The high Arctic contains delicate, relatively pristine ecosystems that are increasingly subject to exported aerial pollution (e.g. nitrogen) and higher than average climatic temperature change. Together these factors may potentially change important biogeochemical processes (e.g. the cycling of carbon and nitrogen) and ecosystem dynamics. This project involving the University of Nottingham, The British Geological Survey and IACR Rothamsted is now entering its second field season. The project concentrates on the release and the subsequent fate of N, entering the tundra ecosystem, as a pulse during the spring thaw. The questions we propose addressing are (i) how important is this event in transferring enhanced N deposition to tundra ecosystems, and how much is lost as run-off to lacustrine and inshore marine environments, (ii) how does enhanced N affect the carbon cycle (i.e. plant growth, decomposition processes) and (iii) what is the impact on soil N mineralizationimmobilization dynamics. Two plot experiments have been set up at contrasting vegetation sites around Kongsfjorden (Brandalspyntyn and Ny-London). We have simulated the release of N from the snowpack by applying 15N label as the snow has melted. An accurate audit regarding the fate of this snowpack N can then be made (i.e. does it remain in the soil, enter the tundra flora and soil microbiology or is it lost from the system). In addition, using techniques for combined 18O+15N analysis of nitrate, we can distinguish between atmospheric- and soil-derived nitrate. This will allow us to assess and source losses of N from the tundra during the brief summer growing season. These complementary approaches will provide a quantitative understanding of the fate of deposited N in the pristine Arctic environment. The overall aim will be to parameterize an N-flux model for this important ecosystem.