A Persistent Norwegian Atlantic Current Through the Pleistocene Glacials

Changes in ocean-circulation regimes in the northern North Atlantic and the Nordic Seas may affect not only the Arctic but potentially hemispheric or even global climate. Therefore, unraveling the long-term evolution of the North Atlantic Current-Norwegian Atlantic Current system through the Pleistocene glaciations could yield useful information and climatological context for understanding contemporary changes. In this work, similar to 50,000km(2) of 3-D seismic reflection data are used to investigate the Pleistocene stratigraphy for evidence of paleo-oceanographic regimes on the mid-Norwegian margin since 2.58Ma. Across 33 semicontinuous regional paleo-seafloor surfaces similar to 17,500 iceberg scours have been mapped. This mapping greatly expands our spatiotemporal understanding of currents and iceberg presence in the eastern Nordic Seas. The scours display a dominant southwest-northeast trend that complements previous sedimentological and numerical modeling studies that suggest northward-flowing currents in the Norwegian Sea during the Pleistocene. This paleo-oceanographic study suggests that through many of the Pleistocene glaciations, the location of surface ocean currents in the Norwegian Sea and, by extension, the eastern North Atlantic, were broadly similar to the present. Plain Language Summary The bridging location of the northern North Atlantic Ocean and the Nordic Seas between low and high latitudes means that environmental changes in one region can potentially be transmitted on a hemispheric or global scale. The Norwegian Atlantic Current crosses this region, and in the present-day setting, it helps to bring heat up from the tropics and toward the Arctic. This heat exchange helps to keep the climate of NW Europe relatively mild. Over a longer time scale (e.g., the last 2.58 million years) the history of this current is poorly known, not least of all how it behaved through different ice ages. In this work we use evidence of floating icebergs in the Norwegian Sea to reconstruct the ocean currents that controlled the drift directions of the icebergs. This has shown that through many of the glacial periods in the last 2.58 million years, there is evidence for the Norwegian Atlantic Current still reaching high latitudes. This has important implications for understanding the main controls and stability of ocean currents in the region and how they may impact regional and global climate.