AMOC-forced southward migration of the ITCZ under a warm climate background

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Kraft, Laura ; Campos, Marilia C. ; Nascimento, Rodrigo A. ; Dias, Bruna B. ; Crivellari, Stefano ; Kochhann, Marcus V. L. ; Bertassoli Jr, Dailson J. ; Venancio, Igor M. ; Santos, Thiago P. ; Baker, Paul A. ; Silva, Cleverson G. ; Chiessi, Cristiano M.

• Document type: Journal article
• Source: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY; v. 661, p. 10-pg., 2025-01-16.

Abstract

Northern northeastern Brazil (NEB) is a climate change hotspot due to its high biological and social vulnerability to ongoing and future hydroclimate changes. Precipitation in this region is influenced by the Intertropical Convergence Zone (ITCZ), which is largely controlled by the strength of the Atlantic Meridional Overturning Circulation (AMOC). Accordingly, the projected weakening of the AMOC due to anthropogenic global warming may substantially change NEB hydroclimate. Heinrich Stadials (HS), past millennial-scale events during which the AMOC was significantly weaker, provide important insights into the AMOC-ITCZ dynamics. This is especially true for those HS that occurred under similar to modern boundary conditions. HS10 (ca. 110 thousand years ago) was the first HS of Marine Isotope Stage 5, providing an ideal target for investigating AMOC-ITCZ dynamics under relatively warm climate conditions. Here we investigate the response of the surface and deep western equatorial Atlantic (WEA) circulation, as well as NEB precipitation to HS10. Therefore, we use foraminiferal carbon and oxygen stable isotopes and bulk sediment major elemental data from a marine sediment core retrieved from the WEA. Our results record a weakening of the AMOC during HS10 and show a concurrent increased WEA upper stratification and precipitation over NEB. We suggest that the mechanism controlling the WEA upper ocean stratification during HS depends on the background climate. Furthermore, we infer that the southward shift of the ITCZ during HS10 was more limited if compared to the shifts that occurred under colder climate background. Our findings provide useful insights into how a weakening of the AMOC under a relatively warm climate can impact the ITCZ and tropical South American precipitation. (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: 22/06440-1 - Wetland expansion in Amazonia during the late Holocene and its implications to the global methane budget
• Grantee: Dailson José Bertassoli Junior
• Support Opportunities: Generation Project Research Grant
• 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: 22/09822-2 - Improvement of analytical routines and software development for analysis of carbon and oxygen stable isotopes by gas isotope ratio mass spectrometry in single specimens
• Grantee: Stefano Crivellari
• Support Opportunities: Scholarships in Brazil - Technical Training Program - Technical Training
• 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: 21/02877-3 - Paleoceanographic evolution of the South Atlantic subtropical gyre over the past 800,000 years based on a multi-proxy approach
• Grantee: Marcus Vinicius Lermen Kochhann
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/24977-0 - Environmental signals recorded in modern sediments of tropical South American rivers
• Grantee: Dailson José Bertassoli Junior
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 23/14028-6 - Orbital-scale variability of heat content in the South Atlantic Subtropical Gyre: assessing seawater temperature via Mg/Ca analysis
• Grantee: Marcus Vinicius Lermen Kochhann
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• 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