Ocean Chemistry


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Ocean Chemistry

  1. 1. Ocean Chemistry
  2. 2. Salinity: amount of dissolved solids • Avg. 3.5% • NaCl is most common salt
  3. 3. • salinity is high when: –high evaporation (hot dry climate) –freezing (only fresh water freezes, leaving salts behind) –low circulation (ex: Mediterranean)
  4. 4. Salinity is low when: • High rainfall • near melting glaciers • near the mouth of a river
  5. 5. Ocean salinity peaks at about 30° N and 30° S because the evaporation rate is very high and the precipitation rate is low. Conversely, salinity is low near the Equator, where precipitation is high and evaporation is low. Courtesy Lawrence Berkeley National Laboratory
  6. 6. Dissolved Gases • O2, CO2, N2 • essential for marine life forms • gases dissolve better in cold water and at high pressure • oceans are “sponges” for carbon dioxide, absorbing up to 2 billion tons/year
  7. 7. Ocean Temperature • Mixed layer: warm upper layer where wind and waves mix heat evenly –light penetrates here –surface water is warmer at equator, colder at poles
  8. 8. Thermocline: zone of rapid temperature decrease, caused by decreased sunlight as depth increases • Warmer, less dense surface water doesn’t mix easily with dense, cold deep water
  9. 9. Thermocline • transition layer between the mixed layer at the surface and the deep water layer. These layers are based on temperature. • In the thermocline, the temperature decreases rapidly from the mixed layer temperature to the much colder deep water temperature.
  10. 10. Deep ocean water : cold, dark • Temperature almost constant at just above freezing from thermocline down to bottom
  11. 11. How Do Temperature and Salinity Affect Mixing in the Oceans? • Click on the image below and learn about Temperature and Salinity differences in Oceans. • Follow the instructions on the screen.
  12. 12. Upwelling • transport of deeper water to shallow levels • Nutrient-rich water rises from deeper levels to replace surface water that drifted away • The nutrients are responsible for supporting the large fish population commonly found in these areas. • The effectiveness of upwelling and its ability to support abundant sea life is greatly dependent upon the depth of the thermocline.
  13. 13. Upwelling
  14. 14. Economic Consequences of El Nino and Lack of Upwelling • The coast of Peru is one of five major fishing grounds in the world (along with the coastal waters of California, Namibia, Mauritania, and Somalia). • The abundance of fish is supported by the upwelling of nutrient rich waters from deeper levels (below the thermocline).
  15. 15. Economic Consequences of El Nino and Lack of Upwelling • During non-El Niño years upwelling brings up colder deep sea water rich in nutrients which can sustain large fish populations.
  16. 16. Economic Consequences of El Nino and Lack of Upwelling • During an El Nino event upwelling does not occur because of a deeper thermocline. • Consequently, warm nutrient-poor water predominates the region and a decrease in the fish population is observed.
  17. 17. Results of Lack of Upwelling • A reduction of the fish population reduces the amount of fishmeal produced and exported (by local industry) to other countries for feeding poultry and livestock. • If the world's fishmeal supply decreases, more expensive alternative feed sources must be used, resulting in an increase in poultry prices worldwide.
  18. 18. When Were the Atlantic and Pacific Oceans Separated by Land? • Click on the image below and learn about differences between ocean chemistry and fossils separated by a thin ‘slice’ (isthmus) of land. • Follow the instructions on the screen.
  19. 19. References • http://www.studyofplace.com/Activities/Act ivity.cfm?ActivityId=8&ActivityItemId=58 • http://www.classzone.com/books/earth_scie nce/terc/content/investigations/es2307/es23 07page01.cfm?chapter_no=investigation • http://www.classzone.com/books/earth_scie nce/terc/content/investigations/es2202/es22 02page01.cfm?chapter_no=investigation