Evolution of the central Nordic Seas over the last 20 thousand years

The deep and surface water paleoceanographic evolution of the central Nordic Seas over the last 20 thousand years was reconstructed using various micropaleontological, isotopic and lithological proxy data. These show a high spatial and temporal complexity of the oceanic circulation when compared with other records from the region. During early deglaciation a collapse of ice sheets surrounding the Nordic Seas released large amounts of freshwater that affected both the surface and bottom water circulation and significantly contributed to Heinrich stadial 1. During the Younger Dryas, the central Nordic Seas were affected by a last major freshwater plume which probably originated from the Arctic Ocean. When major ice rafting had ceased around 11 ka subsurface temperatures started to rise. However, Atlantic Water advection and subsurface temperatures reached their maximum in the central Nordic Seas later than along the eastern continental margin. That spatio-temporal offset is explained by a gradual re-routing and westward expansion of the Atlantic Water flow during times when the Greenland Sea gyre system became more steadily established. In the Greenland Basin, the Holocene thermal maximum ended c. 5.5 ka, and time-coeveal with an increase in sea-ice export from the Arctic. In the Lofoten Basin the cooling occurred later, after 4 ka, and together with a weakening of the overturning processes. The Neoglacial cooling was reached c. 3 ka, together with low solar irradiance, expanding sea ice and a slight decrease in deep convection. At c. 2 ka subsurface temperatures began to rise again due to an increasing influence of Atlantic Waters.