Millennial variability of the Brazil Current and South American climate during the last glacial period

Author(s)

Marília de Carvalho Campos

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola de Artes, Ciências e Humanidades (EACH)
• Defense date: 2016-07-01

Examining board members

Cristiano Mazur Chiessi; André Luiz Belém; Christian Millo; Felipe Antonio de Lima Toledo

• Advisor: Cristiano Mazur Chiessi

Abstract

The Brazil Current (BC) represents the southern branch of the bifurcation of the South Equatorial Current that interacts with the southeastern Brazilian continental margin. Sea surface temperature at BC region plays an important role in controlling the intensity and position of the South Atlantic Convergence Zone, which represents one of the main componets of the South American Monsoon System (SAMS). This atmospheric system is responsible for summer precipitation in a large sector of South America, and, therefore, it is a natural feature of great importance for the national and international political-economic context. Moreover, the BC is markedly influenced by the Atlantic Meridional Overturning Circulation (AMOC) whose past oscillations generated marked global abrupt climatic changes. Presently, the few paleoceanographic records available from the western South Atlantic do not allow a detailed reconstruction of the changes that happened in the BC during the last glacial cycle. This MSc. dissertation aimed at reconstructing the variability of the BC around 32°S during the events Heinrich Stadial (HS) 3 and 2, as well as its impacts on the climate of southeastern South America. Therefore, we investigated one marine sediment core collected in the southern Brazilian continental margin, under the influence of the BC. For this core we produced an age model based on 14C ages, downcore records of carbon and oxygen stable isotopes and Mg/Ca, both in tests of planktonic foraminifera, and X-ray fluorescence in bulk sediment samples. During HSs (notably during HS2), the records show marked increases in sedimentation rate as well as in ln(Ti/Ca) and ln(Fe/Ca), and decrease in the stable carbon isotopic composition as well as sea surface temperature and salinity. Such changes were releted to the weakening of the AMOC, the intensification of the Southern Ocean upwelling, and the strengthening of the SAMS. The occurrence a w-structure in our HS records as well as in North Atlantic and South American records, suggest that such structure is a pervasive feature of HS2, and possibly also HS3 (AU)

• FAPESP's process: 13/25518-2 - Variability of the Brazil Current and its impacts on the South American climate during the last 30,000 years
• Grantee: Marília de Carvalho Campos Garcia
• Support Opportunities: Scholarships in Brazil - Master