Four CARIOCA Lagrangian buoys drifted in the North-East Atlantic Ocean between 38° and 45°N between February and August 2001. Daily cycles of pCO₂, SST and DIC are observed even in winter. Biological rates of carbon consumption, gross and net primary production,are determined in situ from the amplitude of the diel cycles and the time evolution of surface dissolved inorganic carbon. Over the 6 months period, February-August, the ocean in the studied area is a sink for atmospheric CO_2.The mean absorbed flux is equal to 3.8 mmoles/ m²/ day.

Mode Waters provides a privileged pathway for the transport of heat, salt and anthropogenic CO₂ into the ocean interior. The carbon cycle decadal variability in response to environmental changes is investigated using historical and recent data collected during the INDIGO (1985-1987) and OISO (1998-2003) oceanographic campaigns conducted in the South West Indian Ocean, an important zone for Mode Waters formation. The observed change in dissolved inorganic carbon over the 15-year period was 8 µmol/kg in Subantarctic Mode Water (500-800m), which is less than the anthropogenic carbon increase alone (13 µmol/kg). This difference may be explained by natural or climate-induced changes in ocean processes. Predictions from a global ocean-carbon model (OPA-PISCES) are used as a means to help interpret changes in the controlling processes: ocean dynamics, biological activity and air-sea interactions.

Using high-quality data for the CO₂-system and related properties obtained 10-year apart, we estimated decadal increases of anthropogenic CO₂ along the A10 section of the World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP). Increases of anthropogenic CO₂ were found down to an isopycnal surface of 27.3σ_θ (approx. 1000 dbar). In the sub-Antarctic Mode Water (SAMW), the increase was 6.9 ± 2.0 μmol kg^-1 on average, while in the Antarctic Intermediate Water (AAIW), it was 4.2 ± 1.9 μmol kg^-1. The increase in SAMW was larger in the west than that in the east of the section. No significant increases were detected in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW).

Continuous atmospheric measurements from tall towers have the capability to bridge an observational gap between hemispheric and local scales. We present first results from measurements made at such a tower in Germany. We show anti-correlated O₂ and CO₂ high frequency temporal variations which are caused by regional land biotic and fossil fuel emissions. We also show correlated changes in CO₂ concentration with air mass back trajectories, for example showing elevated CO₂ from air masses derived from eastern Europe, and lower, “background” concentrations from air masses derived from the North Atlantic.

We present a statistical analysis of aircraft and surface measurements of the CO₂ mixing ratio over the US Rocky Mountains during 1993 – 2002 at latitudes close to that of the Issyk-Kul station in Kyrgyzstan. Average characteristics of the CO₂ mixing ratio and its annual variations show only small height variability in the troposphere over well mixed mountain regions. Comparison of Issyk-Kul optical data with US aircraft and surface measurements shows satisfactory agreement. Also some differences at low altitudes were obtained owing to possible regional differences between mountain regions of Central Asia and USA.

Systematic measurements of the CO₂ concentration and its carbon isotopic ratio (d¹³C) have been carried out at 7 locations in China since March or July 2003. Seasonal cycles of the CO₂ concentration and d¹³C were clearly observable, especially at Longfengshan, Shangdianzi and Fukang. The d¹³C value of source producing the seasonal CO₂ cycle at each site, d_S, was estimated from the observed CO₂ and d¹³C seasonal cycles.  The average value of d_S derived for the 6 sites was calculated to be -25.6 (±1.8) ‰, which is larger than those observed at mid-latitudes in the western Pacific region, probably due to smaller discrimination of ¹³C by C₄ plants in the continent of China. 

The carbon dioxide transport at the Niwot Ridge AmeriFlux site was investigated in both gravity and streamline coordinates. For this forested site with a 6% slope, both nighttime drainage flow and daytime upslope flow played important roles in the CO₂ budget. Both the CO₂ respiration at night and the CO₂ uptake during the day are underestimated if the horizontal transport of CO₂ is not monitored; and the two components may not cancel out.

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.