Seven CARIOCA lagrangian buoys drifted in the Subantarctic Zone, SAZ, of the Indian and Pacific Ocean between 2001 and 2005. Measurements indicate that pCO₂ in sea water is undersaturated with respect to the atmospheric value and consequently the subantartic zone of the Southern Ocean acts as a sink for atmospheric CO₂ during all seasons. Large observed pCO₂ variability is associated with mixing close to the subantarctic front, with biological activity and local warming. These variabilities are higher than the seasonal cycle in the studied areas.

Simulations with a regional transport model are evaluated in order to determine to which extend the indirect fossil fuel combustion tracer CO or the purely anthropogenic tracer SF₆ can be used to retrieve the contribution of fossil fuel emissions in the atmospheric CO₂ signal.

A detailed comparison of global atmospheric CH₄ retrievals from the space-borne spectrometer SCIAMACHY onboard the European environmental satellite ENVISAT is presented with the atmospheric transport models TM4 and TM5.

Intensive atmospheric sampling field programs are envisioned as a key component of integrated research programs such as the North American Carbon Program (NACP) [Sarmiento and Wofsy, 1999; Wofsy and Harriss, 2002].  The intensive sampling provides unique information about the spatial distribution of CO₂ as well as imposes tight constraints on regional budgets that are difficult to obtain from other means. We summarize what we have learned from the numerous COBRA (CO₂ Budget and Rectification Airborne study) experiments [Gerbig et al., 2003a] that have taken place in 2000, 2003, and 2004.  We present the observed spatial variability of CO₂ [Gerbig et al., 2003a; Lin et al., 2004a] and regional budgets derived from regional air parcel-following experiments [Lin et al., 2004b].  These observations are also used as a critical testbed for modeling frameworks [Gerbig et al., 2003b]. We draw conclusions about ways to maximize the value of intensive atmospheric sampling experiments and the role that such experiments should play within programs like the NACP.

We have constructed an estimate of annual-mean surface fluxes of carbon dioxide for the period 1992-6 using observational constraints from the atmosphere and from the ocean interior. The method interprets in situ observations of carbon dioxide concentration in the ocean and atmosphere using transport estimates from global circulation models.

The global biogeochemical cycle of oxygen is closely linked to that of carbon dioxide, because key biological processes, as well as fossil fuel burning, occur with specific stochiometric ratios. In the ocean, however, several processes – carbonate chemistry (buffer effect), physical transport (dilution), and warming/cooling (solubility changes) – decouple O₂ and CO₂ exchanges. Based on a decade of atmospheric O₂/N₂ and CO₂ data, we estimated spatial and temporal patterns of oceanic APO fluxes, using an inversion of atmospheric transport. Seasonal and interannual variations are interpreted in the light of climate variables.

The Total Carbon Column Observing Network is a new network of ground-based solar observatories, dedicated to column measurements of greenhouse gases.  We present CO₂ column abundances observed in Park Falls, Wisconsin and Lauder, New Zealand during May 2004 – June 2005.  In Park Falls, Wisconsin, the peak-to-peak variation of column-average CO₂ is approximately 13 ppmv.  In Lauder, New Zealand, the peak-to-peak variation of column-average CO₂ is approximately 4 ppmv.  Assuming a secular trend of 2 ppmv yr^-1, we infer a peak-to-peak seasonal amplitude of 11 ppmv and 2 ppmv for Park Falls and Lauder respectively.  These values are higher than model predictions by Olsen and Randerson [2003].

Measurements of atmospheric O₂/N₂ ratio and CO₂ concentration are presented over the period 1989 to present from the Scripps Institution of Oceanography global flask sampling network. The data are used to make estimates of land and ocean sinks over various time scales. The oceanic and land biotic sinks are estimated to be 1.9±0.6 (ocean) and 1.2±0.8 Pg C/yr (land) over the period Jan. 1990-Jan. 2000 and 2.2±0.5 (ocean) and 0.5±0.7 Pg C/yr (land) over the period Jan. 1993-Jan. 2003. These estimates make allowance for oceanic O₂ and N₂ outgassing based on observed changes in ocean heat content and estimates of the relative outgassing per unit warming. The recent ocean sink is consistent, to within the uncertainties, with estimates of the accumulation of anthropogenic CO₂ in the ocean since 1800, assuming the oceanic sink varied over time as predicted by a box-diffusion model. The possibility that the ocean sink is being reduced slightly by climate feedbacks, as predicted by some models, is not ruled out, however.

We address an ongoing debate regarding the geographic distribution of interannual variability in ocean - atmosphere carbon exchange. We find that, for 1983-1998, both novel high-resolution atmospheric inversion calculations and global ocean biogeochemical models place the primary source of global CO₂ air-sea flux variability in the Pacific Ocean. In ocean biogeochemical models, this variability is clearly associated with the El Niño / Southern Oscillation cycle. Both inversion and models indicate that the Southern Ocean is the second-largest source of air-sea CO₂ flux variability, and that variability is small throughout the Atlantic, including the North Atlantic, in contrast to previous studies.