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Deep South Atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation

Deep South Atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation
Deep South Atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation
Carbon release from the deep ocean at glacial terminations is a critical component of past climate change, but the underlying mechanisms remain poorly understood. We present a 28,000-year high-resolution record of carbonate ion concentration, a key parameter of the global carbon cycle, at 5-km water depth in the South Atlantic. We observe similar carbonate ion concentrations between the Last Glacial Maximum and the late Holocene, despite elevated concentrations in the glacial surface ocean. This strongly supports the importance of respiratory carbon accumulation in a stratified deep ocean for atmospheric CO2 reduction during the last ice age. After ?9 ?mol/kg decline during Heinrich Stadial 1, deep South Atlantic carbonate ion concentration rose by ?24 ?mol/kg from the onset of Bølling to Pre-boreal, likely caused by strengthening North Atlantic Deep Water formation (Bølling) or increased ventilation in the Southern Ocean (Younger Drays) or both (Pre-boreal). The ?15 ?mol/kg decline in deep water carbonate ion since ?10 ka is consistent with extraction of alkalinity from seawater by deep-sea CaCO3 compensation and coral reef growth on continental shelves during the Holocene.

Between 16,600 and 15,000 years ago, deep South Atlantic carbonate ion values converged with those at 3.4-km water depth in the western equatorial Pacific, as did carbon isotope and radiocarbon values. These observations suggest a period of enhanced lateral exchange of carbon between the deep South Atlantic and Pacific Oceans, probably due to an increased transfer of momentum from southern westerlies to the Southern Ocean. By spreading carbon-rich deep Pacific waters around Antarctica for upwelling, invigorated interocean deep water exchange would lead to more efficient CO2 degassing from the Southern Ocean, and thus to an atmospheric CO2 rise, during the early deglaciation.
0277-3791
80-89
Yu, Jimin
9558e475-ac9f-44d3-8c1a-b0540e3b7c3d
Anderson, Robert F.
9069c990-0fdb-4c35-91ce-36f2a6b47d39
Jin, Zhangdong
6866d31f-3f81-47c8-998d-0a2afe9f2a92
Menviel, Laurie
c3d3c922-6703-4eee-b292-cb6d38f0bae6
Zhang, Fei
a68149c2-7bf3-4402-a487-a39736bff0e1
Ryerson, Fredrick J.
9386316f-4e42-4d39-b294-08745da10f4a
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Yu, Jimin
9558e475-ac9f-44d3-8c1a-b0540e3b7c3d
Anderson, Robert F.
9069c990-0fdb-4c35-91ce-36f2a6b47d39
Jin, Zhangdong
6866d31f-3f81-47c8-998d-0a2afe9f2a92
Menviel, Laurie
c3d3c922-6703-4eee-b292-cb6d38f0bae6
Zhang, Fei
a68149c2-7bf3-4402-a487-a39736bff0e1
Ryerson, Fredrick J.
9386316f-4e42-4d39-b294-08745da10f4a
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685

Yu, Jimin, Anderson, Robert F., Jin, Zhangdong, Menviel, Laurie, Zhang, Fei, Ryerson, Fredrick J. and Rohling, Eelco J. (2014) Deep South Atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation. Quaternary Science Reviews, 90, 80-89. (doi:10.1016/j.quascirev.2014.02.018).

Record type: Article

Abstract

Carbon release from the deep ocean at glacial terminations is a critical component of past climate change, but the underlying mechanisms remain poorly understood. We present a 28,000-year high-resolution record of carbonate ion concentration, a key parameter of the global carbon cycle, at 5-km water depth in the South Atlantic. We observe similar carbonate ion concentrations between the Last Glacial Maximum and the late Holocene, despite elevated concentrations in the glacial surface ocean. This strongly supports the importance of respiratory carbon accumulation in a stratified deep ocean for atmospheric CO2 reduction during the last ice age. After ?9 ?mol/kg decline during Heinrich Stadial 1, deep South Atlantic carbonate ion concentration rose by ?24 ?mol/kg from the onset of Bølling to Pre-boreal, likely caused by strengthening North Atlantic Deep Water formation (Bølling) or increased ventilation in the Southern Ocean (Younger Drays) or both (Pre-boreal). The ?15 ?mol/kg decline in deep water carbonate ion since ?10 ka is consistent with extraction of alkalinity from seawater by deep-sea CaCO3 compensation and coral reef growth on continental shelves during the Holocene.

Between 16,600 and 15,000 years ago, deep South Atlantic carbonate ion values converged with those at 3.4-km water depth in the western equatorial Pacific, as did carbon isotope and radiocarbon values. These observations suggest a period of enhanced lateral exchange of carbon between the deep South Atlantic and Pacific Oceans, probably due to an increased transfer of momentum from southern westerlies to the Southern Ocean. By spreading carbon-rich deep Pacific waters around Antarctica for upwelling, invigorated interocean deep water exchange would lead to more efficient CO2 degassing from the Southern Ocean, and thus to an atmospheric CO2 rise, during the early deglaciation.

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More information

Published date: 15 April 2014
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 363501
URI: http://eprints.soton.ac.uk/id/eprint/363501
ISSN: 0277-3791
PURE UUID: a80b505c-e5ca-4110-a8ce-b2b2815510d3
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

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Date deposited: 25 Mar 2014 14:04
Last modified: 15 Mar 2024 02:47

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Contributors

Author: Jimin Yu
Author: Robert F. Anderson
Author: Zhangdong Jin
Author: Laurie Menviel
Author: Fei Zhang
Author: Fredrick J. Ryerson

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