Abstract
The primary paths for the transport of Antarctic Bottom Water from the Southern Ocean into the global ocean are the deep western boundary currents east of the Antarctic Peninsula and the Kerguelen plateau1. Previous ship-based observations documented distinct water properties and velocities associated with a deep western boundary current in the Kerguelen region2,3,4,5,6,7, but the mean flow is as yet unconstrained. Here we report measurements from a coherent array of eight current-meter moorings that reveal a narrow and intense equatorward flow extending throughout the water column just east of the Kerguelen plateau. Velocities averaged over two years exceed 20 cm s−1 at depths of about 3,500 m, the strongest mean deep western boundary current flow yet observed at similar depths. We estimate the mean equatorward transport of water colder than 0 ∘C at 12.3±1.2×106 m3 s−1, partially compensated by poleward flow. We also estimate the net equatorward flow of water colder than 0.2 ∘C at about 8×106 m3 s−1, substantially higher than the 1.9×106 m3 s−1 reported from the boundary current that carries dense water from the Weddell Sea into the Atlantic Ocean north of the Falkland plateau8. We conclude that the Kerguelen deep western boundary current is a significant pathway of the global ocean’s deep overturning circulation.
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Acknowledgements
We are deeply indebted to D. McLaughlan and K. Miller for their mooring works. Thanks are extended to the officers, crew and scientists on board RSV Aurora Australis for their help with field observations. Discussions with G. Mizuta and Y. Kashino were helpful. Figure 1a was drawn by L. Bell and K. Kitagawa. Other figures were produced by the PSPLOT library written by K. E. Kohler. In Japan, support was provided by Grants-in-Aid 14403006, 17340138, 20244075, 20540419 and 21310002 for Scientific Research from Ministry of Education, Science, Sports and Culture. In Australia, support was provided by the Cooperative Research Centre program of the Australian government and by the Australian National Antarctic Research Expeditions; this work is a contribution to the Australian Climate Change Science Program, funded jointly by the Department of Climate Change, the Bureau of Meteorology and CSIRO.
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J.A.C., M.W., S.R.R. and Y.F. planned the experiment; M.A.R., Y.F., S.R.R., J.A.C., S.A. and S.S. carried out the observations; Y.F., M.A.R., S.S. and S.A. carried out data processing; Y.F., S.R.R., J.A.C., S.S. and M.W. wrote the manuscript, with other authors commenting.
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Fukamachi, Y., Rintoul, S., Church, J. et al. Strong export of Antarctic Bottom Water east of the Kerguelen plateau. Nature Geosci 3, 327–331 (2010). https://doi.org/10.1038/ngeo842
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DOI: https://doi.org/10.1038/ngeo842
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