The researchers know this because the saltier parts of the ocean are getting saltier and the fresher parts, fresher. ... Records showed that the saltier parts of the ocean increased salinity -- or their salt content -- by 4 percent in the 50 years between 1950 and 2000.

Is ocean salinity increasing?

Evaporation of ocean water and formation of sea ice both increase the salinity of the ocean. ... However these "salinity raising" factors are continually counterbalanced by processes that decrease salinity such as the continuous input of fresh water from rivers, precipitation of rain and snow, and melting of ice.

How does salinity change over time?

Not only that, but changes in evaporation and rainfall, ocean currents, melting ice, and freshwater influx from rivers or streams can influence patterns of sea surface salinity, making some regions saltier and other regions fresher over time.