Award: OCE-1736677

In this study we collected seawater samples in a transect across a broad swath of the Pacific Ocean, from the surface to the seafloor. Samples were filtered so that each seawater sample was divided into water that was truly dissolved, the large particles (>55 micrometers) and the small particles (1 to 55 micrometers). We then measured extremely rare forms of the elements thorium and protactinium in these different portions of the collected waters. Notably, we were able to measure the extremely low levels of these rare forms of these elements in the large particles. The Minnesota laboratory is currently the only laboratory in the world that makes these extremely sensitive measurements. These measurements in turn allow us to more fully characterize the processes discussed below. We and our collaborators have used these measurements to calculate the flux of airborne dust (from sites in Asia), the effects of ocean ridge hotsprings on the chemistry of that portion of the ocean, and the flux of carbon-bearing particles from the surface ocean to the seafloor. All of these calculations are part of the intellect merit of the project, that is the main scientific conclusions of our work. In terms of the broader impacts of our work, that is the ramifications of our work beyond the specific scientific findings, the latter finding is perhaps the most important in this regard. Knowledge of the flux of carbon to the deep ocean is critical to our understanding of the carbon cycle within the ocean and atmosphere, which, of course, involves carbon dioxide in the atmosphere, which in turn is important as carbon dioxide levels affect the earth's climate. Last Modified: 06/24/2023 Submitted by: R. Lawrence Edwards