To celebrate Earth Day, the NASA Earth Observatory recently revealed global measurements of the Earth’s "metabolism."
Data from the Terra and Aqua satellites are helping scientists frequently update maps of the rate at which plant life on Earth is absorbing carbon out of the atmosphere.
Combining space-based measurements of a range of plant properties collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) with a suite of other satellite and surface-based measurements, NASA scientists produce composite maps of our world’s "net primary production" every 8 days. This new measurement is called net production because it indicates how much carbon dioxide is taken in by vegetation during photosynthesis minus how much is given off during respiration.
As you might think, this "net primary production" is variable depending on the seasons.
These maps show the seasonal comparison of net primary productivity. The yellow and red areas show the highest rates, ranging from 2 to 3 kilograms of carbon taken in per square kilometer per year. The green, blue, and purple shades show progressively lower productivity.
As you can see, there is a lot of activity in the oceans.
Plant life in the ocean is somewhat more buffered and therefore not as directly driven by weather patterns, states Wayne Esaias, biological oceanographer at NASA’s Goddard Space Flight Center. The growth of microscopic marine plants (phytoplankton) in the ocean responds more to seasonal changes -- currents, temperature, and sunlight. So, whereas certain areas on land will swing abruptly from very low to very high rates of photosynthetic activity, biological productivity in the ocean is ongoing.
"It doesn’t surprise Earth scientists, but the public might be surprised to learn that there is so much photosynthesis in the oceans," observes Esaias. "When you average the productivity rates over the whole world, the ocean is roughly equal to the land."
Now you might ask: are these new measurements useful?
"This measure can be the basis for monitoring the expansion of deserts, the effects of droughts, and any impacts climate change may have on vegetation growth, health, and seasonality," says Steve Running, MODIS Science Team member and director of the Numerical Terradynamic Simulation Group at the University of Montana.
"We also anticipate that our new productivity maps should help to significantly improve analysis of global crop commodities."
Source: NASA Earth Observatory, April 21, 2003
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