HR: 0800h
AN: PP51E-1358    [Abstracts]
TI: What Role Play Brines in Levee Sedimentation in the Riiser Larsen Sea (Antarctica)?
AU: * Hass, H C
EM: chass@awi-bremerhaven.de
AF: Alfred Wegener Institute for Polar and Marine Research, Wadden Sea Research Station, Hafenstrasse 43, List/Sylt, D-25992 Germany
AU: Kuhn, G
EM: gkuhn@awi-bremerhaven.de
AF: Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, Bremerhaven, 27568 Germany
AU: Mackensen, A
EM: amackensen@awi-bremerhaven.de
AF: Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, Bremerhaven, 27568 Germany
AU: F\"{u}tterer, D K
EM: dfuetterer@awi-bremerhaven.de
AF: Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, Bremerhaven, 27568 Germany
AB: During two expeditions to the Riiser Larsen Sea (RLS) we collected a number of long gravity cores and measured transects using a parametric echosounder system (Parasound). In the western part of the RLS Parasound and bathymetric data reveal that channels dominate the seafloor. None of the channels shows influences of lateral sediment input suggesting that presently the channels are active pathways of dense waters and/or turbidity currents. The channels merge to few large channels on the lower slope. They are usually flanked by levees that sometimes reveal more than 100 m of sound penetration. Granulometry, coarse-fraction analysis, TOC and carbonate, stable oxygen and carbon isotopes among other analyses were carried out on sediment cores from levee tops from the upper part of the continental slope. Results suggest that sediments from the channels feed the levees during flooding events (overbank deposition). Planktic foraminifer and IRD sedimentation occurs predominantly during periods in which flooding events were most energetic, indicated by the current-sorted terrigenous silt fraction being generally coarser than during other periods. High-energy periods coincide generally with warmer climate phases such as MIS 1, 3, and 5. Both, IRD and planktic foraminifer export from the sea surface was significantly reduced during the cold periods such as MIS 2 and 4 indicating severe sea-ice conditions. Channel-overspill events during the cold climate phases were clearly less energetic (finer current-sorted silt fraction). Today, sea-ice that covers about 15 degrees of latitude in winter forms within few weeks. It is suggested that at least part of the enormous quantity of sea ice is formed in coastal polynyas in which consequently also brines form. We suggest that these brines promote channel-flooding events and add to deepwater if they form on the upper slope (warm climate). Under cold climate brines may not reach the seafloor as they occur further north over deeper water, would not cause overspill, and also would not add to deepwater.
DE: 9310 Antarctica
DE: 9604 Cenozoic
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting