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Speaker: Nicolás Strikis of the University of Sāo Paulo
Title: "Persistent anthropogenic drought of tropical South America"
Abstract: Comprehending how the evaporative demand of the atmosphere affects the hydrologic balance is critical to improve our understanding of drought and the consequences of the global warming to water resources. Evaporative demand is thermodynamically linked to temperature; therefore, tropical areas with high hydrological cycle seasonality, like tropical savannah and semi-desert biomes, are prone to severe effects due to the current warming trend, resulting in marked reduction in river flow and groundwater availability. Here we present seasonally-resolved paleoclimate climate reconstruction combining a suite of proxies in a speleothem from central Brazil. The set of geochemical proxies applied to the speleothem shows that evaporative demand has suppressed precipitation, leading to a hydrological deficit driven by the anthropogenic warming trend. A marked change in the hydrologic balance in central eastern Brazil, induced by a severe warming trend, can be assigned starting near 1970s and has no counterpart within the last 150 years. In addition, the isotope record suggests that the regional climate variability is closely related to the Atlantic multidecadal oscillation until the 1970´s, when it became apparently decoupled from the natural modes. These results reinforce the premise of a severe long term drought in the tropics of Southern Hemisphere associated with the anthropogenic warming.