Meridional changes in the South Atlantic Subtropical Gyre during Heinrich Stadials

Tainã M L Pinho,Ana L S Albuquerque,Stefano Crivellari,Marília C Campos,Stefan Mulitza,Rodrigo C Portilho-Ramos,Rodrigo A Nascimento,Cristiano M Chiessi,André Bahr

doi:10.1038/s41598-021-88817-0

Abstract

Subtropical ocean gyres play a key role in modulating the global climate system redistributing energy between low and high latitudes. A poleward displacement of the subtropical gyres has been observed over the last decades, but the lack of long-term monitoring data hinders an in-depth understanding of their dynamics. Paleoceanographic records offer the opportunity to identify meridional changes in the subtropical gyres and investigate their consequences to the climate system. Here we use the abundance of planktonic foraminiferal species Globorotalia truncatulinodes from a sediment core collected at the northernmost boundary of the South Atlantic Subtropical Gyre (SASG) together with a previously published record of the same species from the southernmost boundary of the SASG to reconstruct meridional fluctuations of the SASG over last ca. 70 kyr. Our findings indicate southward displacements of the SASG during Heinrich Stadials (HS) 6-4 and HS1, and a contraction of the SASG during HS3 and HS2. During HS6-4 and HS1, the SASG southward displacements likely boosted the transfer of heat to the Southern Ocean, ultimately strengthening deep-water upwelling and CO2 release to the atmosphere. We hypothesize that the ongoing SASG poleward displacement may further increase oceanic CO2 release.

Highlights

Subtropical gyres are large systems of anticyclonic upper ocean circulation driven by wind stress c url[1, 2], characterized as enormous reservoirs of heat and salt[3]
We present the abundance of G. truncatulinoides as a new proxy for the meridional displacement of the South Atlantic Subtropical Gyre (SASG) on millennial timescales
Our G. truncatulinoides abundance record, together with previously published records, show that the SASG migrated southwards during most Heinrich Stadials (HS) of the last glacial and deglacial periods (i.e., HS6-4 and HS1). These events were probably responsible for the transfer of substantial amounts of heat from the SASG to the Southern Ocean, strengthening deep-water upwelling and C O2 release to the atmosphere

Summary

Introduction

Subtropical gyres are large systems of anticyclonic upper ocean circulation driven by wind stress c url[1, 2], characterized as enormous reservoirs of heat and salt[3]. They are major pathways of energy redistribution between low and high latitudes with a pivotal role on the global climatic s ystem[4]. As part of the subtropical gyres, western boundaries currents (e.g., Brazil Current (BC) and Gulf Stream) transport warm and salty tropical waters towards the poles, and eastern boundaries currents (e.g., Benguela and Canary Currents) transport cold and fresh waters towards the equator. The abundance of G. truncatulinoides in adequately located marine sediment cores is an excellent proxy to track meridional changes in the subtropical gyres

Methods

Discussion

Conclusion