Occurrence and impact of the mega-South Atlantic Convergence Zone over the eastern South America during the last glacial period: a paleoceanographic approach

Abstract

The Brazil Current (BC) plays a fundamental role in the distribution of energy between the hemispheres. It stores and redirects towards the mean latitudes of the Southern Hemisphere a significant portion of heat in periods of weakening of the Atlantic Meridional Overturning Circulation (AMOC). Additionally, the BC influences summer precipitation in a large sector of South America. Recently, anomalies so far unknown of the position and intensity of the South Atlantic Convergence Zone (SACZ) were described for the Heinrich Stadial (HS) 1 and termed "mega-SACZ". Such anomalies were associated to the weakening of the AMOC and had produced dramatic changes in South America climate. Since the HSs can, to some extent, be considered as past analogous of future conditions and that the reduction of up to 44% of the AMOC intensity is predicted to occur until the end of the century, a better understanding of the above described phenomenon is urgently required. This PhD project aims at reconstructing the oceanographic and climatic variability of the western South Atlantic near 10.5°S and of the adjacent portion of the continent during the last glacial and deglacial periods. Thus, we will be able to determine the occurrence and impact of the mega-SACZ over eastern South America during the last glacial period. We will investigate the marine sediment cores M125-95-2/3 collected at a site under the influence of the BC and subject to the delivery of terrigenous sediments from the São Francisco river drainage basin, located mainly under the influence of the SACZ. For this cores we will produce age models based on 14C ages, fluorescence X-ray analyses, oxygen and carbon stable isotope analyses, and Mg/Ca analyses.