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Climate and environmental changes over the Paripiranga-Bahia state documented by stalagmites

Grant number: 20/08459-6
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): August 01, 2020
Effective date (End): October 31, 2020
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Cooperation agreement: National Science Foundation (NSF) and NSF’s Partnership for International Research and Education (PIRE)
Principal Investigator:Francisco William da Cruz Junior
Grantee:Felipe de Godoy Nigro
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:17/50085-3 - PIRE: climate research education in the Americas using tree-ring speleothem examples (PIRE-CREATE), AP.TEM

Abstract

The South America Monsoon System (SAMS) and Intertropical Convergence Zone (ITCZ) are the main responsible by convection over tropical and extratropical regions of South America. In the eastern coastal of Bahia, precipitation is mainly modulated by the easterly waves disturbances (EWD), which propagate westward over the tropical South Atlantic Ocean and are intensified by the Southeast trade winds from June to August (Kousky, 1979; Gomes et al., 2015). Despite several studies have shown that these systems are sensitive to solar variability (Novello et al., 2016; Bird et al., 2011) the interrelationship between SAMS and ITCZ, and how is they affect the behavior of EWD, was not well documented for the last millennium over the central portion of Bahia state. Meehl et al. (2009) reported that peaks in solar forcing increase the energy input to the surface ocean at subtropical latitudes, thereby enhancing evaporation and near-surface moisture, which is carried by the trade winds to the convergence zones. Through this mechanism convective activity in the regions influenced by the upward branches of Hadley cell can be intensified, resulting in strengthened regional tropical precipitation regimes due to enhanced solar forcing (van Loon et al., 2004). This change in Hadley cell could modulate the positions of the ITCZ, as well, modulate the intensity of SAMS, and affect the EWD. To verify the relationship between these convective systems with radiative forcing new paleoclimate records from non-explored study sites is required. This research may contribute to a better understanding of the paleoclimatic variations associated with changes in the intensity of the EWD, as this weather system directly influences the modern climatology of the eastern Brazilian northeast. The speleothems of this region have great potential for paleopluvial reconstruction since their ´18O reflects variation in the rainfall volume of the region (Vuille et al., 2003).For the current project, we propose the study of speleothems collected in caves of Paripiranga-Bahia state (Brazil) where still have a gap of high resolution records for the last millennium. The stalagmites for this study were already collected, and its ´18O as well trace elements record will be integrate with the previously published ´18O records from stalagmites from Brazil. (AU)