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The "African humid period" and the record of marine upwelling from excess ^(230)Th in Ocean Drilling Program Hole 658C

Adkins, Jess and deMenocal, Peter and Eshel, Gidon (2006) The "African humid period" and the record of marine upwelling from excess ^(230)Th in Ocean Drilling Program Hole 658C. Paleoceanography, 21 (4). Art. No. PA4203. ISSN 0883-8305. doi:10.1029/2005PA001200.

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Using a high-resolution ^(230)Th normalized record of sediment flux, we document the deglacial and Holocene history of North African aridity and coastal upwelling at Ocean Drilling Program Hole 658C. At both the end of the Younger Dryas and after the 8.2 ka event, there are significant drops in terrigenous accumulation at our site, indicating an increase in the monsoon moisture flux over Africa at this time. At 5.5 ka, there is an abrupt end to the “African humid period” and a return to stronger upwelling conditions. For carbonate and opal fluxes the ^(230)Th normalization completely changes the shape of each record based on percentage variations alone. This site is a clear example of how variations in one sediment component can obscure changes in the others, and it demonstrates the need for radionuclide measurements more generally in paleoceanography. By taking our new records and a large amount of previous data from this site we conclude that increases in African moisture are tightly coupled to decreases in coastal upwelling intensity.

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Adkins, Jess0000-0002-3174-5190
Additional Information:© 2006 American Geophysical Union. Received 26 August 2005; revised 4 February 2006; accepted 13 June 2006; published 20 October 2006. We thank Joe Ortiz for his analysis of the bulk density data and for conversations over the years. Two anonymous reviewers improved the clarity of the manuscript. J.F.A.’s work was supported by a LDEO postdoctoral fellowship and by the Lamont Climate Center. NSF grant OCE-0318445 supported J.F.A.’s work on this project at Caltech.
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Lamont–Doherty Earth Observatory (LDEO)UNSPECIFIED
Lamont Climate CenterUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20120828-142810744
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Official Citation:Adkins, J., P. deMenocal, and G. Eshel (2006), The “African humid period” and the record of marine upwelling from excess 230Th in Ocean Drilling Program Hole 658C, Paleoceanography, 21, PA4203, doi:10.1029/2005PA001200.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33620
Deposited On:28 Aug 2012 22:36
Last Modified:09 Nov 2021 21:36

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