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A deep-sea coral record of North Atlantic radiocarbon through the Younger Dryas: Evidence for intermediate water/deepwater reorganization

Eltgroth, Selene F. and Adkins, Jess F. and Robinson, Laura F. and Southon, John and Kashgarian, Michaele (2006) A deep-sea coral record of North Atlantic radiocarbon through the Younger Dryas: Evidence for intermediate water/deepwater reorganization. Paleoceanography, 21 (4). Art. No. PA4207. ISSN 0883-8305.

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Our record of Younger Dryas intermediate-depth seawater Δ^(14)C from North Atlantic deep-sea corals supports a link between abrupt climate change and intermediate ocean variability. Our data show that northern source intermediate water (∼1700 m) was partially replaced by (14)^C-depleted southern source water at the onset of the event, consistent with a reduction in the rate of North Atlantic Deep Water formation. This transition requires the existence of large, mobile gradients of Δ^(14)C in the ocean during the Younger Dryas. The Δ^(14)C water column profile from Keigwin (2004) provides direct evidence for the presence of one such gradient at the beginning of the Younger Dryas (∼12.9 ka), with a 100‰ offset between shallow (<∼2400 m) and deep water. Our early Younger Dryas data are consistent with this profile and also show a Δ^(14)C inversion, with 35‰ more enriched water at ∼2400 m than at ∼1700 m. This feature is probably the result of mixing between relatively well ^(14)C ventilated northern source water and more poorly ^(14)C ventilated southern source intermediate water, which is slightly shallower. Over the rest of the Younger Dryas our intermediate water/deepwater coral Δ^(14)C data gradually increase, while the atmosphere Δ^(14)C drops. For a very brief interval at ∼12.0 ka and at the end of the Younger Dryas (11.5 ka), intermediate water Δ^(14)C (∼1200 m) approached atmospheric Δ14C. These enriched Δ^(14)C results suggest an enhanced initial Δ^(14)C content of the water and demonstrate the presence of large lateral Δ^(14)C gradients in the intermediate/deep ocean in addition to the sharp vertical shift at ∼2500 m. The transient Δ^(14)C enrichment at ∼12.0 ka occurred in the middle of the Younger Dryas and demonstrates that there is at least one time when the intermediate/deep ocean underwent dramatic change but with much smaller effects in other paleoclimatic records.

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Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2006 American Geophysical Union. Received 12 July 2005; revised 25 May 2006; accepted 28 June 2006; published 17 November 2006. We wish to thank Jessie Shing-Lin Wang and Diego Fernandez for help with U-Th sample preparation and analysis at Caltech. We thank the staff of the UC Irvine KCCAMS laboratory and the staff of LLNL-CAMS for help with radiocarbon sample preparation and analysis. We are grateful to Steven Cairns at the Smithsonian for providing one of the samples (YD-3) used in this study and to the crew of the R/V Atlantis and DSV Alvin pilots, whose expertise made it possible for us to collect thousands of fossil samples from the New England seamounts. Luke Skinner and Jean Lynch-Stieglitz provided very helpful reviews of the manuscript. This work was supported by NSF grant OCE 0096373.
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Issue or Number:4
Record Number:CaltechAUTHORS:20120828-123314699
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Official Citation:Eltgroth, S. F., J. F. Adkins, L. F. Robinson, J. Southon, and M. Kashgarian (2006), A deep-sea coral record of North Atlantic radiocarbon through the Younger Dryas: Evidence for intermediate water/deepwater reorganization, Paleoceanography, 21, PA4207, doi:10.1029/2005PA001192.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33615
Deposited By: Aucoeur Ngo
Deposited On:28 Aug 2012 21:17
Last Modified:24 Feb 2020 10:30

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