Reduced Penetration of Northern-Sourced Waters Into the South Atlantic During the Last Interglacial Relative to the Holocene

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Dias, B. B. ; Chiessi, C. M. ; Piotrowski, A. M. ; Campos, M. C. ; Jena, P. S. ; Ballalai, J. M. ; Nascimento, R. A. ; Santos, T. P. ; Venancio, I. M. ; Mashayek, A. ; Albuquerque, A. L. S.

• Document type: Journal article
• Source: PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY; v. 40, n. 2, p. 15-pg., 2025-02-01.

Abstract

Specific previous interglacial periods showed millennial-scale climate variability that influenced deep water formation and circulation. However, our understanding about the spread of deep waters formed in the North Atlantic throughout the South Atlantic during interglacial periods remains limited. To reconstruct South Atlantic deep water geometry and the Atlantic Meridional Overturning Circulation (AMOC) differences between the Last Interglacial (LIG) and the Holocene, we present new authigenic neodymium isotope (epsilon Nd) and sortable silt (SS) records from the middepth western South Atlantic. The comparison of our results to other Atlantic epsilon Nd records reveals notable variations in the penetration of northern-sourced waters into the South Atlantic between these two periods. Moderate reduction of northern-sourced waters entrainment in the western South Atlantic was observed during the onset of the LIG (ca. 128-124 ka) compared to the Holocene, with a significant decrease in the eastward spread of this water mass. This reduction may be linked to freshwater inputs into the North Atlantic, which reduced water density. Counterintuitively, when the AMOC was expected to reach its full interglacial mode at the end of the LIG (ca. 120-116 ka), more radiogenic epsilon Nd values and lower SS values indicated a shallow AMOC. Increased mixing with southern-sourced waters during the LIG was likely due to decreased deep convection events at the North Atlantic high latitudes due to fresh subsurface water advection. Our findings suggest that the export and mixing ratio between northern- and southern-sourced waters in the South Atlantic are determined by Northern Hemisphere climate during interglacial periods. (AU)

• FAPESP's process: 19/25179-0 - Penultimate glacial-to-interglacial transition in Northeastern South America and the adjacent ocean
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 22/06452-0 - The South Atlantic on a 2°C warmer planet
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Generation Project Research Grant
• FAPESP's process: 18/15123-4 - Past perspectives on tipping elements of the climate system: the Amazon Rainforest and the Atlantic Meridional Overturning Circulation (PPTEAM)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: Research Grants - Research Program on Global Climate Change - Young Investigators - Phase 2
• FAPESP's process: 20/11452-3 - Carbon storage changes in the mid-depth South Atlantic during the penultimate glacial termination and the Anthropocene
• Grantee: Bruna Borba Dias
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/24349-9 - Assessing the effects of past and future climate change on Amazonian biodiversity (CLAMBIO)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants
• FAPESP's process: 22/01056-9 - The application of neodymium isotopes to reconstruct AMOC variability and its role in the global carbon cycle during the last two glacial terminations
• Grantee: Bruna Borba Dias
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 23/00355-5 - Abrupt changes in the deep western tropical Atlantic Ocean during the last two glacial periods
• Grantee: Partha Sarathi Jena
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 22/09479-6 - Changes in ITCZ-related precipitation over NE South America during the penultimate glacial-to-interglacial transition: assessing fluvial discharge via planktonic foraminiferal Ba/Ca
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor