This project is analyzing the carbon cycle of the Arctic System with the goal of improving our ability to predict the dynamics of carbon in high latitudes. Because the climate system is vulnerable to significant releases of CO2 and CH4 from high latitudes, the responses of these gases to climate change have global consequences. A large release of CO2 and CH4 from high latitude terrestrial and marine systems to the atmosphere has the potential to affect the climate system in a way that may accelerate global warming. Key foci of the project are these general questions: (1) What are the geographic patterns of fluxes of CO2 and CH4 over the Pan-Arctic region and how is the balance changing over time?; and (2) What processes control the sources and sinks of CO2 and CH4 over the Pan- Arctic region and how do the controls change with time? To address these questions, the study brings together diverse regional data on CO2 and CH4 dynamics of the Arctic System using a combination of prognostic and inverse approaches. The project provides an integrative approach to estimating and understanding the exchanges of CO2 and CH4 from terrestrial and marine components of the system including a consideration of the lateral exchange of C between the terrestrial and marine components of the Arctic System.