We used recent ocean bomb radiocarbon inventory estimates for the time of GEOSECS (mid-1970s) and WOCE (mid-1990s) from Peacock [2004] and Key et al. [2004], corrected for missing ocean areas [Naegler 2005], to develop a new parameterisation of the piston velocity – wind speed relationship of CO₂ air-sea gas exchange. For monthly mean climatological winds on a 1°x1° grid, this results in a gas exchange parameter a_q,660 of 0.32±0.04 (in cm hr^-1 m^-2 s²) and a net oceanic CO₂ uptake of 1.53±0.18 PgC/yr for the mid-1990s, when using the Takahashi et al. [2002] pCO₂ data.

Our understanding of biogeochemical and physical processes in the Southern Ocean, which are critically important to future anthropogenic CO₂ uptake and global climate, is limited by the sparse spatial and temporal coverage of existing oceanographic and atmospheric measurements. We will present high-precision horizontal atmospheric O₂ and CO₂ concentration gradients over the Southern Ocean from three independent observing networks. These measurements reveal that, relative to southern mid-latitudes and Antarctica, CO₂ concentrations over the Southern Ocean are high during winter and low during summer (Fig. 1). This suggests a seasonal variation between net CO₂ summertime uptake and wintertime release that is in disagreement with the T99 [Takahashi et al., 2002] dissolved pCO₂ climatology, which predicts year‑round CO₂ uptake, and with the OCMIP‑2 biological ocean general circulation models [BOGCMs, Doney et al., 2004], which either predict year-round CO₂ uptake or opposite seasonality with wintertime uptake and summertime release.

Measurements of concurrent changes in both the atmospheric O₂ and CO₂ mixing ratios have been proven to be useful independent information for the partitioning of anthropogenic CO₂ into its different sinks [e.g. Keeling et al., 1996]. This information is used along with the “classical” partitioning models that make use of CO₂ concentration and (radioactive as well as stable) isotopic composition information [e.g. Keeling et al., 1995]. Global carbon budget reconstruction needs long time series observations of global means. Downscaling to a more regional assessment introduces a closer relation to possible annual and regional variations in prescribed oxidative ratios of biospheric and combustion processes. With the goal of improving the knowledge on the temporal and local variability of the O₂/ CO₂ signal, we present the results of the analysis on an extended data set from the remote station of Lutjewad (The Netherlands) and compare them with the findings of different other sampling stations in Europe, starting from 2001 till present.

First atmospheric δO₂/N₂, CO₂ and δ¹³C flask measurements from vertical aircraft sampling in the lower troposphere above Griffin Forest (GRI), Perthshire, UK, (56°37’N, 3°47’W) and from ground based flask sampling at the high altitude site Jungfraujoch (JFJ), Switzerland (3580m above sea level (a.s.l.), 46°33’N, 7°59’E), and the mountain site Puy de Dôme (PUY), France (1480m a.s.l., 45°46’N, 2°58’E) are presented.

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.

To know regional-to-continental scale CO₂ fluxes between atmosphere and terrestrial biosphere using an inverse model, the CO₂ measurements on plural towers situated in a thousand square kilometer area of West Siberia have been carried out since 2002. The CO₂ concentrations at 80m of the tower during daytime afternoon well represents those of PBL with its difference in ±3 ppm, and 90% of them in ±2 ppm, in clear sky day, when no strong inversion is occurred in winter. The tower observation expands to five sites to date, and additional four sites will be established in a year.

We examine the growth-rate of atmospheric CO₂ in 2002 and 2003. Observations show consecutive increases of greater than 2 ppmv per year for the first time on the Mauna Loa record. We use a statistical regression to show that increasing anthropogenic emissions and ENSO activity are unable to account for the CO₂ growth-rates of 1992 and 1993 following the Pinatubo volcanic eruption, or the anomalously high growth-rate of 2003. Increased forest fires in the northern hemisphere, consistent with remote-sensing and carbon monoxide measurements, seem likely to have contributed significantly to the 2003 anomaly. We hypothesise that the hot and dry Eurasian summer of 2003 led to an increase in forest fire emissions from Siberia, and may also have directly suppressed land-carbon uptake. Model results lead us to expect a steady increase in airborne fraction as climate change weakens the natural carbon sink and accelerates CO₂ rise.

We present 16 months of semi-continuous Ar/N₂ data measured at the Scripps Pier in La Jolla, CA. The concentration of atmospheric Ar/N₂ depends on air-sea heat flux. As the ocean takes up heat, both argon and nitrogen are degassed to the atmosphere; as the ocean cools, they are taken up. This record is the beginning of a long-term monitoring program that will parallel the O₂/N₂ and CO₂ measurement programs at Scripps and may help resolve the oceanic contribution to atmospheric CO₂ variability.

The inventory of nuclear bomb produced ¹⁴C (bomb ¹⁴C) in the ocean is a major constraint of CO₂ exchange between the atmosphere and ocean in numerical models and analytical estimates of gas exchange. New ¹⁴C data in the ocean, improved methods of separating the bomb ¹⁴C from the natural background of ¹⁴C in the ocean, and reassessment of previous inventories are challenging the canonical estimates of the air-sea gas transfer. An improved method of separating natural ¹⁴C from the observed ¹⁴C distribution is being used to estimate the bomb ¹⁴C distribution and inventory. We use GEOSECS ¹⁴C data to represent the global distribution in 1975, and the new WOCE dataset for 1995 to get two time representations of inventory. To reduce the bias error for averaging zonal bomb ¹⁴C inventories from limited observation stations during the GEOSECS times, we use zonal averages given by Peacock [2004] for re-evaluation of 1975 air-sea CO₂ exchange rates. Zonal inventories for 1995 will be from GLODAP mapping results using WOCE data [Key et al. 2004]. Lateral transport models developed by Broecker et al. [1985] are used to assess the regional air-sea CO₂ exchange rates as well as an appropriately weighted global mean. Four independent methods of estimating bomb ¹⁴C inventory in the ocean show that the original estimate by Broecker et al. [1995] could be about 25% too high, the air-sea CO₂ exchange rates derived from this original bomb ¹⁴C inventory could also be too high by a similar amount. Results of this assessment will be presented.

Inverse modeling methods are now commonly used for estimating surface fluxes of carbon dioxide, using atmospheric mass fraction measurements combined with a numerical atmospheric transport model. Michalak et al. [2004] recently developed a geostatistical approach to flux estimation that takes advantage of the spatial and/or temporal correlation in fluxes and does not require prior flux estimates. In this work, a geostatistical implementation of a fixed-lag Kalman smoother is developed and applied to the recovery of gridscale carbon dioxide fluxes for 1997 – 2001 using data from the NOAA-CMDL Cooperative Air Sampling Network.