OPP-PRF: Investigating 2.5k Years of Human History and Atmospheric Transport in Greenland Ice Using High-Resolution Lead Isotopic Records

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Polar ice sheets and glaciers record changes in climate and the environment during recent decades, centuries, and millennia. Lead pollution found in cores extracted from polar ice sheets and glaciers reflects human activities, including mining and smelting related to early silver production, as well as coal, oil, and gasoline burning. Isotopic analyses of lead in glacier ice can be used to identify past changes in emission sources. Lead isotopes will be measured in five Greenland ice cores to identify and quantify changes in Northern Hemisphere anthropogenic emission sources during the past 2500 years and to evaluate linkages between these changes and historical events extending from antiquity to the present. These records have the potential to transform understanding of how events such as plague, social upheaval, warfare, and technological advancements in mining and smelting influenced human history. The investigator will serve as an instructor for the Interdisciplinary Graduate and Early Career Researcher Consilience Workshop on Ice Core Science and Natural Archives in Fall 2022 sharing techniques and preliminary results and will participate in other outreach activities focused on improving accessibility and inclusivity in STEM fields. Lead (Pb) isotopes will be measured in existing discrete meltwater samples collected from four previously analyzed ice cores (NGRIP2, NASAU, RECAP, and NUUS_2015), as well as a fifth core (Tunu_2022) to be collected and analyzed in 2022 as part of an ongoing NSF project (1925417). Recently developed methods allow isotopic measurements of 206Pb, 207Pb, and 208Pb with low uncertainties at concentrations as low as 0.05 ng g-1, making high-resolution analyses in ice cores feasible. Refinement of these new methods as part of the proposed research may further increase resolution and improve interpretive power by reducing required concentrations (down to 0.02 ng g-1) and measurement uncertainties of low abundance 204Pb. If successful, such 204Pb measurements would be among the first used to interpret polar ice records. The proposed measurements will improve resolution of pre-20th-century Pb isotopic records from ice, particularly those from antiquity and the medieval period, for which only a handful of values have been published. Evaluation will leverage collaborations between Desert Research Institute and ancient historians, archaeologists, and atmospheric scientists. The detailed Pb source apportionment resulting from this research will be used to evaluate the accuracy of atmospheric transport and deposition models widely used for ice core interpretation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.