Climate and environmental reconstruction of the last 16,000 years in central-eastern Brazil using a speleothem multiproxy approach
Loading...
Date issued
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Reuse License
Abstract
Paleoclimate archives, such as speleothems, provide critical understanding of past climate
variability. Speleothems are particularly valuable as a continental archive since they occur worldwide,
can be precisely dated via the ²³⁰Th-U dating method and form by the precipitation of calcium
carbonate from percolating drip water within caves, integrating signals from soil, bedrock, and
rainfall. In general, oxygen (δ¹⁸O) and carbon (δ¹³C) isotope ratios have been the most used proxies
in speleothem-based studies, serving as indicators of past hydroclimate and environmental changes.
More recently, multi-proxy approach studies have been growing, since they provide more
comprehensive understanding of the complex processes that influence speleothem formation and
climate signal interpretation.
In South America, speleothem studies have greatly advanced our understanding of the
South American Summer Monsoon (SASM), the continent's dominant climate system that leads
precipitation over tropical South America. The SASM has a NW-SE convection band that extends
over the continent, the South Atlantic Convergence Zone (SACZ). This thesis applies a multi-proxy
approach to reconstruct the hydrological, environmental and temperature evolution of the last
16,000 years from central-eastern Brazil based on a stalagmite collected in São Mateus Cave, Goiás
State. The cave lies in a transitional climate zone between humid tropical and semi-arid regions,
making it highly sensitive to changes in the SASM and SACZ.
The results revealed that central-east Brazil is largely influenced by both tropical and highlatitude
forcings, such as changes in solar radiation, ocean–atmosphere dynamics, and
interhemispheric temperature gradients in several time-scales. During the deglacial period, rapid
temperature and hydrological changes occurred concomitant with abrupt climate shifts in the
Northen Hemisphere. During the Holocene, the earlier period evidences shifting climate and
environmental conditions, likely due to the low insolation. The middle and late Holocene present
more stable conditions responding to the increasing insolation, which is the dominant forcing at
these periods. Finally, the multi-proxy results show pronounced hydrological, environmental and
temperature changes during the during the deglaciation and the Holocene. The São Mateus record
provides new evidence of how SACZ and SASM developed over the last 16,000 years.