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Tracking Spread of the Agulhas Leakage Into the Western South Atlantic and Its Northward Transmission During the Last Interglacial
  • +7
  • João Marcelo Ballalai,
  • Thiago Pereira dos Santos,
  • Douglas Villela de Oliveira Lessa,
  • Igor Martins Venancio,
  • Cristiano Mazur Chiessi,
  • Heather Johnstone,
  • Henning Kuhnert,
  • Felipe Antonio de Lima Toledo,
  • Karen Badaraco Costa,
  • Ana Luiza Albuquerque
João Marcelo Ballalai
Universidade Federal Fluminense

Corresponding Author:[email protected]

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Thiago Pereira dos Santos
Universidade Federal Fluminense - UFF
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Douglas Villela de Oliveira Lessa
Universidade Federal Fluminense - UFF
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Igor Martins Venancio
Instituto de Pesquisas Espaciais - INPE
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Cristiano Mazur Chiessi
Universidade de São Paulo - USP
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Heather Johnstone
Center for Marine Environmental Sciences - MARUM
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Henning Kuhnert
Center for Marine Environmental Sciences - MARUM
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Felipe Antonio de Lima Toledo
Universidade de São Paulo - USP
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Karen Badaraco Costa
Universidade de São Paulo - USP
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Ana Luiza Albuquerque
Universidade Federal Fluminense - UFF
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Abstract

Intensification of the Agulhas Leakage (AL) during glacial terminations has long been proposed as a necessary mechanism for reverting the Atlantic Meridional Overturning Circulation (AMOC) to its interglacial mode. However, lack of records showing the downstream evolution of AL signal and substantial temporal differences between AL intensification and resumption of deep‐water convection have cast doubt on the importance of this mechanism to the AMOC. Here, we analyze a combination of new and previously published data relating to Mg/Ca‐derived temperatures and ice volume‐corrected seawater δ18O records (δ18OIVC‐SW, as a proxy for relative changes in ocean salinity), which demonstrate propagation of AL signal via surface and thermocline waters to the western South Atlantic (Santos Basin) during Termination II and the early Last Interglacial. The saline AL waters were temporally stored in the upper subtropical South Atlantic until they were abruptly released in two stages into the North Atlantic via surface and thermocline waters at ca. 129 and 123 ka BP, respectively. Accounting for age model uncertainties, these two stages are coeval with the resumption of convection in the Labrador and Nordic seas during the Last Interglacial. We propose a mechanism whereby both active AL and a favorable ocean‐atmosphere configuration in the tropical Atlantic were required to allow flux of AL waters into the North Atlantic, where they then contributed to enhancing the AMOC during the Last Interglacial period. Our results provide a framework that connects AL strengthening to the AMOC intensifications that followed glaciations.
Nov 2019Published in Paleoceanography and Paleoclimatology volume 34 issue 11 on pages 1744-1760. 10.1029/2019PA003653