The effect of rainfall on mass transfer across the air-water interface was investigated through the CO₂ absorption experiments in a turbulent open-channel flow with the free surface. The results show that the rainfall enhances both the turbulent mixing near the free surface on the liquid side and the CO₂ transfer across the interface. The mass transfer coefficient on the liquid side is well correlated by both the mean vertical momentum flux of rainfall, M, and the mean kinetic energy of rain droplets impinging on the unit area of the air-water interface, KEF. However, it was not concluded which of M and KEF is a better parameter for expressing the rainfall effects on the mass transfer. The comparison between the mass transfer coefficient obtained in this study and that obtained in wind-driven turbulence suggests that it is of great importance to consider the rainfall effect on the CO₂ exchange rate between the atmosphere and ocean in precisely estimating the global carbon cycle in a climate model.

We have conducted long-term regular monitoring of vertical profiles of ¹³C/¹²C ratio of atmospheric CO₂ over three sites in Siberia and a site in Japan. Time-series and seasonality of the ¹³C/¹²C ratio at each altitude levels at the four site were examined. Apparent isotopic signature was calculated from the relationship between CO₂ mixing ratio and the ¹³C/¹²C ratio in individual vertical profiles.

We apply to Classical Labrador Sea Water (CLSW) the “transit-time distribution” (TTD) method to estimate the inventory and uptake anthropogenic carbon (∆C). A parametric model of TTDs representing bulk-advective and mixing processes is constrained with WOCE CFC data. The constrained TTDs are then used to propagate ∆C into the interior of the CLSW. Compared to many past studies the key advantage of this methodology is that mixing is not assumed to be a negligible component of transport.

Variations in atmospheric oxygen (O₂) are a sensitive indicator of biogeochemical processes involved in the global carbon cycle.  To improve our understanding of these processes, we developed a system for continuous high precision measurements of atmospheric O₂ and CO₂ that is suitable for shipboard use.  This system was employed on two voyages in the Western Pacific sector of the Southern Ocean, in February 2003 and April 2004.  Elevated O₂ concentrations were observed south of New Zealand and across the Chatham Rise suggesting that these regions of ocean are outgassing O₂ in late summer to autumn.

In the present study atmospheric CO₂ retrievals based on Aqua satellite AIRS (Atmospheric Infrared Sounder) instrument observations are compared with forward model predictions. There is quite good agreement in seasonal cycles as well as North-South gradients when averaged over large scales. At smaller scales there are contrasts between upper troposphere CO₂ above continents versus oceans in the retrievals and there are signatures off Africa which seem likely artifacts caused by aerosols. As a consequence retrievals cannot be used at this stage to constrain surface sources and sinks without causing large biases. Interestingly there is good agreement in the shape of the N-S gradient at low-to-mid latitudes in the Northern hemisphere between simulations based on one transport model (LMDZ) and retrievals, but disagreement when comparing with simulations based on a second transport model (TM3). This raises questions about lower to upper troposphere transport and their representation in these models.

We present measurements of atmospheric O₂/N₂ ratio and CO₂ mole fractions from flask samples collected at Hateruma Island and Cape Ochi-Ishi, and onboard cargo ships between Japan and the United States, and Japan and Australia (or New Zealand). Average changes in the O₂ and CO₂ for the 6-year period from 1998 to 2004 are –23.3 ± 0.3 ppm and 10.4 ± 0.1 ppm, respectively. Assuming that the ocean is neither a source nor a sink for the atmospheric O₂, we estimate the CO₂ uptake by the terrestrial biosphere and the ocean to be 1.1 ± 0.6 PgC yr^-1 and 2.0 ± 0.5 PgC yr^-1, respectively.

We use the theoretically ideal tracer ¹⁴CO₂ to estimate the fossil fuel CO₂ enhancement in boundary layer air at two sites in New England and Colorado. Improved D¹⁴C measurement precision of 1.6-2.6‰ provides fossil fuel CO₂detection capability of 0.8-1.5 ppm. Using the tracers CO and SF₆, we obtain two additional independent estimates of the fossil fuel CO₂ component, and we assess the biases in these methods by comparison with the ¹⁴CO₂-based estimates. Large differences are observed between the SF₆-based estimates and those from the ¹⁴CO₂ and CO methods. The CO-based estimates show seasonally coherent biases, underestimating fossil fuel CO₂ in winter and overestimating in summer.

The WLEF TV tower in northern Wisconsin is instrumented to take continuous measurements of CO₂ mixing ratio at 6 levels from 11 to 396m. During the spring and summer of 2004 additional CO₂ measurements were deployed on five 76 m communication towers forming a ring around the WLEF tower with a 100-150 km radius.