Over 122,000 hydrographic stations in the region south of 25S were individually screened against WOCE standards. They were compiled over the years from a number of data sources, but the vast majority were obtained from the National Oceanographic Data Centre (http://www.nodc.noaa.gov), specifically their World Ocean Database (WOA98; WOA2001; Conkright et al., 2002).

The quality control process began with the examination of WOCE property profiles, supplemented in some regions with high quality historical data. Fifty control regions, generally on a basin or sub-basin scale, were identified as having distinct property differences in deep water. Properties of stations in the control regions were averaged on neutral density surfaces and standard deviation envelopes constructed. The first examination was done in T-S space for stations within 5-degree squares. Stations (samples) whose deep T-S points fell outside 2 standard deviations from the deep-water control region mean were rejected (flagged). Roughly 25% of the stations did not pass this first stage.

In the second stage, oxygen and nutrient profiles were examined on a cruise-by-cruise basis, using the appropriate control area data to judge acceptability. Several thousand stations have had entire profiles of oxygen, phosphate, silicate and nitrate flagged because of poor quality. For the acceptable stations, about 0.5% of the individual samples were flagged as outliers. A few hundred cruises were identified that had systematic offsets in at least one property, and additive or multiplicative adjustments were applied to the nearly 11,000 stations affected. The last step in the quality control process was to correct or assign missing water depths to about a quarter of the stations using a 5-minute grid composite of the Southern Ocean bathymetry from satellite radar altimetry data (Smith and Sandwell, 1997) and the GEBCO-1997 (IOC et al., 1997) digital isobaths.