Description: Dinoflagellate cysts have been investigated in surface from the Norwegian-Greenland Sea and short sediment cores Norwegian Sea spanning the last 15,000 years. sediments from the The distribution of single species and assemblages is related to the bathymetry and oceanography of the Norwegian-Greenland Sea. Oceanographic fronts can be recognized in the distribution of species and assemblages. Round protoperidinoid cysts, MuZtispinuZa minuta s.l. and HaZodinium spp., characterize the assemblages from the East Greenland Shelf. Nematosphaeropsis Zabyrinthus and ?Impagidinium paZZidum dominate the assemblages in the central leeland and Greenland Seas. Operculodinium centrocarpum is important in the marginal area of the Arctic domain and dominates clearly the assemblages from the Norwegian Sea. Assernblages from the shelf of north leeland are marked by cysts of Peridinium faeroense. The distribution pattern of single species and assemblages reveals that relatively warm north Atlantic waters only pass through the Faeroe Shetland Canal into the Norwegian-Greenland Sea and further · up into the eastern Arctic Ocean and the Barents Sea. In the southern Norwegian Sea the Atlantic water masses are already modified by advection of surface waters from the North Sea. The development of the Norwegian current has been reconstructed by means of dinoflagellate cysts since termination r •. North Atlantic water masses have almost always influenced the surface water masses in the last 15,000 years. Since ca. 12,000 to 13,000 BP, the influence of warmer North Atlantic waters increased significantly in the NorwegianGreenland Sea. The modern circulation system was established around 10,000 BP. First, the Norwegian current was cooler and less saline, and then obtained its modern hydrographic properties around 6,000 to 7,000 BP. A slight change towards cooler conditions is documented in the western marginal areas in the last 2,000 to 3,000 years. Changes in the oceanography of the Norwegian-Greenland Sea must be related to modifications in the water masses and the circulation system of the entire North Atlantic. The discontinous influx of meltwater may have been an important factor for changes in the oceanography and the ecological conditions.

Description: Numerous studies have addressed the possible existence of large floating ice sheets in the glacial Arctic Ocean from theoretical, modelling, or seafloor morphology perspectives. Here, we add evidence from the sediment record that support the existence of such freshwater ice caps in certain intervals, and we discuss their implications for possible non-linear and rapid behaviour of such a system in the high latitudes. We present sedimentary activities of 230Th together with 234U/238U ratios, the concentrations of manganese, sulphur and calcium in the context of lithological information and records of microfossils and their isotope composition. New analyses (PS51/038, PS72/396) and a re-analysis of existing marine sediment records (PS1533, PS1235, PS2185, PS2200, amongst others) in view of the naturally occurring radionuclide 230Thex and, where available, 10Be from the Arctic Ocean and the Nordic Seas reveal the widespread occurrence of intervals with a specific geochemical signature. The pattern of these parameters in a pan-Arctic view can best be explained when assuming the repeated presence of freshwater in frozen and liquid form across large parts of the Arctic Ocean and the Nordic Seas. Based on the sedimentary evidence and known environmental constraints at the time, we develop a glacial scenario that explains how these ice sheets, together with eustatic sea-level changes, may have affected the past oceanography of the Arctic Ocean in a fundamental way that must have led to a drastic and non-linear response to external forcing. This concept offers a possibility to explain and to some extent reconcile contrasting age models for the Late Pleistocene in the Arctic Ocean. Our view, if adopted, offers a coherent dating approach across the Arctic Ocean and the Nordic Seas, linked to events outside the Arctic.