Boundary scavenging at the East Atlantic margin does not negate use of Pa-231/Th-230 to trace Atlantic overturning

• Published in: Earth and Planetary Science Letters
• Main Authors: Lippold, Jorg, Mulitza, Stefan, Mollenhauer , Gesine, Weyer, Stefan, Heslop, David, Christl, M
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier
• Subjects: Keywords: African margin; AMOC; Boundary scavenging; LGM; North Atlantic Deep Water; Geology; Mathematical models; Oceanography; core analysis; glacial-interglacial cycle; in situ measurement; isotopic composition; Last Glacial Maximum; meridional circulation; ocea 231Pa/ 230Th; African margin; North Atlantic
• Online Access: http://hdl.handle.net/1885/72312; https://doi.org/10.1016/j.epsl.2012.04.005; https://openresearch-repository.anu.edu.au/bitstream/1885/72312/5/EarthScavenging.pdf.jpg; https://openresearch-repository.anu.edu.au/bitstream/1885/72312/7/01_Lippold_Boundary_scavenging_at_the_2012.pdf.jpg

The231Pa/230Th method is a promising tool to reconstruct Ocean circulation over the past Glacial-Interglacial cycle. However, marine particle flux may constrain the applicability of this ratio as a direct quantitative proxy for the strength of Atlantic Meridional Overturning Circulation (AMOC) by influencing the fractionation between the in situ produced231Pa and230Th in ocean water. Here we present231Pa/230Th down-core profiles from high particle flux areas off Namibia and Senegal covering the past ~35ka. The231Pa/230Th profiles at these sites show very different responses to temporal variations of particle fluxes and to changes in water masses. Our results show that sedimentary231Pa/230Th in the Eastern Atlantic margin is linked to particle flux, but controlled primarily by the mode of the AMOC. Our data suggest that during the past ~30ka the high productivity Eastern margin was not capable of importing and storing significant amounts of231Pa from the open Ocean. Consequently, the applicability of the231Pa/230Th proxy to reconstruct past ocean circulation is not hampered by this potentially additional231Pa sink.