Late glacial abrupt climate events in tropical South America

Abstract

Abrupt climate events interrupt large-scale climate variability during the late Pleistocene and drive both global and regional shifts in ecosystem, atmospheric and oceanic processes. Understanding how past abrupt climate events drive changes in these systems is important due to the modern, changing climate. Understanding the signal of these events in the neotropical regions is crucial as some research suggests that the trigger of these events may originate in the tropical regions. Here I present records from two marine and one terrestrial sites in tropical South America, that span the late Pleistocene and early Holocene and capture several of these abrupt warming and cooling events. From these cores I have undertaken high-resolution analysis of pollen, spores, charcoal and dinoflagellates to reconstruct atmospheric, oceanic and ecosystem processes, and Uk’37 to develop sea surface temperature reconstructions. By undertaking multi-proxy analysis from the same sediment sample, chronology errors are reduced allowing direct comparison of marine and terrestrial data. Results show that abrupt climate events drive rapid responses in atmospheric systems, oceanic currents and ecosystems in tropical South America. Recorded changes include expansion of coastal marshes, migrations of Andean vegetation and shifts in planktonic communities in the oceans indicating air temperature changes, sea level fluctuations, migrations of precipitation bands and strengthening and weakening of upwelling intensity. Processes such as sea level change and intensity of the Atlantic Meridional Overturning Circulation lead atmospheric systems during some abrupt climate events i.e., Heinrich Stadial 1. However, such ocean-driven signal is not observed for the Younger Dryas, possibly linked to differential drivers. My research shows evidence for rapid response of Andean vegetation during abrupt climate events, including elevational migration of vegetation boundaries. The findings of this research can be used to ground climate models used to understand anthropogenic climate change.