Here’s the fun part: when salt water finally does freeze, the ice itself is mostly pure fresh water. The salt gets pushed out of the crystal structure as the ice forms. That’s why old sea ice can be melted and drunk—pretty wild, right?
This process is called brine rejection, and it’s a huge deal. As the salt is squeezed out, it makes the surrounding water even saltier and denser. That cold, salty water then sinks, helping drive massive ocean currents around the globe.
Physics 111: Fundamental Physics I: The Physics of Salting Roads
Without this little frozen trick, our planet’s climate would be totally different. So the next time you look at a sea ice sheet, remember it’s not just frozen water—it’s a giant, slow-motion pump moving heat around the Earth.
