Maintenance of Preindustrial Atmospheric pCO2 Levels: Recalibration of a Carbon Isotopic Paleobarometer and PCO2 Mapping of the Late Quaternary Global Ocean

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The carbon-isotopic compositions of long-chain alkenones will be compared to those of coexisting foraminiferal carbonates in representative in representative ocean waters for which the concentration of dissolved carbon dioxide is also known. The objective will be to examine relationships between carbon-isotopic fractionations and CO2 levels, thus calibrating a "CO2 paleobarometer." In cold, high latitude waters, both suspended and sinking materials will be examined in materials collected during the JGOFS North Atlantic Bloom Experiment. Extensive data on the concentration and isotopic composition of dissolved CO2 are already available for that site. Alkenones and carbonates from Southern Ocean transects are also available, as are data on carbonate chemistry and isotopic composition. At lower latitudes with warmer surface waters, materials from the Eastern Equatorial Pacific JGOFS site will be examined. Alkenones will be obtained from suspended particulate organic carbon. Concentrations and isotopic compositions of dissolved CO2 are available from JGOFS reports and the isotopic composition of forams will be determined in the course of this work. Isotopic signals actually reaching the sediment water interface will be examined through analyses of materials from core tops in the Norwegian Sea (high-latitude, low-temperature site) and at the Eastern Equatorial Pacific JGOFS site.