Paleoclimate reconstitution of Northeast Brazil over the last millennia based on speleothems isotope records

• Grant number: 21/12860-0
• Support type: Scholarships abroad - Research Internship - Post-doctor
• Effective date (Start): January 05, 2022
• Effective date (End): April 04, 2022
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal researcher: Francisco William da Cruz Junior
• Grantee: Giselle Utida
• Supervisor abroad: Richard Lawrence Edwards
• Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Research place: University of Minnesota (U of M), United States
• Associated to the scholarship: 20/02737-4 - Teleconections between tropics and extra-tropics of South America, BP.PD

Abstract

The Intertropical Convergence Zone (ITCZ) and the South America Monsoon System (SAMS) are the main responsible for convection over tropical region in South America. Despite previous studies have described the ITCZ variability in different time scales, as well as the SAMS, the relationship between these systems has not been tested yet for the last millennia. Our previous isotope results for stalagmites from Rio Grande do Norte (RN), Northeastern Brazil (NEB), cover the last 3,500 years and indicate that the ITCZ southward migration was also associated with its reduced projection over the continent during the Little Ice Age, resulting in wet conditions at RN and drought at East Amazonia, while the southern area of NEB was dry. Other studies suggest that during the LIA, the South Atlantic Convergence Zone (SACZ), a key feature of the SAMS, was displaced southwestern from its modern position resulting in droughts in southern NEB regions, possibly related to the south displacement of the ITCZ, however this relationship is not well established. The main goal of the research is better comprehend the ITCZ dynamics and its relationship with the SAMS by reconstructing precipitation based on the isotope studies covering the last millennia. The studied sites are from the southern limit of the ITCZ, at RN state, north area of NEB, and the southern limit of NEB, at Bahia (BA), that is affected by the SACZ. Previous U/Th dates obtained in stalagmites from Gruta do Jerônimo (BA) indicate great potential for studies covering the Holocene. A detailed geochronological study of these stalagmites will be essential to continue the paleoprecipitation reconstruction of the region. These samples will be dated by U/Th method at the Minnesota Isotope Laboratory (USA), using a multi-collector inductively coupled plasma mass spectrometry technique (MC-ICP-MS, Thermo-Finnigan NEPTUNE). The results will guide sampling of stalagmites for paleoprecipitation reconstructions from Bahia, and will be compared with NEB and other records of South America to better understand the relationship between ITCZ and SACZ through time.