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Spatiotemporal patterns of variability of South American Monsoon System in Tropical South America during the last centuries based on speleothem and tree-ring records

Grant number: 19/25636-1
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): February 01, 2020
Effective date (End): January 31, 2022
Field of knowledge:Biological Sciences - Botany
Cooperation agreement: National Science Foundation (NSF) and NSF’s Partnership for International Research and Education (PIRE)
Principal Investigator:Gregório Cardoso Tápias Ceccantini
Grantee:Bruno Barcante Ladvocat Cintra
Home Institution: Instituto de Biociências (IB). 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

Paleoclimatic studies based on biological and geological records present great potential for climate reconstructions in different temporal scales (Cruz et al. 2005, Vuille et al. 2012). In Brazil and in a large part of South America, oxygen isotopes in speleothems and tree rings have revealed important climatic patterns such as the variability of the South American Monsoon System (SAMS) since the Holocene (Cruz et al. 2009), interrelations between climate anomalies during periods known as Medieval Climate Annomaly and Little Ice Age, and patterns of climate oscillation during the last centuries (Ballantyne et al. 2011). However, recent hydroclimatic changes have resulted in the occurrence of extreme climatic events potentially aggravated by global warming, which many times escape the current understanding of the functioning of climate in South America. Therefore, a better understanding of the effects of the variability of SAMS over the climate and the occurrence of extreme climate events in tropical-subtropical South America is necessary. In this context, we propose to perform reconstructions of spatial and temporal patterns of climate in South America during the last centuries based on a multiproxy approach, integrating speleothems and tree rings. Justification: Synchronizing paleoclimatic data from speleothems and tree rings should offer new and revealing perspectives to the current understanding of climate changes and their influence over ecosystems, helping the calibration of climate models from IPCC, to forecast extreme droughts and floods in Brazil during the 21st century. Such information is fundamental to support public policies of mitigation and adaptation to hydroclimatic changes, promoted by public administration of natural resources, water and energy, and thereby reducing vulnerability of the population and economy sectors of the country. Furthermore, the implementation of methods and techniques such as cellulose extraction and isotopes analyses will be of high importance and a big challenge, allowing for new approaches and possibilities for Brazil and for our scientific team. Objectives: 1. to build chronologies of stable oxygen isotope records (d18O) obtained from speleothems and tree rings; 2. to identify inter-annual, decadal and multidecadal patterns of spatial and temporal variation of rainfall in tropical-subtropical South America and perform correlations with climate forcings such as solar activity and vulcanism and with climate indices such as El Niño Southern Oscillation (ENSO), Inter-Decadal Pacific Oscillation (IPO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). 3. to perform reconstructions of patterns of spatial-temporal variation of SAMS in tropical-subtropical South America during the last centuries based on multiproxies of tree rings and speleothems. Methods: Climate reconstructions based on stable isotopes in tree rings will be done with different tree species such as Hymenea ssp., Cedrela ssp., Handroanthus ssp., Amburana cearenses, Commiphora leptophloeos, Anadenanthera colubrine e Ararucaria angustifólia. The tree ring data will be compared with speleothem data already sampled in ongoing research. The tree rings will be dated by dendrochronological analyses of ring-widths, wood density and radiocarbon analyses. The stable isotope analyses will be carried out over cellulose samples extracted from individual tree rings. To date speleothem samples, carbonate material obtained from stalagmites will be dated through the 230U/234Th methods. The isotope measurements of C and O in stalagmites will be carried out on the mass spectra of CO2 molecules released during dissolution of CaCO3 by H3PO4. (AU)