The goal of the project is to continue and expand time series measurements of O2/N2 and Ar/N2 ratios and CO2 concentration at stations maintained by the Scripps O2 project. These measurements will enable refined estimates to be made of land and ocean carbon sinks and provide benchmark tests for models depicting the response of ocean biogeochemistry to changing climate on a range of time scales, extending from seasonal, El Nino, to multi-decadal. The measurements are also relevant for quantifying the global loss of O2 from the oceans, or �??deoxyenation�?� and for detecting changes in ocean ventilation and production associated with warming-induced stratification that may influence future deoxygenation. The measurement may enable improved atmospheric inversions that take account of processes internal to the ocean influencing carbon dioxide. The measurements have strong synergistic relationship to measurements by the carbon cycle group of the NOAA Global Monitoring Division, the Argo float program, to measurements made as part of the HIAPERS Pole-to-Pole (HIPPO) mission to survey the distribution of long-lived atmospheric tracers related to carbon dioxide, and to the Scripps CO2 program. The primary proposed activity involves sustaining ongoing time series at a global array of nine stations extending from the Arctic to the Antarctic along a (mostly) Pacific transect. It is proposed that three new sites be added to the flask network. Two of these new sites (Barrow and Macquarie Island) will sustain time series initiated by the Princeton atmospheric O2 program which would otherwise end in January, 2010 because of the planned termination of the Princeton O2 program. A third new site (Greenland Summit) is proposed based on its strategic location and the ease at which logistical support is provided from within the U.S. An integrally related activity involves the assessment and reduction of systematic errors which may impact the ongoing measurements or the merging with these measurements with measurements of other programs. The propject supports interpretive activities related to detecting and reporting such errors. Specifically, the project supports activities to reduce errors, and enables the Scripps O2 program to continue its central role in an international intercalibration effort for O2 measurements, as endorsed by the World Meteorological Organization. Finally, the project supports collaborative interpretive activities with investigators at other institutions to develop methods for incorporating O2/N2 measurements into atmosphere/ocean inversions for detecting trends in land and ocean sinks on decadal time scales.