A French CNR study published in Nature recalculates the role of plankton in transporting carbon from surface waters to the ocean floor. Compared to the latest IPCC estimates of 2021, which put it at 11 Gt C per year, the carbon storage capacity of the oceans is now set at 15 Gt C
The oceans are the Planet’s main carbon well
The oceans are the largest and most valuable “carbon well” of the planet. On their own, they absorb about 1/3 of the anthropogenic CO2 emissions that we produce every year, subtract them from the atmosphere, and thus stem the rise in global warming. But their role is even more important. A study conducted by researchers from the French CNR reveals that carbon storage capacity in the oceans could be 20% higher than previously estimated.
The most reliable numbers are provided by the 6th Report of the Intergovernmental Panel on Climate Change (IPCC), published in 2021. The synthesis of scientific knowledge on the subject sets at about 11 billion tons of carbon (Gt C) the annual capacity of the oceans. The French CNR study, recently published in Nature, revises this figure upwards and brings it to about 15 Gt C.
Plankton, sea snow and ocean carbon storage
To achieve this result, Researchers have analyzed data collected from oceanographic expeditions around the world from the 1970s to today and have been able to reconstruct carbon flows from the surface to the bottom. At the heart of the process driving carbon storage in the oceans is the plankton and the so-called “sea snow“.
“Plankton devours carbon dioxide and, as it grows, converts it into organic tissue through photosynthesis,” the authors explain. At death, the plankton tends to descend towards the bottom, breaking down into particles, which form the sea snow. “Being denser than seawater, these particles sink into the seabed, storing carbon and providing essential nutrients for a wide range of deep-sea organisms, from tiny bacteria to deep-sea fish,” the authors continue.
What implications does the new estimate have for ocean carbon storage capacity? The team of researchers specifies that this 20% more does not translate into an immediate advantage – that is, on human scale issues – to counter the climate crisis. “This absorption process takes place over tens of thousands of years, and is therefore not enough to compensate for the exponential increase in CO2 emissions caused by global industrial activity since 1750,” they specify. But it allows us to recalibrate our understanding of the role of the oceans as a major player in the long-term regulation of the global climate.
