A fully calibrated and updated mid-Holocene climate reconstruction for Eastern South America

Abstract

Investigating the extent and climate implications of the mid-Holocene (MH - around 6000 years ago) is essential in better understanding the uncertainties associated with the ongoing and future projections of global warming. South America (SA) contains the biome with the largest biodiversity in the world, its population exceeds 400 million people, and its economy is mainly agricultural. Thus, studies involving South America's climate variability have become a subject of significant importance over the years. Paleoclimate archives provide unique indirect measurements, helping us to characterize past climates. However, the derived radiometric ages from several paleoarchives in SA published before the 2000s have not yet been calibrated, which represents a large source of uncertainty. In this article, we present a climate reconstruction for eastern SA during the MH with fully calibrated age models. We compiled 173 paleoclimate records, where 50 of them were calibrated in this study using Bayesian methods. Through this multiproxy approach and the elaboration of a new homogeneous quality index for proxies, our novel climate reconstruction sheds new light on the regional climate of SA climate during MH. All high quality (higher than 1) paleoarchives agree at regional scale. Compiled paleodata confirms reduced rainfall in Amazonia and a warmer and drier Southern SA, indicating an overall weakening of the South American Summer Monsoon during the MH. North East Brazil coast show higher than present moisture during the MH, while the border between Northeast Brazil and Southern SA shows divergent behavior, pointing to a local erratic rainfall regime with inputs of higher than present moisture conditions, most likely caused by changes in precipitation over the South Atlantic Convergence Zone, and a weaker than present South Atlantic Subtropical High during MH.