The Arctic and subarctic Pacific Ocean is experiencing rapid change as a result of climate warming and associated feedbacks (Grebmeier et al., 2006;Gregg et al., 2003;Serreze et al., 2007). The northeastern Pacific Ocean and the Bering Sea are characterized as high nutrient, low chlorophyll (HNLC) regions due to limited iron (Fe) inputs. Global satellite-based measurements of primary production suggest a large decrease in the North Pacific region (−9.3%) between the early 1980s and the early 2000s, associated with increasing sea surface temperatures and decreasing terrestrial dust deposition, thus enhancing this region's HNLC status (Gregg et al., 2003). Climate change may impact nutrient cycling by affecting sources and bioavailability of Fe and macronutrients to pelagic phytoplankton (e.g., Aguilar-Islas et al., 2008;Kipp et al., 2018). There also may be changes in the seasonality of nutrient deposition, altering the relevance and impact of different terrestrial nutrient sources.

Industrial activities release aerosols containing toxic metals into the atmosphere, where they are transported far from their sources, impacting ecosystems and human health. Concomitantly, long-range-transported mineral dust aerosols play a role in Earth’s radiative balance and supply micronutrients to iron-limited ecosystems. To evaluate the sources of dust and pollutant aerosols to Alaska following the 2001 phase-out of leaded gasoline in China, we measured Pb-Sr-Nd isotopic compositions of particles collected in 2016 from snow pits across an elevational transect (2180–5240 m-a.s.l) in Denali National Park, USA. We also determined Pb flux and enrichment from 1991–2011 in the Denali ice core (3870 m-a.s.l). Chinese coal-burning and non-ferrous metal smelting account for up to 64% of Pb deposition at our sites, a value consistent across the western Arctic. Pb isotope ratios in the aerosols did not change between 2001 and 2016, despite the ban on lead additives. Emissions estimates demonstrate that industrial activities have more than compensated for the phase-out of leaded gasoline, with China emitting ∼37,000 metric tons year –1 of Pb during 2013–2015, approximately 78% of the Pb from East Asia. The Pb flux to Alaska now equals that measured in southern Greenland during peak pollution from North America.

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