Beryllium isotope record from the Sabrina Coast details ice sheet dynamics related to upwelling deep water from 350,000 years ago to the present

Along the Sabrina Coast, extensive canyon systems, mapped in high resolution during the RV Investigator voyage IN2017_V01, cut through the continental slope and rise. These essential conduits for transporting water masses to and from the continental shelf provide a pathway for upwelling warm deep water (e.g., Donda et al., 2024). Beryllium isotope ratios (¹⁰Be/⁹Be) can be used as an indicator of upwelling deep water due to differing beryllium concentrations in surface water, deep water (von Blanckenburg et al., 1996; Jeromson et al., 2024), and meltwater from continental ice shelves (Yokoyama et al., 2016, Valletta et al., 2018) in that deep ocean water beryllium isotope ratios are higher than that sourced from continents (Wittmann et al., 2017, Jeromson et al., 2024). Records of beryllium isotope variability from the Southern Ocean are scarce, and primarily encompass the Last Glacial Period through the Holocene (Sjunneskog et al., 2007, Yokoyama et al., 2016, Behrens et al., 2022, Sproson et al., 2022) or focus on spatial variability (White et al., 2019, Jeromson et al., 2024). 

Here, we present the longest known beryllium isotope record from the continental rise, extracted from between two canyons off the Sabrina Coast. The site is adjacent to the Sabrina Subglacial Basin, the Totten Glacier, and Moscow University Ice Shelf. This 16 m-long beryllium isotope record elucidates the relationship between the Antarctic Ice Sheet and upwelling Circumpolar Deep Water from 350,000 years ago to the present. Glacial periods exhibit low beryllium ratios, indicating a greater contribution of beryllium from the continent due to the more proximal location of the Antarctic Ice Sheet to the study site and absence of upwelling deep water. The balance shifts during interglacial periods, and higher beryllium ratios indicate a greater presence of upwelling deep water through canyons along the continental slope and rise. The data presented here demonstrates the usefulness of beryllium isotopes in determining periods with higher ‘continental’ or ‘oceanic’ beryllium contribution along the Antarctic continental rise, which may be used as a proxy for ice sheet advance or retreat as it relates to upwelling Circumpolar Deep Water.