The Atlantic's central role in the global thermohaline circulation suggests that this basin should be an important laboratory for understanding the ocean carbon cycle and possible temporal variations in that cycle. Here we present the set up and results from an oceanic box model inversion which focuses on the transport and divergence of total inorganic carbon (TIC) and anthropogenic carbon within the Atlantic.

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.

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.

GOSAT is a satellite to measure the column densities of CO₂ and CH₄ from space globally, and it is scheduled to be launched in 2008. It has a short wavelength infrared (SWIR) Fourier transform spectrometer (FTS) which measures both the ground surface scattered solar light over land and the right reflected light (sun-glint) over ocean. Column densities of CO₂ and CH₄ will be retrieved from the SWIR (i.e. 1.6 µm and 2.0 µm bands) data and the optical path length from oxygen A-band (0.76 µm). A cloud and aerosol sensor composed of three spectral image sensors (0.380, 0.678 and 1.62 µm) is equipped, viewing the wider area than FTS. This is a joint project among Ministry of Environment of Japan (MOE), National Insitutite for Environmental Studies (NIES) and Japan Aerospace Exploration Agency (JAXA).

The Orbiting Carbon Observatory is a NASA ESSP mission that is scheduled for launch in September 2008 [Crisp et al., 2004]. The space-based observatory will sample the dry air, column averaged mole fraction of CO₂ (X_CO2) based on analysis of reflected solar radiation, between ~0.78 and 2.0 microns, acquired by three grating spectrometers. To fulfill the mission’s science objectives, the OCO validation activities are focused on demonstrating that space-based retrievals of X_CO2 have random errors no larger than 0.3% (1 ppm) over a network of ground based validation sites on monthly time scales [Miller et al., 2005]. Furthermore, space-based retrievals of X_CO2 will be compared to measurements from this network of ground-based stations to detect and mitigate geographically coherent biases on regional to continental scales. We describe plans and progress to date of the OCO validation program, which consists primarily of a series of ground-based, Fourier Transform Spectrometers (FTS), that measure X_CO2 in the same spectral regions as the space-based spectrometers.

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.

A time series transect has been established in subantarctic surface water off the south east coast of New Zealand.  The 60 km long transect extends from the coast (45-46.20^oS 170-43.20^oE) to a station at 45-50.00^oS 171-30.00^oE. and sea surface temperature, salinity and pCO₂ have been measured bi-monthly since 1998 . SST, pCO₂ and pH of the subantarctic surface water show seasonal cycles that can be fitted with simple harmonic curves.  Temperature has a mean value of 10.4^oC, with an amplitude of 2.1^oC, the maximum occurring in late summer.  pCO₂ has a mean value of 360 matm, an amplitude of 10 matm, the maximum occurring in early spring.  The phase of the pCO₂ and temperature curves are offset by 158 days, indicating that change in sea water temperature is not the major factor affecting pCO₂ in this area.  The relative effects of temperature, biological utilization and air-sea gas exchange on the seasonal change in pCO₂ are determined using a simple model.  The model results reproduce the timing of the observed pCO₂, however the amplitude of the changes is not well reproduced.

Measurements of the radiocarbon content of atmospheric carbon dioxide are a potentially powerful, yet relatively unexplored method of improving the understanding of natural carbon dynamics and verifying fossil fuel emissions. Development of ¹⁴CO₂ as a tracer has been limited by measurement capabilities given that seasonal and spatial variation in D¹⁴C is currently of the same order as traditional instrument precision: 3-5 per mil. We have demonstrated 1-2 per mil reproducible measurement precision at the Center for Accelerator Mass Spectrometry of Lawrence Livermore National Laboratory. Here we present preliminary measurements of the natural variability of ¹⁴CO₂ from the SIO network of background air sampling stations.