TY - JOUR

T1 - Boundary scavenging at the East Atlantic margin does not negate use of 231Pa/ 230Th to trace Atlantic overturning

AU - Lippold, Jörg

AU - Mulitza, Stefan

AU - Mollenhauer, Gesine

AU - Weyer, Stefan

AU - Heslop, David

AU - Christl, Marcus

N1 - Funding information: We thank Augusto Mangini, Evelyn Böhm, Sibylle Reuter, Frank Wombacher and Alexander Hofmann for helpful impulses and/or extensive lab work. We thank Alexander Thomas and one anonymous reviewer for improvement of the manuscript. This study has been funded by the German Science Foundation DFG (grant Ma821/38-2 and Li1815/2 ). Gesine Mollenhauer and Stefan Mulitza were funded through the DFG Research Centre/Excellence Cluster “The Ocean in the Earth System”. Samples were supplied through the assistance of the University of Bremen, Geosciences Department and MARUM. We thank Dirk Nürnberg (IFM-GEOMAR Kiel) and Gerhard Kuhn (AWI Bremerhaven) for readily providing help with the opal measurements.

PY - 2012/6/1

Y1 - 2012/6/1

N2 - The 231Pa/ 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 produced 231Pa and 230Th in ocean water. Here we present 231Pa/ 230Th down-core profiles from high particle flux areas off Namibia and Senegal covering the past ~35ka. The 231Pa/ 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 sedimentary 231Pa/ 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 of 231Pa from the open Ocean. Consequently, the applicability of the 231Pa/ 230Th proxy to reconstruct past ocean circulation is not hampered by this potentially additional 231Pa sink.

AB - The 231Pa/ 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 produced 231Pa and 230Th in ocean water. Here we present 231Pa/ 230Th down-core profiles from high particle flux areas off Namibia and Senegal covering the past ~35ka. The 231Pa/ 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 sedimentary 231Pa/ 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 of 231Pa from the open Ocean. Consequently, the applicability of the 231Pa/ 230Th proxy to reconstruct past ocean circulation is not hampered by this potentially additional 231Pa sink.

KW - Pa/ Th

KW - African margin

KW - AMOC

KW - Boundary scavenging

KW - LGM

KW - North Atlantic Deep Water

UR - http://www.scopus.com/inward/record.url?scp=84861337716&partnerID=8YFLogxK

U2 - 10.1016/j.epsl.2012.04.005

DO - 10.1016/j.epsl.2012.04.005

M3 - Article

AN - SCOPUS:84861337716

VL - 333-334

SP - 317

EP - 331

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

ER -