Which among the following statements regarding vertical distribution of salinity is correct?

The correct answer is option 2, i.e Increasing salinity of seawater causes its density to increase.

Key Points

• Salinity is the term used to define the total content of dissolved salts in seawater.
• It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater.
• It is usually expressed as parts per thousand or ppt.
• The relation between salinity of seawater with depth and its density is as follows:

• Salinity changes with depth, but the way it changes depends upon the location of the sea. Hence, Option 1 is NOT correct.
• Salinity at the surface varies as it increases by the loss of water to ice or evaporation, or decreased by the input of freshwaters, such as from the rivers.
• Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’ Hence, Option 3 is NOT correct.
• The lower salinity water rests above the higher salinity dense water.
• Salinity in general increases with depth and there is a distinct zone called the halocline where salinity increases sharply.
• Other factors being constant, increasing salinity of seawater causes its density to increase. Hence, Option 2 is correct.