The meridional overturning circulation (MOC) in the Southern Ocean is investigated using hydrographic observations combined with satellite measurements of sea surface height. A three-dimensional (spatial and vertical) estimate of the isopycnal eddy diffusivity in the Southern Ocean is obtained using the theory of Ferrari and Nikurashin that includes the influence of suppression of the diffusivity by the strong, time-mean flows. It is found that the eddy diffusivity is enhanced at depth, reaching a maximum at the critical layer near 1000 m. The estimate of diffusivity is used with a simple diffusive parameterization to estimate the meridional eddy volume flux. This estimate of eddy volume flux is combined with an estimate of the Ekman transport to reconstruct the time-mean overturning circulation. By comparing the reconstruction with, and without, suppression of the eddy diffusivity by the mean flow, the influence of the suppression on the overturning is illuminated. It is shown that the suppression of the eddy diffusivity results in a large reduction of interior eddy transports and a more realistic eddy-induced overturning circulation. Finally, a simple conceptual model is used to show that the MOC is influenced not only by the existence of enhanced diffusivity at depth but also by the details of the vertical structure of the eddy diffusivity, such as the depth of the critical layer.

#### mapped_gamma_all_sources_2005

Neutral Density (Jackett & McDougall, 1997) for the year 2005 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2006

Neutral Density (Jackett & McDougall, 1997) for the year 2006 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2007

Neutral Density (Jackett & McDougall, 1997) for the year 2007 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2008

Neutral Density (Jackett & McDougall, 1997) for the year 2008 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2009

Neutral Density (Jackett & McDougall, 1997) for the year 2009 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2010

Neutral Density (Jackett & McDougall, 1997) for the year 2010 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2011

Neutral Density (Jackett & McDougall, 1997) for the year 2010 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2012

Neutral Density (Jackett & McDougall, 1997) for the year 2012 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_gamma_all_sources_2013

Neutral Density (Jackett & McDougall, 1997) for the year 2013 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2005

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2005 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2006

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2006 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2007

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2007 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2008

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2008 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2009

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2009 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2010

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2010 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2011

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2011 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2012

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2012 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_pv_all_sources_2013

The potential vorticity calculated from the vertical gradient of the neutral density (ie. PV = f/rho_0 d(gamma)/dz) for the year 2013 (with annual and semi-annual harmonics) from 75S to 30S.

#### mapped_streamfunction_abs_all_sources_2006

The absolute geostrophic streamfunction on depth surfaces for the year 2006 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2007

The absolute geostrophic streamfunction on depth surfaces for the year 2007 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2008

The absolute geostrophic streamfunction on depth surfaces for the year 2008 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2009

The absolute geostrophic streamfunction on depth surfaces for the year 2009 (including annual and semi-annual harmonics), calculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2010

The absolute geostrophic streamfunction on depth surfaces for the year 2010 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2011

The absolute geostrophic streamfunction on depth surfaces for the year 2011 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2012

The absolute geostrophic streamfunction on depth surfaces for the year 2012 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_all_sources_2013

The absolute geostrophic streamfunction on depth surfaces for the year 2013 (including annual and semi-annual harmonics), caluculated using the TEOS-10 routine gsw_geo_strf_dyn_height (McDougall & Barker 2011).

#### mapped_streamfunction_abs_gamma_all_sources_26_2005

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2005 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2006_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2006 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2007_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2007 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2008_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2008 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2009_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2009 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2010_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2010 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2011_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2011 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2012_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2012 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### mapped_streamfunction_abs_gamma_all_sources_26_2013_no_cycle

The absolute geostrophic streamfunction on isopycnal surfaces for the year 2013 (including annual harmonics but NO semi-annual harmonics due to file size constraints), caluculated using the TEOS-10 routine gsw_geo_strf_isopycnal that implements the approximate streamfunction of (McDougall & Klocker 2010).

#### Diffusion_Coefficients_Filtered

The cross-stream diffusivity in the Southern Ocean (75S to 30S) for the period 2005 to 2015. The diffusion coefficients are calculated using the theory of Ferrari and Nikurashin (2010). The dataset includes the suppressed and unsupressed diffusivities, as well as the supression factor (the ratio of the unsuppressed and suppressed diffusivity)