Presenter: Eleanor Bates (University of Hawaii)

Description:
Constraining the residence time of iron and other bioactive trace metals in the surface ocean is critical for understanding their temporal variability. Export through sinking particles is the primary output of trace metals from the surface ocean, but rarely quantified directly. We deployed trace metal clean particle interceptor (PIT) sediment traps at 150 m on Hawaii Ocean Time-series cruises in the North Pacific subtropical gyre on a near-monthly basis throughout 2021. The flux of labile iron peaked in May along with Al, suggesting an increased deposition of aerosol iron, but was surprisingly steady throughout summer and winter. This corresponded to an iron turnover time on the order of 2 – 4 months in both seasons. We also observed large seasonality in Ni fluxes reaching a maximum in June that might be caused by increased need for superoxide dismutase metalloenzymes in summer. Export fluxes and turnover times for several other metals will also be presented.