The waters at the surface of the North Atlantic Ocean are saltier than those of any other ocean - but not near Canada! The reasons for this high salinity are related to the flow of currents, the rate of evaporation, precipitation, river inflow, and melting of sea ice. Currents may bring high salinity water into the North Atlantic from surrounding saltier seas. The rate of evaporation plays a role in determining salinity. The higher the rate of evaporation, the higher the salinity, because the salt to water concentration increases as water evaporates. Increased levels of precipitation, as in equatorial regions, will decrease salinity by diluting the salt water. River inflows also dilute salt concentrations, and so too does the melting of sea ice. The outflow from the Mediterranean sea brings very salty water into the North Atlantic, and is the largest contributing factor to the salinity of this part of the ocean.

Around the Canadian coast, the Atlantic waters are not as salty. The Gulf Stream, which originates in the warm climate of the Gulf of Mexico also has a high evaporation rate. It has a salinity value of about 35%. Water from the Gulf Stream that enters the North Atlantic retains this value. This is about the closest that high salinity water gets to Canada's east coast! There are factors in Atlantic Canada that reduce salinity. For one, the precipitation rate is higher than the rate of evaporation, so that rainwater dilutes the Atlantic Ocean near the Maritimes, lowering salinity values. Rivers along the east coast also bring fresh water into the ocean, again lowering salinity values. The melting of Arctic sea ice, further reduces the salinity of surface waters along Canada’s Atlantic coasts.