Deep water variability on the southern Agulhas Plateau: Interhemispheric links over the past 170 ka

Molyneux, Elizabeth G., Hall, Ian Robert ORCID: https://orcid.org/0000-0001-6960-1419, Zahn, Rainer and Diz Ferreiro, Paula 2007. Deep water variability on the southern Agulhas Plateau: Interhemispheric links over the past 170 ka. Paleoceanography 22 (4) , PA4209. 10.1029/2006PA001407

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Abstract

Sortable silt mean grain sizes together with oxygen and carbon isotopic data produced on the benthic foraminiferal species Fontbotia wuellerstorfi are used to construct high-resolution records of near-bottom flow vigour and deep water ventilation at a core site MD02-2589 located at 2660 m water depth on the southern Agulhas Plateau. The results suggest that during glacial periods (marine oxygen isotope stages 2 and 6, MIS 2 and MIS 6, respectively), there was a persistent contribution of a well-ventilated water mass within the Atlantic to Indian oceanic gateway with a δ 13C signature similar to present-day Northern Component Water (NCW), e.g., North Atlantic Deep Water (NADW). The records of chemical ventilation and near-bottom flow vigor reflect changes in the advection of northern source waters and meridional variability in the location of the Antarctic Circumpolar Current and its associated fronts. We suggest that during Termination II (TII), changes in chemical ventilation are largely decoupled from near-bottom physical flow speeds. A mid-TII climate optimum is associated with a low-flow speed plateau concurrent with a period of increased ventilation shown in the benthic δ 13C of other Southern Ocean records but not in our benthic δ 13C of MD02-2589. The climate optimum is followed by a period of southern cooling around 128 ka coincident with a stronger influence of NCW to interglacial levels at around 124 ka. All proxy records show a near synchronous and rapid shift during the transition from MIS 5a-4 (73 ka). This large event is attributed to a rapid decrease in NADW influence and replacement over the Agulhas Plateau by southern source waters.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	G Geography. Anthropology. Recreation > GC Oceanography Q Science > QE Geology
Uncontrolled Keywords:	benthic isotopes; sortable silt mean grain size; North Atlantic Deep Water
Additional Information:	Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/1944-9186/ (accessed 20/02/2014).
Publisher:	American Geophysical Union
ISSN:	0883-8305
Date of First Compliant Deposit:	30 March 2016
Last Modified:	26 May 2023 11:57
URI:	https://orca.cardiff.ac.uk/id/eprint/30497

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