SGER: The Utility of the 227Ac and 228Ra Isotope Pair as Tracers of Upwelling Intensity and Lateral Transport

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AbstractOCE-0120385Obtaining a suitable tracer that can estimate lateral mixing of shelf waters into the open ocean or can determine the intensity of upwelling in response to ENSO forcing has been hindered by (1) the timescale of these processes (decadal), (2) the fact that simple mixing of radioisotopes with older water masses can result in an aging artifact, and (3) the effects of multiple endmembers. Based on some preliminary results, a PI from the University of South Carolina-Columbia has demonstrated that the activity ratio of 228Ra/227Ac shows great promise as a tracer of lateral mixing processes in the ocean. Because this proposed application is so novel, the PI will use SGER funds to improve the analytical technique for determining these radionuclides and the parent isotopes, as well as carry out additional field tests to verify the utility of this approach. The PI also plans to develop an in-line cartridge system that can be installed on ships of opportunity thereby increasing the spatial distribution of ex228Ra/ex227Ac activity ratios of surface waters to determine the stability of lateral mixing rates on timescales of years to decades.