Oxygen isotope anomaly in tropospheric CO(2) and implications for CO(2) residence time in the atmosphere and gross primary productivity

The abundance variations of near surface atmospheric CO(2) isotopologues (primarily (16)O(12)C(16)O, (16)O(13)C(16)O, (17)O(12)C(16)O, and (18)O(12)C(16)O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, and stratospheric photochemistry. Oxygen isotopes, in particular, are affected by the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO(2) biogeochemical cycles, Δ(17)O (=ln(1 + δ(17)O) − 0.516 × ln(1 + δ(18)O)) provides an alternative constraint on the strengths of the associated cycles involving CO(2). Here, we analyze Δ(17)O data from four places (Taipei, Taiwan; South China Sea; La Jolla, United States; Jerusalem, Israel) in the northern hemisphere (with a total of 455 measurements) and find a rather narrow range (0.326 ± 0.005‰). A conservative estimate places a lower limit of 345 ± 70 PgC year(−1) on the cycling flux between the terrestrial biosphere and atmosphere and infers a residence time of CO(2) of 1.9 ± 0.3 years (upper limit) in the atmosphere. A Monte Carlo simulation that takes various plant uptake scenarios into account yields a terrestrial gross primary productivity of 120 ± 30 PgC year(−1) and soil invasion of 110 ± 30 PgC year(−1), providing a quantitative assessment utilizing the oxygen isotope anomaly for quantifying CO(2) cycling.