Constructing the Residual Circulation of the ACC from Observations

By Richard Karsten, John Marshall. 2002

194 citations recorded by the source corpus.

The dynamics of the meridional overturning of the Antarctic Circumpolar Current (ACC) are best described in terms of a residual circulation that sums the transport of the wind-driven Ekman layer to the transport associated with eddies. Here an attempt is made to infer the residual circulation from observations by combining altimetric data and gridded hydrographic data to estimate eddy fluxes and winds to estimate Ekman transport. At the surface, a flow directed equatorward on the poleward flank of the ACC, and directed poleward on the equatorward flank of the ACC, is deduced. This convergence of flow into the axis of the ACC drives the subduction of the Antarctic Intermediate Water. Weak southward residual flow on the equatorward boundary of the ACC indicates that here Ekman transport is offset by eddy fluxes. The sense of the deduced residual circulation suggests that buoyancy is gained by the ocean through air‐sea flux poleward of the ACC, in broad agreement with observations. The surface residual circulation is mapped down to depth to yield two counterrotating meridional cells associated with the transformation of North Atlantic Deep Water and Subantarctic Mode Water into Antarctic Intermediate Water. The circulation suggested by these cells agrees remarkably well with the subsurface distribution of salinity and dissolved oxygen. The dependence of the residual circulation estimate on the magnitude of assumed eddy transfer and mixing coefficients is discussed.

Subfields: Atmospheric Science, Global and Planetary Change, Oceanography

View Paper: https://www.semanticscholar.org/paper/7cc8b3ca8b905fed08f8bdb05fae82f8154477a9

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Citations in the corpus

The Role of Mesoscale Eddies in the Rectification of the Southern Ocean Response to Climate Change (2010, background): “Averaging zonally—and not along streamlines (see, e.g., Karsten and Marshall 2002; Treguier et al. 2007)—seems sufficient for highlighting the role of the transient eddies in cancelling the time-mean cross-isopycnal flow; as a result, vertical and closed contours are virtually missing in Cres (Fig.”
Comparison between three implementations of automatic identification algorithms for the quantification and characterization of mesoscale eddies in the South Atlantic Ocean (2011, background): “Mesoscale activity is believed to play a central role in the maintenance of the frontal structures of the ACC (Karsten and Marshall, 2002) and in the southward flux of heat and deep water masses as part of the Atlantic meridional overturning circulation (MOC) (de Szoeke and Levine, 1981; Nowlin and ”
Eddy stirring in the Southern Ocean (2011, background): “The main thrust of progress has been provided by a large body of work articulated around residual mean theory [e.g., Marshall, 1997; Speer et al., 2000; Karsten and Marshall, 2002; Bryden and Cunningham, 2003; Marshall and Radko, 2003, 2006; Olbers and Visbeck, 2005].”
Description of the Earth system model of intermediate complexity LOVECLIM version 1.2 (2010, result): “All those values are in relatively good agreement with the data-based estimates and in the range of the values given by other models (Ganachaud and Wunsch, 2000; Karsten and Marshall, 2002; Gregory et al., 2005; Rahmstorf et al., 2005).”
Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean (2010, methodology): “For instance, Marshall et al. (1993), Speer et al. (2000), and Karsten and Marshall (2002) have all employed some version of this technique.”
Residual-Mean Solutions for the Antarctic Circumpolar Current and Its Associated Overturning Circulation (2003, methodology): “…in Table 1 we find B̃ L Lo y x C 5 5 12 Svres Dbo (where 1 Sv [ 106 m3 s21), broadly consistent with the analysis of Marshall (1997) who found residual circulations of 10–15 Sv, but somewhat smaller than the 20 Sv or so of overturning implied by air–sea fluxes—see Karsten and Marshall (2002a).”
Evidence for Enhanced Eddy Mixing at Middepth in the Southern Ocean (2009, background): “Modiﬁed from Karsten and Marshall (2002). velocity and stratiﬁcation are taken to be horizontally local and slowly varying in the sense of Pedlosky (1984); hence each horizontal location only depends on z .”
The Role of Eddies in Determining the Structure and Response of the Wind-Driven Southern Hemisphere Overturning: Results from the Modeling Eddies in the Southern Ocean (MESO) Project (2006, background): “Karsten and Marshall (2002) diagnose a similar southward flow of 8 Sv of the lightest waters across 50°S, and extending to about 54°S, in their TEM analysis of the overturning circulation combining satellite observations of eddy activity and the time-mean observed interior state.”
Recent advances in observing mesoscale ocean dynamics with satellite altimetry (2012, background): “The position and strength of meandering jets were monitored in the Gulf Stream, the Kuroshio and the Antarctic Circumpolar Current (ACC) (Kelly and Gille, 1990; Qiu, 1992; Gille, 1994), and eddy–mean interactions were also investigated (Tai and White, 1990; Morrow et al., 1994).”
The Dependence of Southern Ocean Meridional Overturning on Wind Stress (2011, methodology): “The choice of an exponential temperature profile was motivated by observations (Karsten and Marshall 2002a), laboratory studies (Cenedese et al. 2004), and modeling results (Karsten et al. 2002; Henning and Vallis 2005; Wolfe and Cessi 2009).”
Estimates and Implications of Surface Eddy Diffusivity in the Southern Ocean Derived from Tracer Transport (2006, methodology): “Holloway (1986) (see also Keffer and Holloway 1988; Stammer 1998; Karsten and Marshall 2002) proposed that eddy diffusivities could be estimated from maps of the rms height field variability using scaling arguments.”