Deep water variability on the southern Agulhas Plateau

Interhemispheric links over the past 170 ka

Elizabeth Molyneux, Ian R. Hall, Rainer Zahn, Paula Diz

Research output: Contribution to journalLiterature review

14 Citations (Scopus)

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 delta C-13 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 delta C-13 of other Southern Ocean records but not in our benthic delta C-13 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.

Original languageEnglish
Article numberPA4209
Number of pages14
JournalPaleoceanography
Volume22
Issue number4
DOIs
Publication statusPublished - 13 Nov 2007

Keywords

  • antarctic circumpolar current
  • last glacial maximum
  • atlantic thermohaline circulation
  • inter-ocean exchange
  • scale climate-change
  • North-Atlantic
  • carbon-isotope
  • benthic foraminifera
  • ice core
  • bipolar seesaw

Cite this

Deep water variability on the southern Agulhas Plateau : Interhemispheric links over the past 170 ka. / Molyneux, Elizabeth; Hall, Ian R.; Zahn, Rainer; Diz, Paula.

In: Paleoceanography, Vol. 22, No. 4, PA4209, 13.11.2007.

Research output: Contribution to journalLiterature review

Molyneux, Elizabeth ; Hall, Ian R. ; Zahn, Rainer ; Diz, Paula. / Deep water variability on the southern Agulhas Plateau : Interhemispheric links over the past 170 ka. In: Paleoceanography. 2007 ; Vol. 22, No. 4.
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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 delta C-13 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 delta C-13 of other Southern Ocean records but not in our benthic delta C-13 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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T1 - Deep water variability on the southern Agulhas Plateau

T2 - Interhemispheric links over the past 170 ka

AU - Molyneux, Elizabeth

AU - Hall, Ian R.

AU - Zahn, Rainer

AU - Diz, Paula

PY - 2007/11/13

Y1 - 2007/11/13

N2 - 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 delta C-13 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 delta C-13 of other Southern Ocean records but not in our benthic delta C-13 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.

AB - 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 delta C-13 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 delta C-13 of other Southern Ocean records but not in our benthic delta C-13 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.

KW - antarctic circumpolar current

KW - last glacial maximum

KW - atlantic thermohaline circulation

KW - inter-ocean exchange

KW - scale climate-change

KW - North-Atlantic

KW - carbon-isotope

KW - benthic foraminifera

KW - ice core

KW - bipolar seesaw

U2 - 10.1029/2006PA001407

DO - 10.1029/2006PA001407

M3 - Literature review

VL - 22

JO - Paleoceanography and Paleoclimatology

JF - Paleoceanography and Paleoclimatology

SN - 0883-8305

IS - 4

M1 - PA4209

ER -