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Stanley, Rachel Assistant Scientist, Marine Chemistry & Geochemistry


How will the ocean respond to global climate change? Currently, the ocean takes up about one quarter of the CO2 emitted by fossil fuel burning but this number could easily change in the future. In order to predict the future CO2 balance of the planet, we need to gain a mechanistic understanding of the marine carbon cycle. How does CO2 cross from the atmosphere to the ocean? Improved understanding of air-sea gas exchange will aid in answering that important question. What happens to the CO2 when it is in the ocean? Photosynthetic organisms fix CO2 into organic carbon. Some fraction of this organic carbon is exported to the deep ocean where it is separated from the atmosphere for hundreds of years. What controls the amount of photosynthetic production in the ocean? The fraction of organic carbon that is exported? In order to address these questions, I use dissolved gases as tracers to aid in understanding the global biogeochemical cycles of CO2 and O2. Noble gases are ideal tracers for physical processes affecting CO2 and O2, especially air-sea gas exchange, since they are biologically and chemically inert. The heavier noble gases Kr and Xe respond primarily to diffusive gas exchange whereas the lighter noble gases He and Ne are also sensitive to bubble processes. Thus measurements of a suite of noble gases can be used to separate and quantify different processes within air-sea gas exchange. Measurements of the triple isotopic signature of oxygen and of the ratio of O2/Ar both discretely and using an at-sea equilibrator inlet mass spectrometer (EIMS), lead to large datasets on gross production and net community production rates in the upper ocean. These rate data can be used in combination with numerical modeling to investigate issues of biological productivity and its variations and feedbacks.

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