Glacial Dust Surpasses Both Volcanic Ash and Desert Dust in Its Iron Fertilization Potential

The subarctic Pacific Ocean and Bering Sea comprise the second‐largest high nitrate, low chlorophyll region in the world, where primary production is limited by the availability of iron (Fe). To estimate the potential impact of different terrestrial aerosol Fe sources on marine ecosystems, we performed a suite of laboratory assessments following established protocols, including: (1) leaching with Milli‐Q water, (2) sequential extractions, (3) complete acid digestions, (4) X‐ray diffraction, and (5) grain size analysis. Measurements were performed on 20 fine‐grained (