Paleoceanographic reconstruction of the western equatorial Atlantic during the last 100 kyr: proxy analysis and numerical modelling

• Grant number: 24/20195-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: May 01, 2025
• End date: August 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Geological Oceanography
• Principal Investigator: Luigi Jovane
• Grantee: Thauana Rodrigues Gonçalves
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

This PhD project focuses on the reconstruction of paleoceanographic conditions in the Western Equatorial Atlantic (WEA) over the last 100,000 years, aiming to understand the effects of freshwater discharges on the Atlantic Meridional Overturning Circulation (AMOC) and associated climate dynamics. The study investigates periods of abrupt climate change, particularly Heinrich Stadial (HS), which are known for the significant influx of freshwater from the melting Laurentide ice sheet into the North Atlantic, leading to a significant reduction in the formation of North Atlantic Deep Water (NADW), influencing the intensity of the AMOC and shifting the Intertropical Convergence Zone (ITCZ). The project integrates high-resolution paleoclimate data from marine sediment cores with climate simulations conducted using the Hadley Centre Climate Model (HadCM3). Proxy data, including Fe/Ca, Ti/Ca and Fe/K ratios, magnetic susceptibility and grain size, reveal information about terrigenous input from riverine sources, indicating increased sediment transport linked to intensified precipitation patterns. These paleo-proxies are analyzed together with numerical experiments (hose experiments) to simulate the AMOC response to variable freshwater pulses in the WEA and the North Atlantic. Through comparison of model data, this approach seeks to elucidate the delayed oceanic response to the southward migration of the ITCZ during HS events and its influence on AMOC variability. The results will contribute to a more detailed understanding of the hydrographic conditions of the WEA during past climate events, assessing how changes in Amazon River discharge and ITCZ dynamics impacted global ocean circulation patterns.