Climate and environmental changes in southwestern Amazon Basin over the last 3000 years based on speleothem isotope records, Brazil

• Autor(a) principal: Godoy, Marcela Eduarda Della Libera de
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/44/44142/tde-19102021-090419/
• topic: Amazon; Amazônia; Espeleotemas; Isótopos estáveis; Paleoambiente; Paleoclima; Paleoclimate; Paleoenvironment; Sistema de Monção Sul-Americano; South American Monsoon System; Speleothems; Stable isotopes

The variability of the South American Monsoon System (SAMS) is of uttermost relevance for understanding climate patterns over South America since it is the most important precipitation regime acting over the continent. The SAMS occurs during austral summer and spring due to a major influx of vapor from tropical Atlantic Ocean into the continent, when a zone of deep convection is then established over southwestern Amazon basin, at the monsoon core region. Past monsoon changes have been documented through oxygen isotope analysis (18O) from speleothems and became one of the main proxies utilized to retrieve continental paleoclimatic data. The results from monitoring program performed at the cave site indicate that the incorporation of oxygen isotopes in the CaCO3 of speleothems formation is closely linked to the meteoric water cycle in the region, holding relevant information about local rainfall amount and precipitation along the moisture transport from ocean to continent. However, the patterns of SAMS for last millenniums have not yet been deeply discussed for the Amazon region. The current work is based on high resolution speleothem isotope records from Cuíca cave (Pimenta Bueno-RO) that were used to reconstruct paleoclimatic and paleoenvironmental records from Southwestern Amazon Basin for the last 3000 years. Cuíca speleothem 18O record reveals three climatic periods in the SAMS characterized by wetter, drier and wetter climate corresponding to the e first millennia of the record from 3000-2000 B.P., the Medieval Climate Anomaly (1250-700 B.P. - MCA) and Little Ice Age (500-150 B.P. - LIA), respectively. In addition, comparison of Cuíca cave data with previous studies from South America brought up new evidence of an east-west precipitation dipole over the Amazon Basin, mainly during intensifications in SAMS activity, as identified in the LIA climate event. A high correlation between 13C and 18O data is here interpreted as a response of biogenic CO2 production in soil to changes in precipitation. Both 13C and 18O records are used here to check if the population dynamics of pre-Columbian cultures from Southwestern Amazonia are related with paleoclimatic and paleoenvironmental changes in the region. Statistical analysis of 18O record reveal persistent decadal and multidecadal variability in SAMS intensity associated with Atlantic ocean climate modes. In summary, the new high-resolution 18O and 13C records from southwestern Amazon contributes to further assess monsoon variations at its core region to better understand the impact of atmospheric circulation in Amazon on hydrological conditions over the periphery of SAMS domain.