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Density Structure of the Ocean

Density Structure of the Ocean. Density Controls. Controlled by: 1.) Temperature 2.) Salinity 3.) Pressure Density increases with increasing salinity Density increases with decreasing temperature. Density increases with increasing pressure.

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Density Structure of the Ocean

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  1. Density Structure of the Ocean

  2. Density Controls • Controlled by: • 1.) Temperature • 2.) Salinity • 3.) Pressure • Density increases with increasing salinity • Density increases with decreasing temperature. • Density increases with increasing pressure. • Density of oceans ranges from 1.020 g/cm3 to 1.030 g/cm3

  3. Three Density Zones • Surface Zone (mixed layer)-Upper layer of the ocean • Temperature and salinity are constant because of mixing by wind and waves. • Top 100 meters (photic zone) • 2% of ocean water by volume • Pycnocline Zone-Middle layer of the ocean • Density increases rapidly with depth • 18% of ocean water by volume • Depth varies with latitude. • Temperature drops rapidly in this zone (thermocline). Salinity increases rapidly (halocline). • Deep Zone-Deepest ocean layer extending to the ocean floor. • Relatively constant density • 80% of ocean water by volume • Temperature and Salinity constant

  4. Density, Temp., Salinity Changes with Depth

  5. Pycnocline • Zone in which density increases with increasing depth. • From 0-1,000 meters • Increasing density farther down as temperature gets colder.

  6. Halocline • Zone of rapid salinity increase or decrease with depth. • Often coincides with thermocline.

  7. Halocline

  8. Thermocline • Temperature changes rapidly with depth. • Both thermocline and halocline contribute to form pycnocline since temperature and salinity affect density.

  9. Changes with Latitude

  10. Thermohaline Circulation • Vertical water circulation in the oceans. Results in top-to-bottom exchange of water. • Driven by density (Density Currents) • Thermohaline: Thermo (temperature) Haline (Salinity).

  11. Upwelling • Upwelling zones are areas where thermohaline circulation is upward toward the ocean surface. • Cold water and nutrients are brought to the surface. • Increased diversity of life in upwelling zones • Great fishing in upwelling zone. • Upwelling zones include areas of the west coast of California, west coast of South America, and South Africa. • Caused by wind blowing water off the surface and water moving upward to take its place.

  12. Upwelling

  13. Downwelling • Downwelling zones are areas where thermohaline circulation is downward.

  14. Vertical Water Masses • Surface Water: 0-200 meters • Central Water: To the bottom of the thermocline • Intermediate Water: to about 1,500 meters • Deep water: to about 4,000 meters • Bottom water: in contact with the seafloor

  15. NADW: North Atlantic Deep Water: -Forms at 50-60 degrees north latitude -34.9 PPT salinit -2 to 4 degrees celsius -Sinks and moves south AABW: Antarctic Bottom Water (1,000 years to go from south pole to equator) - 34.8 ppt salinity - is -0.5 degrees celsius AAIW: Antarctic Intermediate Water -Forms at 40 degrees south - is 5 degrees celcius and salinity of 34.4 ppt

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