Numerical simulations of sediment drift evolution to reconstruct current conditions and sediment transport mechanisms under fundamentally different extreme polar climate situations adopting high-resolution records from ODP Leg 178, offshore the Antarctic Peninsula
Zusammenfassung der Projektergebnisse
The Regional Oceanic Modeling System (ROMS) has been used to simulate current system west of the Antarctic Peninsula. On the basis of the analyses of seismic data and three ODP sites, suspended sediment transport processes for 4 different clay grain size classes have been further implemented within the model system. Moreover, different numerical experiments have been set up to examine the potential sediment sources and influences of the variations at the boundaries. The simulation results in the drift regions and their vicinities have been analysed. Our simulations reveal that sediment transport patterns in the study area, especially in the region of Drift7 are strongly influenced by the bottom current. Although no mesoscale variation (e.g. eddy events) is found in the models, the active current of the Antarctic Bottom Water (AABW) reaches peak velocities of up to 29.5 cm/s. The flow is southwestward along the continental slope off the Antarctic Peninsula. The bottom current in this region is even stronger than the surface current. Sediments derived from melting ice-raft debris were identified as a likely source for Drift 4 and Drift 7. The sediments settle down along the continental slope and the strong bottom current transports them into the drift regions. Numerical experiments to test potential sediment sources show that the erosion flux within the model does not play a significant role for the evolution of the drifts west of the Antarctic Peninsula. Furthermore, single point sediment influx sources, spatially separated two point sources, or even lines of several sources are not strong enough to provide sufficient sediments for Drift 4 and Drift 7. Grain size class experiments yield different results for the coarsest clay class and the three finer clay classes: Only the three finer grain size clays are found in the regions of Drift 4 and Drift 7, where the bottom flow is strong. The horizontal distribution patterns of these three grain size clays are quite similar indicating only negligible differences for the transport patterns of the fine clays. The suspended sediment concentrations in the Drift 7 region are higher than those of Drift 4. This reinforces the key role of the strong bottom current for the sediment transport pattern; the stream at Drift 7 is more efficient in transporting fine clays into the drift region. The simulated characteristics of the bottom water properties and the strong flow need to be verified by long term hydrographic and hydrodynamic observations. Since clay is cohesive, future versions of the sediment transport model should include algorithms for cohesive sediments that have to be developed for the ROMS environment. The simulations run so far were forced by present conditions (forcing, climatology, initial data, and the grid data). However, a paleo-climatology and the information about the paleo-ocean are required as input to obtain a better understanding of the Neogene history of the bottom currents and their influence on the sediment transport patterns. In order to have complete view on the important factors of the evolution of Drift 4 and Drift 7, a suitable morphology model should be considered in the future studies.
Projektbezogene Publikationen (Auswahl)
- 2006. Depositional patterns at Drift 7, Antarctic Peninsula: alongslope versus down-slope sediment transport as indicators for oceanic currents and climatic conditions. Marine geology, 233(1-4), 49-62
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
Guennewig, P., Huhn, K., Uenzelmann-Neben, G.
- 2007. Sediment Transport Modeling on the Gateway south of South Africa using ROMS. 10th SAGA Biennial Technical Meeting and Exhibition, 22-26 Oct, 2007, Wild Coast, South Africa., 2007
Li, X., Uenzelmann-Neben, G. & K. Huhn
