Exchange rates within the Global Carbon Cycle, between oceans, atmosphere and terrestrial biosphere – including the anthropogenic CO₂ production – are being traced by concentration and isotope ratio measurements of atmospheric CO₂. The background value of the stable isotope ratio of oxygen in atmospheric CO₂ is determined by oxygen exchange with the ocean surface waters. During contact with leaf water, the signature of this then evaporation-enriched groundwater (the extent still being dependent on plant physiological and environmental parameters), will be imprinted on CO₂ diffusing back out of the leaf stomata. From water cycle studies the continental effect (Rayleigh-distillation) is known, leading to precipitation strongly depleted in d¹⁸O over e.g. Siberia. This signal is also transferred into plant material. These main mechanisms within the ¹⁸O-cycle are known or under investigation. The d¹⁸O source term for atmospheric CO₂ derived from biomass burning and anthropogenic fossil fuel combustion, however, is less well-known.

Mt. Cimone Observatory is a background station for the measurement of greenhouse gases and other atmospheric pollutants located on the top of the highest peak of the Italian Northern Appenines. Continuous Measurements of atmospheric CO₂ were started in March 1979 by the Italian Air Force Meteorological Service using NDIR analysers. A number of case studies are presented in order to show the influence of certain polluted or vegetated areas on the concentration of carbon dioxide. Chemical tracers are used to asses the origin of the air masses together with an analysis of the back trajectories.

The Dole-Morita effect (DME) describes the d¹⁸O enrichment of atmospheric O₂ with respect to ocean water [Dole 1935, Morita 1935]. The magnitude of the DME (23.8 ± 0.1‰ at present, Horibe et al. [1973]) varies over geologic time scales, and might have changed as a result of human activity. Such variations are preserved in the air enclosed in polar firn and ice. Here, we explore the potential effects of human activity on the DME. We estimate that global changes in the land biosphere may have led to a decrease in the DME in the order of 0.07‰ over the last 150 years. We then predict profiles of d¹⁸O-O₂ in firn air resulting from a range of atmospheric scenarios using a model [Severinghaus and Battle, submitted] and compare the simulated profiles to measurements of air samples extracted from polar firn.

We present measurements of atmospheric O₂/N₂ ratio and CO₂ mole fractions from flask samples collected at Hateruma Island and Cape Ochi-Ishi, and onboard cargo ships between Japan and the United States, and Japan and Australia (or New Zealand). Average changes in the O₂ and CO₂ for the 6-year period from 1998 to 2004 are –23.3 ± 0.3 ppm and 10.4 ± 0.1 ppm, respectively. Assuming that the ocean is neither a source nor a sink for the atmospheric O₂, we estimate the CO₂ uptake by the terrestrial biosphere and the ocean to be 1.1 ± 0.6 PgC yr^-1 and 2.0 ± 0.5 PgC yr^-1, respectively.

Changes in dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) in the water column are quantified for meridional hydrographic sections through the Atlantic from 63 ˚N to 60 ˚S between 1988/1993 and 2003/2005.  Changes are most pronounced in the upper 1000 m water column.  DIC changes range from -5 to 40 µmol/kg and AOU changes by a similar amount.  The remainder is caused by changes in positions of fronts, gyres, remineralization and ventilation as manifested by changes in watermass properties.  In particular AOU increases of similar magnitude as increases in DIC point towards a significant contribution of oxidation of organic matter to the DIC increase.  The large changes in biogeochemical properties of the upper water column of the Atlantic have been one of the big surprises in the decadal reoccupation of the transects.

In order to further our understanding of the biophysical and biogeochemical mechanisms that control the fate of fossil fuel carbon emissions, we are simulating an hourly global atmospheric carbon dioxide concentration field ([CO₂]) for the year 2000 with realistic diurnal, synoptic and seasonal variability, including quantified errors.  In addition, we are simulating carbonyl sulfide (COS) for a continental mixed temperate forest to test a hypothesis that errors in seasonal simulations of CO₂ result from incorrect specification of springtime onset of photosynthesis rather than incorrect timing of ecosystem respiration.

A one-dimensional (1d) physical-biological-chemical model was developed and tested by Antoine and Morel [1995, AM95 hereafter], with the aim of assessing upper ocean carbon fluxes. This model was specifically designed to be driven by satellite data, and it was used to evaluate the upper ocean CO₂ fluxes at station P in the NE Pacific. Another validation of this model has been carried out at the DYFAMED station (NW Mediterranean), where time series of biological and physical observations are available. This validation is a first step before the basin-scale application to the Mediterranean Sea, as presented here for the period 1998-2000.

Anthropogenic CO₂ releases to the atmosphere have changed the total inorganic carbon concentration of ocean by no more than 3-4% at any location. Main differences between three approaches [Poisson and Chen, 1987; Gruber et al., 1996; Friis, 2005] are presented that define marine anthropogenic CO₂ (C_T^ant) as deduced from total inorganic carbon. All definitions are based on a back-calculation technique that was independently proposed by Brewer [1978] and Chen and Millero [1979]. The overall importance of this presentation is in the comparability of anthropogenic CO₂ findings from described methods with these derived from global bookkeeping approaches or full carbon model results.