Opal and barium records of six sediment cores for the last 400 ka

• Main Authors: Bonn, Wolfgang J, Gingele, Franz, Grobe, Hannes, Mackensen, Andreas, Fütterer, Dieter K
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1998
• Subjects: ANT-IV/3; ANT-IX/3; ANT-V/4; ANT-VI/3; ANT-VIII/6; Atka Bay; AWI_Paleo; Camp Norway; Eastern Weddell Sea; Southern Ocean; Gravity corer (Kiel type); Lazarev Sea; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Polarstern; PS08; PS08/347; PS10; PS10/816; PS12; PS12/248; PS12/536; PS1375-3; PS1506-1; PS1575-1; PS16; PS16/534; PS1648-1; PS18; PS18/185; PS1821-6; PS2038-2; Silicon Cycling in the World Ocean; SINOPS; SL; South Orkney; Antarc*; Antarctic; Antarctic Ocean; NADW; North Atlantic Deep Water; North Atlantic; Sea ice; Weddell Sea
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.728665; https://doi.org/10.1594/PANGAEA.728665

Records of biogenic opal and barium were measured in sediment cores at the Antarctic continental margin in the area of the Weddell, Lazarev and Cosmonaut seas. These records provide a qualitative and quantitative tool to estimate changes in palaeoproductivity over the last 400 ka. The stratigraphy of the investigated cores is calibrated to a lithostratigraphy, adjusted to a stable isotope record from the eastern Weddell Sea, which is supported by a Th-dating method. We present evidence that interglacial productivity along the Antarctic continental margin is twice as high compared to subantarctic sites near South Orkney. A glacial/interglacial pattern with high productivity during peak warm stages can be observed back to 400 ka. High interglacial productivity is linked to a reduced sea-ice coverage, which is regulated by the heat flux introduced by North Atlantic Deep Water (NADW) to the Antarctic Ocean. Generally, good correlations between the barium and opal records of the sediment cores indicate that dissolution of opal in the water column and the sediment does not obscure the surface productivity signal. Therefore, in this area biogenic opal in combination with other proxies, can be used for palaeoproductivity estimates. Palaeoproductivity is also assessed quantitatively from the barium record using the approaches of Dymond et al. (Dymond, J., Suess, E., Lyle, M., 1992. Barium in deep-sea sediments: a geochemical proxy for paleoproductivity. Paleoceanography 7, 163-181) and Francois et al. (Francois, R., Honjo, S., Manganini, S.J., Ravizza, G.E., 1995. Biogenic barium fluxes to the deep sea: implications for paleoproductivity reconstructions. Glob. Biochem. Cycles 9(2), 289-303). Palaeoproductivity rates obtained by both methods show a good temporal correspondence. In peak warm stages, higher values are computed with the approach of Dymond et al. (1992). Though some barium may be provided by lateral advection of material, as indicated by Th data near South Orkney, both methods provide values, which are ...