The Neodymium Isotope Fingerprint of Adelie Coast Bottom Water

Adelie Land Bottom Water (ALBW), a variety of Antarctic Bottom Water formed off the Adelie Land coast of East Antarctica, ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first dissolved neodymium (Nd) isotope and concentration measurements for ALBW. The summertime signature of ALBW is characterized by epsilon(Nd) = -8.9, distinct from Ross Sea Bottom Water, and similar to Weddell Sea Bottom Water. Adelie Land Shelf Water, the precursor water mass for wintertime ALBW, features the least radiogenic Nd fingerprint observed around Antarctica to date (epsilon(Nd) = -9.9). Local geology around Antarctica is important in setting the chemical signature of individual varieties of Antarctic Bottom Water, evident from the shelf water signature, which should be considered in the absence of direct wintertime observations. Plain Language Summary To understand the evolution of water masses back in time and elucidate the Southern Ocean's role in past climate change requires proxy data. Neodymium isotopes are commonly used but need to be better characterized in the modern ocean and especially where bottom water formation occurs. Adelie Land Bottom Water (ALBW) is a variety of Antarctic Bottom Water formed off the Adelie Land coast of East Antarctica. It ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first direct seawater analyses for Nd isotopes and concentrations in the Australian sector of the Southern Ocean. Our data reveal a distinctively unradiogenic signature of waters on the Adelie Land Shelf, precursor of ALBW, and show that the summertime signature of ALBW is distinct from Ross Sea Bottom Water and similar to Weddell Sea Bottom Water. Antarctic Bottom waters are not uniform around the continent and carry Nd isotope fingerprints characteristic of their formation area (local geology). This makes these water masses traceable back in time and is hence important for paleoceanography and for the study of past climate change.