Here’s where it gets weird. When seawater starts to freeze, it doesn’t turn into a solid block of salty ice. It actually rejects the salt. The ice crystals that form are mostly pure freshwater ice, squeezing the salt out like a grumpy lemon.
That leftover, super-salty water sinks down into the ocean. This is called brine rejection, and it’s a big deal. It creates super-dense, cold water that drives massive ocean currents. So yes, the ocean’s freezer problems actually help the whole planet’s plumbing work!
Have you ever tasted old sea ice? Don’t. It’s still salty on the outside, but if you melted the ice itself, you could drink it. Nature’s own distillation system—how cool is that?
Pressure makes a difference, too
There’s another twist: pressure. The deeper you go, the more pressure pushes down on the water. And pressure actually lowers the freezing point even more. So the water in the deep abyss stays liquid at temperatures that would freeze your toes off back on the surface.
PPT - Surface Circulation Pathways PowerPoint Presentation, free
This is why you can have liquid water at -2°C way down in the ocean trenches. It’s like the ocean is playing hard to get with the ice. “Nope, not freezing yet. Try harder, cold wind!”
So next time you watch a documentary about deep-sea creatures, remember: they live in water that’s technically colder than the ice cube in your drink. And they’re doing fine. Show-offs.
