Assessing the Terrestrial and Atmospheric Nitrogen Cycle

Despite nitrous oxide (N2O) being a major ozone depleting species and greenhouse gas, its sources and emission rates are not well understood. There are large uncertainties in soil emissions, both from natural processes and fertilizer use, as well as discrepancies in ocean emissions. Improved understanding of N2O emission processes over the surface of the globe is needed to accurately quantify past, present, and future impacts on stratospheric O3 and climate. We address these issues by using an interdisciplinary approach that integrates observations (from NOAA, the Advanced Global Atmospheric Gases Experiment, and other networks) and bottom-up as well as top-down modeling. Using the N2O emissions obtained from the process model combined with N2O observations, we will refine our estimate of global and regional annual N2O emissions for 5 different sources over the last 15 years with MIT's Integrated Global System Model (ISGM)-CAM3 Model.

Incorporating a variety of projections simulated in the MIT IGSM, we will assess the impact of potential future climate on soil N2O emissions, and how potential future land use change and the extent of anthropogenic combustion-related activities may affect these emissions. We will explore the response of terrestrial biogeochemical systems, assess various mitigation pathways, and calculate current and possible future stratospheric ozone loss due to the predicted N2O emissions. Overall, this project will enhance our understanding of the impact of N2O emissions not only on the nitrogen cycle, but also on climate and on stratospheric O3.