Recent change in organic carbon flux to Arctic Ocean deep basins: Evidencefrom acid volatile sulfide, manganese and rhenium discord in sediments

Evidence of recent large-scale change in redox conditions in Arctic Ocean b asin sediments is found in profiles of solid phase acid volatile sulfide (A VS), Mn, and Re. AVS occurs at 2.5-5.5 cm in sediment cores collected from all major Arctic basins implying that presently there is a sufficient suppl y of organic carbon (OC) to deplete O-2 and form sulfide. Be, which is mobi le under oxic conditions but precipitates under suboxic or anoxic condition s, is not found enriched in the sediments suggesting that AVS is a recent p roduct of enhanced OC fluxes. Estimated diffusion rates suggest that AVS pr oduction is recent and that a change from ode to anoxic diagenesis has take n place within the past 50 y. The most likely origin for such widespread ch ange is the ice climate, and we infer that reduction in ice cover over the past several decades has led to enhanced OC fluxes to the sea floor.