COMPARISON OF INDEPENDENT Δ14CO2 RECORDS AT POINT BARROW, ALASKA

Two independent programs have collected and analyzed atmospheric CO2 samples from Point Barrow, Alaska, for radiocarbon content (Delta C-14) over the period 2003-2007. In one program, flask collection, stable isotope analysis, and CO2 extraction are performed by the Scripps Institution of Oceanography's CO2 Program and CO2 is graphitized and measured by accelerator mass spectrometry (AMS) at Lawrence Livermore National Laboratory. In the other program, the University of California, Irvine, performs flask collection, sample preparation, and AMS. Over 22 common sample dates spanning 5 yr, differences in measured Delta C-14 are consistent with the reported uncertainties and there is no significant bias between the programs.