Why does ocean salinity vary so much across the globe?
Some parts of the ocean are nearly fresh water while others are saltier than the Dead Sea.
The answer
Ocean salinity averages about 35 parts per thousand but varies significantly due to evaporation, precipitation, river discharge, and ice formation. The Red Sea and Persian Gulf can exceed 40 parts per thousand due to intense evaporation and limited freshwater input. By contrast, the Baltic Sea averages only 7 to 8 parts per thousand because of heavy river runoff and limited connection to the open ocean. Near melting glaciers, salinity can drop further still. These variations drive thermohaline circulation, the global ocean conveyor belt, because saltier, colder water is denser and sinks, pulling surface water in its wake and driving deep ocean currents that redistribute heat around the planet.
Source: Woods Hole Oceanographic Institution
- salinity
- thermohaline circulation
- ocean chemistry
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