Why is the Mediterranean Sea saltier than the rest of the Atlantic Ocean?

• A. The ratio of evaporation to precipitation is very high
• B. There is more freshwater input from rivers
• C. Ocean currents remove fresh water from the area
• D. Salinity is uniform in the Atlantic and Mediterranean

Answer: (A)

Salinity rises in a basin when evaporation removes water but leaves salts behind, and when there isn’t enough fresh water to dilute that salt. The Mediterranean is warm and in a relatively dry region, so evaporation is very high while precipitation and river runoff are comparatively low. It’s also only loosely connected to the Atlantic through the narrow Strait of Gibraltar, so there isn’t enough inflow of less-salty water to offset the evaporation. That combination concentrates salts over time, making the Mediterranean Sea saltier than the surrounding Atlantic.

The other ideas don’t fit as well: more freshwater input would dilute salinity; large-scale currents are not the primary reason for this high salinity; and salinity isn’t uniform between the two regions.