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Southern Ocean carbon sink enhanced by sea-ice feedbacks at the Antarctic Cold Reversal


The Southern Ocean occupies 14% of the Earth’s surface and plays a fundamental role in the global carbon cycle and climate. It provides a direct connection to the deep ocean carbon reservoir through biogeochemical processes that include surface primary productivity, remineralization at depth and the upwelling of carbon-rich water masses. However, the role of these different processes in modulating past and future air–sea carbon flux remains poorly understood. A key period in this regard is the Antarctic Cold Reversal (ACR, 14.6–12.7 kyr bp), when mid- to high-latitude Southern Hemisphere cooling coincided with a sustained plateau in the global deglacial increase in atmospheric CO2. Here we reconstruct high-latitude Southern Ocean surface productivity from marine-derived aerosols captured in a highly resolved horizontal ice core. Our multiproxy reconstruction reveals a sustained signal of enhanced marine productivity across the ACR. Transient climate modelling indicates this period coincided with maximum seasonal variability in sea-ice extent, implying that sea-ice biological feedbacks enhanced CO2 sequestration and created a substantial regional marine carbon sink, which contributed to the plateau in CO2 during the ACR. Our results highlight the role Antarctic sea ice plays in controlling global CO2, and demonstrate the need to incorporate such feedbacks into climate–carbon models.

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Fig. 1: Intercomparison of Antarctic ice core with marine proxy records from independent referenced studies.
Fig. 2: The South Atlantic sector of the Southern Ocean with the locations of the Patriot Hills in the Ellsworth Mountains, the EDML ice core and marine cores MD07-313421 and TN057-134.
Fig. 3: Stratigraphic and chronological details of the Patriot Hill BIA.
Fig. 4: Marine biomarkers from Patriot Hills BIA.
Fig. 5: Regional climate proxy and model intercomparisons with the Patriot Hills record.
Fig. 6: Schematic depicting events across mid- to high-latitude Southern Ocean during the LGT.

Data availability

The data supporting this study is available at National Oceanic and Atmospheric Administration Paleoclimatology Database ( The data from core MD07-3134 are available on the PANGEA Database at and Source data for Figs. 1, 4 and 5 and Extended Data Fig. 1 are available with the paper.


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C.J.F., C.S.M.T., L.M., N.R.G., L.S.W. and A.C. are supported by their respective Australian Research Council (ARC) and Royal Society of NZ fellowships, and C.J.F. and A.G.C. thank Keele University for a Research Development Award that underpinned this research at Keele University IceLab and Exeter University. Fieldwork was undertaken under ARC Linkage Project (LP120200724), supported by Linkage Partner Antarctic Logistics and Expeditions, whose enduring support we acknowledge. CSIRO’s contribution was supported in part by the Australian Climate Change Science Program (ACCSP), an Australian Government Initiative. S.D. acknowledges financial support from Coleg Cymraeg Cenedlaethol and the European Research Council (ERC grant agreement no. 25923). M.E.W. acknowledges support from the Deutsche Forschungsgemeinschaft (grant no. We2039/8-1). Finally, we thank H. Glanville for comments on the final draft of the manuscript, and A. Jeffery for advice on SEM analysis.

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C.J.F., C.S.M.T., A.B. and A.C. conceived this research. C.J.F., C.S.M.T., A.B., M.E.W., D.E., M.R., D.P.T., T.D.vO., A.D.M., M.A.J.C., S.D., M.I.B., N.C.M., J.V., A.R., L.M., H.M., CM, J.Y., M.M., A.G.C., M.R.P.H., A.P., J.L. and L.S.W. undertook analysis and sampling. C.J.F., C.S.M.T., A.B., M.E.W., M.R.P.H. and A.C. wrote the manuscript with input from all the authors.

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Correspondence to C. J. Fogwill.

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Extended data

Extended Data Fig. 1 Reproducibility of fOM signal.

Reproducibility of fOM signal. 5 m resolved fOM concentration (Component 1; TRYLIS in red), plotted against data from a second parallel transect from the Patriot Hills transect (~3 m resolved black dashed line). The dashed lines represent replicate samples from the same transect which were taken in 2014/15 and measured in 2015 at UNSW Icelab (black dots), and subsequently reanalysed in 2019 at Keele Icelab (red triangles). The records are synchronised from water stable isotopes, site survey data and DGPS, and taken within 4 m of one another from a parallel transect (inset). Source data

Supplementary information

Supplementary Information

Supplementary Sections 1–9, Figs. 1–7 and Tables 1–3.

Source data

Source Data Fig. 1

Numerical data used to generate graphs in the figure.

Source Data Fig. 4

Numerical data used to generate graphs in the figure.

Source Data Fig. 5

Numerical data used to generate graphs in the figure.

Source Data Extended Data Fig. 1

Numerical data used to generate graphs in the figure.

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Fogwill, C.J., Turney, C.S.M., Menviel, L. et al. Southern Ocean carbon sink enhanced by sea-ice feedbacks at the Antarctic Cold Reversal. Nat. Geosci. 13, 489–497 (2020).

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