Salinity

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Salinity

• Total amount of solid material dissolved in water
• Typical salinity is 3.5 or 35o/oo
• Six elements make up 99 of dissolved solids in
  seawater

Fig. 5.12
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Constituents of ocean salinity

• Average seawater salinity 35
• Main constituents of ocean salinity
• Chloride (Cl)
• Sodium (Na)
• Sulfate (SO42)
• Magnesium (Mg2)

Figure 5-13
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Measuring salinity

• Evaporation
• Chemical analysis
• Principle of constant proportions
• Major dissolved constituents in same proportion
  regardless of total salinity
• Measure amount of chlorine (chlorinity)
• Electrical conductivity
• Salinometer

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Salinity

• Salinity total amount of solid material
  dissolved in water
• Can be determined by measuring water conductivity
  
• Typically expressed in parts per thousand ()

Figure 5-15
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Pure water vs. seawater
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Salinity variations

• Open ocean salinity 33 to 38 o/oo
• Coastal areas salinity varies more widely
• Influx of freshwater lowers salinity or creates
  brackish conditions
• Greater rate of evaporation raises salinity or
  creates hypersaline conditions
• Salinity may vary with seasons (dry/rain)

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Salinity variations
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How to change salinity

• Add water
• Remove water
• Add dissolved substances
• Remove dissolved substances

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Surface salinity variation

• Pattern of surface salinity
• Lowest in high latitudes
• Highest in the tropics
• Dips at the Equator
• Surface processes help explain pattern

Figure 5-20
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Processes affecting seawater salinity

• Processes that decrease seawater salinity
• Precipitation
• Runoff
• Icebergs melting
• Sea ice melting
• Processes that increase seawater salinity
• Sea ice forming
• Evaporation

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Processes that add/subtract water
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The hydrologic cycle
Figure 5-19
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Surface salinity variation

• Pattern of surface salinity
• Lowest in high latitudes
• Highest in the tropics
• Dips at the Equator
• Surface processes help explain pattern

Figure 5-20
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Processes affecting seawater salinity

• Processes that decrease seawater salinity
• Precipitation
• Runoff
• Icebergs melting
• Sea ice melting
• Processes that increase seawater salinity
• Sea ice forming
• Evaporation

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Ocean buffering

• Ocean pH 8.1 (slightly basic)
• Buffering protects the ocean from experiencing
  large pH changes

Figure 5-18