Evidence of poorly ventilated deep Central Indian Ocean during the last glaciation

Bharti, Nisha; Bhushan, Ravi; Skinner, Luke C; Muruganantham, M.; Jena, Partha Sarathi; Dabhi, Ankur J.; Shivam, Ajay

doi:10.1016/j.epsl.2022.117438

Cited by 14 publications

(16 citation statements)

References 90 publications

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“…The sedimentary aU and Mn / Ti levels show a consistent downcore pattern with generally more reducing conditions during peak glacial times and rapid (re)oxygenation during glacial terminations. These observations are consistent with recent radiocarbon-based evidence suggesting that the deep Indian Ocean was generally more poorly ventilated during the last ice age (Bharti et al, 2022;Gottschalk et al, 2020b;Ronge et al, 2020). Preserved opal fluxes are persistently low during cold periods, while aU and Mn / Ti values are consistent with increasingly reducing conditions.…”

Section: Dynamics Of Bottom Water Oxygenation In the Azsupporting

confidence: 91%

Bottom water oxygenation changes in the southwestern Indian Ocean as an indicator for enhanced respired carbon storage since the last glacial inception

et al. 2022

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Abstract. We present downcore records of redox-sensitive authigenic uranium (U) and manganese (Mn) concentrations based on five marine sediment cores spanning a meridional transect encompassing the Subantarctic and Antarctic zones in the southwestern Indian Ocean covering the last glacial cycle. These records signal lower bottom water oxygenation during glacial climate intervals and generally higher oxygenation during warm periods, consistent with climate-related changes in deep-ocean remineralized carbon storage. Regional changes in the export of siliceous phytoplankton to the deep sea may have entailed a secondary influence on oxygen levels at the water–sediment interface, especially in the Subantarctic Zone. The rapid reoxygenation during the deglaciation is in line with increased ventilation and enhanced upwelling after the Last Glacial Maximum (LGM), which in combination conspired to transfer previously sequestered remineralized carbon to the surface ocean and the atmosphere, contributing to propel the Earth's climate out of the last ice age. These records highlight the still insufficiently documented role that the Southern Indian Ocean played in the air–sea partitioning of CO2 on glacial–interglacial timescales.

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Section: Dynamics Of Bottom Water Oxygenation In the Azsupporting

confidence: 91%

Bottom water oxygenation changes in the southwestern Indian Ocean as an indicator for enhanced respired carbon storage since the last glacial inception

et al. 2022

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“…The deep Indian Ocean, where the number of glacial-interglacial measurements is not large enough to reliably produce basin-scale trends, is conspicuously absent and is a logical target for future work. The Indian and Pacific Oceans have been lumped together in past studies, but recent work suggests some major deviations in Indian deep-sea 14 C ventilation ( 60 ). Whatever the case, the magnitude of the glacial-interglacial Pacific Ocean 14 C ventilation changes shown in our study should widen the aperture of paleoceanographic research beyond ocean and atmospheric influences on the North Atlantic and Southern Ocean, to construct an integrated view of deep-sea dynamics since the last ice age.…”

Section: Discussionmentioning

confidence: 99%

Global reorganization of deep-sea circulation and carbon storage after the last ice age

et al. 2022

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Using new and published marine fossil radiocarbon ( 14 C/C) measurements, a tracer uniquely sensitive to circulation and air-sea gas exchange, we establish several benchmarks for Atlantic, Southern, and Pacific deep-sea circulation and ventilation since the last ice age. We find the most 14 C-depleted water in glacial Pacific bottom depths, rather than the mid-depths as they are today, which is best explained by a slowdown in glacial deep-sea overturning in addition to a “flipped” glacial Pacific overturning configuration. These observations cannot be produced by changes in air-sea gas exchange alone, and they underscore the major role for changes in the overturning circulation for glacial deep-sea carbon storage in the vast Pacific abyss and the concomitant drawdown of atmospheric CO 2 .

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“…The production ratio of 231 Pa/ 230 Th in the water columns is shown in the horizontal dashed line. ( E ) Radiocarbon age offsets between benthic foraminifera and the atmosphere (B-Atm) as a proxy for subsurface water mass ventilation from the Indian Ocean core SS172/4040 ( 42 ). The error bar is 2 SD.…”

Section: Resultsmentioning

confidence: 99%

“…Deep ocean ventilation changes via NADW and/or AABW formation likely served as the primary driver of the observed deglacial DO variability. Strengthened NADW formation that supplied oxygen-rich surface water to the deep ocean resulted in a better ventilated deep Atlantic ( 2 , 19 , 41 ) and, possibly, Indian Ocean ( 42 ) during the B-A/ACR (Fig. 1E).…”

Section: Resultsmentioning

confidence: 99%

Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation

Wang,

Costa,

et al. 2024

Sci. Adv.

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Ocean dissolved oxygen (DO) can provide insights on how the marine carbon cycle affects global climate change. However, the net global DO change and the controlling mechanisms remain uncertain through the last deglaciation. Here, we present a globally integrated DO reconstruction using thallium isotopes, corroborating lower global DO during the Last Glacial Maximum [19 to 23 thousand years before the present (ka B.P.)] relative to the Holocene. During the deglaciation, we reveal reoxygenation in the Heinrich Stadial 1 (~14.7 to 18 ka B.P.) and the Younger Dryas (11.7 to 12.9 ka B.P.), with deoxygenation during the Bølling-Allerød (12.9 to 14.7 ka B.P.). The deglacial DO changes were decoupled from North Atlantic Deep Water formation rates and imply that Southern Ocean ventilation controlled ocean oxygen. The coherence between global DO and atmospheric CO 2 on millennial timescales highlights the Southern Ocean’s role in deglacial atmospheric CO 2 rise.

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Evidence of poorly ventilated deep Central Indian Ocean during the last glaciation

Cited by 14 publications

References 90 publications

Bottom water oxygenation changes in the southwestern Indian Ocean as an indicator for enhanced respired carbon storage since the last glacial inception

Bottom water oxygenation changes in the southwestern Indian Ocean as an indicator for enhanced respired carbon storage since the last glacial inception

Global reorganization of deep-sea circulation and carbon storage after the last ice age

Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation

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