Award: OCE-1260376

Marine phytoplankton are important players in the global carbon cycle and facilitate the transfer of carbon dioxide between the ocean and atmosphere. They require trace amounts of metals such as iron, zinc, and copper that are present in very low concentrations in the ocean for growth. Changes in the supply and availability of these metals in marine waters can greatly impact phytoplankton productivity and community structure. Metal-rich dust particles from continents are suspended into the atmosphere during wind storms and are transported over the ocean where they fall to its surface and partially dissolve. This is a major pathway for delivery of trace metals to remote ocean regions; however, there are few observations of the supply and distribution of trace metals to ocean waters. We made high-resolution measurements of the concentrations of various trace metals and their stable isotopes across the North Atlantic along the CLIVAR section A16N in 2003 and 2013. We quantified changes in large-scale features in the particulate iron and dissolved and particulate aluminum distributions arising from mineral aerosol deposition on surface waters in the equatorial and sub-tropical North Atlantic. Increases in the particulate trace metal concentrations in these dust-driven features between the two occupations of A16N suggest that dust deposition likely increased by ~20% over the last decade. These observations of increased inventories of particulate iron and aluminum in the upper water column support recent work linking declining atmospheric aerosol loads over the North Atlantic during this time period to shifts in precipitation patterns, suggesting increased aerosol delivery to the surface ocean is occurring mainly due to wet deposition processes and highlighting the importance of accurate representation of dust deposition processes for modelling iron biogeochemistry in the ocean. Observations of ocean trace metal distributions and understanding of how they move through the marine environment allow us to include trace metal micronutrients in models of ocean biogeochemistry and marine ecosystems, thus improving our ability to predict how marine ecosystems will respond to future environmental changes. The ability to model and predict these dynamics is important for society to effectively respond to changes in ocean chemistry and productivity. This project has supported graduate students at the University of Washington. Last Modified: 07/12/2016 Submitted by: Joseph A Resing