This is the coolest part. When seawater freezes, the ice that forms is actually mostly freshwater. The salt gets pushed out as the crystals form.
Imagine a bouncer at a club. The water molecules are the VIPs, linking arms and forming a solid barrier. The salt ions? They’re the rowdy party-goers getting kicked out onto the sidewalk. That’s why old sea ice tastes almost like freshwater when you melt it.
This leftover salt makes the surrounding water even more salty and dense, which then sinks to the bottom. This process, called brine rejection, actually helps drive global ocean currents. So frozen seawater is basically the unsung hero of planetary climate control. Neat, huh?
Does This Affect Real Life? (Yes, and It’s Hilarious)
Ever wonder why ships in the Arctic don’t just freeze solid into the ice? It’s because the ice is less salty. So a ship can get trapped, but the hull isn’t usually destroyed by the salt concentration.
Also, this is why polar bears can drink melted sea ice. The ice is so low in salt that it’s relatively safe for them to hydrate. Meanwhile, the fish swimming below are doing just fine in that super-cold brine. They have special antifreeze proteins in their blood. Show-offs.
PPT - Surface Circulation Pathways PowerPoint Presentation, free
And here’s a fun party trick: If you freeze seawater at home, the first ice that forms will be salt-free. The leftover liquid? That’s your super-concentrated brine. Do not drink it. Seriously, don't.
