Ocean absorbs more carbon than expected, study shows – 12/06/2023 – Environment

The ocean absorbs, through phytoplankton, 20% more carbon than previously estimated, according to a scientific study published this Wednesday (6) in the journal Nature.

“It’s an important calculation and reinforces the role of ocean biology in absorbing carbon in the long term,” Frédéric Le Moigne, oceanographer and marine biologist at the CNRS (French National Center for Scientific Research), co-author of this study, told AFP. with Chinese and American researchers.

The new calculation reaches 15 billion tons per year, that is, an increase of 20% compared to the calculations mentioned by the IPCC (acronym in English for Intergovernmental Panel on Climate Change), in 2021, according to a statement from the CNRS.

Absorption occurs thanks to phytoplankton, which transforms CO_two in organic tissue by photosynthesis. When they die, some of this phytoplankton flows from the ocean’s surface in the form of “marine snow.”

To measure these “marine snow” flows, researchers rely on existing data on carbon concentration in the ocean, measured by oceanographic ships, the researcher points out.

“Thanks to this digital simulation, it was possible to reconstruct global and especially regional flows where no flow measurement was carried out”, he adds.

It is “calculating how much [carbono] it actually reaches the bottom of the ocean”, at an average depth of 3,800 meters, without being devoured by marine organisms, says Le Moigne.

Upon reaching the bottom of the ocean, this “marine snow” turns into sediment and stone, absorbing carbon for very long periods.

The calculation made by scientists shows that “preserving biodiversity is crucial to guarantee this process of biological carbon absorption, as we are facing an even more important flow than previously thought”, highlights the researcher from Lemar (Laboratory of Environmental Sciences Marine) from Plouzané, near Brest.

“Global warming could weaken this biological absorption process”, he warns.

Currently, it is estimated that the ocean absorbs around 30% of the carbon released into the atmosphere by human activities, mainly through the dissolution of carbon in the polar seas.