Anthropogenic Asian Aerosols provide Fe to the North Pacific

Paulina Pinedo-Gonzalez1, Nicholas Hawco2, Randelle M Bundy3, Virginia Armbrust3, Michael J Follows4, B. B. Cael5, Angelicque E White6, Sara Ferrón6, David M Karl6 and Prof Seth John7, (1)Lamont -Doherty Earth Observatory, Geochemistry, Palisades, NY, United States, (2)University of Southern California, Earth Sciences, Los Angeles, CA, United States, (3)University of Washington, School of Oceanography, Seattle, WA, United States, (4)Massachusetts Institute of Technology, Cambridge, MA, United States, (5)University of Hawaii, Department of Oceanography, Honolulu, United States, (6)University of Hawaii, Department of Oceanography, Honolulu, HI, United States, (7)University of Southern California, Department of Earth Sciences, Los Angeles, CA, United States
Iron is a globally important micronutrient which is known to limit phytoplankton productivity in much of the world ocean. The deposition of mineral dust in aerosols is considered one of the primary sources of Fe to the surface ocean, yet recent work has suggested that anthropogenic processes may contribute to aerosol Fe. Atmospheric models generally reproduce similar patterns and quantities of Fe deposition to the oceans, but they differ greatly on whether anthropogenic Fe is a significant source of Fe to the oceans, with estimates of the fraction of soluble Fe delivered from anthropogenic emissions ranging from insignificant to supplying well over half of the global supply of aerosol Fe. This study presents results from a field campaign in 2017 following a latitudinal transect at 158° W from 21° to 42° N in the North Pacific. Iron isotope data, with high-resolution analyses of other metals, show the first in situ evidence of anthropogenic Fe in seawater. This suggests that anthropogenic fossil fuel burning may be delivering Fe to the iron-limited North Pacific, impacting phytoplankton productivity and carbon cycling, changing our understanding of how anthropogenic fossil fuel combustion affects the global oceans.