georefid:2012-035586SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2013-07-08T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1016/j.gloplacha.2011.10.001<gco:CharacterString>North Atlantic Deep Water and Antarctic Bottom Water variability during the last 200 ka recorded in an abyssal sediment core off South Africa</gco:CharacterString>2012-01-01publicationgeorefid:2012-035586doi:10.1016/j.gloplacha.2011.10.001Krueger, S.University of Leipzig, Institute of Geophysics and Geology, Leipzig, GermanyauthorLeuschner, D. C.University of Hamburg, GermanyauthorEhrmann, W.Alfred Wegener Institute for Polar and Marine Research, GermanyauthorSchmiedl, G.authorMackensen, A.authorElsevier, Amsterdam, NetherlandspublisherdocumentHardcopyGlobal and Planetary Change80-81180-189Benthic delta (super 13) C values (F. wuellerstorfi), kaolinite/chlorite ratios and sortable silt median grain sizes in sediments of a core from the abyssal Agulhas Basin record the varying impact of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) during the last 200 ka. The data indicate that NADW influence decreased during glacials and increased during interglacials, in concert with the global climatic changes of the late Quaternary. In contrast, AABW displays a much more complex behaviour. Two independent modes of deep-water formation contributed to the AABW production in the Weddell Sea: 1) brine rejection during sea ice formation in polynyas and in the sea ice zone (Polynya Mode) and 2) super-cooling of Ice Shelf Water (ISW) beneath the Antarctic ice shelves (Ice Shelf Mode). Varying contributions of the two modes lead to a high millennial-scale variability of AABW production and export to the Agulhas Basin. Highest rates of AABW production occur during early glacials when increased sea ice formation and an active ISW production formed substantial amounts of deep water. Once full glacial conditions were reached and the Antarctic ice sheet grounded on the shelf, ISW production shut down and only brine rejection generated moderate amounts of deep water. AABW production rates dropped to an absolute minimum during Terminations I and II and the Marine Isotope Transition (MIS) 4/3 transition. Reduced sea ice formation concurrent with an enhanced fresh water influx from melting ice lowered the density of the surface water in the Weddell Sea, thus further reducing deep water formation via brine rejection, while the ISW formation was not yet operating again. During interglacials and the moderate interglacial MIS 3 both brine formation and ISW production were operating, contributing various amounts to AABW formation in the Weddell Sea. Abstract Copyright (2012) Elsevier, B.V.completedQuaternary geologyAgulhas BasinAgulhas Plateaualgaealkali metalsAntarctic Bottom WaterAtlantic OceanC-13/C-12Cape BasincarbonCenozoicclastic sedimentsclay mineralogycoresdeep-sea sedimentationFontbotia wuellerstorfiForaminiferaglacial environmentGlobigerinaGlobigerina bulloidesGlobigerinaceaGlobigerinidaeHoloceneinterglacial environmentInvertebrataisotope ratiosisotopeskaolinite/chlorite ratioLeg 177marine sedimentationmarine sedimentsmetalsmicrofossilsmineral compositionnannofossilsNorth Atlantic Deep WaterO-18/O-16Ocean Drilling ProgramODP Site 1089oxygenpaleo-oceanographyplanktonic taxaPlantaePleistocenepolynyaspotassiumProtistaQuaternaryRotaliinasedimentationsedimentssiltSouth AtlanticSouthern Oceanstable isotopesupper PleistocenevariabilityWeddell Seaurn:org.iodp:exp:177urnlargerWorkCitationcampaignurn:org.iodp:exp:177:site:1089urnlargerWorkCitationstudyurn:org.iodp:exp:177urnlargerWorkCitationcampaignEnglishgeoscientificInformation9.533828.3230-41.5130-40.5611