New Scientist - Ocean Absorption Of CO2 Fell Far More Quickly Than Expected In 2023; Extreme Heat May Be Why

The ocean may have removed much less carbon dioxide from the atmosphere than expected in 2023, mainly due to high ocean temperatures. If climate change continues to rapidly weaken the planet’s ocean and land carbon sinks, it will be even more difficult to avoid dangerous levels of warming. The ocean currently absorbs a quarter of the world’s CO2 emissions from the atmosphere each year. However, warming temperatures are expected to weaken this natural carbon sink and observations from 2023 – the hottest year on record – suggest this process may be happening even faster than anticipated.

“As the world warms, the wonderful free service that is being provided to us by the ocean and the land will decline in strength, so the fraction of CO2 from fossil fuels that are stored in the atmosphere will increase,” says Scott Denning at Colorado State University, who wasn’t involved with the new research.

Jens Müller at ETH Zürich in Switzerland and his colleagues modelled the flux of CO2 from the oceans to the atmosphere in 2023, excluding the polar oceans. They based the model on direct measurements at different parts of the ocean, as well as observations of sea surface temperature, wind speed and the activity of plankton.

Overall, the researchers found that the ocean carbon sink was about 10 per cent weaker than expected given a strong El Niño weather pattern emerged early in the year. Historically, a shift to warm El Niño conditions helps the tropical Pacific absorb more carbon dioxide by suppressing the deep waters upwelling to the surface there, limiting how much CO2 they release into the air. But in 2023, this effect was diminished by an increase in CO2 released from the Atlantic and Pacific Oceans outside the tropics. This researchers attributed the rise to record-high sea surface temperatures in large areas of both oceans, which reduced the water’s capacity to absorb CO2.

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https://www.newscientist.com/article/2459408-extreme-heat-may-rapidly-sap-the-oceans-ability-to-absorb-co2/

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