SeaWiFS The Meaning of Ocean Color The Role of Phytoplankton The Carbon Absorbing Oceans
  • What is ocean color?
  • Why is ocean color important?
  • How is ocean color measured?

    Vegetation: False Color
    False color image of vegetation representing ocean color. What is "false color" ?

    Calibration Scale Red areas contain the most life, while the purple areas are nearly empty of life. Ocean areas of high productivity support more life than less productive areas. It is as simple as more food = more fish. More oxygen is produced and carbon dioxide consumed in these highly productive areas of the ocean.

  • What is ocean color?

    The "color" of the ocean is determined by the interactions of light with the water. We see color when light is reflected by objects around us. White light is made up of a spectrum or combination of colors, which are broken apart by water droplets in a rainbow. When light hits the surface of an object, the different colors can be absorbed, transmitted, scattered, or reflected in differing intensities. The color we see depends on which colors are reflected. For example, a book that appears red to us absorbs more of the green and blue parts of the white light shining on it, and reflects the red parts. The light which is scattered or transmitted by most objects is usually not apparent to our eyes.

    The substances in seawater which most affect the color reflected are, phytoplankton, inorganic particles, dissolved organic chemicals, and the water itself. Phytoplankton contain chlorophyll, which absorbs red and blue light and reflects green light. Particles can reflect and absorb light, which reduces the clarity (light transmission) of the water. Dissolved organic matter strongly absorbs blue light, and its presence can interfere with measurements of chlorophyll.

    When we look at the ocean or observe it from space, we see that the ocean is blue because water absorbs red and reflects blue light. Using instruments that are more sensitive than the human eye, we can measure a wide array of blue shades, which reveal the presence of varying amounts of phytoplankton, sediments, and dissolved organic chemicals.

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    Updated: January 27, 2003