Significance Anthropogenic lead (Pb) is widespread and far reaching in the environment. However, it was thought that western Arctic Ocean seawater was pristine based on low dissolved Pb and proxy data. By measuring Pb isotopes on seawater with extremely low concentrations, this study shows that anthropogenic Pb is pervasive in western Arctic Ocean seawater, and much of the dissolved Pb is from remobilization of previously deposited aerosols from the high-Pb emission period of the 20th century. Thus, historic Pb pollution still impacts Arctic seawater, and accelerated melting of permafrost and ice and increased coastal erosion may enhance this remobilization. This study also demonstrates that dissolved Pb isotopes are a sensitive tracer of contaminant and particulate sources in Arctic seawater.