Iron Protection, Removal, and Transport along Anoxic Margins and Impacts on the Open Ocean.

Oxygen is depleted in anoxic waters of the world ocean. Often iron limits primary production along anoxic coastal waters, where iron cycling is complex and not well understood. In this project, researchers from the University of California Los Angeles (UCLA) will investigate iron cycling and transport in the anoxic waters in the Eastern Tropical South Pacific (ETSP). This is an area where many ocean chemistry measurements were made by the 2013 US GEOTRACES cruise. This project will also examine the impacts of iron on the subtropical Pacific productivity. The researchers aim to understand: (1) the formation, maintenance, and transport the iron plume, and (2) the impact of anoxic iron cycling on the biogeochemistry of the tropical and subtropical Pacific Ocean. This project will improve our ability to detect and interpret biogeochemical variations in a major region of the world ocean. Researchers from UCLA will investigate iron cycling across many physical and chemical gradients in the ETSP, where the cycles of iron, oxygen, nitrogen, and carbon are coupled. They will test the importance of Fe release from benthic sediments and sinking particles. They will also test the idea that organic matter protects dissolved iron in the water column from being removed. Finally, they will test the importance of ocean circulation in iron transport and cycle. These tests will be carried out by developing and analyzing a series of simulations with an eddy-resolving model of the iron cycle that represents the important processes and comparing them against observations. When the model is configured to best explain observations, that model will be used to explore the importance of iron in large scale primary production, oxygen distribution, and nitrogen-containing gases. The configured model will be help the larger community better equipped to study iron cycling in the ocean. 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.