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Break-up of the Atlantic deep western boundary current into eddies at 8° S

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Abstract

The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago1. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10–40) × 106 m3 s-1 of water2,3,4,5, transporting North Atlantic Deep Water—from the overflow regions between Greenland and Scotland and from the Labrador Sea—into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8° S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.

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Figure 1: Circulation in the western tropical Atlantic.
Figure 2: Distribution of eddy kinetic energy and alongshore velocity at the western boundary at 11° S.
Figure 3: FLAME model results.

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Acknowledgements

This study was supported by the German Bundesministerium für Bildung, Wissenschaft und Forschung (BMBF) as part of the German CLIVAR/Marin programme.

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  1. Leibniz-Institut für Meereswissenschaften, Düsternbrooker Weg 20, 24105, Kiel, Germany

    M. Dengler, F. A. Schott, C. Eden, P. Brandt, J. Fischer & R. J. Zantopp

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  1. M. Dengler
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  2. F. A. Schott
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  3. C. Eden
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  4. P. Brandt
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  5. J. Fischer
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  6. R. J. Zantopp
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Correspondence to M. Dengler.

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Dengler, M., Schott, F., Eden, C. et al. Break-up of the Atlantic deep western boundary current into eddies at 8° S. Nature 432, 1018–1020 (2004). https://doi.org/10.1038/nature03134

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