13 
observations tend to cluster at some ’’standard” levels. Since older oceanographic 
techniques were not conducted to meeting target depths, the spikes on the histogram may 
indicate target depth rather than those actually sampled. 
Latitude 
Latitude 
Fig.8: Percentage of rejected observations (red) and number 
of observations in 1-degree latitude zones (blue). 
An example of our quality check for the area 100-110°E 30-20°S in the Pacific Ocean is 
shown in Fig-6. The procedure described above effectively removes outliers. Thus, a couple 
of profiles with obviously erroneous sample depths could not be identified as outliers by the 
statistical check for T and S only, but were rejected by the statistical check on sample depth. 
The statistical check was repeated three times. Each time the percentage of outliers per 
cruise was computed. A certain fraction of cruises was found to have a much higher 
percentage of rejected observation. Such cruises were flagged and excluded from the further 
analysis. The percentage of rejected observations (Fig. 7) varies with depth, depending on