Award: OCE-1658392

Iron is an important element that helps to sustain life in the ocean. Yet, it is very scarce in seawater, and the small amounts that are present are rapidly used by marine life living in the sunlit surface ocean. It is also difficult to measure the small amounts of iron in the ocean, making it difficult to understand what factors are responsible for variations in the distribution of this important element in the ocean. An ongoing observational program called GEOTRACES was designed to increase the number of measurements of dissolved iron and other so-called ?trace metals? (metals that occur in very small or ?trace? concentrations) in the ocean. This program has greatly increased the number of measurements of dissolved iron in the ocean in the last decade, and has measured iron concentrations in many different ocean environments throughout the world. Our project was designed to take advantage of the large number of new iron observations from the GEOTRACES program. The goal of our project was to build computer models to describe how iron gets into the ocean, how it is distributed across the ocean, and ultimately how it is removed from the ocean. These kinds of models will help scientists to better understand what factors are affecting how much iron is in the ocean, and where it is most concentrated. Ultimately, this can help us understand how the supply of iron to the ocean might change in the future, and how sea life will be affected by this. One of the big parts of this project involved making a new and improved model the describes the ocean currents in the deep sea. We used observations of chemicals emitted from hydrothermal vents (underwater volcanoes) on the sea floor to help us better represent the deep sea currents in a computer model of the ocean circulation. Since these seafloor hydrothermal vents are a major source of iron to the ocean, we used that computer model to simulate where the iron that comes out of those vents is going to go. We found that a lot of it sticks onto sinking particles in the ocean and gets carried down into the deepest parts of the sea. Luckily, these really deep waters eventually come back to the surface in the Southern Ocean, and they can bring some of this iron from hydrothermal vents into the sunlit zone where it can help sustain marine life. This project is part of a bigger collaboration that is also going to investigate the iron that gets into the ocean from windblown dust, and from seafloor sediments. We are building a computer model and comparing it to the GEOTRACES iron observations to get a good understanding of where all the iron is coming from, and how these different sources of iron could affect the sea life. When we finish building this new model, we are going to implement it in a big climate model to see if these iron supplies might change in the future, and how that could affect marine life. This project has also helped to train a new generation of oceanographers by supporting the career of a postdoctoral scholar. We have also used funding from this project to develop and promote new computational tools for oceanographers to use. This project helped us to make our computer model of the ocean currents publicly available, and to hold a workshop to train other oceanographers in our field how to use this model to study the distribution of elements in the ocean. As oceanographers make more observations of life-sustaining elements such as iron in the ocean, and models are developed to explain those observations, we are learning more about the processes that drive life in our oceans. This knowledge will help humans to be better stewards of the blue planet on which we live. Last Modified: 10/29/2020 Submitted by: Timothy Devries