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The response of the Antarctic Circumpolar Current to recent climate change

Nature Geoscience volume 1, pages 864869 (2008) | Download Citation

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Abstract

Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30 and 60 S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress.

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Acknowledgements

We acknowledge the role of J. Dunn in developing and making available the CSIRO ocean data archives, and K. Lorbacher for her assistance in the data analysis. The study was initiated during visits of C.W.B. and A.D. at CSIRO Marine Research Laboratories in Hobart, supported by an Ernst Froehlich Fellowship (C.W.B.) and a grant from DAAD (A.D.). This research was supported in part by the CSIRO Wealth from Oceans Flagship, the Australian government’s Cooperative Research Centre (CRC) programme through the ACE CRC, and the Australian Greenhouse Office. The paper is a contribution to The Future Ocean Cluster at Kiel University.

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  1. Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Düsternbrooker Weg 20, 24105 Kiel, Germany

    • C. W. Böning
    • , A. Dispert
    • , M. Visbeck
    •  & F. U. Schwarzkopf
  2. Centre for Australian Weather and Climate Research—a partnership of the Bureau of Meteorology and CSIRO, Wealth from Oceans Flagship, and the Australian Climate and Ecosystems Cooperative Research Centre, Hobart, Tasmania 7000, Australia

    • S. R. Rintoul

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Correspondence to C. W. Böning.

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DOI

https://doi.org/10.1038/ngeo362

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