Changes in Amazon River freshwater and sediment discharge during Heinrich Stadials of the last 250 kyr

• Grant number: 24/06541-8
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: February 01, 2025
• End date: March 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Cristiano Mazur Chiessi
• Grantee: Júlia Grigolato Iani
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 18/15123-4 - Past perspectives on tipping elements of the climate system: the Amazon Rainforest and the Atlantic Meridional Overturning Circulation (PPTEAM), AP.PFPMCG.JP2

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) plays a crucial role in global oceanic circulation, influencing heat distribution in the Atlantic Ocean and impacting climate patterns worldwide. Several studies show the intricate relationship between AMOC and precipitation in the Amazon Basin, a vital aspect for the ecological and climatic sustainability of the Amazon Forest. Projections of a major AMOC slowdown (or even a collapse) within the 21st century, prompted the scientific community to explore in detail past AMOC slowdown events, particularly Heinrich Stadials (HS), due to similar mechanisms, to better project how future AMOC slowdowns may affect Amazonian climate. However, high temporal resolution Amazon River paleoenvironmental information is only available for HSs of the last glacial period (71 - 11.7 thousand years before the present, ka), with a marked focus on the last deglaciation (i.e., 19 - 11.7 ka). This project aims to determining inter- and intra-HSs changes in precipitation over the Amazon Basin over the last 250 kyr. Marine sediment cores recently collected in sites under the influence of the Amazon River discharge will be used in this study. Analyzes of stable oxygen isotopes, Ba/Ca and Mg/Ca in planktonic foraminifera will be used to reconstruct variations in Amazon freshwater discharge (related to the amount of precipitation over the basin) and western equatorial Atlantic Sea surface temperatures (related to AMOC strength), while the optical stimulated luminescence sensitivity of quartz and feldspar will allow reconstructing changes in the source siliciclastic sediment discharge (related to the main locus of precipitation within the basin). This project will contribute to a comprehensive understanding of the complex interactions between AMOC dynamics and Amazonian climate that is essential for addressing future environmental changes in Amazonia.