A shift in the mechanism of CO2 uptake in the Southern Ocean under high emission-scenario

The Southern Ocean is a major region of ocean carbon uptake, but its future changes remain uncertain under climate warming. Here we show the projected shift in the Southern Ocean CO2 sink using a suite of Earth System Models, revealing changes in the mechanism, position and seasonality of the carbon uptake. Dominant CO2 uptake shifts from the Subtropical to the Antarctic region under the high-emission scenario by the end of the 21st century. The warming-driven sea-ice melt, increased ocean stratification, mixed layer shoaling, and a weaker vertical carbon gradient will together reduce the winter outgassing in the future, which will trigger the switch from mixing-driven outgassing to solubility-driven uptake in the Antarctic region during the winter season. The future Southern Ocean carbon sink will be poleward-shifted, operating in a hybrid mode between biologically-driven summertime and solubility-driven wintertime uptake with further amplification of biological uptake by the increasing Revelle Factor.

Gregor L., Tjiputra J., Hauck J., Ito T., Danek C., Vichi M., Thomalla S., Monteiro P. & Mongwe P., 2023. A shift in the mechanism of CO2 uptake in the Southern Ocean under high emission-scenario. Research Square. Article.

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