Ocean Color Viewed from Space

Microscopic plant life is at the base of the marine food web and is the primary food and energy source for the ocean ecosystem. Phytoplankton convert nutrients into plant material by using sunlight with the help of the green pigment chlorophyll. The chlorophyll pigments in the plants absorb light, and the plants themselves scatter light. Together, these processes change the color of the ocean as seen by an observer looking downward into the sea. Very productive water with a high concentration of plankton appears blue-green. Very pure water appears deep-blue, almost black.

From space, variations in ocean color can be measured with sensitive instruments. Ocean and land plants are green because chlorophyll absorbs red light but reflects blue and yellow light. Satellite instruments measure the amount of reflected light of different wavelengths. These amounts allow scientists to estimate the productivity of Earth's land masses and oceans. The false color images below show these estimates of plankton distribution and productivity in the world's oceans.

False Color Images of Ocean Color

Click on the map to see a larger view

The plankton populations are dependent on a variety of factors, including ocean currents, temperature, availability of nutrients, amount of sunlight, and ocean depth. Many different species of plankton contribute to ocean color, although only a few species, occurring in great numbers, are found at any one time or place. The individual plants live at various depths, from the surface to nearly 100 meters, but prefer the surface sunlit regions with sufficient light to support photosynthesis.

In the ocean, as on land, plants are the foundation of the food chain on which all other organisms depend. The productivity of the ocean is very important to human activities and to the overall health of the planet. Remote-sensing of the productivity of the oceans through the use of instruments aboard satellites helps us better understand this vast frontier.

Science Journal

• Print out a blank map and outline the ocean regions with higher productivity. Consider the colors in the legend from green to red to be areas high in productivity. Color these areas red on your map using a colored pencil, pen or crayon.
• Color the lesser productive areas on your map in blue.
• Compare/contrast productivity near the coastal areas with that in the mid-ocean regions.
• Compare the productivity of ocean water near the equator with that in the northern and southern latitudes in these areas:
  • in the mid-Atlantic
  • in the mid-Pacific
  • eastern coastline of North and South America
  • western coastline of North and South America
  • western coastline of Asia
• In the region of the equatorial Pacific, where is the ocean most productive?
• In the region of the equatorial Atlantic, where is the ocean most productive?
• Compare/contrast the productivity in the oceans in the northern and southern hemispheres.
• Can you think of any factors that cause the differences?
• Predict at least three factors that affect the productivity of the oceans.

Continental Vegetation Detected from Space

Click on the map to see a larger view

Science Journal

• Locate and label these areas of high productivity on your map. Color them in green.
  • Amazon Rainforest in South America
  • Congo Rainforest in Africa
  • New Guinea in Southeast Asia
  • the southeastern USA in North America
• What are some of the similarities and differences of these regions?
• Locate and label these areas of low productivity on your map. Color them in brown.
  • the Sahara Desert in Africa
  • the Australian Desert
  • the Arctic Tundra in Northern Alaska
  What are some of the similarities and differences of these regions?
  • Predict at least three factors affecting the productivity of the land masses. Do these factors explain the differences you observed?

Summary

On land, we can judge the productivity of an environment by observing its "greenness." Tropical rain forests are more productive than deserts or arctic tundra. These differences in color can be observed from space. From space, sensitive instruments can measure variations in amounts of reflected light. This data is then mathematically sorted with formulas that estimate productivity from the measurements. False color images are produced like those you have examined in this lesson. The images indicate the presence of plants through detection of the plant pigment clorophyll. Photographs taken from space can show differences in the productivity of the land and oceans, but not with the precision and detail that the false color images yield.

This movie shows the distribution of plant life on Earth from satellite measurements in space. As the movie plays and Earth rotates, observe the pattern visible in the different latitudes. Make some generalizations.

Image Credits

these pages

Tell us what you think about this page.