How cold can the ocean get before it starts to freeze?

Question

I was thinking about this story idea (I like to make up stories for only myself sometimes) but I'm curious, how cold can the oceans get throughout the planet without freezing? Like a planet with no ice on it whatsoever?

Answer 1

dont know,very cold though, the salt will make it harder, so will the waves, its not easy to freeze water that is constantly being ajitated, id say at leas -5to-10deggres celsius

Answer 2

It all depends on the salinity of the water. E.g. the Mediterranean is much more salty than the Baltic. But at 3.5% salinity, which is the average, sea water will freeze at about -2 Celsius. That is: if the water is still and no waves.

Waves will tend to make a slush as we often see here near the Norwegian coast.

It is worth mentioning that water is the heaviest at 4 Celsius. If it was like the other elements; heavier when colder, then ice would sink at the bottom of the sea and stay there forever. During the summer, only the top layer of the sea would be liquid and the ocean ability to store energy would be greatly reduced. The climate on earth would be quite different!

The fact that the water is heaviest at 4 Celsius is the reason why the temperature is 4 Celsius at the bottom of all oceans, whether at the equator of under the North Pole.