceans. It just has to stay cold for a long time. That’s happened several times in the last billion years:
When the Earth Froze
Snowball Earth

Don’t forget that there are underwater vents spewing heated water from the earth’s interior. Even if you froze the top mile or two of water you’d likely keep liquid water down at these vents for a very long time (till the earth itself cooled off).