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Physical Oceanography

Physical Oceanography. Salinity. Salinity.

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Physical Oceanography

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  1. Physical Oceanography Salinity

  2. Salinity Salt has always been a valuable commodity to mankind. Its antiseptic and preservative powers have long been known. Salt has always been used as currency and the word ‘salary’ is derived from the word ‘salt.’ Even today, many tropical societies use salt as currency.

  3. Seawater • Average seawater is composed of three things: water (96.5%), salt (3.5%) and trace amounts of cosmic dust. • The most abundant ions in salt are chlorine (Cl-) and sodium (Na+), which together make up about 86% of all salts in the ocean.

  4. What is Salinity? • Salinity = total mass (grams) of dissolved material in 1 kg of seawater • Average salinity = 35g salt/kg of seawater = 35 parts per 1000 = 35‰, or 3.5% • This is equivalent to 2.5 teaspoons of salt in 1 L of water

  5. Examples of Salinity

  6. Terminology • Hypersaline Water: salinity > 47 ‰ • Brine: salinity from 36-47 ‰ • Brackish Water: salinity < 17 ‰ (mixture of fresh and salty, mostly in bays, inlets and river mouths)

  7. Are the following hypersaline, brine, brackish, normal, or a combination?

  8. How is Ocean Salinity Measured • How well it conducts electricity A salinometer: a water sample is placed in it – you get a digital readout of the salinity Greater Conductivity = Higher Salinity

  9. 2. Measure the refraction of light A refractor is used to measure the amount of ‘bending’ that occurs when light passes through water. Greater Refraction = Higher Salinity

  10. CTD Sensor Lowered over the side of a ship, it measures conductivity, temperature and pressure/density all at once.

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