The oceans store more carbon than thought — but not enough to save the planet

The Southern Ocean. An analysis that includes data on marine salinity concludes that the global ocean holds more carbon than previously estimated. Credit: Peter Barritt/Alamy

The oceans take up around 10% more of humanity’s carbon emissions than previously thought. This uptake slows global warming but worsens problems such as ocean acidification.

Researchers think the oceans absorb roughly one-quarter of CO2 emissions from human activities. But estimates of the precise size of this ‘carbon sink’ vary.

Jens Terhaar at the University of Bern in Switzerland and his colleagues analysed models and observations of carbon flowing in and out of the ocean. They found three factors that influence the size of the carbon sink.

One is how salty the waters are in a particular zone in the Southern Ocean around Antarctica. A second is the strength of an ocean-current pattern in the North Atlantic Ocean. The third is a measure of how much CO2 seawater can absorb in given atmospheric conditions. By focusing on how these three factors feed into climate models, the scientists were able to match the models to observations more accurately, thus reducing uncertainties in the size of the carbon sink.

The extra uptake would balance out only two to four years of global CO2 emissions at current rates.

Nature, 27 September 2022. Press release.

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