High-quality data of total inorganic carbon (TCO₂) and other oceanographic parameters have been acquired repeatedly between 1994 and 2003 along 137ºE (WOCE P9) in the western North Pacific. They indicate the significant increase in TCO₂, apparent oxygen utilization (AOU) and preformed TCO₂ in the water columns between 20ºN and 30ºN, in particular, in the North Pacific Subtropical Mode Water (NPSTMW). The increase in the preformed TCO₂ suggests the 0.9 to 1.1 mol m^-2 yr^-1 accumulation of the anthropogenic CO₂ in this region. However, the change in the preformed TCO₂ associated with the change in the formation region and/or advection of NPSTMW is also suggested.

Tropical drought can significantly impact inter-annual variations in the terrestrial CO₂ fluxes. Concentrations and carbon isotope ratios of atmospheric CO₂ can help to quantify this impact, however, their use requires a model estimation of the terrestrial isotope disequilibirum, i.e. the difference between the isotopic signature of photosynthesis and respiration, which can only be achieved by accurately accounting for changes in relative contributions of C3 and C4 plants (C4 fraction) and physiological effects of root-zone water stress.

Satellite measurements of total column CO₂ can be used in inverse models to help isolate sources and sinks; however, using satellite concentrations in inversions may introduce spatial, temporal, and clear-sky errors. Using a coupled ecosystem-atmosphere model, we found that using satellite measurements to represent temporal averages will introduce large errors into the inversion and that inverse models must sample the concentrations at the same time as they are measured.  Spatial and local clear-sky errors are much smaller than the instrumental errors, although they increase with domain heterogeneity. Inverse models can minimize sampling errors by using homogenous regions and sampling the CO₂ concentrations at the same time as the satellite.

Spatial and temporal characteristics of land and ocean sources and sinks of carbon remain elusive. Better understanding of the anthropogenic influences on these carbon cycle dynamics is a common goal. This experiment is one of the efforts to reach a middle ground of flux estimates for regions larger than experimental plots and flux tower footprints, but smaller than continents and ocean basins. This work tests the hypothesis that including well-calibrated continuous North American continental CO₂ measurements in the observation data used in a global inversion will provide a constraint that improves inversion estimates of the source and sink regions within North America. These continuous data are collected at tall towers and flux towers. The experiment follows the TransCom 3 synthesis inversion framework, using the NASA Goddard Space Flight Center Parameterized Chemistry and Transport Model (PCTM) with Goddard Earth Observing System, version 4 (GEOS-4) meteorological data. Seasonal fluxes are estimated for a recent year for sub-regions within North America and at continent and basin scale globally. Methods of preparing the continental continuous CO₂ measurements for the inversion will be tested. Initial inversion results will be presented along with recommendations for applicability to other global regions and use of the method to evaluate additional sites for the measurement network.

CO₂ and methane are important greenhouse gases, both contributing in increasing amounts towards positive radiative forcing. It is hence important to gain maximum understanding of the carbon cycle in the atmosphere, and the scale of carbon trace gas sources and sinks, not only globally but also on a more regional level. The Orbiting Carbon Observatory (OCO) satellite, scheduled for launch in 2008, is designed for dedicated global mapping of CO₂. In order to investigate the usefulness of a variety of methods, including retrievals from satellite mapping, some preliminary inverse modelling using a Bayesian synthesis technique is performed using pseudodata generated to represent possible future measurement regimes. This study will focus on the ability of in-situ measurements within Australia to reduce the uncertainties in Australian continental CO₂ flux estimates. The specific measurements investigated include a Ghan railway transect between Adelaide (34.9°S, 138.6°E) and Darwin (12.5°S, 130.9°E), and a number of continuous permanent sites. The reduction in flux uncertainties from additional measurements compared to a background inversion is examined, from which it is concluded that measuring on the Ghan railway is potentially worthwhile for reducing uncertainties associated with flux estimates.

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.

High-frequency atmospheric CO₂ measurements should become increasingly available by the end of this decade from a variety of sources, including low-Earth orbiting satellites. If of sufficient accuracy, these should allow the functioning of the global carbon cycle to be monitored at fine time/space resolutions using atmospheric transport inversions. Since traditional direct inversion methods (e.g., Bayesian synthesis) become computationally infeasible at these resolutions, we use an approximate method, variational data assimilation, to estimate surface CO₂ fluxes at spatial resolutions ranging from 10x10 degrees to 1x1 degrees and at time resolutions ranging from 2 weeks to 1 hour. We assess its performance using simulated data, including the effects of realistic transport and data errors.

Measurements of the partial pressure of CO₂ in surface seawater (pCO₂^w) have been made frequently and extensively in the western North Pacific (3-35°N, 132-142°E) since 1990. Based on the time series analysis of pCO₂^w data, we obtained a “climatological view” of seasonal variation in pCO₂^w in the western North Pacific. We have examined the relationship between pCO₂^w and sea surface temperature (SST). The pCO₂^w–SST relationship varies spatially and temporally. The pCO₂^w showed an average growth rate of 1.6 µatm yr^-1 (nearly equal to that of the air, pCO₂^a) with large variability (±8.9µatm yr^-1). In 1998, larger growth rates of pCO₂^w occurred in the subtropical gyre and the western equatorial Pacific, which was probably associated with the 1997/98 El Niño phenomena. To know processes affecting long-term variations in pCO₂^w, we have examined seasonal variation in growth rate of pCO₂^w. The linear growth rate of pCO₂^w during the winter season ranged from 1.3±0.2 to 2.1±0.2µatm yr^-1 with an average of 1.7±0.2µatm yr^-1. During spring/summer seasons, the average growth rate of pCO₂^w was larger than 2µatm yr^-1 north of 27°N, and within the range from 0 to 1µatm yr^-1 in the North Equatorial Current. These increases were mostly caused by the oceanic uptake of anthropogenic CO₂, and to some extent, other processes controlling the pCO₂^w change: thermodynamic effect, lateral transport and vertical mixing, and biological activity.