Abstract In order to quantify the role of oceanic and terrestrial CO 2 exchange on the atmospheric record collected at Ny-Ålesund, Spitsbergen, we have employed a high resolution, regional atmospheric transport model. The three-dimensional Eulerian dispersion model has been developed at the Swedish Meteorological and Hydrological Institute, and is driven by observed meteorology. The model has a detailed description of the atmospheric boundary layer, which is allowed to vary during the course of the day. The domain is located over the Arctic and covers the Northern Atlantic down to circa 50°N and large parts of Siberia and the regions affected by anthropogenic activities in Europe and Russia. In the model we can test different oceanic and terrestrial uptake scenarios, and by comparing with the measurements at Ny-Ålesund we may constrain the regional budget of CO 2. The model is successful in discriminating between the different processes affecting CO 2 measured at Spitsbergen while the absolute values, which depend on the chosen source functions, and boundary conditions, remains to be determined.