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Late quaternary paleoclimate in Brazil from oxygen and carbon isotope ratios on speleothems


Stable oxygen and carbon isotope of speleothems precisely dated by U/Th method have become important proxies of climate change in the late pleistocene and holocene in (sub) tropical regions. In this way, Brazil is one the most potential countries for these isotopic studies. First, cave occurrences are widely distributed within its territory and cover a broad latitudinal range. Second, the previous speleothems studies demonstrated a summer insulation forcing of changes in rainfall regimes over southern-southeastern Brazil during the late quaternary (cycles of ~23.000 years). In addition the past climate in this region was also impacted on millennial time-scales by cooler climate conditions in northern hemisphere during Heinrich events. The present proposal aims to extend these studies for different tropical sites in Brazil by addressing questions about climate regional variability during late pleistocene and holocene. It proposes to investigate the following problems: 1) is the precipitation associated with the South American Summer Monsoon (SASM) responding to changes in the summer insulation on long-term time scales and how insulation affects large-scale atmospheric circulation in South America?; 2) How are the rapid climate shifts of the last glacial period and holocene expressed in the southern hemisphere tropics? What is the impact of large-scale mode of natural climate variability such as El Niño-Southern Oscillation and North Atlantic Oscillation on short-term changes of past rainfall in the SASM region? In conjunction with our paleoclimate studies, we propose a stable isotope and geochemistry study in water samples. This work is important for understanding how the rainfall d180 signal is transferred from precipitation to the karts system and is finally recorded in speleothems calcite and also how the chemical composition of cave drips forming speleothems is associated to rainfall variations. (AU)

Articles published in Pesquisa FAPESP Magazine about the research grant:
Historias de aguas antiguas 
Ancient Waters and their stories 
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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
NOVELLO, VALDIR F.; CRUZ, FRANCISCO W.; KARMANN, IVO; BURNS, STEPHEN J.; STIRKIS, NICOLAS M.; VUILLE, MATHIAS; CHENG, HAI; EDWARDS, R. LAWRENCE; SANTOS, ROBERTO V.; FRIGO, EVERTON; et al. Multidecadal climate variability in Brazil's Nordeste during the last 3000 years based on speleothem isotope records. Geophysical Research Letters, v. 39, . (06/06761-0)

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