Nitrous oxide cycling in the Western Arctic Ocean from stable isotopic and concentration data
Nitrous oxide is a potent greenhouse gas in the troposphere and an ozone-depleting substance in the stratosphere, yet its sources and sinks in the ocean are neither well-quantified nor well understood. Nitrous oxide is both produced and consumed by microbial processes; it is produced by different processes dependent upon the amount of oxygen present locally. The Arctic Ocean may represent an important source of nitrous oxide to the atmosphere. High nitrous oxide saturations were recently observed in productive shallow Arctic shelf waters. This research will test the hypotheses that productive shelf regions of the Western Arctic Ocean (e.g., Chukchi and Beaufort seas) stimulates nitrous oxide production and contributes to offshore transport of nitrous oxide toward the central Arctic. Besides developing an important baseline data set for the Arctic science community, this project will contribute to STEM workforce development in numerous manners. It will support an early-career female scientist during the formative years of her career. It will provide summer educational research opportunities to undergraduate students. It will develop seminars for elementary school teachers and provide short classroom presentations at a local public school and contribute to an afterschool non-profit effort devoted to providing high quality educational programs to at risk youth. The primary goal of this research is to evaluate nitrous oxide cycling in the Western Arctic Ocean from its concentrations, stable isotopes and isotopomers. The project will use isotopic and isotopomer measurements from both shelf and offshore waters to constrain estimates of nitrous oxide cycling in the Arctic. The data will be used to evaluate 1) the pathways of nitrous oxide production from either nitrification following organic matter decomposition in the water column or coupled nitrification-denitrification in the sediments and 2) how these processes influence nitrous oxide exchanges between the surface layer and the atmosphere. Comparisons of observations at coastal and shelf stations in the Bering and Chukchi seas with those offshore in the Deep Canadian Basin will allow the evaluation of the effects of mixing and long-range transport on geochemical signals. The measurements will also serve as a baseline for future assessment of change. The project profits from leveraging of other investments by NSF and the principal investigators' international collaborators, benefitting from measurements and samples collected during the U.S. GEOTRACES Arctic section and the 2016 CHINARE Arctic cruises.