Collaborative Research: In situ measurements of oxygen and nitrate with profiling floats deployed at ocean time-series stations

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In this project, researchers at the Monterey Bay Aquarium Research Institute and the University of Washington will construct and deploy Apex profiling floats equipped with ISUS optical nitrate sensors, Aanderaa oxygen optodes and Wet Labs ECO fluorometers. Two floats per year will be deployed at the HOT (Hawaii Ocean Time series) station, BATS (Bermuda Atlantic Time Series) station and at Ocean Station Papa in the Gulf of Alaska. Two additional float will be deployed each year in the Southern Ocean. These floats will provide time series observations of biogeochemical processes at these sites with temporal resolution that cannot be sustained by the current shipboard observations. With life spans for each float of four years, the float network will also provide significantly improved spatial resolution around each of the deployment sites near the end of this project. These float-based sensors provide the potential to study a variety of processes. The project leaders recently demonstrated that profiling floats can provide time series observations of Net Community Production below the mixed layer based on dissolved oxygen measurements. The continuous measurements of NCP demonstrate that the euphotic zone of the subtropical ocean produces oxygen (net autotrophic) and that episodic events of high NCP are not required to sustain a positive autotrophic balance. These measurements thus may resolve a fundamental controversy as to whether the oligotrophic ocean is net heterotrophic or net autotrophic. Near the BATS site the floats will likely provide significantly improved understanding of the role of eddies in sustaining elevated primary production rates. At high latitudes, the floats will provide an unparalled view of the interaction of vertical mixing with timing of the spring bloom. Two types of Broader Impacts will result from this work. The project will "stimulate and support the development and dissemination of next-generation instrumentation, multi-user facilities, and other shared research and education platforms." And secondly, by making the data from this research directly available in real time to the research and education, it will "advance discovery and understanding while promoting teaching, training and learning." Information about the project and the data stream it produces will also be made available on a dedicated web site.