Early Pliocene Nordic Seas Palaeoceanography – Relation with Ocean Gateways

Tuesday, 16 December 2014
Stijn De Schepper1,2, Michael Schreck3,4, Kristina M Beck5, Gunn Mangerud5, Jens J Matthiessen3 and Bjørg Risebrobakken1,2, (1)Bjerknes Centre for Climate Research, Bergen, Norway, (2)Uni Research, Uni Research Climate, Bergen, Norway, (3)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (4)KOPRI Korea Polar Research Institute, Arctic Research Centre, Incheon, South Korea, (5)University of Bergen, Bergen, Norway
In the northern high latitude oceans, organic-walled phytoplankton is often the only microfossil group present in the sediment record that can be used for palaeoceanographic and palaeoenvironmental studies. Recently collected dinoflagellate cyst and acritarch records from the Norwegian and Iceland Seas reveal a wide-scale, major assemblage turnover including extinction of several taxa, disappearance of heterotrophic species and decrease in productivity around 4.5 Ma. These changes can most likely be attributed to a reorganization of the ocean circulation and can be interpreted as the establishment of a more modern-like Norwegian Atlantic Current and proto-East Greenland Current. The timing at around 4.5 Ma corresponds favorably to the shoaling of the Central American Seaway and northward flow of Pacific water via the Bering Strait into the North Atlantic, the latter being evidenced by the first arrival of Pacific molluscs in the Iceland (Tjörnes section). The changes in ocean circulation are not restricted to the Nordic Seas, with increased sediment accumulation at several North Atlantic drifts (e.g. Gloria and Eirik drifts) also illustrating important changes in the North Atlantic deep-water circulation.