Re: Which of the four major oceans has the highest salinity?

Hi Adam:

That's a difficult question to answer specifically, because salinity varies quite a lot within each ocean, and varies seasonally as well. However, the one place you'll find consistently high salinity is in the North East Atlantic, between about 30 and 40 degrees North latitude. That's because at about 35 degrees North latitude is the Straits of Gibraltar, which is where the Mediterranean empties into the Atlantic. The Mediterranean is extremely salty because the atmosphere above it is characterized by warm, dry winds, and there is much more evaporation than precipitation. As you might guess, when the water evaporates away, it leaves behind the salt, and therefore water of higher salinity.

The density of water is function of both salinity and temperature, and lighter (i.e. less dense water) tends to ride on top of heavier (more dense) water. The water exiting the Mediterranean is fairly heavy because it's so salty and actually leaves along the bottom, while less salty Atlantic water flows into the Mediterranean at the surface. The water in the bottom of the Mediterranean, although high in salinity, is quite warm, which makes it fairly light- lighter than the cold salty water at the bottom of the Atlantic. So, the Mediterranean water sits sort of in the "middle" of the water column, at about 700 to 1000 meters depth. That salty Mediterranean water spreads out and mixes, but is still identifiable several thousand miles away.

Hope that helps!
Rob Campbell, MAD Scientist