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Promising regions for detecting the overturning circulation in Atlantic Pa/Th: a model-data comparison
  • +2
  • Jeemijn Scheen,
  • Jörg Lippold,
  • Frerk Pöppelmeier,
  • Finn Süfke,
  • Thomas F. Stocker
Jeemijn Scheen
Climate and Environmental Physics, University of Bern, Switzerland, Oeschger Centre for Climate Change Research, University of Bern, Switzerland, Department of Estuarine and Delta Systems, NIOZ Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands

Corresponding Author:[email protected]

Author Profile
Jörg Lippold
Institute of Earth Sciences, Heidelberg University, Germany
Frerk Pöppelmeier
Climate and Environmental Physics, University of Bern, Switzerland, Oeschger Centre for Climate Change Research, University of Bern, Switzerland
Finn Süfke
Institute of Earth Sciences, Heidelberg University, Germany
Thomas F. Stocker
Climate and Environmental Physics, University of Bern, Switzerland, Oeschger Centre for Climate Change Research, University of Bern, Switzerland

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.
20 Feb 2024Submitted to ESS Open Archive
26 Feb 2024Published in ESS Open Archive