Closing The Surface Ocean CO2 Budget in The N Pacific Using Underway 13C/12C, pCO2, DIC and O2/Ar Measurements

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A fundamental question facing oceanographers is how the ocean carbon cycle will respond to future climate change and how this response will feed back on atmospheric CO2 levels, ocean acidification and climate. The response of the ocean carbon cycle to climate change will involve interactions between physical, biological and chemical processes. Yet for the most of the world ocean we do not understand well the links between these processes often because of a lack of observations. As a result, the magnitude or even direction of change expected for the ocean carbon cycle in the future is unclear. Furthermore, the lack of observations prevents us from validating carbon cycle models used to predict future changes in atmospheric and oceanic CO2 levels. The Ocean Carbon and Climate Change report (OCCC, 2004) specifically identified the North Pacific Ocean as a high priority region for focusing studies of the processes controlling ocean-atmosphere carbon fluxes. In this project, a research team at the University of Washington will take a novel approach to increase the observational data on the spatial and temporal variations of the surface ocean pCO2, dissolved inorganic carbon (DIC) and 13C isotopic composition of CO2. They will use a new analytical technique, Cavity Ring Down Spectroscopy (CRDS), that allows for continuous measurement of the del13C and concentration of both dissolved CO2 gas and DIC. A container ship will be employed to make monthly underway measurements of pCO2, DIC and del13C along with O2/Ar, O2, pH, nitrate, chlorophyll and particles at 5-10 km resolution along a North Pacific transect from Hong Kong to Long Beach, California, in particular in the Transition Zone separating the subtropical and subarctic regimes where oceanic CO2 uptake rates are 5-20x higher than the global average. They will use the underway measurements of pCO2, DIC, del13C and O2/Ar to close the surface CO2 budget in the North Pacific and quantify the impact of sea surface temperature changes, organic carbon export and physical transport of DIC on the air-sea CO2 flux over an annual cycle. Broader Impacts. The proposed application of multiple analytical methods to continuously measure air-sea CO2 flux, biological productivity, DIC and 13C using a container ship sampling platform is innovative and potentially will result in data that could significantly benefit the broader ocean communities involved in carbon cycle modeling and remote sensing. The project is expected to significantly help improve predictions of future climate change. Research results will be incorporated into both undergraduate and graduate course curricula, and there will be active graduate and undergraduate student participation. Project results will be incorporated into existing outreach talks using faculty and graduate students in the School of Oceanography coordinated through the Program on Climate Change at the University of Washington.