Primary Production Rates in the N. Atlantic for O2 Isotopes and O2/Ar

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Because of the mounting evidence that the ocean's biological pump changes with natural climate shifts, a major task of oceanographers over the coming decade is to separate natural from anthropogenic shifts in the strength of the ocean's biological pump. Despite its global importance, the ocean's biological pump rate is not really well known. Variability of primary production rates on short time and space scales makes difficult the accurate measurement of rates using traditional 14C-based methods. There is a clear need to use alternative primary production rate measurement methods that are more accurate, less time consuming to apply and can integrate over longer time/space scales. In this research, a scientist from the University of Washington will determine, on a detailed spatial and temporal scale, the annual cycle of gross primary production and net community production rates across the subarctic N. Atlantic Ocean. He will make almost monthly measurements (~50/month over 3 years) of both the triple isotopic composition of dissolved oxygen gas (17') and the dissolved oxygen and argon gas ratio (O2/Ar) on surface seawater samples collected during repeated container ship crossings of the N. Atlantic with ~1' of longitude resolution across the basin. These sample collections will be made as part of the CARBOOCEAN program through a collaboration with researchers at U. Kiel. Additionally, in collaboration with another NSF-funded expedition, he will measure the same rates in the subarctic N. Atlantic in Spring 2008 where floats, seagliders and satellites will be used to examine the biological response during the spring bloom to mesoscale physical forcing (e.g. fronts, storms, eddies). This suite of measurements will permit determination of the annual cycle of gross primary production and net community production across the subarctic N. Atlantic Ocean, clarify the impact that spatial and temporal variations of net community production have on surface pCO2 levels and net air-sea CO2 uptake, and examine the relationship between mesoscale variability in primary production rates and physical forcing during the spring bloom in the N. Atlantic. The broader impacts of the proposed research include helping to improve predictions of future global warming due to atmospheric CO2 increases. The proposed work involves a substantial collaboration with the European oceanographic community and will support an undergraduate student in the research.