Abstract

Over the last century, the supply of Pb by anthropogenic pollution has strongly exceeded the natural supply to the atmosphere, altering its cycling and resulting in serious human health consequences, and making its way into the oceans. The Arctic Ocean, while remote, has not been isolated from the impacts of Pb pollution. Over the past decade, observational campaigns associated with the GEOTRACES program have greatly expanded our knowledge of Pb cycling in the Arctic Ocean and have identified that at present, dissolved Pb (dPb) concentrations in the Arctic Ocean are considered low. Nevertheless, Pb isotope signatures suggest that anthropogenic pollution impacts the Arctic Ocean. Building on the new wealth of observations, we developed the first three-dimensional model simulating dPb in Inuit Nunangat, the Western Arctic Ocean, to assess our current understanding of Pb cycling, quantify the role of anthropogenic pollution, and to use dPb as a tracer of circulation of Atlantic and Pacific water masses. With simulations from 2002-2021, we find that current and historical anthropogenic pollution account for at least 28% of dPb addition to the Western Arctic Ocean. Advected water from the Pacific and North Atlantic Oceans convey elevated pollution-derived dPb concentrations to the Arctic and play a key role, contributing 43% to the annual dPb budget. Lastly, using dPb as tracer, we track the seasonal extension of warm Atlantic Water along the West Greenland shelf where it is a potential source of heat to marine-terminating glaciers, and we trace occasional dense overflows of Atlantic Water into the deep Baffin Bay interior.