Increased nitrogen (N) delivery to coastal areas is one of the major consequences of human perturbation to the nitrogen cycle, and has important impacts on coastal productivity and trace gas emissions. Motivated by this observation, this research is a first effort to model river nutrient transport in the Community Climate System Model (CCSM). Leached N fluxes from the DAYCENT model, which serves as the basis for the soil agricultural biogeochemistry model that eventually will be developed within the CCSM Land Model (CLM), will be coupled to the CLM River Transport Model (RTM). (DAYCENT is the daily time step version of the Century Model, a soil organic matter model that simulates daily trace gas fluxes and soil water dynamics). Modeled river N fluxes will be compared to observational databases and to simple empirical estimates of N export derived from statistical correlations. Modeled N export fluxes to coastal areas will be used to evaluate coastal N budgets, through comparison to modeled and measured atmospheric N inputs and to estimated natural coastal nitrification rates. The broader impacts of the proposed study include the development of a framework for the simulation of river solute transport in the CCSM, which will contribute to the more complete representation of the global N cycle in the CCSM and will provide important boundary conditions for the coupling of the CLM with regional coastal models.
