Climate and environmental changes over Amazon Basin documented by stalagmites

Abstract

The South America Monsson 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 Amazon Basin. Reconstructing tropical hydroclimate history has been difficult, particularly in the Amazon Basin, one of Earth's major centers of deep atmospheric convection, largely because most study sites are located on the periphery of the basin (most in the Peruvian Andes) and interpretations can be complicated by sediment preservation, uncertainties in chronology, and topographical setting. 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 cold 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 Rondonia 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 d18O record will be integrate with the previously published d18O records from Peruvian Andes (Bird et al., 2011) and from southern border of Amazon Basin (Novello et al., 2016) for the understanding of SAMS evolution through the Amazon Basin. (AU)