Historical Global observations of oceanic radiocarbon conducted prior to GEOSECS (NCEI Accession 0157456)

The collected CO2 was analyzed for the 14C/C ratio by counting techniques at the SIO, LDEO or University of Washington laboratories. The measurements are reported as Δ14C, which includes a correction for mass dependent fractionation using measurements of δ13C in the CO2 samples. When measurements of δ13C were not available, estimates of δ13C were used to calculate Δ14C.

Further details are available in the original publications. In some samples from Broecker et al. (1960), isotopic fractionation occurred while sampling. Δ14C is not affected by fractionation, due to the δ13C correction, but the reported δ13C in these cases is not representative of oceanic δ13C. We omit δ13C measurements on samples assumed to have experienced fractionatation (δ13C less than -2.8 permil or greater than +2.8 permil), though we caution that some of the retained δ13C data from Broecker et al. (1960) may not be reliable.

In some samples from Fairhall and Young (1985), a date range rather than a single date was given for the sample date. We use the midpoint of the date range for these samples. Linick (1978) updates Δ14C measurements previously reported by Bien et al. (1960; 1965), among others.

We use the Δ14C data of Linick (1978) for these samples, filling in temperature and salinity data from Bien et al. (1960; 1965) that was missing in Linick (1978). Observations of dissolved inorganic carbon concentration from Fairhall and Young (1985) were converted from mM to µmol/kg by assuming constant density of 1.025 kg/l. The datafile contains 14 columns: Cruise Name, Sample Identification Number, Latitude, Longitude, Date, Depth (m), Temperature (°C), Salinity, Δ14C (/mille), Δ14C uncertainty (/mille), δ13C (/mille), δ13C uncertainty (/mille), Dissolved Inorganic Carbon concentration (µmol/kg), Source.

Missing data is denoted with values of -999.