Eddy diffusivities in the Southern Ocean from an eddying model (SODIFF)
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NSF proposal
Main Objectives

  • Estimate robust horizontal and vertical distributions of Lagrangian (cross-stream) diffusivities in POP (~50,000 floats in Southern Ocean)
  • Compare Lagrangian diffusivities with Eulerian diffusivities estimated from eddy flux/ mean tracer gradient relations
  • Help with DIMES float analysis: Mean flow estimation, relation of Eulerian and Lagrangian mean, coordinate system orientation (shear dispersion reduction) ...
  • Passive tracer deployment for Eulerian analysis, and possibly Nakamura

    Results from previous deployments

    Lagrangian diffusivities

  • Robust estimate: cross-stream diffusivity, spatial variability of mean flow needs to be taken into account
  • Lagrangian cross-stream diffusivity depth invariant in ACC core (need to reassess with more floats)
  • non isotropic diffusivities, coordinate system orientation matters (magnitudes, depth dependence very sensitive, can reconcile previous Nakamura and Lagrangian estimates)
  • need enough floats (rotational parts..etc.)

    figure pdf
    Depth dependence of Lagrangian diffusivities depends on time lag used and coordinate system orientation.

    Eulerian and Lagrangian comparison

    figure pdf
    Eulerian (red) and Lagrangian (black) cross-stream diffusivities as a function of time lag for all deployment patches and depths.
    Lagrangian diffusivities generally overestimate Eulerian eddy transport.
    Better correlation for P2 and deep 1500m deployments.
    figure pdf
    Along-stream average of binned cross-stream diffusivities

    Talks and Figures (DIMES and SODIFF)

    DIMES Oct 2011
    Float dispersion Figures
    OS 2008 poster
    DIMES meeting Feb 2008 talk
    DIMES meeting WHOI Oct 2008 talk
    CASPO seminars SIO talk Oct 15
    AGU 2008 poster
    IAPSO Montreal talk
    DIMES Montreal talk
    EGU 2010 poster
    Talk Austin

    DIMES Planning Page
    planning page