Award: OCE-1658380

This project involved using a new global-scale dataset of ocean measurements of dissolved iron and three metal isotopes (230Th, 232Th, and 231Pa). Iron is a key nutrient in the oceans and is often found a low enough concentrations in surface waters to limit the growth rates of the phytoplankton (the ocean "plants" that carry out photosynthesis). Thus, the availability of iron is important to know as it can affect marine ecosystem photosynthesis rates (also called primary production), which forms the base of ocean food chains. Iron is removed from the oceans through uptake by biology and to the sea floor mainly through sinking organic matter when the iron containing organisms have died. Iron is unusual for nutrients, in that there a second process removing iron from the oceans, known as particle scavenging. Iron has a strong tendence to stick to sinking particles that it encounters. The sinking particles then remove the iron to the sediments. Each of the metal isotopes are also subject to removal by particle scavenging. We modified an existing Earth System Model to simulate dFe and the three isotopes. Then we used the extensive new ocean measurements from the GEOTRACES program to study particle scavenging in the oceans, and then to improve the model representation of particles scavenging. The result is an enhanced capability to simulate ocean iron distributions more accurately. Thus, the ESM will be better able to predict what will happen to iron and primary production in the future due to the impacts of climate change. Last Modified: 09/08/2022 Submitted by: Jefferson Moore