Glaciations in the Barents Sea area

The main objective is improved knowledge of the Late Cenozoic evolution of the Barents Sea area. The following results have been achieved: 1) A new, consistent high-resolution stratigraphic and palaeo-environmental framework has been established, based on biostratigraphy and paleomagnetic data from ODP boreholes on the Yermak Plateau and new regional high-resolution seismic data. This indicates that the base of the ODP holes is ca 6 million years, 2.5 million years older than previously assumed. Sedimentological and geochemical data indicate that 4 millions years ago terrigenous sediment supply and sources changed abruptly in response to a regional tectonic uplift event. Probably this event, together with contemporary uplift and tilting along the northwestern European continental margin preconditioned the landmasses for glacial buildup during intensification of the Northern Hemisphere Glaciation. The results further suggest that the final deepening/widening of the Arctic-Atlantic gateway, the Fram Strait, between 6.5 and 5 million years ago likely contributed to the intensification of the North Atlantic thermohaline circulation, increased moisture and build-up of glacial ice both in Scandinavia and the sub-aerially exposed Svalbard/Barents Sea, culminating in the first large-scale coastline-shelf edge glaciations at ~2.75 million years ago. 2) A first order numerical 3D thermomechanical model has been used to simulate the growth and sensitivities of the Eurasian ice-sheet complex (EISC) up to the last Glacial Maximum (LGM). The model experiments were kick-started from initial isostatically-adjusted topography, sea level and ice extent of the marine isotope stage MIS3 for ~37.200 years ago, which represent a relative warm interglacial climate with small terrestrial-based ice sheets over Fennoscandia, Svalbard and terrestrial areas in the Barents Sea. The maximum EISC was an amalgamation of three distinctly different ice sheet types ? the marine-terminating Celtic Ice Sheet, the large, terrestrial based Fennoscandian Ice Sheet, and the marine-based Barents (and Kara) Sea Ice Sheet. Both modeling and empirical results show asynchronous growth and decay of the three ice sheets of the Euasian ice sheet-complex. The north-eastern sector of EISC, in north-western Russia reached its maximum extent when deglaciation had started in the west. The peaks in total ice area (4.8 million km2) and volume (7.3 million km3) occured at 19.000 and 19.500 years ago respectively, relatively late compared to the global LGM timeframe. The late timing of peak glaciation reflects the relatively slow incursion of the Fennoscandian Ice sheet into continental Europe along its eastern margins, and is reflected in a late eastward migration of ice divides. 3) Areas of streaming ice flow are linked to high erosion potential, and reflected in mapped areas of high cumulative potential glacial erosion from MIS3 until the last glacial maximum. Westwards ice-streaming in the central Barents Sea, perpendicular to Bjørnøyrenna is a persistent feature of the model experiments, supporting the insights garnered from quantifying the subglacial roughness of the former ice bed and from seafloor imprints. The source areas for glacial drainage of ice and sediments towards the shelf break in the west reached far into the ice sheet in the Russian Barents Sea. Independent validation of modelled ice-thickness loading scenarios is carried out through glacio-isostatic modelling, revealing that the modelled ice reconstructions of GlacBar show a better fit with measured emergence isobases than previous ice models.

The existing Plio-Pleistocene chronological stratigraphic framework of the western Barents Sea margin is based on ambiguous records with few datings. To overcome existing inconsistencies, an integrated multi-proxy chronology is proposed. Based on materia l from ODP leg 151 (Yermak Plateau), industry well 7216/11 at the SW Barents Sea margin and a regional grid of seismic, a new high-resolution stratigraphic and palaeo-environmental framework will be established for the Barents Sea area for the last 5 Ma. The evolution of the Barents Sea - Fennoscandian Ice Sheets (BSFIS) will be reconstructed through a close integration of empirical and numerical approaches. Empirical approaches include glacial geomorphological and stratigraphic mapping and sedimentolog ical analyses. Modelling approaches will use a 3D numerical ice sheet model which assimilates data from the empirical studies to provide reconstructions of the BSFIS thickness, extent, thermomechanical signature and associated dynamics over the last glaci al cycle. A numerical flowline model of basal sediment transport will allow 1) estimation of rates of ice stream flow, advance and retreat and 2) patterns and rates of subglacial erosion, transport and deposition. The project will allow enhanced risk ass essment of Barents Sea reservoirs by providing better age control on crucial events, more reliable and complete understanding of marine ice sheet evolution and improved understanding of glacial erosion and sediment transport. It will have a significant im pact on the understanding of marine ice sheet dynamics and will significantly improve the existing models of geological evolution of glaciated continental shelves, which is important as polar shelves are increasingly becoming targets for resource explora tion and exploitation worldwide. It will include knowledge-building through several Master students, one PhD and four Post Docs.