Salinity

Definition of Salinity

• The concentration of ions in a liter of water• The number of grams of dissolved solids in

1000 g of water. – Ex: a 1000 g sample of seawater containing 34.7 g

of dissolved material has a salinity of 34.7 parts per 1000 g

– In the above example, what is the remaining 96.53%?

What units describe salinity?When we measure salinity, we use these

descriptive terms:– ‰ = a percent sign with the extra zero to indicate

not parts per hundred, but parts per thousand– ppt = parts per thousand

Variability in Salinity

Even though the proportions of the ions remain the same throughout the ocean (principal of constant proportions), the concentration of ions changes with:– Evaporation– PrecipitationQ: what do you think the salinity would look like in the

middle of the ocean, along the equator, compared to near the edges of the continents?

World Ocean Salinity

• Average is 35 ‰• Red Sea is 40 ‰, Mediterranean Sea is 38 ‰

Q: Why? Look at a map!• Black Sea is 18 ‰, Baltic Sea is 8 ‰

Q: Why? Look at a map!

Variability in Salinity cont.

Other influences on salinity that we’ll cover later:– Temperature– Pressure– Density

Start thinking about how each of these would impact the salinity of the seawater. . . .