Promising regions for detecting the overturning circulation in Atlantic Pa/Th: a model-data comparison

Type Article
Acceptance Date 2024-02-26 IN PRESS
Language English
Author(s) Scheen JeemijnORCID1, Lippold Jörg2, Pöppelmeier Frerk3, Süfke Finn2, Stocker Thomas F.3
Affiliation(s) 1 : Department of Estuarine and Delta Systems, NIOZ Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands
2 : Institute of Earth Sciences, Heidelberg University, Germany
3 : Oeschger Centre for Climate Change Research, University of Bern, Switzerland
Source ESS Open Archive / submitted to Paleoceanography and Paleoclimatology (Authorea, Inc.) In Press
DOI 10.22541/essoar.170898721.10752966/v1
Note This is a preprint and has not been peer reviewed. Data may be preliminary.
Abstract

The Atlantic Meridional Overturning Circulation (AMOC) is a critical component of the climate system, strongly influencing the climate via ocean heat transport. The AMOC had different characteristics during glacial periods and is expected to change under anthropogenic climate forcing. To reconstruct past AMOC strength, the Pa/Th (protactinium-231 to thorium-230) ratio measured in marine sediments serves as a unique proxy. However, this ratio reflects not only circulation changes, but also effects from biological particle export and benthic nepheloid layers. Therefore, it remains an open question which regions exhibit a reliable AMOC signal in their sedimentary Pa/Th. This study, utilising the Bern3D model and a compilation of sediment cores with 11 newly published cores, suggests that equatorial West Atlantic Pa/Th is as sensitive to AMOC changes as the Bermuda Rise region. Additionally, the Pa/Th response to AMOC changes observed in part of the northern North Atlantic, which is opposite to regions further south, is caused by AMOC-induced changes in particle production. Cores in this region are promising to reconstruct AMOC strength, despite exhibiting an AMOC-to-Pa/Th relationship opposite from usual and high levels of opal. Additional cores in the North Atlantic at 40-60°N between 1 and 2 km depth are desirable for the application of Pa/Th. Our results suggest a new focus of Pa/Th reconstructions on the equatorial West Atlantic and the northern North Atlantic, which appear to be better suited to quantify past AMOC strength.

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Preprint 72 9 MB Open access
Supplement to the preprint 19 4 MB Open access
SI_1_sediment_measurements 24 KB Open access
SI_2_age_models 36 KB Open access
SI_3_compilation_Kd_to_sigma 31 KB Open access
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