The ocean margins form the transition zone between terrestrial and open ocean areas and represent up to 30% of total ocean productivity, yet their role in the global carbon cycle is ill quantified. In order to address this issue, a bi-weekly time-series program was established in Santa Monica Bay in January 2003 to measure the seasonal evolution of the upper ocean carbon cycle at this coastal site. Our measurements reveal a strong seasonal cycle with an amplitude in salinity normalized dissolved inorganic carbon (DIC) reaching nearly 200 µmol/kg and pCO₂ changes of more than 200 µatm. The seasonal cycle of DIC is characterized by a maximum in late winter/early spring, which is caused by upwelling bringing high DIC concentrations from the upper thermocline during this time of the year. The concomitant supply of high levels of nutrients fuels an intense bloom, whose strength varies from year to year in response to large interannual variations in upwelling. In 2003 and 2004, substantial surface DIC decreases were observed under nitrate depleted conditions i) right after the occurrence of upwelling, and i) about three months after upwelling. This implies that during these times, either organic matter production occurred with a very high stoichiometric C:N ratio and/or an additional source of new nitrogen existed that supplied nitrogen without supplying DIC. The seasonal cycle of pCO₂ follows that of DIC with a late winter/early spring maximum, whose levels far exceed that of the atmosphere, and a summer-time minimum with undersaturated pCO₂ values. Annually, Santa Monica Bay acts as a weak to moderate sink for atmospheric CO₂. We suggest that this is mainly due to biological production and in part driven by the uptake of anthropogenic CO₂.

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.

To examine concentration variations of atmospheric CO₂ in the sub-tropical region of East Asia, systematic air sampling with subsequent laboratory analysis has been made in the southernmost part of Japan since June 1993. A time series of measured CO₂ concentrations was analyzed for long-term trend, seasonal cycle and interannual variability, and the temporal CO₂ variations deduced were interpreted in terms of atmospheric transport and CO₂ flux regions.

The results of an optimisation of inter-annual methane sources and sinks calculated by inversion of atmospheric observations are presented and analysed for the 1984-2003 period. We focus our presentation on sources trend and inter-annual variability. Comparisons with bottom-up estimates are presented for biomass burning and wetlands emissions (only in the poster).

Results of airborne CO₂ and CO observations from the NSF/NCAR C-130 platform during the Gulf of Tehuantepec Experiment (GOTEX 2004) and the Airborne component of the Carbon in the Mountains Experiment (ACME 2004) will be presented. A modified commercial vacuum ultraviolet fluorescence instrument monitored CO mixing ratios. CO measurements were used to help identify air masses recently influenced by combustion emissions. CO₂ mixing ratios were measured using a pressure- and temperature-controlled LI-COR 6252 analyzer.  Control of time response allowed operation of the CO₂ instrument in two modes for application to either low altitude eddy covariance or higher altitude mixing ratio measurements. Performance will be assessed, including accuracy estimates derived from intercomparison activities.

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.

We have developed a carbon flux inversion method for using a mesoscale meteorological model (CSU-RAMS) within a Maximum Likelihood Ensemble Filter (MLEF, Zupanski 2005; Zupanski and Zupanski 2005). The MLEF is a variant of the Ensemble Kalman Filter, and is used to optimize model state variables and parameters based on continuous observations of CO₂ mixing ratio. The method does not require the development of a model adjoint, but rather relies on transformation of variables to efficiently obtain estimates of fluxes with uncertainties and dynamical model error from an ensemble of forward model simulations. We demonstrate this method using a mesoscale simulation of weather, transport, and the surface carbon budget over the continental USA during the summer. The estimation procedure decomposes the total surface flux into photosynthesis and respiration (which are assumed to be modeled correctly to first order), plus an unknown but time-invariant fractional error in each.  These residuals are estimated for each model grid cell over a moving window in time, allowing atmospheric observations to be integrated over sufficient time to obtain constraint. Model error can also be estimated by this procedure, and the method can be extended to larger domains and longer integrations.

We have employed a Multi-parameter Linear Regression (MLR) analysis procedure to determine the uptake of anthropogenic CO₂ between two east-west hydrographic surveys of the North Pacific that occurred in 1994 and 2004. The results revealed water column integrated uptake rates of anthropogenic CO₂ that ranged from 1.1 to 1.3 mol m^-2 yr^-1 depending on location. The combined effect of the tilted density surfaces and the younger waters with higher anthropogenic CO₂ concentrations leads to higher total column inventories in the western North Pacific.

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.

The spatial and temporal variations of atmospheric CO₂ at 8-13 km from April 1993 to March 2005 were observed by measuring CO₂ concentrations in samples collected biweekly from a commercial airliner between Australia and Japan. The 12-year record between 30N and 30S revealed several characteristics for CO₂ interannual variabilities in the upper troposphere. The most significant year-to-year change was found in a large increase in the growth rate during 1997/98 and 2002/03 that were associated with the ENSO events. During these years, changes in north-to-south gradient of latitudinal distribution and seasonal cycle were observed compared to data during the normal years.