Biogeochemical cycles of climate-active gases CH4, N2O and DMS in Arctic and Subarctic Marine Waters

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Arctic and Subarctic marine waters play a large role in controlling the atmospheric concentration of various gases that influence Earth's climate. Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases acting to warm the planet, while dimethylsulfide (DMS), a trace gas produced by marine microbes, promotes the formation of clouds and atmospheric aerosols that back-scatter incoming solar radiation and act to cool the planet. The concentration and sea-air exchange of these 'climate-active' gases are influenced through the interplay of physical, chemical and biological processes, and sensitive to climate-driven shifts in oceanic conditions. At present, the magnitude of these potential climate-dependent changes is poorly constrained by direct observations. The proposed research program will collect fundamental data on the concentrations and biological / chemical cycles of DMS, CH4 and N2O in surface ocean waters. The principle research objectives are to: 1) quantify the spatial and temporal variability of these gases in Arctic and Subarctic marine waters across a range of oceanographic conditions; and 2) use isotope-labeling experiments to quantify the rates of key production and consumption in the DMS, CH4 and N2O cycles. The results from this work will advance our understanding of potential climate-dependent changes in the oceanic production of these gases over the coming decades. ******Ship-based field surveys will be used to map the concentrations of CH4, N2O and DMS in coastal and offshore waters of the Subarctic Pacific, and in the Canadian Arctic Ocean. Measurements will be conducted using a suite of analytical methods we have developed over the past decade. Isotope labeling experiments will be used to follow the production and consumption of DMS through various pathways, and quantify the cycling of CH4 and N2O through different precursor compounds. The results of the proposed work will provide new mechanistic insight into the factors regulating oceanic CH4, N2O and DMS concentrations, and their potential response to climate-sensitive variables. This, in turn, will be of great relevance to understanding the future evolution of the global climate system. *****