"With three years of observations we can see seasonal changes in plant and algae chlorophyll levels very well, but we don't yet have a long enough record to distinguish multi-year cycles like El Nio from fundamental long-term changes caused by such things as higher carbon dioxide levels in the atmosphere," Behrenfeld concluded.

"The SeaWiFS record provides a baseline against which future estimates of Earth system carbon cycling can be compared," said Feldman.

NASA plans to produce a five-year record using SeaWiFS observations and extend the continuous biological record with two Earth Observing System (EOS) spacecraft, Terra, launched in December 1999, and Aqua, scheduled for launch later this year. This constellation of EOS satellites allows U.S. scientists to examine practically every aspect of Earth's atmosphere, oceans and continents from space in an unprecedented way.

The new biological record benefits ongoing studies of desertification and changes in growing-season lengths by joining an existing 20-year record of land plant productivity based on observations from meteorological satellites with the new generation of spacecraft instruments. These records will compliment ongoing observations obtained on land and at sea.

"SeaWiFS not only adds finer detail to our observing capability, it supplies essential continuity between data records that is critical to long-term monitoring of changes in the biosphere," says biogeochemist James Randerson of the California Institute of Technology, a co-author on the study.

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Contact: Cynthia M. O'Carroll
Cynthia.M.OCarroll.1@gsfc.nasa.gov
301-614-5563
NASA/Goddard Space Flight Center
28-Mar-2001