A Shift in the Mechanisms of CO2 Uptake under High Emissions in the Southern Ocean

Mongwe et al., (2024)


The Southern Ocean is a key region for natural and anthropogenic carbon dioxide (CO2) uptake, contributing about one-third of the global ocean's total annually. In the present climate, CO2 uptake predominantly occurs in the Subtropics during winter, driven by gas solubility. South of the subtropical front, CO2 uptake is driven by primary production during summer and is partly compensated by seasonal upwelling of CO2-rich water driving outgassing in winter, with the largest effect in the Antarctic region. Using a suite of nine state-of-the-art Earth System Models under the high-emission scenario, we find that the region of dominant CO2 uptake shift to the Antarctic region in the future. Ocean warming is projected to weaken gas solubility and diminish CO2 uptake in the subtropics. South of the Polar Front, the warming-driven sea-ice melt and the accumulation of anthropogenic dissolved inorganic carbon in the upper ocean lead to the shutting down of seasonal CO2 outgassing and shifting the carbonate system from being nonthermal to thermal-driven in winter. The Antarctic region will then operate in a hybrid mode of winter-summer CO2 uptake, driven by solubility and primary production, respectively.

Reference: Mongwe, P., Gregor, L., Tjiputra, J., et al. (2024). Projected poleward migration of the Southern Ocean CO2 sink region under high emissions. Commun Earth Environ, 5, 232. https://doi.org/10.1038/s43247-024-01382-y

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