Award: OCE-1736277

This project is part of a larger program called GEOTRACES (http://www.geotraces.org), which seeks to identify processes that control the distribution of trace elements in the ocean. As the fourth U.S. contribution to the international GEOTRACES program, the research cruise focused on the Pacific Ocean between Alaska and Tahiti (Pacific Meridional Transect or PMT). Our contribution to this effort was to measure a suite of naturally occurring radium isotopes. The main value of radium isotopes is that they can provide rates of important processes such as the input of trace elements to the oceans from ocean boundaries such as the land-ocean interface, deep-sea sediments, and hydrothermal vents. We made several key contributions to the GEOTRACES PMT program through our radium isotope measurements made in parallel with the major GEOTRACES trace elements. Much of our effort was focused on using radium-226 to better understand barium cycling in the ocean, which in turn will improve the use of barium as a proxy for past ocean productivity. We used a water mass analysis to separate ocean mixing sources of these elements from other processes affecting their distribution such as particle formation, particle dissolution, input from deep-sea sediments, and hydrothermal activity. This project contributed to gender and racial diversity in the marine sciences through the support of multiple graduate students (M.S., Ph.D.), a high school student, an undergraduate student, and a postdoctoral researcher. It also enhanced infrastructure for research through an international partnership with colleagues and students in France. Last Modified: 11/29/2021 Submitted by: Matthew A Charette