Partitioning of ocean and land uptake of COz as inferred by measurements from the NOAA Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network

Abstract. Using •13C measurements in atmospheric CO 2 from a cooperative global air sampling network, we determined the partitioning of the net uptake of CO2 between ocean and land as a function of latitude and time. The majority of •13C measurements were made at the Institute of Arctic and Alpine Research (INSTAAR) of the University of Colorado. The network included 40 sites in 1992 and constitutes the most extensive data set available. We perform an inverse deconvolution of both CO2 and •13C observations, using a two-dimensional model of atmospheric transport. New features of the method include a detailed calculation of the isotopic disequilibrium of the terrestrial biosphere from global runs of the CENTURY soil model. Also, the discrimination against •3C by plant photosynthesis, a a function of latitude and time, is calculated from global runs of the SiB biosphere model. Uncertainty due to the longitudinal structure of the data, which is not represented by the model, is studied through a bootstrap analysis by adding and omitting measurement sites. The resulting error estimates for our inferred sources and sinks are of the order of 1 GTC (1 GTC = 10 •5 gC). Such error bars do not reflect potential systematic errors arising from ou