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Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age

Wang, Xingchen Tony and Sigman, Daniel M. and Prokopenko, Maria G. and Adkins, Jess F. and Robinson, Laura F. and Hines, Sophia K. and Chai, Junyi and Studer, Anja S. and Martínez-García, Alfredo and Chen, Tianyu and Haug, Gerald H. (2017) Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age. Proceedings of the National Academy of Sciences of the United States of America, 114 (13). pp. 3352-3357. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:20170316-111615042

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Abstract

The Southern Ocean regulates the ocean’s biological sequestration of CO_2 and is widely suspected to underpin much of the ice age decline in atmospheric CO_2 concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the ^(15)N/^(14)N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher ^(15)N/^(14)N across the Southern Ocean during the Last Glacial Maximum (LGM), 18–25 thousand years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the surface Antarctic Zone, respectively.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1073/pnas.1615718114 DOIArticle
http://www.pnas.org/content/114/13/3352PublisherArticle
http://www.pnas.org/content/114/13/3352?tab=dsPublisherSupporting Information
ORCID:
AuthorORCID
Hines, Sophia K.0000-0001-9357-6399
Additional Information:© 2017 National Academy of Sciences. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved February 15, 2017 (received for review September 20, 2016). We thank two anonymous reviewers for their constructive comments. This work was supported by National Science Foundation Grants OCE-1234664 (to M.G.P. and D.M.S.), PLR-1401489 (to D.M.S.), and OCE-1503129 (to J.F.A.), the Charlotte Elizabeth Procter Fellowship of the Graduate School at Princeton University (to X.T.W.), the Grand Challenges Program of Princeton University (D.M.S.), European Research Council Grant 278705 (to L.F.R.), and Natural Environmental Research Council Grant NE/N003861/1 (to L.F.R.). Author contributions: X.T.W., D.M.S., M.G.P., and G.H.H. designed research; X.T.W., D.M.S., and M.G.P. performed research; X.T.W., J.F.A., L.F.R., S.K.H., A.S.S., A.M.-G., and T.C. contributed new reagents/analytic tools; X.T.W. and J.C. analyzed data; and X.T.W. and D.M.S. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1615718114/-/DCSupplemental.
Funders:
Funding AgencyGrant Number
NSFOCE-1234664
NSFPLR-1401489
NSFOCE-1503129
Princeton University UNSPECIFIED
European Research Council (ERC)278705
Natural Environmental Research Council (NERC)NE/N003861/1
Subject Keywords:Southern Ocean | nutrient consumption | atmospheric CO2 | ice ages
Record Number:CaltechAUTHORS:20170316-111615042
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170316-111615042
Official Citation:Xingchen Tony Wang, Daniel M. Sigman, Maria G. Prokopenko, Jess F. Adkins, Laura F. Robinson, Sophia K. Hines, Junyi Chai, Anja S. Studer, Alfredo Martínez-García, Tianyu Chen, and Gerald H. Haug Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age PNAS 2017 114 (13) 3352-3357; published ahead of print March 15, 2017, doi:10.1073/pnas.1615718114
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75180
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:16 Mar 2017 18:36
Last Modified:31 Oct 2017 16:28

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