The Global Ocean Data Analysis Project (GLODAP) is a synthesis activity for ocean surface to bottom biogeochemical data collected through chemical analysis of water samples. Data for 13 core variables (salinity, oxygen, phosphate, nitrate, silicate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, CCl4 and SF6) are subjected to primary and secondary quality control to identify outliers and correct for measurement biases.