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Evolution of South Atlantic density and chemical stratification across the last deglaciation

Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Vazquez Riveiros, Natalia; Hodell, David A.

Authors

Jenny Roberts

Julia Gottschalk

Luke C. Skinner

Victoria L. Peck

Sev Kender

Henry Elderfield

Claire Waelbroeck

Natalia Vazquez Riveiros

David A. Hodell



Abstract

Explanations of the glacial-interglacial variations in atmospher¬ic pCO2 invoke a significant role for the deep ocean in the stor¬age of CO2. Deep ocean density stratification has been pro¬posed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data sup¬ports the presence of a "chemical divide" between intermedi¬ate and deep water in the glacial Atlantic Ocean, which indi¬rectly points to an increase in deep ocean density stratifica¬tion. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e. tempera¬ture and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected δ18O measurements on the benthic foraminifer Uvigerina spp. from deep and intermediate water-depth marine sediment cores to reconstruct the changes in density of sub-Antarctic South Atlantic water masses over the last deglaciation (i.e. 22-2 ka before present). We find that a major breakdown in the physical density stratification signifi¬cantly lags the breakdown of the deep-intermediate chemical divide, as indicated by the chemical tracers of benthic foramin¬ifer δ13C and foraminifer/coral 14C. Our results indicate that chemical destratification likely resulted in the first rise in at¬mospheric pCO2, whereas the density destratification of the deep South Atlantic lags the second rise in atmospheric pCO2 during the late deglacial period. Our findings emphasise that the physical and chemical destratification of the ocean are not be as tightly coupled as generally assumed.

Citation

Roberts, J., Gottschalk, J., Skinner, L. C., Peck, V. L., Kender, S., Elderfield, H., …Hodell, D. A. (2016). Evolution of South Atlantic density and chemical stratification across the last deglaciation. Proceedings of the National Academy of Sciences, 113(3), https://doi.org/10.1073/pnas.1511252113

Journal Article Type Article
Acceptance Date Nov 17, 2015
Online Publication Date Jan 4, 2016
Publication Date Jan 19, 2016
Deposit Date May 16, 2016
Publicly Available Date May 16, 2016
Journal Proceedings of the National Academy of Sciences
Print ISSN 0027-8424
Electronic ISSN 1091-6490
Publisher National Academy of Sciences
Peer Reviewed Peer Reviewed
Volume 113
Issue 3
DOI https://doi.org/10.1073/pnas.1511252113
Public URL http://eprints.nottingham.ac.uk/id/eprint/33314
Publisher URL http://www.pnas.org/content/113/3/514
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf

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2015-12-03 Open-access version.pdf (1.2 Mb)
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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf





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