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Salinity. How much salt is there?. The oceans contain as much as 50 quadrillion tons (50 million billion tons) of dissolved solids
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How much salt is there? • The oceans contain as much as 50 quadrillion tons (50 million billion tons) of dissolved solids • If the salt in the sea could be removed and spread evenly over Earth's land surface it would form a layer more than 500 feet thick (152.4 meters), about the height of a 40-story building. • Seawater is 220 times saltier than fresh lake water. • Unrefined sea salt contains 98.0% sodium chloride and up to 2.0% other minerals (salts).
Composition of Sea Salt • Together there are over 100 minerals, composed of 80 chemical elements, in sea salt. • The composition of a single crystal of ocean salt is so complicated that no laboratory in the world can produce it from its basic 80 chemical elements.
How much salt is there relative to water? • Yes, there is a lot of salt in the ocean, but there is a lot more water. In ocean waters of average salt content (35 psu), the weight of water is over 28.5 times greater than the weight of salt it contains. • Oceanographers use the measure of salinity to describe the relative amount of salt to water.
What is salinity? • A measure of the quantity of dissolved solids in ocean water. In general, salinity reflects the total amount of dissolved solids in ocean water in parts per thousand (0/00) by weight. Salinity is now measured as practical salinity units (psu). That is, a salinity of 35 ppt meant 35 pounds of salt per 1,000 pounds of seawater.
Open ocean salinity is generally in the range from 32 to 37.
35 psu or 3.5%
Sources of Salinity • Chemical weathering of rocks, providing 21.5 billion tons of dissolved solids per year • Volcanic eruptions, providing mostly sulfur and chlorine • Most common salt is sodium chloride NaCl
What processes affect salinity?
Processes affecting salinity • Increased salinity caused by: • Evaporation of water • Formation of sea ice • Decreased salinity caused by: • Addition of freshwater by rivers, melting ice caps • Dissolved solids being removed by marine organisms to make shells and bones • Dissolved solids being removed as chemical precipitates • precipitation
Determined mostly by salinity near the poles, rather than by temperature Determined mostly by surface temperature near the equator rather than by salinity Density of sea water