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Ocean's 'biological pump' absorbs more carbon than previously estimated

Ocean's 'biological pump' absorbs more carbon than previously estimated
Researchers say the ocean's euphotic zone, the depth at which sunlight penetrates surface water throughout the ocean, is much deeper than thought. Photo by Alexandra_Koch/Pixabay

April 6 (UPI) -- New research suggests the ocean's "biological carbon pump" is more efficient at absorbing carbon than scientists previously estimated.

In spring, as the ocean surface in the Northern Hemisphere warms, phytoplankton bloom in great numbers. As these green microorganisms sprawl across the blue seas, they take in sunlight and convert it into food -- just like plants.

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During the photosynthesis process, CO2 gets absorbed and oxygen is emitted. When phytoplankton die, much of the absorbed carbon sinks to the bottom of the ocean.

According to new analysis by scientists at the Woods Hole Oceanographic Institution in Massachusetts, scientists have previously underestimated the efficiency of this natural carbon pump.

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The study is based on a fresh survey of the dimensions of the ocean's euphotic zone, the depth at which sunlight penetrates surface water throughout the ocean.

The amount of sunlight available to phytoplankton communities varies greatly across different parts of the ocean, but the latest study suggests the euphotic zone is bigger than previously thought.

In light of the new data on the ocean's sunlit zone, scientists estimate the ocean's biological pump absorbs roughly twice as much carbon as previously estimated.

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Instead of attempting to measure the presence of light at various ocean depths, scientists used chlorophyll sensors to determine the presence of phytoplankton and more quickly estimate the extent of a region's euphotic zone.

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The scientists hope future studies of the ocean's carbon pump will use a naturally occuring thorium isotope to measure the rate at which carbon particles sink to the bottom.

"Using the new metrics, we will be able to refine the models to not just tell us how the ocean looks today, but how it will look in the future," WHOI geochemist Ken Buesseler said in a news release. "Is the amount of carbon sinking in the ocean going up or down? That number affects the climate of the world we live in."

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