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Radium Isotopes as Tracers of Boundary Inputs of Nutrients and Trace Elements to the Coastal and Open Ocean

Lauren Kipp, Ph.D., 2018
Matthew Charette, Advisor

Nutrients and trace metals are vital for supporting life in the ocean, but the boundary processes that control the distributions of these elements are poorly constrained. Radium isotopes are well suited to studying inputs of elements from ocean margins, and in this thesis I have applied the quartet of radium isotopes to investigate boundary inputs, including seafloor hydrothermal vents, continental shelves, and rivers.
First, radium isotope ratios were used to constrain the age of hydrothermal plumes in the Atlantic and Pacific Oceans. These radium-derived ages were applied to determine the iron residence time in the Pacific plume, providing an important constraint on the hydrothermal delivery of iron to the deep ocean. Next, 228Ra was used to show that shelf inputs to the Arctic Ocean have increased over the last decade, implying that the fluxes of other shelf-derived materials are also increasing and could impact primary production in this basin. Radium isotopes also provided constraints on the ventilation times of intermediate waters and the residence times of deep waters in the Western Arctic. Finally, a study of the Mackenzie River illustrated the importance of deltaic and estuarine processing on the delivery of riverine solutes to the coastal Arctic Ocean.