Editorial Type:
Article
Article Type:
Research Article

Objective Detection of Oceanic Eddies and the Agulhas Leakage

Francisco J. Beron-Vera Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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Yan Wang Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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María J. Olascoaga Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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Gustavo J. Goni National Oceanic and Atmospheric Administration/Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida

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George Haller Institute for Mechanical Systems, ETH Zürich, Zurich, Switzerland

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Print Publication:
01 Jul 2013
DOI:
https://doi.org/10.1175/JPO-D-12-0171.1
Page(s):
1426–1438
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Abstract

Mesoscale oceanic eddies are routinely detected from instantaneous velocities derived from satellite altimetry data. While simple to implement, this approach often gives spurious results and hides true material transport. Here it is shown how geodesic transport theory, a recently developed technique from nonlinear dynamical systems, uncovers eddies objectively. Applying this theory to altimetry-derived velocities in the South Atlantic reveals, for the first time, Agulhas rings that preserve their material coherence for several months, while ring candidates yielded by other approaches tend to disperse or leak within weeks. These findings suggest that available velocity-based estimates for the Agulhas leakage, as well as for its impact on ocean circulation and climate, need revision.

Corresponding author address: F. J. Beron-Vera, RSMAS/AMP, University of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149. E-mail: fberon@rsmas.miami.edu

Abstract

Mesoscale oceanic eddies are routinely detected from instantaneous velocities derived from satellite altimetry data. While simple to implement, this approach often gives spurious results and hides true material transport. Here it is shown how geodesic transport theory, a recently developed technique from nonlinear dynamical systems, uncovers eddies objectively. Applying this theory to altimetry-derived velocities in the South Atlantic reveals, for the first time, Agulhas rings that preserve their material coherence for several months, while ring candidates yielded by other approaches tend to disperse or leak within weeks. These findings suggest that available velocity-based estimates for the Agulhas leakage, as well as for its impact on ocean circulation and climate, need revision.

Corresponding author address: F. J. Beron-Vera, RSMAS/AMP, University of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149. E-mail: fberon@rsmas.miami.edu
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  • Arnold, V. I., V. V. Kozlov, and A. I. Neishtadt, 2006: Mathematical Aspects of Classical and Celestial Mechanics. Dynamical Systems III, Vol. 3, Encyclopedia of Mathematical Sciences, 3rd ed. Springer-Verlag, 517 pp.

  • Batchelor, G. K., 1964: An Introduction to Fluid Dynamics. Cambridge University Press, 660 pp.

  • Beal, L. M., and Coauthors, 2011: On the role of the agulhas system in ocean circulation and climate. Nature, 472, 429–436.

  • Beron-Vera, F. J., M. J. Olascoaga, and G. J. Goni, 2008: Oceanic mesoscale eddies as revealed by Lagrangian coherent structures. Geophys. Res. Lett., 35, L12603, doi:10.1029/2008GL033957.

    • Search Google Scholar
    • Export Citation

  • Biastoch, A., C. W. Böning, J. R. E. Lutjeharms, and F. U. Schwarzkopf, 2009: Increase in Agulhas leakage due to pole-ward shift of the Southern Hemisphere westerlies. Nature, 462, 495–498.

    • Search Google Scholar
    • Export Citation

  • Chelton, D. B., M. G. Schlax, R. M. Samelson, and R. A. de-Szoeke, 2007: Global observations of large oceanic eddies. Geophys. Res. Lett., 34, L15606, doi:10.1029/2007GL030812.

    • Search Google Scholar
    • Export Citation

  • Chelton, D. B., P. Gaube, M. G. Schlax, J. J. Early, and R. M. Samelson, 2011a: The influence of nonlinear mesoscale eddies on near-surface oceanic chlorophyll. Science, 334, 328–332.

    • Search Google Scholar
    • Export Citation

  • Chelton, D. B., M. G. Schlax, and R. M. Samelson, 2011b: Global observations of nonlinear mesoscale eddies. Prog. Oceanogr., 91, 167–216.

    • Search Google Scholar
    • Export Citation

  • Conti, C., D. Rossinelli, and P. Koumoutsakos, 2012: GPU and APU computations of Finite Time Lyapunov Exponent fields. J. Comput. Phys., 231, 2229–2244.

    • Search Google Scholar
    • Export Citation

  • Doglioli, A. M., B. Blanke, S. Speich, and G. Lapeyre, 2007: Tracking coherent structures in a regional ocean model with wavelet analysis: Application to Cape Basin eddies. J. Geophys. Res.,112, C05043, doi:10.1029/2006JC003952.

  • Early, J. J., R. M. Samelson, and D. B. Chelton, 2011: The evolution and propagation of quasigeostrophic ocean eddies. J. Phys. Oceanogr., 41, 1535–1555.

    • Search Google Scholar
    • Export Citation

  • Fang, F., and R. Morrow, 2003: Evolution, movement and decay of warm-core Leeuwin Current eddies. Deep-Sea Res. II, 50, 2245–2261.

  • Froyland, G., C. Horenkamp, V. Rossi, N. Santitissadeekorn, and A. S. Gupta, 2012: Three-dimensional characterization and tracking of an Agulhas Ring. Ocean Modell., 52–53, 69–75.

    • Search Google Scholar
    • Export Citation

  • Fu, L. L., D. B. Chelton, P.-Y. Le Traon, and R. Morrow, 2010: Eddy dynamics from satellite altimetry. Oceanography (Wash. D.C.), 23, 14–25.

    • Search Google Scholar
    • Export Citation

  • Garth, C., F. Gerhardt, X. Tricoche, and H. Hans, 2007: Efficient computation and visualization of coherent structures in fluid flow applications. IEEE Trans. Visualization Computer Graphics, 13, 1464–1471.

    • Search Google Scholar
    • Export Citation

  • Garzoli, S. L., P. L. Richardson, C. M. Duncombe Rae, D. M. Fratantoni, G. J. Goni, and A. J. Roubicek, 1999: Three Agulhas rings observed during the Benguela Current Experiment. J. Geophys. Res., 20 (C9), 20 971–20 986.

    • Search Google Scholar
    • Export Citation

  • Goni, G., and W. Johns, 2001: Census of warm rings and eddies in the North Brazil Current retroflection region from 1992 through 1998 using TOPEX/Poseidon altimeter data. Geophys. Res. Lett., 28, 1–4.

    • Search Google Scholar
    • Export Citation

  • Gordon, A., 1986: Inter-ocean exchange of thermocline water. J. Geophys. Res., 91 (C4), 5037–5050.

  • Haller, G., 2001: Distinguished material surfaces and coherent structures in 3D fluid flows. Physica D, 149, 248–277.

  • Haller, G., 2005: An objective definition of a vortex. J. Fluid Mech., 525, 1–26.

  • Haller, G., and F. J. Beron-Vera, 2012: Geodesic theory of transport barriers in two-dimensional flows. Physica D, 241, 1680–1702.

  • Henson, S. A., and A. C. Thomas, 2008: A census of oceanic anticyclonic eddies in the Gulf of Alaska. Deep-Sea Res. I, 55, 163–176.

  • Isern-Fontanet, J., E. García-Ladona, and J. Font, 2003: Identification of marine eddies from altimetric maps. J. Atmos. Oceanic Technol., 20, 772–778.

    • Search Google Scholar
    • Export Citation

  • Jorba, À., and C. Simó, 1996: On quasi-periodic perturbations of elliptic equilibrium points. SIAM J. Math. Anal.,27, 1704–1737.

  • Lehahn, Y., F. d'Ovidio, M. Lévy, Y. Amitai, and E. Heifetz, 2011: Long range transport of a quasi isolated chlorophyll patch by an Agulhas ring. Geophys. Res. Lett., 38, L16610, doi:10.1029/2011GL048588.

    • Search Google Scholar
    • Export Citation

  • Le Traon, P.-Y., F. Nadal, and N. Ducet, 1998: An improved mapping method of multisatellite altimeter data. J. Atmos. Oceanic Technol., 15, 522–534.

    • Search Google Scholar
    • Export Citation

  • Lugt, H. J., 1979: The dilemma of defining a vortex. Recent Developments in Theoretical and Experimental Fluid Mechanics, U. Muller, K. G. Riesner, and B. Schmidt, Eds., Springer-Verlag, 309–321.

  • Mézic, I., V. A. F. S. Loire, and P. Hogan, 2010: A new mixing diagnostic and the Gulf of Mexico oil spill. Science, 330, 486.

  • Morrow, R., F. Birol, and D. Griffin, 2004: Divergent pathways of cyclonic and anti-cyclonic ocean eddies. Geophys. Res. Lett., 31, L24311, doi:10.1029/2004GL020974.

    • Search Google Scholar
    • Export Citation

  • Okubo, A., 1970: Horizontal dispersion of flotable particles in the vicinity of velocity singularity such as convergences. Deep-Sea Res. Oceanogr. Abstr., 12, 445–454.

    • Search Google Scholar
    • Export Citation

  • Olson, D., and R. Evans, 1986: Rings of the Agulhas Current. Deep-Sea Res., 33, 27–42.

  • Ottino, J., 1989: The Kinematics of Mixing: Stretching, Chaos and Transport. Cambridge University Press, 364 pp.

  • Peacock, T., and J. Dabiri, 2010: Introduction to focus issue: Lagrangian coherent structures. Chaos, 20, 017501, doi:10.1063/1.3278173.

    • Search Google Scholar
    • Export Citation

  • Ridgway, K. R., and J. R. Dunn, 2007: Observational evidence for a Southern Hemisphere oceanic supergyre. Geophys. Res. Lett., 34, L13612, doi:10.1029/2007GL030392.

    • Search Google Scholar
    • Export Citation

  • Rio, M.-H., and F. Hernandez, 2004: A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model. J. Geophys. Res.,109, C12032, doi:10.1029/2003JC002226.

  • Robinson, A. R., Ed., 1983: Eddies in Marine Science. Springer-Verlag, 609 pp.

  • Souza, J. M. A. C., C. de Boyer Montegut, and P. Y. Le Traon, 2011: Comparison between three implementations of automatic identification algorithms for the quantification and characterization of mesoscale eddies in the South Atlantic Ocean. Ocean Sci. Discuss., 8, 483–531.

    • Search Google Scholar
    • Export Citation

  • Turiel, A., J. Isern-Fontanet, and E. Garcia-Ladona, 2007: Wavelet filtering to extract coherent vortices from altimetric data. J. Atmos. Oceanic Technol., 24, 2103–2119.

    • Search Google Scholar
    • Export Citation

  • Weiss, J., 1991: The dynamics of enstrophy transfer in two-dimensional hydrodynamics. Physica D, 48, 273–294.

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