Mass Spectrometric Measurements of 231 Pa and 230 Th in the Water Column of the Tropical Atlantic: Evaluation of Water Mass Ventilation Ages and Boundary Scavenging

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ABSTRACTOCE-9811260One of the classical problems of oceanography is determining the pathways and velocities of the deep circulation. Geochemical tracers of various types have been used to tackle this problem, but each of them seems to raise new questions whenever they are applied. In this project, researchers at the Woods Hole Oceanographic Institution will continue development of a new analytical technique for measuring 230Th and 231Pa in small volumes of seawater and propose to apply the technique to the estimation of ventilation ages of deep water (i.e., a back-calculation of the time when the water mass in question was in contact with the atmosphere before downmixing). Besides studies with Deep Western Boundary Current (DWBC) water, they will also apply the technique to samples from different water masses collected on an equatorial Atlantic transect in collaboration with other colleagues who will provide comparative chlorofluorocarbon (CFC) data. The combination of 230/231 with 3He/3H, an important older technique, and/or CFC data is expected to clarify the impact of mixing and source water isotopic signature on calculated ventilation ages.