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.

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.

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.

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.

We present an analysis of terrestrial net CO₂ fluxes from North America for the period 2000-2004. These fluxes consist of hourly maps at ~70km×100km resolution that are consistent with observed atmospheric CO₂ mixing ratios, as well as with varying climatic conditions across different ecosystems as observed from space. The flux maps are created in a newly developed ensemble data assimilation system that consists of the atmospheric Transport Model v5 (TM5), the Vegetation Photosynthesis Respiration Model (VPRM), and an efficient Bayesian least-squares algorithm to optimize the fluxes from different biomes in VPRM against CO₂ mixing ratios from the NOAA-CMDL observing network. The stochastic nature of the ensemble data assimilation system allows us to consistently include uncertainty on net CO₂ fluxes from the neighboring oceans and more distant continents in the flux estimates for North America.

With the increasing temporal and spatial density of CO₂ flux and concentration observations from worldwide tower networks, the importance of interpreting the data is becoming more conspicuous. Previous work shows that tower observations might be able to catch synoptic, regional, and local signals of CO₂ simultaneously. Thus a study that can explain CO₂ transport and the response of the ecosystem to the weather change simultaneously is necessary and will help the development of the regional inverse modeling technique in the future.

Physical processes in the Southern Ocean are known to profoundly impact the global carbon cycle, but this region is one of the most difficult to simulate consistently in ocean general circulation models (OGCMs). Here we show that Southern Hemisphere winds, by altering the volume of light, actively-ventilated ocean water as well as the relative contribution to this volume from Ekman transport, exert strong control over both the magnitude and distribution of anthropogenic carbon uptake in an OGCM. These results are provocative in suggesting that climate warming, by increasing the magnitude of the wind stress at high southern latitudes, may act as a negative feedback on the global carbon cycle.