GEOSECS SIGMA0: σ₀ data

σ₀ from GEOSECS: Geochemical Ocean Sections Study, a global survey of the three-dimensional distribution of chemical, isotopic, and radiochemical tracers in the ocean. The expeditions were in the Atlantic from July 1972 to May 1973; the Pacific from August 1973 to June 1974, and the Indian Ocean from December 1977 to March 1978.