Changes in dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) in the water column are quantified for meridional hydrographic sections through the Atlantic from 63 ˚N to 60 ˚S between 1988/1993 and 2003/2005.  Changes are most pronounced in the upper 1000 m water column.  DIC changes range from -5 to 40 µmol/kg and AOU changes by a similar amount.  The remainder is caused by changes in positions of fronts, gyres, remineralization and ventilation as manifested by changes in watermass properties.  In particular AOU increases of similar magnitude as increases in DIC point towards a significant contribution of oxidation of organic matter to the DIC increase.  The large changes in biogeochemical properties of the upper water column of the Atlantic have been one of the big surprises in the decadal reoccupation of the transects.

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.

The CARBOOCEAN consortium aims at an accurate scientific assessment of the marine carbon sources and sinks within space and time. It will determine the ocean’s quantitative role for uptake of atmospheric carbon dioxide (CO₂), the most important manageable driving agent for climate change. Since the ocean has the most significant overall potential as a sink for anthropogenic CO2, the correct quantification of this sink is a fundamental necessary condition for all realistic prognostic climate simulations. Target is to reduce the present uncertainties in the quantification of net annual air-sea CO₂ fluxes by a factor of 2 for the world ocean and by a factor of 4 for the Atlantic Ocean.

In the CHIOTTO project (http://www.chiotto.org) as part of the CarboEurope cluster of projects (http://www.carboeurope.org) a network of 8 tall tower stations has been set up in Europe. Most towers are equipped for continuous high precision measurements of ambient CO₂, CH₄, CO and SF₆. Some stations are also equipped for continuous measurement of ²²²Rn and flask sampling. First measurement results are presented and evaluated using forward and inverse model calculations.

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.

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.

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.

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.

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.