North Atlantic Deep Water and Antarctic Bottom Water variability during the last 200 ka recorded in an abyssal sediment core off South Africa

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doi: 10.1016/j.gloplacha.2011.10.001
Author(s): Krueger, S.; Leuschner, D. C.; Ehrmann, W.; Schmiedl, G.; Mackensen, A.
Author Affiliation(s): Primary:
University of Leipzig, Institute of Geophysics and Geology, Leipzig, Germany
University of Hamburg, Germany
Alfred Wegener Institute for Polar and Marine Research, Germany
Volume Title: Global and Planetary Change
Source: Global and Planetary Change, Vol.80-81, p.180-189. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181
Note: In English. 86 refs.; illus., incl. 1 table, sketch map
Summary: Benthic δ13C 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.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Agulhas Basin; Agulhas Plateau; Algae; Alkali metals; Antarctic Bottom Water; Atlantic Ocean; C-13/C-12; Cape Basin; Carbon; Cenozoic; Clastic sediments; Clay mineralogy; Cores; Deep-sea sedimentation; Fontbotia wuellerstorfi; Foraminifera; Glacial environment; Globigerina; Globigerina bulloides; Globigerinacea; Globigerinidae; Holocene; Interglacial environment; Invertebrata; Isotope ratios; Isotopes; Kaolinite/chlorite ratio; Leg 177; Marine sedimentation; Marine sediments; Metals; Microfossils; Mineral composition; Nannofossils; North Atlantic Deep Water; O-18/O-16; ODP Site 1089; Ocean Drilling Program; Oxygen; Paleo-oceanography; Planktonic taxa; Plantae; Pleistocene; Polynyas; Potassium; Protista; Quaternary; Rotaliina; Sedimentation; Sediments; Silt; South Atlantic; Southern Ocean; Stable isotopes; Upper Pleistocene; Variability; Weddell Sea
Coordinates: S405611 S405611 E0095338 E0095338
S415130 S415130 E0283230 E0283230
S412602 S412602 E0251518 E0251518
Record ID: 2012035586
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands