Time series of CO, δ¹³CO, and δC¹⁸O at Towers 1, 2, and 3. CO mole fraction (top), δ¹³CO (middle), and δC¹⁸O (bottom) for Towers 1 (green), 2 (blue), and 3 (red) for the two years of the measurement campaign. Error bars are 1 sigma standard deviation of a standard gas which was run as a sample for each month of measurement. This standard is calibrated for both δ¹³C and δ¹⁸O, and thus provides a metric for the instrument precision and accuracy. DOI: https://doi.org/10.1525/elementa.136.f2