Spatial variability and controls on the authigenic 10Be/9Be ratio in Arctic shelves and deep ocean sediments

The authigenic ¹⁰Be/⁹Be ratio retrieved from marine sediments is a promising proxy for reconstructing Arctic paleoceanography, particularly the interplay of riverine and marine influences on the extensive continental shelves and in deep basins. This study investigates the spatial variability of authigenic ¹⁰Be/⁹Be ratios in surface sediments from the Kara and Laptev Seas, tracing its variations from river mouths to the open ocean. Calculated ¹⁰Be/⁹Be ratios of the water column are compared with measured ratios in surface sediments to identify controlling factors such as reversible scavenging, co-precipitation, and water mass mixing. Results confirm that authigenic ¹⁰Be/⁹Be records the different water masses, with low ¹⁰Be/⁹Be on the shelves and increasing ¹⁰Be/⁹Be towards the deep sea. However, while sediments on the continental shelves faithfully capture the riverine ¹⁰Be/⁹Be signature, offsets emerge in deeper basins due to incomplete reversible scavenging and/or coprecipitation leading to lower authigenic ¹⁰Be/⁹Be in deep sea sediments compared to the local water column. This study highlights the potential of ¹⁰Be/⁹Be as a geochemical proxy for Arctic watermass mixing while emphasizing the complexity of interacting sedimentary and oceanographic processes influencing authigenic ¹⁰Be/⁹Be in Arctic Ocean sediments.