COLLABORATIVE RESEARCH: Understanding trends and biogeochemical controls of Southern Ocean air-sea CO2 fluxes from ocean and atmospheric measurements in the Drake Passage

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AbstractThe Antarctic Circumpolar Current is the strongest wind-driven ocean current on the planet with transports estimated to between 95 - 184 x 10^6 m3s-1. [For comparison the Earth's entire river flow is estimated to be ~ 1^6 m3s-1] . Encircling the Antarctic continent, it has a natural 'chokepoint' in the form of the Drake Passage. This project is a renewal of a long term monitoring time series effort measuring the underway surface partial pressure of carbon dioxide (pCO2) in several annual transects across the Drake Passage on the R/V-IB LM Gould. In all some 100 plus transects over the past 8 years have now been accumulated of pCO2, along with discrete samples of other parameters of interest to studying the carbon system such as total CO2 (TCO2) values, isotopic (13C/12C and 14C/12C) ratios in surface TCO2. Additionally, measurements of oxygen, nutrients and such physical hydrography as may be determined from ship launched XBTs and XCTDs along the cruise tracks will be continued. The measurement set provides an opportunity to describe seasonal cycles on CO2 and biogeochemical nutrients in the Drake Passage, to compare temporal trends and inter-annual variability in the carbonate system for an important part of the Southern Ocean, and to further understand regional and hemispheric atmospheric-ocean exchanges associated with the biogeochemical controls on Southern Ocean air-sea CO2 fluxes.The project will also consider collocated measurement of atmospheric oxygen along with a more rigorous determination of atmospheric CO2 to better anchor the surface pCO2 determinations with the atmospheric record.