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

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 dept...

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Bibliographic Details
Published in:Paleoceanography
Main Authors: Molyneux, Elizabeth G., Hall, Ian Robert, Zahn, Rainer, Diz Ferreiro, Paula
Format: Article in Journal/Newspaper
Language:English
Published: American Geophysical Union 2007
Subjects:
GC Oceanography
QE Geology
Antarctic
Southern Ocean
The Antarctic
Indian
Antarc*
NADW
North Atlantic Deep Water
North Atlantic
Online Access:https://orca.cardiff.ac.uk/id/eprint/30497/
https://doi.org/10.1029/2006PA001407
https://orca.cardiff.ac.uk/id/eprint/30497/1/Molyneux%202007.pdf
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Summary: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.

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