Relative terrestrial exposure ages inferred from meteoric ¹⁰Be and NO₃⁻ concentrations in soils along the Shackleton Glacier, Antarctica

Abstract. Modeling studies and field mapping show that increases in ice thickness during glacial periods were not uniform across Antarctica. Rather, outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced the greatest changes in ice thickness. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, thereby providing a record of past ice sheet behavior. We collected soil surface samples and depth profiles every 5 cm to refusal (up to 30 cm) from eleven ice-free areas along the Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet (EAIS) and measured meteoric ¹⁰Be and NO₃⁻ concentrations to calculate and estimate surface exposure ages. Using ¹⁰Be inventories from three locations, calculated maximum exposure ages range from 4.1 Myr at Roberts Massif near the Polar Plateau to 0.11 Myr at Bennett Platform further north. When corrected for inheritance of ¹⁰Be from prior exposure, the ages (representing a minimum) range from 0.14 Myr at Roberts Massif to 0.04 Myr at Thanksgiving Valley. We correlate NO₃⁻ concentrations with meteoric ¹⁰Be to estimate exposure ages for all locations with NO₃⁻ depth profiles but only surface ¹⁰Be data. These results indicate that NO₃⁻ concentrations can be used in conjunction with meteoric ¹⁰Be to help interpret EAIS dynamics over time. We show that the Shackleton Glacier has the greatest fluctuations near the Ross Ice Shelf while tributary glaciers are more stable, reflecting the sensitivity of the EAIS to climate shifts at TAM margins.