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Mean-flow and topographic control on surface eddy-mixing in the Southern Ocean

journal contribution
posted on 2023-05-17, 14:10 authored by Sallee, JB, Speer, K, Stephen Rintoul
Surface cross-stream eddy diffusion in the Southern Ocean is estimated by monitoring dispersion of particles numerically advected with observed satellite altimetry velocity fields. To gain statistical significance and accuracy in the resolution of the jets, more than 1,5 million particles are released every 6 months over 16 years and advected for one year. Results are analyzed in a dynamic height coordinate system. Cross-stream eddy diffusion is highly inhomogenous. Diffusivity is larger on the equatorward flank of the Antarctic Circumpolar Current (ACC) along eddy stagnation bands, where eddy displacement speed approaches zero. Along such bands, diffusivities reach typical values of 3500 m2 s-1. Local maxima of about 8-12.103 m2 s-1 occur in the energetic western boundary current systems. In contrast, diffusivity is lower in the core of the Antarctic Circumpolar Current with values of 1500-3000 m2 s-1, and continues to decrease south of the main ACC system. The distribution of eddy diffusion is set at three scales: at circumpolar scale, the mean flow reduces diffusion in the ACC and enhances it on the equatorward side of the current; at basin scale, diffusion is enhanced in the energetic western boundary current extension regions; at regional scale, diffusion is enhanced in the wake of large topographic obstacles. We find that the zonally average structure of eddy diffusion can be explained by theory which takes mean flow into account; however, local values depend on eddy propagation, not simply described by a single wave speed, and topography.


Publication title

Journal of Marine Research










Institute for Marine and Antarctic Studies


Sears Foundation Marine Research

Place of publication

Yale Univ, Kline Geology Lab, 210 Whitney Avenue, New Haven, USA, Ct, 06520-8109

Rights statement

Copyright 2011 Journal of Marine Research

Repository Status

  • Restricted

Socio-economic Objectives

Antarctic and Southern Ocean oceanic processes

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