Poorly ventilated deep ocean at the Last Glacial Maximum inferred from carbon isotopes: A data-model comparison study

Menviel, L.; Yu, J.; Joos, Fortunat; Mouchet, A.; Meissner, K. J.; England, M. H. (2017). Poorly ventilated deep ocean at the Last Glacial Maximum inferred from carbon isotopes: A data-model comparison study. Paleoceanography, 32(1), pp. 2-17. American Geophysical Union 10.1002/2016PA003024

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Atmospheric CO₂ was ~90 ppmv lower at the Last Glacial Maximum (LGM) compared to the late Holocene, but the mechanisms responsible for this change remain elusive. Here we employ a carbon isotope-enabled Earth System Model to investigate the role of ocean circulation in setting the LGM oceanic δ¹³C distribution, thereby improving our understanding of glacial/interglacial atmospheric CO₂ variations. We find that the mean ocean δ¹³C change can be explained by a 378 ± 88 Gt C(2σ) smaller LGM terrestrial carbon reservoir compared to the Holocene. Critically, in this model, differences in the oceanic δ¹³C spatial pattern can only be reconciled with a LGM ocean circulation state characterized by a weak (10–15 Sv) and relatively shallow (2000–2500 m) North Atlantic Deep Water cell, reduced Antarctic Bottom Water transport (≤10 Sv globally integrated), and relatively weak (6–8 Sv) and shallow (1000–1500 m) North Pacific Intermediate Water formation. This oceanic circulation state is corroborated by results from the isotope-enabled Bern3D ocean model and further confirmed by high LGM ventilation ages in the deep ocean, particularly in the deep South Atlantic and South Pacific. This suggests a poorly ventilated glacial deep ocean which would have facilitated the sequestration of carbon lost from the terrestrial biosphere and atmosphere.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Physics Institute

UniBE Contributor:

Joos, Fortunat

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

0883-8305

Publisher:

American Geophysical Union

Language:

English

Submitter:

Monika Wälti-Stampfli

Date Deposited:

06 Jun 2017 11:02

Last Modified:

05 Jul 2017 02:30

Publisher DOI:

10.1002/2016PA003024

BORIS DOI:

10.7892/boris.100806

URI:

https://boris.unibe.ch/id/eprint/100806

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