scholarly journals Carbon isotope evidence for changes in Antarctic Intermediate Water circulation and ocean ventilation in the southwest Pacific during the last deglaciation

2004 ◽  
Vol 19 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Helen C. Bostock ◽  
Bradley N. Opdyke ◽  
Michael K. Gagan ◽  
L. Keith Fifield
Keyword(s):  
Carbon Isotope ◽  
Water Circulation ◽  
Intermediate Water ◽  
Last Deglaciation ◽  
Antarctic Intermediate Water ◽  
Southwest Pacific ◽  
Ocean Ventilation ◽  
Isotope Evidence ◽  
The Last Deglaciation

Antarctic Intermediate Water penetration into the Northern Indian Ocean during the last deglaciation

2018 ◽  
Vol 500 ◽  
pp. 67-75 ◽  
Author(s):  
Zhaojie Yu ◽  
Christophe Colin ◽  
Ruifang Ma ◽  
Laure Meynadier ◽  
Shiming Wan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Intermediate Water ◽  
Last Deglaciation ◽  
Northern Indian Ocean ◽  
Water Penetration ◽  
Antarctic Intermediate Water ◽  
The Last Deglaciation

scholarly journals Opening the window to the Southern Ocean: The role of jet dynamics

2018 ◽  
Vol 4 (10) ◽  
pp. eaao4719 ◽  
Author(s):  
Andreas Klocker
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Global Climate ◽  
Control Valve ◽  
Intermediate Water ◽  
Surface Mixed Layer ◽  
Last Deglaciation ◽  
Antarctic Intermediate Water ◽  
Topographic Features ◽  
Ocean Ventilation

The surface waters of the Southern Ocean act as a control valve through which climatically important tracers such as heat, freshwater, and CO2 are transferred between the atmosphere and the ocean. The process that transports these tracers through the surface mixed layer into the ocean interior is known as ocean ventilation. Changes in ocean ventilation are thought to be important for both rapid transitions of the ocean’s global overturning circulation during the last deglaciation and the uptake and storage of excess heat and CO2 as a consequence of anthropogenic climate change. I show how the interaction between Southern Ocean jets, topographic features, and ocean stratification can lead to rapid changes in Southern Ocean ventilation as a function of wind stress. For increasing winds, this interaction leads from a state in which tracers are confined to the surface mixed layer to a state in which tracers fill the ocean interior. For sufficiently high winds, the jet dynamics abruptly change, allowing the tracer to ventilate a water mass known as Antarctic Intermediate Water in the mid-depth Southern Ocean. Abrupt changes in Antarctic Intermediate Water ventilation have played a major role in rapid climate transitions in Earth’s past, and combined with the results presented here, this would suggest that jet dynamics could play a prominent role in contributing to, or even triggering, rapid transitions of the global climate system.

14C Offsets and Apparently Non-Synchronous δ18O Stratigraphies between Nannofossil and Foraminiferal Pelagic Carbonates

1991 ◽  
Vol 35 (2) ◽  
pp. 274-290 ◽  
Author(s):  
Charles K. Paull ◽  
Scott J. Hills ◽  
Hans R. Thierstein ◽  
Georges Bonani ◽  
Willi Wölfli
Keyword(s):  
Taxonomic Composition ◽  
South Atlantic ◽  
Last Deglaciation ◽  
Regional Patterns ◽  
Ocean Ventilation ◽  
Beta Counting ◽  
Accelerator Mass Spectrometer ◽  
Direct Interpretation ◽  
Mid Atlantic Ridge ◽  
The Last Deglaciation

AbstractMultiple stratigraphies of subtropical South Atlantic cores reveal significant stratigraphic discrepancies between the nannofossil and the foraminiferal carbonates. Variations in the stratigraphic signals carried in the nannofossil-dominated <38 μm fraction and foraminifera-dominated >38 μm fraction were measured with detailed stratigraphies of δ18O, δ13C, 14C, grain size, percentage carbonate, percentage aragonite, and taxonomic composition across the last deglaciation in INMD box core 111 No. 9. Three other cores (INMD box cores 113 and 115, and V 22–174), also from the shallow flanks of the mid-Atlantic ridge in the South Atlantic (10°–17° S), contain similar stratigraphies indicating that these cores represent regional patterns. The onset of the deglacial δ18O shift in foraminiferal carbonate occurs 6 to 20 cm deeper than the δ18O shift in the nannofossil fraction. Nineteen accelerator mass spectrometer 14C dates of various fractions (<38 μm, 38–62 μm, 62–150 μm, 150–250 μm, >355 μm, and G. ruber) from INMD Box 111 show that the components within an individual core slice may differ by up to 4900 14C years. Twelve traditional 14C dates (determined by beta counting) of the >38 and <38 μm fractions from six levels in INMD Box 111 No. 6 confirm the large offsets. The observed isotopic offsets are not explained by an individual process, and suggest that multiple causes have left a lumpy stratigraphic record. However, the variability in the data illustrates the difficulty in accurately measuring the chronology of deglaciation, reopens the question of which components of pelagic sediment best monitor surface water conditions, and complicates the direct interpretation of benthic-planktonic age differences in terms of ocean ventilation changes.

Antarctic Intermediate Water circulation in the tropical and subtropical South Atlantic

1995 ◽  
Vol 100 (C7) ◽  
pp. 13441 ◽  
Author(s):  
Toshio Suga ◽  
Lynne D. Talley
Keyword(s):  
South Atlantic ◽  
Water Circulation ◽  
Intermediate Water ◽  
Antarctic Intermediate Water

scholarly journals Regional carbon isotope syntheses from the last deglaciation

2017 ◽  
Vol 25 (3) ◽  
pp. 154-154
Author(s):  
Andreas Schmittner ◽  
G Martínez-Méndez ◽  
AC Mix ◽  
J Repschläger
Keyword(s):  
Carbon Isotope ◽  
Last Deglaciation ◽  
The Last Deglaciation

scholarly journals Changes in productivity and intermediate circulation in the northern Indian Ocean since the last deglaciation: new insights from benthic foraminiferal Cd /thinsp;Ca records and benthic assemblage analyses

2020 ◽  
Author(s):  
Ruifang Ma ◽  
Sophie Sépulcre ◽  
Laetitia Licari ◽  
Frédéric Haurine ◽  
Franck Bassinot ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Primary Productivity ◽  
Arabian Sea ◽  
Bottom Water ◽  
Geochemical Data ◽  
Intermediate Water ◽  
Last Deglaciation ◽  
Northern Indian Ocean ◽  
Surface Productivity ◽  
The Last Deglaciation

Abstract. We have measured Cd / Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate water circulation and paleo-nutrient content since the last deglaciation. Intermediate water Cdw records estimated from the benthic Cd / Ca reflect past changes in surface productivity and/or intermediate-bottom water ventilation. The benthic foraminiferal assemblages are consistent with the geochemical data. These results suggest that during the last deglaciation, the Heinrich Stadial 1 and Younger Dryas (HS1 and YD, respectively) millennial-scale events were marked by a decrease in Cdw values, indicating an enhanced ventilation of intermediate-bottom water masses. Benthic foraminifer assemblages indicate that surface primary productivity was low during the early Holocene (from 10 to 6 cal kyr BP), resulting in low intermediate water Cdw at both sites. From ~ 5.2 to 2.4 cal kyr BP, the benthic foraminiferal assemblages indicate meso- to eutrophic intermediate water conditions, which correspond to high surface productivity. This is consistent with a significant increase in the intermediate water Cdw in the southeastern Arabian Sea and the northeastern BoB. The comparison of intermediate water Cdw records with previous reconstructions of past Indian monsoon evolution during the Holocene suggests a direct control of intermediate water Cdw by monsoon-induced changes in upper water stratification and surface primary productivity.

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