WHICH IS SALTIER ATLANTIC OCEAN OR MEDITERRANEAN SEA?

The Med is measurably saltier than the Atlantic.

Numerous rivers flow into the Med basin: the biggest is the Nile, but the Danube and many hundred others flow into the Black Sea and then the Straits at Istanbul. Same with southern Europe and north Africa. These rivers carry salts and dissolved solids into the Med, where the water evaporates rapidly compared to any other ocean. It is the combination inflow of the relatively fresh river water and the rapid evaporation of pure water from the hot Meditterannean Sea that removes pure water that makes the Med salty (more saline, technically speaking.)

Also: Many millions of tons of Atlantic salt water flow in through the Strait of Gibraltar every hour to make up for the evaporation. Once in the Med, that Atlantic water evaporates also, leaving the Atlantic’s “salt” in the Med’s water.