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OCEAN STRATIFICATION

OCEAN STRATIFICATION. SURFACE AND DEPTH SALINITY VARIATIONS. Surface variations Varies with latitude Lowest at high latitudes Highest at tropics of Cancer and Capricorn Dips near the Equator. Surface Variations. Why vary at the surface? High Latitudes: low salinity Lots of precipitation

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OCEAN STRATIFICATION

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  1. OCEAN STRATIFICATION

  2. SURFACE AND DEPTH SALINITY VARIATIONS • Surface variations • Varies with latitude • Lowest at high latitudes • Highest at tropics of Cancer and Capricorn • Dips near the Equator

  3. Surface Variations • Why vary at the surface? • High Latitudes: low salinity • Lots of precipitation • Melting of ice • Runoff • Limited evaporation

  4. Surface Variations • Why vary at the surface? • Tropics of Capricorn and Cancer: High salinity • Warm air descends here • Evaporation rates are high • Little precipitation • Little runoff

  5. Surface Variation • Why vary at the surface? • Equator: • Warm temperatures • High evaporation rates • Increased precipitation • Increased runoff • Kind of offset one another

  6. Depth Salinity Variation • Low latitude regions • High salinity at surface • Dips to intermediate level with depth • High latitude regions • Low salinity at surface • Goes to intermediate level with depth • Approaches value of low latitude version at depth • Salinity varies little with ocean depth

  7. The Halocline • Rapid change in salinity with depth • Between 300m – 1000m • Low latitude: • Curve is a decrease in salinity • High latitude: • Curve is an increase in salinity

  8. SEAWATER DENSITY • Pure water = 1.000g/cm3 at 4°C • Seawater: • Dissolved substances increase density • 1.022 – 1.030g/cm3

  9. The ocean is layered • Ocean Stratification • Lower density floats on top • Higher density at bottom

  10. Density is affected by… • Temperature: • Density increases as temperature decreases • Greatest influence • Salinity: • Density increases as salinity increases • Has more effect at poles • Pressure: • Density increases as pressure increases • Least effect

  11. Density curves – low-latitude • Density remains fairly constant till 300m • Good surface mixing from currents, waves and tides • Below 300m: • Density increases rapidly with depth to 1000m • Below 1000m: • Density remains constant

  12. Density curve – High latitudes • Very little variation with depth • High density at surface – low water temp • High density below the surface –low water temp • Straight line

  13. Pycnocline and Thermocline • Pycnocline: • Layer of rapidly changing density with depth • Thermocline: • Layer of rapidly changing temperature with depth • Typically occurs between 300-1000m

  14. Thermoclines in High Latitudes • Cold year round surface water • Thermocline and pycnocline rarely develop • Only during the short summer • Long days of sunlight • Stays isothermal and isopycnal

  15. Why is it important? • Pycnocline=barrier to mixing • Results from combined effects of halo and thermoclines • Results in a layered ocean

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