A multi-box inverse model will be used to investigate the transport, divergence and decadal changes in the concentration of CO2 (carbon dioxide) within the Atlantic Basin. The model includes most of the long line data collected during the WOCE/JGOFS (World Ocean Circulation Experiment and Joint Global Ocean Flux Study) period 1990-1999) and, currently, is made up of 40 boxes and 21 density layers. The models' carbon transport results will be compared both to previous observation based results, as well as to the results of models participating in the ocean carbon model intercomparison project. To better understand the significance of the box model synthesis circulation and ocean carbon cycle which are based on an assumed steady-state within a system which is known to be varying, the analysis of the mean circulation variance will be extended within the Atlantic portion of a global ocean state estimation product. In addition, the project will be extended to include investigation of the divergence of oxygen and nutrient transports in the inverse model and of the inferred rates of organic carbon, opal, and calcium carbonate export from the surface ocean. This approach will be combined with chlorofluorocarbon (CFC) and radiocarbon age based estimates of biogeochemical cycling for which an extensive data- and model-based analysis of possible CFC age biases will be performed.
Intellectual Merit: The proposed work is unique in that it is the first to combine both zonal and meridional observations in a physically consistent fashion over the full extent of the Atlantic Ocean to investigate the location and magnitude of oceanic uptake and outgassing of CO2. Such syntheses have been performed in the past for properties other than carbon and have been shown to not always produce the same results as single transect studies. The proposed inclusion of biogeochemical cycling rates within the model and from the tracer-age based approaches will provide new data based basin-scale estimates of biogenic material export from the Atlantic surface ocean that can be compared to other methods as well as to other oceanic regions.
Broader Impacts: Estimates of oceanic CO2 uptake are necessary for accurate prediction of future atmospheric CO2 content and direct estimates of inorganic carbon flux divergences will provide a constraint on the estimates made through surface pCO2 measurements and numerical models. This research represents an interdisciplinary component of the international WOCE synthesis program and will provide groundwork for analyzing CLIVAR (CLImate VARiability and predictability program) observations in the future. A second important aspect of the work is the investigation into the variance of the flow field with the focus on determining how well the hydrography represents the "mean" in a time-varying flow field. The work is necessary to establish the context in which repeat sections are most useful. A portion of the funds will support a young, female scientist in the process of establishing herself in interdisciplinary research, as well as a student who will be introduced to both observational and numerical modeling aspects of physical and chemical oceanography. A. Macdonald is taking an active part in the New England Centers for Ocean Sciences Education Excellence (NE-COSEE), participating and presenting in COSEE "Telling Your Story" workshops. She is currently working with 3 teachers in local schools to share components of her work on ocean circulation, the carbon cycle and data analysis with middle and high school students.
This study is a contribution to the U.S. CLIVAR program and the U.S. Carbon Cycle program.
