Transport, Removal and Accumulation of sediments Numerically Simulated for Paleo-Oceans and Reconstructed from cores of The Eirik Drift (TRANSPORTED)

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The Western Boundary Undercurrent (WBUC) is a crucial component of the global ocean conveyor belt and is driven by Deep Water Formation (DWF) in the Greenland, Labrador, Norwegian and Iceland Seas. Seismic profiles imaging the Eirik Drift indicate a high variability in velocities and flowpath of the WBUC since the early Miocene and provide indications on the area of DWF from the Miocene to present day. We aim at identifying the mechanisms involved in shifts of DWF sites and redirection of the WBUC. Grain size data is available for ODP Leg 105 Site 646 and IODP Expedition 303 Sites U1305-1307 drilled at the Eirik Drift (iodp.tamu.edu). The distinction into clay (less than 0.004 mm), silt (0.004-0.063 mm), and sand (more than 0.063 mm) is sufficient to deduce resolvable velocities of the WBUC for the different periods. Three-dimensional velocities and sediment transports will be simulated with the Regional Ocean Modelling System (ROMS). ROMS will be localized to the North Atlantic and therefore yield detailed information about DWF sites and ocean currents. Seismic profiles collected in the area of the Eirik Drift (Uenzelmann-Neben (2013)) provide horizon depths, thicknesses of sedimentary units, and location and orientation of depocentres. In combination with the grain size data ground truth data is provided for the sediment transport patterns modelled by ROMS. With the numerical approach we can single out or neglect effects and thereby perform sensitivity studies regarding the influence of changing climate conditions and tectonic configurations on deep ocean currents and sediment transport. Müller-Michaelis and Uenzelmann-Neben (2014) attributed variable sediment deposition in the Eirik Drift to changes in strength and pathway of the WBUC, which originated in alternating sites of DWF. This hypothesis can be tested by the regional simulations and the climatic conditions responsible for the changes in DWF sites can be identified. The pathway of the WBUC is additionally affected by tectonic events, e.g., subsidence of the Greenland-Scotland Ridge or closing of the Central American Seaway. The influence of tectonic alterations on strength and pathway of the WBUC as well as on sedimentation rate and grain size will be studied in this project. We will, hence, link modifications in sedimentation rates and grain sizes recorded in the cores from Sites 646 and U1305-1307 to climatic and tectonically forced alterations of flowpaths and velocities of the WBUC.