by K. Buesseler, May 2020 in TheConversion

The big idea

The ocean plays a major role in the global carbon cycle. The driving force comes from tiny plankton that produce organic carbon through photosynthesis, like plants on land.

When plankton die or are consumed, a set of processes known as the biological carbon pump carries sinking particles of carbon from the surface to the deep ocean in a process known as marine snowfall. Naturalist and writer Rachel Carson called it the “most stupendous snowfall on Earth.”

Some of this carbon is consumed by sea life, and a portion is chemically broken down. Much of it is carried to deep waters, where it can remain for hundreds to thousands of years. If the deep oceans didn’t store so much carbon, the Earth would be even warmer than it is today.

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What still isn’t known

Our study reveals that scientists need to use using a more systematic approach to defining the ocean’s vertical boundaries for organic carbon production and loss. This finding is timely, because the international oceanographic community is calling for more and better studies of the biological carbon pump and the ocean twilight zone.

The twilight zone could be profoundly affected if nations seek to develop new midwater fisheries, mine the seafloor for minerals or use it as a dumping ground for waste. Scientists are forming a collaborative effort called the Joint Exploration of the Twilight Zone Ocean Network, or JETZON, to set research priorities, promote new technologies and better coordinate twilight zone studies.

To compare these studies, researchers need a common set of metrics. For the biological carbon pump, we need to better understand how big this flow of carbon is, and how efficiently it is transported into deeper water for long-term storage. These processes will affect how Earth responds to rising greenhouse gas emissions and the warming they cause.