The lateral transport of atmospherically derived carbon across the landscape continues to receive inadequate attention in global carbon cycle science (Cias et al. 2006; Cole et al in press). Although smaller in magnitude than net primary production, the transport of organic and inorganic carbon represents a 2.1Pg C yr-1 flux into the world’s major rivers of which 1.1Pg C yr-1r is exported to the ocean and 1Pg C yr-1 is degassed across the rivers and estuarine surface (IPCC 2001, Sabine et al. 2004). Organic matter in the oceans is one of the largest stores of reactive organic carbon within the global carbon cycle.
Terrestrial organic materials can enter aquatic systems as dissolved organic carbon (DOC), particulate organic carbon (POC), dissolved inorganic carbon (DIC), particulate inorganic carbon (PIC). Each species results from the processes of photosynthesis or respiration or in the case of a fraction of DIC, the chemical weathering of soil carbonate and silicate minerals (Figure 1). Each form can influence the aquatic system it enters significantly, driving levels of productivity in estuaries and coastal margins. However, rivers have short memories, and short term weather patterns, land-use change, and abrupt changes in climate can have immediate effects on carbon transport. Many of these disturbances are confounded by positive and negative feedbacks from humans influence on the environment as well as regional variation in environmental characteristics such as topography and lithology.
As ecosystems science continues to develop, we as researchers are compelled to investigate the physical drivers of observed changes in river carbon chemistry. NASA emphasizes the challenge to ‘improve our understanding and predictive capability of the highly integrated earth system’. To date, the use of satellite remote sensing has primarily focused on retrospective analyses. However management requires tough decisions to be made now based on future predictions. This project will improve our ability to predict changes in ecosystem structure and function, highlighting the impact that these changes will have on future levels of terrestrial carbon export in rivers.