Earth Sciences and Ecology Question #313

Judy, a 14 year old female from the Internet asks on December 20, 1997,

What is the percentage of salt in the ocean?

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The answer

Barry Shell answered on December 20, 1997

"It is because we all came from the sea and it is an interesting biological fact that all of us have in our veins the exact same percentage of salt in our blood exists in the ocean and therefore we have salt in our blood, in our sweat, in our tears. We are tied to the ocean and when we go back to the sea, whether it is to sail or to watch it, we are going back to which we came." - President J. F. Kennedy, To Be or Not To Be

The percentage of salt in seawater is called "salinity."

  • Salinity is defined as the total amount of solid matter dissolved in a kilogram of seawater -- not including organic matter -- in parts per thousand
  • Average salinity = 34.7 (3.47%)
  • A volume of seawater weighing 1 kilogram (1000 grams), contains 34.7 grams of dissolved chemical
  • Six constituents comprise 99% of the dissolved chemical components; the most abundant are chloride and sodium, but there are also magnesium, calcium, sulfate (SO4) and potassium
  • Salinity typically - but not always - increases with depth
  • The distribution of salinity is affected by evaporation, melting, freezing, precipitation, river inflow

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