Future Applications of 234Th in Aquatic Ecosystems

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ABSTRACTOCE-0354757One of the biggest problems facing the oceanographic community today is a lack of knowledge regarding the spatial and temporal variability of particle export from the upper ocean. Over the past decade, Thorium-234 has been increasingly used as a technique to examine particle fluxes on timescales of days to weeks. Although a powerful tool, there are still a number of questions regarding the interpretation of 234Th disequilibrium. These questions concern 234Th speciation, reactivity, sample collection and analysis, and modeling. These issues introduce uncertainty and debate regarding the appropriateness of using 234Th as an in-situ tracer for the export of particulate organic carbon (POC) and associated biogenic and other particle reactive elements. Understanding these issues is of paramount importance if 234Th is to be successfully used as a proxy for particle cycling and flux by the oceanographic community. With support through this award from NSF, international experts in the collection and application of 234Th in aquatic ecosystems will come together in a workshop to discuss and define current 234Th issues and to devise a coherent strategy as to how to resolve them. Included in this group are several renowned radiochemists and geochemists not directly involved in 234Th research, to provide outside perspective into the current status and future directions of the field. The deliberations of four working groups will form the basis for discussion at the meeting. Their thematic areas include (1) new methodologies and techniques, (2) modeling and synthesis, (3) 234Th/C ratios and their interpretation, and (4) 234Th speciation in seawater.The results of this workshop will be disseminated to the wider community via an overview article in EOS and a series of working group articles.