Atlantic Ocean ventilation changes across the last deglaciation and their carbon cycle implications

Skinner, L. C. and Freeman, E. and Hodell, D. and Waelbroeck, C. and Riveiros, N. Vazquez and Scrivner, A. E. (2020) Atlantic Ocean ventilation changes across the last deglaciation and their carbon cycle implications. Paleoceanography and Paleoclimatology. ISSN 2572-4517 DOI https://doi.org/10.1029/2020PA004074

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Official URL: https://doi.org/10.1029/2020PA004074

Abstract

Changes in ocean ventilation, controlled by both overturning rates and air‐sea gas exchange, are thought to have played a central role in atmospheric CO2 rise across the last deglaciation. Here we constrain the nature of Atlantic Ocean ventilation changes over the last deglaciation using radiocarbon and stable carbon isotopes from two depth transects in the Atlantic basin. Our findings broadly cohere with the established pattern of deglacial Atlantic overturning change, and underline the existence of active northern sourced deep‐water export at the Last Glacial Maximum (LGM). We find that the western Atlantic was less affected by incursions of southern‐sourced deep water, as compared to the eastern Atlantic, despite both sides of the basin being strongly influenced by the air‐sea equilibration of both northern‐ and southern deep‐water end‐members. Ventilation at least as strong as modern is observed throughout the Atlantic during the Bølling‐Allerød (BA), implying a ‘flushing’ of the entire Atlantic water column that we attribute to the combined effects of AMOC reinvigoration and increased air‐sea equilibration of southern sourced deep‐water. This ventilation ‘overshoot’ may have counteracted a natural atmospheric CO2 decline during interstadial conditions, helping to make the BA a ‘point of no return’ in the deglacial process. While the collected data emphasize a predominantly indirect AMOC contribution to deglacial atmospheric CO2 rise, via far field impacts on convection in the Southern Ocean and/or North Pacific during HS1 and the YD, the potential role of the AMOC in centennial CO2 pulses emerges as an important target for future work.

Item Type: Article
Uncontrolled Keywords: 2020AREP; IA77
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
07 - Gold Open Access
12 - PhD
Journal or Publication Title: Paleoceanography and Paleoclimatology
Identification Number: https://doi.org/10.1029/2020PA004074
Depositing User: Sarah Humbert
Date Deposited: 18 Jan 2021 17:16
Last Modified: 21 Jan 2021 01:59
URI: http://eprints.esc.cam.ac.uk/id/eprint/5986

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