Dominance of benthic fluxes in the oceanic beryllium budget and implications for paleo-denudation records

Abstract

The ratio of atmosphere-derived ¹⁰Be to continent-derived ⁹Be in marine sediments has been used to probe the long-term relationship between continental denudation and climate. However, its application is complicated by uncertainty in ⁹Be transfer through the land-ocean interface. The riverine dissolved load alone is insufficient to close the marine ⁹Be budget, largely due to substantial removal of riverine ⁹Be to continental margin sediments. We focus on the ultimate fate of this latter Be. We present sediment pore-water Be profiles from diverse continental margin environments to quantify the diagenetic Be release to the ocean. Our results suggest that pore-water Be cycling is mainly controlled by particulate supply and Mn-Fe cycling, leading to higher benthic fluxes on shelves. Benthic fluxes may help close the ⁹Be budget and are at least comparable to, or higher (~2-fold) than, the riverine dissolved input. These observations demand a revised model framework, which considers the potentially dominant benthic source, to robustly interpret marine Be isotopic records.