Ocean Circulation


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  • Gyres rotate clockwise in northern hemisphere and counter clockwise in southern hemisphere. Western boundary currents are warm and transport heat away from equatorial regions. Eastern boundary currents are colder and move colder water towards equator.
  • Caption for Item 1: SATELLITES SEE GULF STREAM WARM WATERS This is a NASA satellite image of the warm waters of the Gulf Stream running up the U.S. eastern seaboard. The Gulf Stream shows up as a winding rope of orange and yellow (indicating warm waters) against the cooler green and blue waters. Credit: MODIS Ocean Group NASA/GSFC SST product by U. Miami
  • Caption for Item 4: NORTH ATLANTIC OCEAN CIRCULATION SYSTEM The Gulf Stream moves warm surface water from the equator north through the Atlantic, where the water cools and gets saltier. As it approaches the Norwegian Sea, it becomes dense enough to sink. It then slowly travels through the deep water southward into the Southern hemisphere, with the return flow to the North occurring at the surface. Credit: NASA GSFC
  • Ocean conveyor belt moves heat around the globe. One trip around the conveyor belt can take 1000 years or more.
  • Brings nutrient rich cold water to the surface nourishing marine life.
  • These two images show sea surface temperatures, blue is coldest water and red is warmest. On the left, a summer upwelling event reveals cold up-welled water near the coast with filaments streaming offshore. On the right, the same region without upwelling shows the relatively warm surface water of the California Current moving much closer to shore. Graphic courtesy of PISCO, the Partnership for Interdisciplinary Studies of Coastal Oceans , at Oregon State University
  • Ocean Circulation

    1. 1. Ocean Circulation
    2. 2. Salinity <ul><li>Amount of salts and minerals dissolved in water </li></ul><ul><li>Varies throughout </li></ul><ul><li>Average = 35 ppt or 3.5% </li></ul>
    3. 3. Density <ul><li>Salt water is more dense than fresh water </li></ul><ul><li>Cold water is more dense than warm water </li></ul><ul><li>Pycnocline – area of rapid increase in density with depth </li></ul>
    4. 4. Temperature <ul><li>Warm water expands and stays above colder water </li></ul><ul><li>Only fresh water evaporates or freezes. The salt is left behind. </li></ul><ul><li>Thermocline – area of rapid decrease in temperature as depth increases </li></ul>
    5. 5. Pressure <ul><li>Increases with depth </li></ul><ul><li>Every 33 feet = 1 atmosphere </li></ul>
    6. 6. Waves <ul><li>Wind speed </li></ul><ul><li>Wind duration </li></ul><ul><li>Fetch (distance over which wind blows) </li></ul>
    7. 8. Surface Circulation <ul><li>Controlled by temperature, wind, and coriolis effect </li></ul>
    8. 12. Currents Affect Climate <ul><li>Warm currents make warmer climates </li></ul><ul><li>California vs. East Coast </li></ul><ul><li>Gulf Stream warms Europe </li></ul>
    9. 13. Climate Affects Currents <ul><li>Global warming & cooling can alter currents </li></ul><ul><li>Changes in precipitation or evaporation can change salinity and density </li></ul>
    10. 14. Deep Ocean Currents <ul><li>Controlled by density differences and the pull of the moon </li></ul>
    11. 15. Circulation Cells – Not Convection! <ul><li>Heat source is above the water not below </li></ul>
    12. 18. Water Masses <ul><li>Distinctive combinations of temperature and salinity </li></ul>
    13. 19. Upwelling