An Optimal Approach for Assessment of Dust Fluxes to the Ocean Using 232 Th and 230 Th

Journal article

Plain Language Summary: Calculating how much desert dust lands on the ocean is important because the dust provides nutrients to tiny marine plants which controls their growth. Directly measuring dust falling on the ocean is difficult as the ocean is so large and mostly remote. One method to calculate dust input rates uses measurements of two types of the element thorium. A problem with this method is that the dust deposition rate appears to increase when measured at greater water depths—something that does not fit with dust landing on the ocean surface. We used equations and a known dust input to predict thorium concentrations at different ocean depths. We then used our predictions to back‐calculate the dust input using the existing calculation method. We found that the method calculates the correct amount of dust near the surface ocean, but at greater depths it produces dust deposition rates that are almost two times too large. This happens because the two types of thorium follow different pathways, and so do not spend the same amount of time in the ocean. We developed a new version of the method that removes the increases with depth and gives a better estimate of dust deposition.

Authors: Rowland, GH; Henderson, GM

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Global Biogeochemical Cycles
• Volume: 40
• Issue: 5
• Article number: e2026GB009099
• Publication date: 2026-05-12
• Acceptance date: 2026-04-28
• DOI: 10.1029/2026gb009099
• EISSN: 1944-9224
• ISSN: 0886-6236
• Language: English
• Keywords: dust; thorium; ocean; scavenging; flux; residence time