Five million years of Antarctic Circumpolar Current strength variability

• Published in: Nature (London) Vol. 627; no. 8005; pp. 789 - 796
• Main Authors: Lamy, Frank, Winckler, Gisela, Arz, Helge W., Farmer, Jesse R., Gottschalk, Julia, Lembke-Jene, Lester, Middleton, Jennifer L., van der Does, Michèlle, Tiedemann, Ralf, Alvarez Zarikian, Carlos, Basak, Chandranath, Brombacher, Anieke, Dumm, Levin, Esper, Oliver M., Herbert, Lisa C., Iwasaki, Shinya, Kreps, Gaston, Lawson, Vera J., Lo, Li, Malinverno, Elisa, Martinez-Garcia, Alfredo, Michel, Elisabeth, Moretti, Simone, Moy, Christopher M., Ravelo, Ana Christina, Riesselman, Christina R., Saavedra-Pellitero, Mariem, Sadatzki, Henrik, Seo, Inah, Singh, Raj K., Smith, Rebecca A., Souza, Alexandre L., Stoner, Joseph S., Toyos, Maria, de Oliveira, Igor M. Venancio P., Wan, Sui, Wu, Shuzhuang, Zhao, Xiangyu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28.03.2024; Nature Publishing Group
• Subjects: 704/106/2738; 704/106/413; Antarctic Circumpolar Current; Antarctic ice sheet; Atmospheric forcing; Climate change; Continental interfaces, environment; Cooling; Cores; Density gradients; Future climates; Glacial periods; Global cooling; Global warming; Heat; Heterogeneity; Humanities and Social Sciences; Jet stream; multidisciplinary; Ocean circulation; Ocean currents; Ocean, Atmosphere; Oceans; Pleistocene; Pliocene; Reconfiguration; Science; Science (multidisciplinary); Sciences of the Universe; Sediments; Water circulation; Wind; Drake Passage; South Pacific; Southern Ocean
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-024-07143-3

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability 1 – 3 . Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity 4 . Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles 5 – 8 , the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling 9 and increasing global ice volume 10 . Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings 11 – 13 . We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability 14 . A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO 2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming. The strength of the Antarctic Circumpolar Current, as traced in sediment cores from the Pacific Southern Ocean, shows no linear long-term trend over the past 5.3 Myr; instead, the strongest flow occurs consistently in warmer-than-present intervals.