In salinity, why do variations occur?

This doesn't sound very much, but it would take three 6 m shipping containers full of salt to make an Olympic-size swimming pool as salty as the sea. ... Variation in salinity. The salinity of the ocean varies from place to place, especially at the surface. read more

The higher the salt content per unit volume the higher the salinity, and the more dense the solution, which is why salt water is heavier than fresh water per unit volume. Variations in the oceans happen because of the addition of fresh water, through runoff from the land through rivers or by rain falling at sea. read more