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A polar equal-area grid with 501 by 501 points about 24-km apart was designed to optimally estimate property fields shown in the Southern Ocean Atlas.
Ellipses of influence with a fixed 2:1 anisotropy in the zonal:meridional correlation lengths were aligned zonally, to conform to the predominant flow in the Southern Ocean.
Correlation lengths for mapping were specified as a function of the bathymetry. Ellipse axes are: 666 x 333 km for bottom depths > 4000 m, 444 x 222 km for bottom depths between 1000-4000 m, 222 x 111 km for bottom depths < 1000 m.
The top panel is the salinity field at 400m from the WOA98 climatology contoured at the original one-degree grid provided by NODC.
The middle panel shows the stations with data acceptable to NODC, objectively mapped using the Southern Ocean Atlas mapping parameters and grid characteristics.
The bottom panel shows what results from the application of that same mapping technique to data from quality controlled stations in the Southern Ocean Atlas Database.
Southern Ocean Database maps of different properties at the same depth display similar patterns, whereas the WOA98 maps do not appear to be as closely coupled. We attribute the difference to the improved mapping scheme and the better quality of the SO database.
Additional examples of the combined improvement of Southern Ocean Database maps (right panels) over the WOA98 maps (left panels) for the 2000-m, 3000-m, and 4000-m levels are shown below.
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