Horizontal distribution of salinity

Geography glossary

Topic: Oceans: Hydrological Cycle, Relief of the Ocean Floor, Temperature and Salinity · NCERT: Class 11, Ch 12 "Water (Oceans)"

Meaning

Surface salinity changes from place to place. It is highest in the subtropics, where evaporation is high and rain is low. It is lower at the rainy equator and lowest near the poles and at river mouths. Isohalines are lines on a map joining places of equal salinity. By ocean:

  • The Atlantic averages about 36‰ and is the saltiest ocean.
  • The Indian Ocean averages about 35‰.
  • The Pacific falls from 35 to 31‰ in the western North Pacific because of Arctic meltwater.

Estuaries and the Arctic swing between 0 and 35‰ with the seasons.

Example

The Atlantic peaks at about 37‰ between 20°N–30°N and 20°W–60°W, in the dry subtropics. The Red Sea reaches up to 41‰ because it is nearly landlocked and evaporation is intense.

Don't confuse with

  • Vertical distribution of salinity: this is how salinity changes with depth. It changes mostly near the surface and hardly at all in deep water.

Related concepts

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