Project: Collaborative Research: GEOTRACES Arctic Section: Nd isotopes and REEs in the Arctic

NSF Award Abstract:
In this project, investigators participating in the 2015 U.S. GEOTRACES Arctic expedition will measure neodymium isotopes and rare earth elements in seawater, sediment, and particulates collected from the western Arctic Ocean. In common with other national initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. Neodymium and rare earth elements are oceanographic tracers, and data from this research will provide benchmarks for other trace element and isotope studies to better understand their cycles and how future environmental changes will impact this important ocean basin. The project will support the training of undergraduate, graduate, and post-doctoral researchers, and results will be disseminated via public outreach activities.

Neodymium (Nd) isotopes are tracers of water mass sources, transport and mixing, and rare earth elements (REEs) show systematic fractionations during environmental processes. Together they provide a powerful tool for analyzing provenances and processes in the oceans that reflect the changing environmental controls on the distribution of trace elements and their isotopes (TEIs). Inherent logistical difficulties make the Arctic Ocean especially scarce in TEI data (including Nd isotopes and REE concentrations), which hinders understanding and application of these tracers. In this study, researchers will examine Nd and REE concentrations in seawater, sediment, and particulate samples collected in the western Arctic Ocean, with the aim of (1) assessing Arctic circulation and water mass mixing in light of Nd isotopes and REEs; (2) attempting to quantify particle-dissolved exchanges of TEIs and; (3) using Nd isotopes and REEs to characterize the sources, sinks and exchanges of TEIs. It is expected that through improved understanding of the Nd isotope and REEs tracers, scientists will be able to relate these findings to other TEIs and to the broader understanding of Arctic oceanographic change in the past, present, and future.