Late Pleistocene deep-water circulation in the subantarctic eastern Atlantic

We present three new benthic foraminiferal delta(13)C, delta(18)O, and total organic carbon time series from the eastern Atlantic sector of the Southern Ocean between 41degreesS and 47degreesS. The measured glacial delta(13)C values belong to the lowest hitherto reported. We demonstrate a coincidence between depleted late Holocene (LH) delta(13)C values and positions of sites relative to ocean surface productivity. A correction of +0.3 to +0.4 [parts per thousand VPDB] for a productivity-induced depletion of Last Glacial Maximum (LGM) benthic delta(13)C values of these cores is suggested. The new data are compiled with published data from 13 sediment cores from the eastern Atlantic Ocean between 19degreesS and 47degreesS, arid the regional deep and bottom water circulation is reconstructed for LH (4-0 ka) and LGM (22-16 ka) times. This extends earlier eastern Atlantic-wide synoptic reconstructions which suffered from the lack of data south of 20degreesS. A conceptual model of LGM deep-water circulation is discussed that, after correction of southernmost cores below the Antarctic Circumpolar Current (ACC) for a productivity-induced artifact, suggests a reduced formation of both North Atlantic Deep Water in the northern Atlantic and bottom water in the southwestern Weddell Sea. This reduction was compensated for by the formation of deep water in the cone of extended winter sea-ice coverage at the northern rim of the Weddell Sea, where air-sea gas exchange was reduced. This shift from LGM deep-water formation in the region south of the ACC to Holocene bottom water formation in the southwestern Weddell Sea, can explain lower preformed delta(13)C(DIC) values of glacial circumantarctic deep water of approximately 0.3parts per thousand to 0.4parts per thousand. Our reconstruction brings Atlantic and Southern Ocean delta(13)C and Cd/Ca data into better agreement, but is in conflict, however, with a scenario of an essentially unchanged thermohaline deep circulation on a global scale. Benthic delta(18)O-derived LGM bottom water temperatures, by 1.9degreesC and 0.3degreesC lower than during the LH at deepest southern and shallowest northern sites, respectively, agree with the here proposed reconstruction of deep-water circulation in the eastern South Atlantic Ocean. (C) 2001 Elsevier Science B.V. All rights reserved.