Dating the Anthropocene in deep-sea sediments: how much carbon is buried in the Irminger Basin?

Abstract

Evaluation of biogeochemical processes in Anthropocene deep-sea sediments require accurate dating techniques. Here we show the results of an approach using high resolution low level background gamma spectrometry with two simultaneous hyper-pure germanium (HPGe) detectors. The quantitative role of the deepest zones (>3000 m depth) of the Irminger Basin (Subpolar North Atlantic Ocean) as a carbon sink during the Anthropocene is evaluated combining a chronology based in the natural radionuclide 210Pb with sedimentological analysis and elemental composition. The average sedimentation rate of the central Irminger is 1.28 ± 0.18 mm·yr−1, with a mean weighted flux to the sediment for inorganic and organic carbon of 46 ± 15 g·Cinorg·m−2·yr−1 and 8 ± 1 g·Corg·m−2·yr−1. The biogenic fraction of the mass flux is increased since the XXth century. The contribution of the deepest zones of the Irminger Basin to the Anthropocene carbon sequestration in the North Atlantic Ocean is considerable at basin-scale.