Climate and environmental changes over the Tocantins state documented by stalagmites

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. Despite several studies have shown that both systems are sensitive to solar variability (Novello et al., 2016; Bird et al., 2011) the interrelationship between SAMS and ITCZ 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. To verify the relationship between these convective systems with radiative forcing new paleoclimate records from non-explored study sites is required. The understanding of SAMS variability during the last millennia have been improved by studies involving ´18O and trace elements on speleothems. For the current project, we propose the study of speleothems collected in caves of Tocantins 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. Among the objectives are make new paleoclimate records based on the isotopic analyses and trace elements in speleothems in order to fill the gap of paleoclimate records on the State Tocantins (Brazil), identify changes in rainfall, vegetation, erosion and soil dynamics on the proxies above, identify climate patterns on the SAMS during the last millennium, and its relationship with the ITCZ and associate the paleoclimate records with climate models for a better understanding of climate mechanism responsible by SAMS variability.