Geochemical Tracers of Arctic Ocean Processes: A Study of Gallium, Barium, and Vanadium

• Main Author: Whitmore, Laura M.
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2020
• Subjects: GEOTRACES; continental margin; shelf processes; trace elements; Biogeochemistry; Environmental Chemistry; Geochemistry; Oceanography; Arctic Ocean; North Atlantic; Sea ice
• Online Access: https://aquila.usm.edu/dissertations/1780; https://aquila.usm.edu/context/dissertations/article/2841/viewcontent/auto_convert.pdf

The Arctic Ocean is linked to the global oceans and climate through its connectivity with the North Atlantic Ocean and the regional thermohaline deep water formation sites. It’s also a region undergoing rapid environmental change. To inform the community of potential changes in geochemical and biogeochemical cycles, this dissertation addresses three dissolved geochemical tracers (gallium, barium, and vanadium) as indicators of Arctic Ocean processes. Gallium is tested as a replacement for nutrient-type tracers in an effort to deconvolve Pacific and Atlantic derived waters in the Arctic Ocean basins. These water masses carry different heat and salt content and can influence sea ice melt, buoyancy, and deep water formation; thus, the accurate assignment and quantification of these waters is critical. It is shown that use of dissolved gallium yields a more realistic separation of these water types than is provided by the nutrient tracers. In contrast to gallium, dissolved barium and vanadium distributions are substantially modified by regional margin processes. Yet, the two elements differ in their behavior on the shelf: shelf processes create a benthic source of barium and a sink for vanadium. More specifically, particle scavenging coupled with reducing shelf sediments appear to remove vanadium from the water column. The source of barium is less clear, but, in part, particulate formation associated with biological activity likely shuttles barium from surface waters to shelf bottom waters where dissolution of the particulate barium is a source. The influences of these processes are observed throughout the upper water column of the western Arctic Ocean and, to some extent, Arctic Ocean deep waters. Furthermore, this work is pertinent to questions related to the net effect of marginal basin shelves on oceanic V & Ba cycling, their isotopic balance, and how climate induced changes in shelf biogeochemical cycling will impact geochemical cycling.