South Atlantic Subtropical Gyre northern boundary oscillations during the last 800 thousand years based on Globorotalia truncatulinoides relative abundance

• Grant number: 22/13436-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2022
• End date: November 30, 2023
• Field of knowledge: Interdisciplinary Subjects
• Principal Investigator: Cristiano Mazur Chiessi
• Grantee: Giovana Thomazini Hammer
• Host Institution: Escola de Artes, Ciências e Humanidades (EACH). 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

Oceanic gyres are important components of the climatic system which comprehend large wind-driven ocean current systems. Acting as a mechanism of meridional redistribution of energy in the oceans, they can directly impact on import climate system forcings such as atmospheric CO2 concentration. The South Atlantic Subtropical Gyre (SASG) recently became the focus of studies due to transporting heat to the Southern Ocean among other aspects. By transferring heat to the Southern Ocean the SASG influences the temperature meridional gradient in that ocean's mid-latitudes controlling the southern hemisphere westerlies intensity. The westerlies intensity in turn plays an important role in Southern Ocean CO2 release to the atmosphere. One way that heat content transferred through the SASG to the Southern Ocean can vary is through meridional changes in the SASG. Here, the relative abundance of the planktonic foraminifera Globorotalia truncatulinoides from a sediment core collected from the western South Atlantic will be used as a paleoceanographic proxy for reconstructing the northern boundary meridional changes of the SASG during the last 800 thousand years. This project aims to test the following hypotheses: (i) the SASG northern boundary has undergone meridional changes during the last 800 thousand years; and (ii) the former being true, SASG poleward displacements are related to increasing the CO2 release from the Southern Ocean to the atmosphere.