Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean

Abstract

Ocean acidification may lead to seasonal aragonite undersaturation in surface waters of the Southern Ocean as early as 2030 (ref. 1). These conditions are harmful to key organisms such as pteropods2, which contribute significantly to the pelagic foodweb and carbon export fluxes in this region3. Although the severity of ocean acidification impacts is mainly determined by the duration, intensity and spatial extent of aragonite undersaturation events, little is known about the nature of these events, their evolving attributes and the timing of their onset in the Southern Ocean. Using an ensemble of ten Earth system models, we show that starting around 2030, aragonite undersaturation events will spread rapidly, affecting 30% of Southern Ocean surface waters by 2060 and >70% by 2100, including the Patagonian Shelf. On their onset, the duration of these events will increase abruptly from 1 month to 6 months per year in less than 20 years in >75% of the area affected by end-of-century aragonite undersaturation. This is likely to decrease the ability of organisms to adapt to a quickly evolving environment4. The rapid equatorward progression of surface aragonite undersaturation can be explained by the uptake of anthropogenic CO2, whereas climate-driven physical or biological changes will play a minor role.

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Figure 1: Duration of aragonite undersaturation events in months per year.
Figure 2: Spatial extent and regional progression of aragonite undersaturation events.
Figure 3: Transition time from short (1 month per year) to long (6 months per year) aragonite undersaturation events.

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Acknowledgements

We acknowledge support from the National Science Foundation Ocean Acidification Program (OCE-1314209). This is IPRC publication no. 1152 and SOEST publication no. 9508.

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T.F. prepared and analysed the model output. C.H. analysed the model output and wrote the paper. All authors were involved in the study design, discussed the results and commented on the manuscript.

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Correspondence to Claudine Hauri.

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The authors declare no competing financial interests.

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Hauri, C., Friedrich, T. & Timmermann, A. Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean. Nature Clim Change 6, 172–176 (2016). https://doi.org/10.1038/nclimate2844

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