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

详细信息    查看全文

• 作者：L. Menviel ; J. Yu ; F. Joos ; A. Mouchet ; K. J. Meissner ; M. H. England
• 刊名：Paleoceanography
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：32
• 期：1
• 页码：2-17
• 全文大小：5.0MB
• ISSN：1944-9186

文摘

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.