Earth-monitoring satellites are being used to track everything from deforestation to the spread of plankton in the Arctic Ocean.
In September 2007 less sea ice covered the Arctic than at any point since the U.S. government began keeping records of its decline. All told, it covered 502,000 square miles (1.3 million square kilometers) less ocean than even the year before—a loss equal to an area the size of California and Montana combined. But what might be bad news for polar bears and other animals dependent on sea ice could be good news for the alga known as phytoplankton.
"Because these plants are photosynthetic, it's not surprising to find that as the amount of sea ice cover declined, the amount of [photosynthesis] increased," says biological oceanographer Kevin Arrigo of Stanford University's School of Earth Sciences, who led an effort to use the MODIS (Moderate Resolution Imaging Spectroradiometer) devices on NASA's Terra and Aqua satellites to determine changes in phytoplankton growth.
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