Why water in the arctic that’s below freezing, not frozen?

Question

I was watching a documentary about a team that was planning to go down to the lowest point on the ocean floor somewhere in the arctic.

While the gentleman in the sub was going down, the narrator stated “at this depth, the water outside the submarine is below freezing”.

Soo… why is it not frozen? Does it have to do with the salt content in the water?

ELI5, thanks!

In: Earth Science

Answer 1

Salt water freezes at a lower temperature then fresh water. This is for example why people use salt in the winter to thaw ice. But this also allows salt water to be cooled to a bit under freezing without actually forming ice.