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NSF PR 02-29 - April 25, 2002

Satellite Data to Predict Plankton Blooms by Analyzing Ocean Color

Scientists analyzing satellite data on ocean color are gaining new insights into ocean productivity and climate.

A green ocean is a productive ocean; the light from the sun fuels the "bloom" of phytoplankton, tiny ocean plants that turn the sea's surface a light green each spring. This production in turn drives ocean food webs. New research, published in the journal Science on April 26, assesses the color of the ocean and finds that it may yield clues about the relation between marine ecosystems and the climate system. The research was funded by the National Science Foundation (NSF).

David Siegel, a scientist at the University of California, Santa Barbara, and colleagues analyzed ocean color data from the satellite Sea-viewing Wide Field of view Sensor (called "Sea WiFS") to address the factors regulating the spring bloom of phytoplankton in the north Atlantic Ocean. "The productivity of the ocean [from blooms] is well established," said Siegel. "What we don't know is how it gets recycled. We're trying to get at how the ocean's biological pump works." The biological pump is the mechanism by which carbon dioxide is exported from the surface ocean into the deep ocean via sinking particles, like the remains of phytoplankton as they die off after blooms. It is a critical factor in understanding global climate change.

From the satellite is information Siegel and colleagues were able to deduce the conditions required to start a spring bloom: appropriate amounts of light reaching down into the water column, a condition that occurs when ocean waters "turn over" or mix, in spring.

"When viewed from space, the north Atlantic spring bloom is among the largest mass greenings observed on the Earth's surface," said Siegel. The blooming progresses at speeds of 20 kilometers per day, leaving a green wake in its path.

Jim Yoder, a co-author of the paper, on leave from the University of Rhode Island Graduate School of Oceanography and currently division director of ocean sciences at the National Science Foundation said, "We used satellite and other data to observe the start of the phytoplankton growth period in the north Atlantic Ocean, and we were able to explain the timing of the spring growth period in the entire north Atlantic."

Previous research on spring blooms was done at sea with microscopes and other tools. But by using satellites, Siegel and Yoder were able to evaluate the process using tens of thousands of data points, rather than just a few.

One advantage provided by satellite ocean color data is measurements that cover the entire north Atlantic during all seasons and years. Such measurements, if correctly interpreted, are a tool for studying natural phytoplankton variability - an important characteristic of marine ecosystems. The results of the present study illustrate an approach for using satellite measurements to study the year-to-year ecosystem variability associated with changes to the climate system and to the location and strength of ocean currents.

The research was also funded by NASA.


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