US GEOTRACES GP17-ANT: Dissolved Gallium, Barium, and Vanadium as interface, process, and circulation tracers in the Amundsen Sea

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and isotopes in the oceans. By measuring trace elements and isotopes on coordinated expeditions, oceanographers can learn about processes that control their inputs, outputs, and movement through the ocean. The National Science Foundation is supporting a U.S. GEOTRACES sampling expedition in the Southern Ocean and Amundsen Sea in 2023-2024. This project will focus on the measurement of dissolved gallium, barium, and vanadium to infer several processes such as the distribution of different water types – like glacial meltwater or warm ocean water – sediment supply of trace elements, and the effects of biological productivity on metal cycling in this under-sampled region. The project will support an early career investigator and an undergraduate student researcher and results will be shared with the public through several planned outreach activities. Utilizing filtered seawater and sea ice samples, this study will use isotope-dilution and ICP-MS methodology to determine concentrations of dissolved gallium, barium, and vanadium. Leveraging distributions of dissolved gallium, barium, and vanadium in their relative ratios with other parameters of interest (e.g., iron and aluminum) this study will investigate: (1) how sea ice processes intersect with water column trace element cycling through material supply, uptake, and remineralization; (2) how local sedimentary processes (reductive versus non-reductive sediments) influence the regional distribution of trace elements; and (3) if a linear-mixing approach, with dissolved gallium in addition to historically used tracers, can be used to constrain circulation of different water types in this region. This study will thus assess the connectivity of Amundsen Sea waters to the off-shelf region, the influence of polynyas on geochemical cycles, and the relative supply of trace elements from terrestrial, cryosphere, sedimentary, and oceanic inputs. These points are particularly pertinent in the Amundsen Sea as a locus of rapid, climate-induced destabilization of the region’s ice sheets and since the Amundsen Sea has connectivity with the Ross Sea, where deep waters are formed, and the circumpolar current, a productive region that influences the chemistry of global water masses. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.