Beryllium isotope variations recorded in the Ad´elie Basin, East Antarctica reflect Holocene changes in ice dynamics, productivity, and scavenging efficiency

Abstract

The Ad´elie Basin is a relatively small (~1600 km2), semi-enclosed continental shelf bathymetric depression located adjacent to the Wilkes Subglacial Basin, a basin underlying a sector of the East Antarctic Ice Sheet that contains ~3–4 m sea level equivalent of ice. Located within the Ad´elie Basin is a ~184 m thick laminated sediment deposit, the Ad´elie Drift, ideal for examining regional changes in ice sheet and ocean dynamics. Here, we examine the ratio of reactive beryllium-10 to reactive beryllium-9 ((10Be/9Be)reac) in a marine sediment core obtained from the Ad´elie Drift to assess these changes during the Holocene epoch (11.7 ka BP to present). The (10Be/9Be)reac record provides insight into changes in freshwater input, primary productivity, and scavenging efficiency, while removing the influence of particle size on 10Be concentration. During the early Holocene, (10Be/9Be)reac ratios indicate increased meltwater discharge from ca. 11.7 to 10 ka BP, as grounded ice retreated from the Ad´elie Basin and adjacent bathymetric highs. After ~10 ka BP, beryllium isotopes are influenced by scavenging efficiency and dilution controlled by ocean currents and accumulation rate, operating alongside meltwater input, suggesting there are additional factors to consider when using (10Be/9Be)reac as a proxy for ice shelf cover and glacial dynamics.