Life in the Open Ocean. Joseph J. Torres

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Life in the Open Ocean - Joseph J. Torres


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Ocean Atlantic Arctic Indian Pacific Southern Ocean area (106 km2) 82.22 14.06 73.48 165.38 20.33 Mean depth (m) 3600 1117 3963 4200 4000–5000 Maximum depth (m) 9560 4440 7725 11 034 7235 Location of maximum depth Puerto Rico Trench Eurasia Basin Java Trench Marianas Trench South Sandwich Trench

      The continents define the boundaries of the ocean basins. Within each of the basins, a characteristic circulation transports large quantities of water with all the elements that such bodies of water contain, including plants, animals, gases, salt, and heat. Energy for the water movement is provided by the radiation of the Sun and the rotation of the Earth. The Sun’s heat drives circulation within the atmosphere, producing the Earth’s prevailing wind patterns that in turn drive surface ocean circulation. Deep ocean circulation, which has a more profound vertical component, is driven by changes in seawater density. Cooler or more saline water will sink below a warmer or less saline body of water. Since the density of seawater is determined by its temperature and salinity, solar radiation ultimately is responsible for deep‐ocean circulation as well. Latitudinal gradients in temperature cause heat loss or gain across the ocean–atmosphere interface. Changes in salinity result from evaporation, precipitation, and in polar regions from the freezing and melting of sea ice. An understanding of the influence of the Earth’s rotation on ocean circulation is less intuitive; that influence is described in the next section.

Schematic illustration of the Polar Oceans.

      Source: NASA.

      Ocean Circulation

      Surface Currents: Ocean Gyres and Geostrophic Flow

Schematic illustration of geostrophic (surface) currents.

      Source: NASA.

Schematic illustration of thermohaline (deep) currents.

      Source: NOAA.

       Coriolis Force

      The Coriolis force, as it applies to water movement in the oceans, is a result of the fact that the vast majority of the ocean’s volume is only loosely coupled to the surface of the Earth. The “no slip” condition, discussed in the section on viscosity, applies only to the boundary formed by the ocean bottom. The remaining volume of the ocean moves with the Earth as it rotates, but there is slippage due to the near absence of frictional coupling.


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