Beryllium isotope signatures of ice shelves and sub-ice shelf circulation

Be isotopes are a useful tracer of sediment source and transport pathways but have not been widely tested in glacio-marine environments. We measured Be isotopes in a range of depositional environments from open marine, sub-ice shelf and subglacial settings throughout Prydz Bay, one of Antarctica's largest ice drainage systems. We find that strong sub-ice shelf and bottom current circulations can advect ¹⁰Be-rich open marine sediments into an ice shelf cavity, and ¹⁰Be-poor terrestrial sediments onto the continental shelf at the ice shelf outflow, meaning that ¹⁰Be concentrations reflect sub-ice shelf circulation patterns rather than depositional environment. However, HCl-extractable ¹⁰Be/⁹Be ratios can provide a more robust discrimination of sediment deposited in open marine and sub-ice shelf settings. Thus, Be isotopes are a useful tracer of both environmental setting and sub-ice shelf circulation strength in both modern and paleo-ice sheet margins.