Lee et al. (2015) and Kim et al. (2024) observed that the deep waters of the Indian and Pacific Southern Ocean sectors have high ²⁰⁶Pb/²⁰⁷Pb ratios ~1.20, significantly higher than upper waters and those further north. It seems likely that this observation reflects the input of high crustal ²⁰⁶Pb/²⁰⁷Pb Pb/ Pb Pb from the Antarctic continent. In 2024, the RVIB Nathaniel B. Palmer sampled in the region of the Amundsen Sea from November 29, 2023 to January 28, 2024 covering both deep water sites and shallower sites on the continental margin and shelf (NSF sponsored GEOTRACES cruise GP17-ANT). We present dissolved Pb isotope data (0.2 µm Acropak-filtered) from samples from that cruise. Relevant processes that may affect Pb isotopes in this region include dissolved and adsorbed particulate Pb from glacial and sea ice meltwater, reversible exchange with glacial debris and biogenic particles, regional productivity patterns, Fe/Mn redox cycling on the continental shelf, and volcanic and anthropogenic inputs. We find that the upper waters have higher ²⁰⁶Pb/²⁰⁷Pb than deeper waters on the shelf. In the Dotson Trough, low externally-derived ²⁰⁶Pb/²⁰⁷Pb is seen in the inflowing deep waters on the eastern martin and high crustal ²⁰⁶Pb/²⁰⁷Pb is seen in the outflowing shallow waters. A high resolution circulation model by Pierre St Laurent shows that “tracer” particles introduced deep (700-800m) at the base of the glacial edge rise to the upper water column due to meltwater buoyancy and then disperse throughout the wider shelf in the upper 200m residing for a year or two in the “winter water” layer leftover from the deep winter mixed layer.

[1] Lee et al. (2015) Geochim. Cosmochim. Acta 170: 126-144.

[2] Kim et al. (2024) Trans. Am. Geophys. Union, OS23H-05