Reconstruction of changes in the carbonate system in intermediate waters of the Southwest Atlantic over the past 25,000 years through the calibration and application of a new proxy based on calcareous nannofossils

• Grant number: 24/16858-9
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: January 01, 2025
• End date: December 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Geological Oceanography
• Principal Investigator: Renata Hanae Nagai
• Grantee: Amanda Gerotto
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 20/14356-5 - The Santos Bifurcation: present and past, AP.PFPMCG.TEM

Abstract

Understanding the variations in the biogeochemical parameters of the ocean that control air-sea carbon dioxide (CO2) fluxes is essential to clarifying the role of the oceans in climate regulation. The carbonate ion (CO32-) has profound implications for this flux, as it determines the carbonate saturation of seawater and, consequently, the preservation and dissolution of CaCO3. Water masses generated in the Southern Hemisphere, such as Antarctic Intermediate Water, show significant variability in the Atlantic Meridional Overturning Circulation, impacting the carbonate [CO32-] seawater concentration since the Last Glacial Maximum. This research project aims to assess potential changes in the carbonate system in the Southwest Atlantic associated with changes in circulation over the past 25,000 years. To achieve this, the calibration and application of the ks shape factor will be carried out, derived from morphological attributes of calcareous nannofossils and their potential relationships with environmental variables (total alkalinity, total carbon dioxide, pH, and calcite saturation) from surface samples collected between 23°S and 28°S at depths ranging from 700 to 2400 meters. These relationships will be assessed through a redundancy analysis, and subsequently, the normalized ks factor will be applied to sedimentary records collected in the same region to reconstruct changes in the carbonate system since the Last Glacial Maximum.