Glacial related and bottom current controlled sedimentation processes on the West Antarctic continental margin.
Description:
Even though the Antarctic ice sheet often limits the research activities, investigation of its behaviour is highly required. The Cenozoic glaciation history of Antarctica plays a key role in regulating world climate, atmosphere and ocean circulating system. The waxing and waning of the Antarctic ice shield influences albedo effects and sea level variations. As an example, the sea level during the last glacial maximum in the late Quaternary was about 120 m below the present sea level. Accordingly, the reconstruction of the Antarctic climate history is an important condition for the understanding of the sources of global climate changes and sea level variations. In order to derive the basic parameters to forecast the climatic developments and to model the future behaviour of the polar ice caps we have to understand the coherences of developments that happened in the past.
The investigation of sedimentary pattern on seismic profiles shows evidences of the ice dynamic and glacial history. Such data indicate that grounding and eroding ice streams developed on the continental shelves in glacial times. During glacial maxima they advanced to the shelf edge and supplied enormous masses of sediment material to the continental slope and rise (see Fig. 1). Thus, sediment accumulations on the Antarctic continental margin provide a record of the continental shelf glacial development. The aim of this project is the study of the sediment accumulations on the continental margin of the southern Pacific sector of the West Antarctic continental margin, based on the interpretation of seismic profiles, in correlation with magnetic and ocean drilling data (see Fig. 2). We study the pre- and post glacial sedimentation history in the Bellingshausen and Amundsen Sea, and on the western Antarctic Peninsula margin, focussing the following questions:
- When did the supply of glacially transported sediments across the shelf edge started?
- Did it occur simultaneous on the entire South Pacific margin of West Antarctica?
- Is it possible to differentiate glacial-interglacial cycles via seismic profiling?
- How did bottom currents influence the development of sediment accumulations?
- How much sediment had been deposited in what time?
Figures:
Figure 2: Schematic model of sediment transport processes along the continental margin of the Bellingshausen Sea. Sparse bathymetric ship track data over the wide continental shelf between Alexander Island and Thurston Island, acquired on RV Polarstern cruises in 1994 and 2001, reveal depressions that may be parts of major cross-shelf glacial transport pathways. They show a broad trough in front of sediment Depocentre B, with water depths of up to 680 m in the centre and about 450 m at the rim. The existence of this trough is confirmed by additional bathymetric data recently collected on RRS James Clark Ross and is consistent with our interpretation of Depocentre B being a wide deep-sea trough-mouth fan. A further, but shallower, outer shelf depression was observed farther northeast along the shelf-edge in front of sediment Depocentre A and may indicate the presence of a further, smaller glacial trough. The locations of the sediment drifts along the Antarctic Peninsula are schematically imaged.
Figure 1: Transport processes of eroded sediment material across the slope and depositional processes on the continental rise along the West Antarctic margin during glacial maxima.
References:
- Scheuer, C., Gohl, K., Larter, R.D., Rebesco, M., and Udintsev G. (2006). Variability in Cenozoic sedimentation along the continental rise of the Bellingshausen Sea, West Antarctica. Marine Geology, 227, 279-298.