How Do Temperature and Salinity Affect Mixing in the Oceans?
ES2202  Variations in a Salty Ocean

Anyone who has ever tasted seawater knows that it is truly salty. The salty residue left on swimsuits after they’ve been in the ocean is further evidence of the ocean’s salinity. Salinity is a measure of how much salt is dissolved in water.

The average salinity of seawater for all Earth’s oceans is about 35 grams of dissolved salts per kilogram of seawater. This is shown as 35 parts per thousand, or 35‰. The symbol ‰ is read "permill." It is similar to percent, but it refers to parts per thousand instead of parts per hundred.


The Red Sea and the Mediterranean Sea contain some of the saltiest water on Earth. In some areas, these bodies of water show salinity measurements as high as 40‰.

What do you think the temperature is like at these locations? What do you think causes seawater to have higher or lower salinity?

In this investigation, you will examine the relationship between temperature and salinity in the oceans and how both of these qualities affect the density of seawater. Ultimately, you’ll estimate densities for water masses and use them to predict how water will mix in the oceans.

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