Sediment tracers support Arctic isolation from the Atlantic during glacials
A single peer-reviewed study in Communications Earth & Environment adds evidence supporting past isolation of the Arctic Ocean and Nordic Seas from the Atlantic. Beryllium isotope ratios in sediments differed sharply from intervals with stronger Atlantic-water influence. Researchers tested alternative explanations with a mass-balance model. The measurements add to a debate about ancient ocean circulation, while the precise geometry and timing of the proposed ice barriers remain uncertain.
Science··Evening
Glacial sediments show weaker Atlantic influence
A single peer-reviewed study in Communications Earth & Environment adds measurements supporting the interpretation that the Arctic Mediterranean, a region combining the Nordic Seas with the Arctic Ocean, became isolated from the North Atlantic during past glacials. Beryllium isotope ratios in sediments were substantially lower than Atlantic ratios during two glacial intervals. Different forms of beryllium were used to trace mixing between marine and river waters. Sediments from warmer interglacial intervals showed stronger Atlantic-water influence.[1]
Samples from different basins are compared
Researchers analysed 84 sediment samples and ten procedural controls used to monitor contamination. The seafloor sampling sites lay between 1,073 and 2,802 metres beneath the surface. Low isotope ratios appeared in sediments assigned to two distinct glacial intervals in the past. Similar results across sites with different depths and sedimentation conditions were assessed in terms of water-mass composition. Uncertainty in sediment dating limits the precision of the timing assigned to disconnection and renewed exchange.[1]
Scenarios interrupting inflow are tested
A mass-balance model compared reduced atmospheric beryllium input, closure of the Bering Strait and interruption of Atlantic inflow. The first scenario could not reproduce the observed depletion by itself, while Bering Strait closure increased the modeled ratio. Removing Atlantic inflow generated a stronger decline. The authors propose that extensive ice barriers may have interrupted water exchange. This interpretation concerns ancient ocean conditions; the study does not suggest that an equivalent barrier exists today.[1]
