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Ocean Circulation and Climate: Structures, Dynamics, and Variability

This chapter explores the basic structures and dynamics of ocean circulation, including Ekman transport, geostrophic currents, surface ocean circulation, subtropical gyres, boundary currents, and deep ocean circulation. It also discusses the role of oceans in controlling climate and their contribution to the hydrological cycle and global climate variability.

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Ocean Circulation and Climate: Structures, Dynamics, and Variability

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  1. Chapter 7: The Ocean General Circulation and Climate • This chapter discusses: • Basic structures and dynamics • Ekman transport • Geostrophic currents • Surface ocean circulation • Subtropical gyre • Boundary currents • Deep ocean circulation • Thermohaline conveyor belt • (Materials are drawn heavily from D. Hartmann’s textbook and online materials by J.-Y. Yu of UCI.)

  2. The Role of Oceans in Controlling Climate

  3. The Role of Oceans in the Hydrological Cycle 97% of the Earth’s free water 86% of the global evaporation 78% of global precipitation

  4. The Role of Oceans in Global Climate Variability

  5. 1. Basic Ocean Structures • Area: covers 70% of the Earth’s surface • Volume: 97% of all the water on the Earth • Depth: 4 kilometers • Density: 1034-1035 kg/m3 (Pure water: 1000 kg/m3) over 90% of the ocean. Depends on temperature and salinity. cold water  high density loss of water by evaporation  increase salinity  high density precipitation and river discharge  decrease salinity  low density • Heat capacity: high • Temperature: less variable than in the atmosphere • Freezing point: –1.9°C, not at 0°C because of salinity • Surface is not level due to currents, waves, atmospheric pressure differences, and variations in gravity. • Two main forms of circulation: wind-driven circulation (horizontal, surface waters, fast) thermohaline circulation(vertical, deep waters, slow)

  6. Basic Ocean Structures

  7. Compare the state of the atmosphere: pressure, temperature, humidity

  8. Annual Mean Ocean Surface Temperature

  9. Annual Zonal Mean Ocean Surface Temperature

  10. Annual Mean Ocean Surface Salinity

  11. Annual Zonal Mean Ocean Salinity

  12. Relative proportions of dissolved salts in seawater

  13. See also Figure 7.2 in GPC

  14. Ocean Meridional Overturning (Global)

  15. Ocean Meridional Overturning in Atlantic

  16. Vertical Structure of the Oceans

  17. Vigorous mixing processes lead to uniform conditions within the surface mixed layer.

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