Seafloor Phosphorus Weathering and Earth System Response to Geologic Perturbations

This project examines how phosphorus that is released during the reaction of seawater with basalt on the seafloor could help to explain why some time intervals in Earth’s past record caused animal extinctions and environmental change, while others do not. As a major nutrient, phosphorus is a critical element of strategic importance. Understanding how it is cycled in the oceans today and in the past is important for predicting long-term, future changes that can harm coastal fisheries. Studying how the supply of phosphate may have varied through time also clarifies its availability in rocks to support agriculture and protect the domestic food supply. Phosphorus plays an important role in controlling how much organic carbon is removed from the oceans. The burial of organic carbon from the oceans is one of the main levers that can dictate whether the Earth experiences a catastrophic or a minor environmental event in response to perturbations such as massive volcanic eruptions. However, the current picture of how phosphorus cycles through the ocean, and thus how it influences the cycling of carbon, may be oversimplified and thus motivates this project. To mechanistically link deep Earth processes to surface phosphorus cycling, this research combines modeling, proxies for environmental conditions, and case studies through Earth history to test the role of seafloor weathering on climate perturbations in the last ~500 million years. This project investigates (1) how seawater chemistry and mantle processes impact seafloor phosphorus weathering; (2) the impacts of the seafloor phosphorus weathering flux on phosphate availability; and (3) the role of phosphorus weathering in modulating the sensitivity to perturbation. The project will also advance scientific literacy and communication in carbon management, a growing geoscience career field. This will be accomplished through a new lab activity focused on enhanced rock weathering as a carbon sequestration strategy, and a course on the carbon economy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.