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Investigation of current conditions and sediment transport pattern along the Antarctic Peninsula using a numerical ocean circulation model

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Guennewig, P. , Huhn, K. and Uenzelmann-Neben, G. (2006): Investigation of current conditions and sediment transport pattern along the Antarctic Peninsula using a numerical ocean circulation model , ICDP und IODP/ODP Kolloqium, 27.-29. March, Greifswald. .
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Abstract:

During the last decade, higher latitudes, particularly the Antarctic continental margin, were main target areas to investigate climate shifts and global ocean circulation over long-time periods. In such a way during several cruises a unique data base, including numerous multi channel reflection seismic profiles, bathymetric maps, shallow gravity measurements, and in particular core data from ODP Leg 178, was collected along the Antarctic Peninsula. These data monitored a number of asymmetric sediment mounds on the continental slope which were interpreted as sedimentary drifts. These drifts serve as an excellent achieve for the geological environment and current conditions during their formation.In particular, Drift 7 is the best monitored sedimentary mound in this area. Detailed information about spatial extension, internal structures, sedimentary sequences, and grain size distribution exist. These data enable on one hand the identification of sediment sources, the reconstruction of sediment transport pathways and transport mechanisms, as well as current velocities. On the other hand, different theories about controlling parameters for the evolution of drifts could be developed such as: Is an initial topography necessary for the formation of such a sedimentary structure?Therefore, numerical oceanic circulation models enable extensive parameter sensitivity studies combining multidisciplinary datasets as model input parameters to test different hypotheses. Thus, we are using the Regional Ocean Model System (ROMS) - an academic hydrostatic ocean circulation model, based on the finite difference method to investigate the environmental situation and current conditions during the evolution of Drift 7. Major aim of this project is the reconstruction of depositional and re-depositional processes from observed sediment structure of Drift 7. Therefore, ROMS included a complex sediment transport module to compute particle transport within the water column as well as sediment suspended in the benthic boundary layer at the seafloor using an advection equation for sediment suspended.For the first series of experiments, we developed a 3d model to obtain qualitative information about ocean currents and sediment distribution under recent conditions along the Antarctic Peninsula, Bellingshausen Sea. The study area is situated between 84°S - 72°S and 70°W - 65°W. We use a realistic topography with a resolution of 5° and a horizontal grid width of 14 km whereas the water column is vertically subdivided into 20 depth levels. We calculate the current field and sediment distribution during a time interval of one year. This simulations supply first information about sediment transport pathways, where should major sediment sources be expected, what ocean currents must exist to accumulate drift bodies and changed the ocean currents over the last centuries?However, next step will be the simulation of past situations to keep e.g. sea level changes, temperature variations, as well as wind, wave and tidal effects into account. Furthermore, we develop coevally a simplified 3d slope model to analyse (a) which initial topography is necessary to accumulate sediment drift and (b) how long must be an episode of current activity to generate the drift.

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