A new mechanism for millennial scale positive precipitation anomalies over tropical South America

Author(s)

Campos, Marilia C. ^[1] ; Chiessi, Cristiano M. ^[1] ; Prange, Matthias ^[2] ; Mulitza, Stefan ^[2] ; Kuhnert, Henning ^[2] ; Paul, Andre ^[2] ; Venancio, Igor M. ^[3] ; Albuquerque, Ana Luiza S. ^[4] ; Cruz, Francisco W. ^[5] ; Bahr, Andre ^[6]

Affiliation

^[1] Univ Sao Paulo, Sch Arts Sci & Humanities, Sao Paulo, SP - Brazil

^[2] Univ Bremen, MARUM Ctr Marine Environm Sci, Bremen - Germany

^[3] Natl Inst Space Res INPE, Ctr Weather Forecasting & Climate Studies CPTEC, Cachoeira Paulista - Brazil

^[4] Fluminense Fed Univ, Grad Program Geochem, Niteroi, RJ - Brazil

^[5] Univ Sao Paulo, Inst Geoci, Sao Paulo, SP - Brazil

^[6] Heidelberg Univ, Inst Earth Sci, Heidelberg - Germany

• Document type: Journal article
• Source: QUATERNARY SCIENCE REVIEWS; v. 225, DEC 1 2019.
• Web of Science Citations: 0

Abstract

Continental and marine paleoclimate archives from northwestern and northeastern South America recorded positive precipitation anomalies during Heinrich Stadials (HS). These anomalies have been classically attributed to enhanced austral summer (monsoon) precipitation. However, the lack of marine paleoclimate records off eastern South America as well as inconsistencies between southeastern South American continental and marine records hamper a comprehensive understanding of the mechanism responsible for (sub-) tropical South American hydroclimate response to HS. Here we investigate piston core M125-95-3 collected off eastern South America (10.94 degrees S) and simulate South American HS conditions with a high-resolution version of an atmosphere-ocean general circulation model. Further, meridional changes in precipitation over (sub-) tropical South America were assessed with a thorough compilation of previously available marine paleorecords. Our ln(Ti/Ca) and ln(Fe/K) data show increases during HS6-Younger Dryas. It is the first core off eastern South America and the southernmost from the Atlantic continental margin of South America that unequivocally records HS-related positive precipitation anomalies. Based on our new data, model results and the compilation of available marine records, we propose a new mechanism for the positive precipitation anomalies over tropical South America during HS. The new mechanism involves austral summer precipitation increases only over eastern South America while the rest of tropical South America experienced precipitation increases during the winter, challenging the widely held assumption of a strengthened monsoon. South American precipitation changes were triggered by dynamic and thermodynamic processes including a stronger moisture supply from the equatorial North Atlantic (tropical South Atlantic) in austral winter (summer). (C) 2019 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 16/10242-0 - Occurrence and impact of the mega-South Atlantic Convergence Zone over the eastern South America during the last glacial period: a paleoceanographic approach
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Scholarships in Brazil - Doctorate
• 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: 18/06790-7 - Variability of the Brazil Current and South American climate during the last glacial cycle: assessing sea-surface temperatures via Mg/Ca analyses and pulses of terrigenous sediments via X-ray fluorescence analyses
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate