Vertical profiles of CO2 above eastern Amazonia suggest a net carbon flux to the atmosphere and balanced biosphere between 2000 and 2009: VERTICAL PROFILES OF CO2 ABOVE EASTERN AMAZONIA

From 2000 until January 2010 vertical profiles were collected above eastern Amazonia to help determine regional-scale (similar to 105-106 km2) fluxes of carbon cycle-related greenhouse gases. Samples were collected aboard light aircraft between the surface and 4.3 km and a column integration technique was used to determine the CO2 flux. Measured CO2 profiles were differenced from the CO2 background determined from measurements in the tropical Atlantic. The observed annual flux between the coast and measurement sites was 0.40 +/- 0.27 gC m-2 d-1 (90% confidence interval using a bootstrap analysis). The wet season (January-June) mean flux was 0.44 +/- 0.38 gC m-2 d-1 (positive fluxes defined as a source to the atmosphere) and the dry season mean flux was 0.35 +/- 0.17 gC m-2 d-1 (July-December). The observed flux variability is high, principally in the wet season. The influence of biomass burning has been removed using co-measured CO, and revealed the presence of a significant dry season sink. The annual mean vegetation flux, after the biomass burning correction, was 0.02 +/- 0.27 gC m-2 d-1, and a clear sink was observed between August and November of -0.70 +/- 0.21 gC m-2 d-1 where for all of the dry season it was -0.24 +/- 0.17 gC m-2 d-1.