Past to future South Atlantic meridional overturning circulation: pathways and low...
Abstract
Negative synergies between climate change and deforestation may force the Amazon rainforest to cross a tipping point, resulting in large-scale substitution of rainforest by non-forest ecosystems. However, this possible dieback of the Amazon rainforest remains highly uncertain at least in part due to another similarly uncertain tipping element of the climate system, namely the Atlantic meridional overturning circulation. A potential shutdown of the Atlantic meridional overturning circulation would cause major changes in surface heat distribution in the Atlantic Ocean, strongly affecting Amazonian precipitation. Indeed, such changes have been repeatedly recorded in geological archives. Here we propose to reconstruct past climate and environmental changes in Amazonia and the adjacent ocean for the last ca. 250 kyr in unprecedented temporal resolution, grounded in a comprehensive calibration of paleoenvironmental proxies. Therefore, we will analyze geochemical, isotopic and biological parameters in (i) modern tropical South American fluvial sediments to calibrate paleoclimatic and paleoenvironmental proxies, and (ii) western tropical Atlantic marine sediment cores to reconstruct past climate and environmental conditions. This project will provide an in-depth understanding of the responses and internal feedbacks of Amazonia and the western tropical Atlantic for (i) abrupt climate changes, (ii) warmer than preindustrial climates, and (iii) environmental boundary conditions significantly different from preindustrial, helping to constrain possible future scenarios for Amazonia and the adjacent ocean. Also, this project will consolidate a top-level research group on paleoceanography and paleoclimatology at EACH/USP. (AU)