The South Atlantic salinity minimum is associated with Antarctic Intermediate Water (AAIW).
The TS plots indicate that the lowest salinities occur at depths near 800 meters. In the vicinity of the minimum salinity, temperature is not as strong an indicator of salinity as it is in the thermocline above, but latitude and longitude might be exploited to sharpen our estimates of salinity.
Data characterizing the salinity minimum were obtained from the profiles that had been interpolated to pressure levels. To avoid low near-surface salinities each profile's minimum was sought between 100 dbar and dbar the bottom of the interpolated profile. Due to salinity inversions a profile might have more than one minimum.
The mean fields at the salinity minimum can be estimated as inverse-square-distance weighted averages within overlapping shingles. Weighted standard deviations about the mean fields give an idea of the variability at the salinity minimum. The number of data used to compute the statistics within each shingle can be seen on a similar plot.