What drives spatial variability in water-column beryllium-10 inventories?

Columbia University, New York NY

Investigators

Abstract

The distribution of naturally occurring radioactive isotopes in the ocean can be used to understand the movement of water and particles through the ocean. Measurements of these same isotopes in ocean sediments can, in turn, be used to reconstruct ocean processes back through time. The objective of this project is to measure the isotope beryllium-10 in samples of seawater, ocean particles, and sediment samples from the South Pacific Ocean. The samples were collected on previous oceanographic expeditions, which provides important context for interpreting the new data. The team will use the new data set to test the hypothesis that the distribution of beryllium-10 in the ocean is primarily controlled by particles settling through the ocean water column rather than by ocean circulation. Increased understanding of what controls the distribution of beryllium-10 in the ocean today will improve scientists’ ability to interpret past changes in sediment beryllium-10. The project will support two early career investigators and support development of broadly available earth science education programs. Co-located seawater, particle, and sediment core top samples will be selected from the South Pacific GEOTRACES expeditions GP16 and GP17-OCE. This beryllium isotope data set will provide new constraints on beryllium-10 particle scavenging and oceanic transport dynamics across a wide range of water masses and depositional environments, as well as the impact of these dynamics on the sedimentary beryllium-10 record. The data will be used to examine a variety of first-order questions in marine Be distributions, such as the magnitude and length-scale of boundary scavenging on basin-wide beryllium-10 distributions, potential sensitivity of Pacific beryllium-10 inventories to changes in Atlantic scavenging processes, and the relative impact of local scavenging versus boundary scavenging on sedimentary beryllium-10 deposition rates. In addition, the data will provide points of comparison for dynamic marine Be isotope models and refine scientists’ ability to interpret changes in beryllium-10 fluxes and 10Be/9Be ratios within the sedimentary record. 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.