High Accuracy 14C Measurements for Atmospheric CO2 Samples from the South Pole and Point Barrow, Alaska by Accelerator Mass Spectrometry

• Main Authors: H.A.J. Meijer, M.H. Pertuisot, J. van der Plicht
• Format: Dataset
• Language: unknown
• Published: ESS-DIVE: Deep Insight for Earth Science Data 2006
• Subjects: 14C; C14; Atmospheric C14; Atmospheric 14C; Atmospheric 14CO2; Flask samples; Flask sampling; accelerator mass spectrometry; accelerator mass spectroscopy; Center for Isotope Research; University of Groningen; Sample date; Smoothed 14CO2 concentration; Smoothed seasonal 14CO2 concentration; Smoothed total 14CO2 concentration; Scripps; South Pole; Barrow; Point Barrow; South pole; Alaska
• Online Access: https://search.dataone.org/view/ess-dive-b63dc13b25ea6b6-20180809T224555864343

Accelerator mass spectrometry (AMS) was used to obtain 14 CO 2 measurements from flasks collected at the South Pole and Point Barrow, Alaska, USA, at the Scripps Institute of Oceanography network station (Keeling et al., 1989) (see also http://cdiac.ess-dive.lbl.gov/trends/co2/sio-bar.html). Air samples for years 1985-1991, originally collected in 5-liter flasks, had been stored in Pyrex sealed-off tubes after stable isotope analysis (Roeloffzen et al., 1991). These samples were more or less evenly distributed over time. Typically, the extracted CO 2 from 2-5 flasks from consecutive weekly measurements were put together in one flame-off tube. The tubes were broken in the standard inlet arrangement of a dual inlet stable isotope ratio mass spectrometer, and a stable isotope measurement was performed using the same instrument used in the original analyses (Roeloffzen et al., 1991). Then, the CO 2 was cryogenically trapped and converted to graphite (Aerts-Bijma et al., 1997). For the majority of the samples the amount of CO 2 was sufficient for our regular, 2 mm diameter AMS targets, containing about 1.5 mg of C. For most of these, two targets could be produced from one CO 2 flask. In some cases, however, the amount of CO 2 was only sufficient for a smaller target. Individual standard samples were graphitized along with the corresponding atmospheric CO 2 samples, so that any day to day variability in the graphitization circumstances would be visible in the standard samples. The 14 C is reported as ∆ 14 C as per Stuiver and Polach 1977. More information about 14 C standards can be found at: http://www.c14dating.com/agecalc.html. More information about sample preparation and analysis at the Groningen AMS can be found at: http://www.rug.nl/ees/onderzoek/programmas/radiocarbonams/sampleTreatmentAms The primary literature reference for the material presented here is Meijer et al. (2006). The statistical analysis included curve fitting described by Cleveland (1979). A seasonal pattern was then fit to the residuals, and the data are given in terms of these trends and departures from them.